diff --git a/include/malloc.h b/include/alloc.h
similarity index 85%
rename from include/malloc.h
rename to include/alloc.h
index c215f56c0..f2dcf6d46 100644
--- a/include/malloc.h
+++ b/include/alloc.h
@@ -1,5 +1,5 @@
-#ifndef GUARD_MALLOC_H
-#define GUARD_MALLOC_H
+#ifndef GUARD_ALLOC_H
+#define GUARD_ALLOC_H
 
 #define HEAP_SIZE 0x1C000
 #define malloc Alloc
@@ -19,4 +19,4 @@ void *AllocZeroed(u32 size);
 void Free(void *pointer);
 void InitHeap(void *pointer, u32 size);
 
-#endif // GUARD_MALLOC_H
+#endif // GUARD_ALLOC_H
diff --git a/include/global.h b/include/global.h
index cc8df049f..1bca4c344 100644
--- a/include/global.h
+++ b/include/global.h
@@ -25,6 +25,14 @@
 #define INCBIN_S32 {0}
 #endif // IDE support
 
+// Invalid / Out of Bound Placeholder values
+#define INVALID_U8 0xFF
+#define INVALID_U16 0xFFFF
+#define INVALID_U32 0xFFFFFFFF
+#define INVALID_S8 -1
+#define INVALID_S16 -1
+#define INVALID_S32 -1
+
 #define ARRAY_COUNT(array) (size_t)(sizeof(array) / sizeof((array)[0]))
 
 #define SWAP(a, b, temp)    \
diff --git a/ld_script.txt b/ld_script.txt
index ddafe6ecf..c629c9f34 100644
--- a/ld_script.txt
+++ b/ld_script.txt
@@ -43,7 +43,7 @@ SECTIONS {
     {
         asm/crt0.o(.text);
         src/main.o(.text);
-        src/malloc.o(.text);
+        src/alloc.o(.text);
         src/dma3_manager.o(.text);
         src/gpu_regs.o(.text);
         src/bg.o(.text);
diff --git a/src/alloc.c b/src/alloc.c
new file mode 100644
index 000000000..2944bc1c6
--- /dev/null
+++ b/src/alloc.c
@@ -0,0 +1,210 @@
+#include "global.h"
+
+static void *sHeapStart;
+static u32 sHeapSize;
+static u32 malloc_c_unused_0300000c; // needed to align dma3_manager.o(.bss)
+
+#define MALLOC_SYSTEM_ID 0xA3A3
+
+struct MemBlock {
+    // Whether this block is currently allocated.
+    bool16 flag;
+
+    // Magic number used for error checking. Should equal MALLOC_SYSTEM_ID.
+    u16 magic;
+
+    // Size of the block (not including this header struct).
+    u32 size;
+
+    // Previous block pointer. Equals sHeapStart if this is the first block.
+    struct MemBlock *prev;
+
+    // Next block pointer. Equals sHeapStart if this is the last block.
+    struct MemBlock *next;
+
+    // Data in the memory block. (Arrays of length 0 are a GNU extension.)
+    u8 data[0];
+};
+
+void PutMemBlockHeader(void *block, struct MemBlock *prev, struct MemBlock *next, u32 size)
+{
+    struct MemBlock *header = (struct MemBlock *)block;
+
+    header->flag = FALSE;
+    header->magic = MALLOC_SYSTEM_ID;
+    header->size = size;
+    header->prev = prev;
+    header->next = next;
+}
+
+void PutFirstMemBlockHeader(void *block, u32 size)
+{
+    PutMemBlockHeader(block, (struct MemBlock *)block, (struct MemBlock *)block, size - sizeof(struct MemBlock));
+}
+
+void *AllocInternal(void *heapStart, u32 size)
+{
+    struct MemBlock *pos = (struct MemBlock *)heapStart;
+    struct MemBlock *head = pos;
+    struct MemBlock *splitBlock;
+    u32 foundBlockSize;
+
+    // Alignment
+    if (size & 3)
+        size = 4 * ((size / 4) + 1);
+
+    for (;;) {
+        // Loop through the blocks looking for unused block that's big enough.
+
+        if (!pos->flag) {
+            foundBlockSize = pos->size;
+
+            if (foundBlockSize >= size) {
+                if (foundBlockSize - size < 2 * sizeof(struct MemBlock)) {
+                    // The block isn't much bigger than the requested size,
+                    // so just use it.
+                    pos->flag = TRUE;
+                } else {
+                    // The block is significantly bigger than the requested
+                    // size, so split the rest into a separate block.
+                    foundBlockSize -= sizeof(struct MemBlock);
+                    foundBlockSize -= size;
+
+                    splitBlock = (struct MemBlock *)(pos->data + size);
+
+                    pos->flag = TRUE;
+                    pos->size = size;
+
+                    PutMemBlockHeader(splitBlock, pos, pos->next, foundBlockSize);
+
+                    pos->next = splitBlock;
+
+                    if (splitBlock->next != head)
+                        splitBlock->next->prev = splitBlock;
+                }
+
+                return pos->data;
+            }
+        }
+
+        if (pos->next == head)
+            return NULL;
+
+        pos = pos->next;
+    }
+}
+
+void FreeInternal(void *heapStart, void *pointer)
+{
+    if (pointer) {
+        struct MemBlock *head = (struct MemBlock *)heapStart;
+        struct MemBlock *block = (struct MemBlock *)((u8 *)pointer - sizeof(struct MemBlock));
+        block->flag = FALSE;
+
+        // If the freed block isn't the last one, merge with the next block
+        // if it's not in use.
+        if (block->next != head) {
+            if (!block->next->flag) {
+                block->size += sizeof(struct MemBlock) + block->next->size;
+                block->next->magic = 0;
+                block->next = block->next->next;
+                if (block->next != head)
+                    block->next->prev = block;
+            }
+        }
+
+        // If the freed block isn't the first one, merge with the previous block
+        // if it's not in use.
+        if (block != head) {
+            if (!block->prev->flag) {
+                block->prev->next = block->next;
+
+                if (block->next != head)
+                    block->next->prev = block->prev;
+
+                block->magic = 0;
+                block->prev->size += sizeof(struct MemBlock) + block->size;
+            }
+        }
+    }
+}
+
+void *AllocZeroedInternal(void *heapStart, u32 size)
+{
+    void *mem = AllocInternal(heapStart, size);
+
+    if (mem != NULL) {
+        if (size & 3)
+            size = 4 * ((size / 4) + 1);
+
+        CpuFill32(0, mem, size);
+    }
+
+    return mem;
+}
+
+bool32 CheckMemBlockInternal(void *heapStart, void *pointer)
+{
+    struct MemBlock *head = (struct MemBlock *)heapStart;
+    struct MemBlock *block = (struct MemBlock *)((u8 *)pointer - sizeof(struct MemBlock));
+
+    if (block->magic != MALLOC_SYSTEM_ID)
+        return FALSE;
+
+    if (block->next->magic != MALLOC_SYSTEM_ID)
+        return FALSE;
+
+    if (block->next != head && block->next->prev != block)
+        return FALSE;
+
+    if (block->prev->magic != MALLOC_SYSTEM_ID)
+        return FALSE;
+
+    if (block->prev != head && block->prev->next != block)
+        return FALSE;
+
+    if (block->next != head && block->next != (struct MemBlock *)(block->data + block->size))
+        return FALSE;
+
+    return TRUE;
+}
+
+void InitHeap(void *heapStart, u32 heapSize)
+{
+    sHeapStart = heapStart;
+    sHeapSize = heapSize;
+    PutFirstMemBlockHeader(heapStart, heapSize);
+}
+
+void *Alloc(u32 size)
+{
+    AllocInternal(sHeapStart, size);
+}
+
+void *AllocZeroed(u32 size)
+{
+    AllocZeroedInternal(sHeapStart, size);
+}
+
+void Free(void *pointer)
+{
+    FreeInternal(sHeapStart, pointer);
+}
+
+bool32 CheckMemBlock(void *pointer)
+{
+    return CheckMemBlockInternal(sHeapStart, pointer);
+}
+
+bool32 CheckHeap()
+{
+    struct MemBlock *pos = (struct MemBlock *)sHeapStart;
+
+    do {
+        if (!CheckMemBlockInternal(sHeapStart, pos->data))
+            return FALSE;
+        pos = pos->next;
+    } while (pos != (struct MemBlock *)sHeapStart);
+
+    return TRUE;
+}
diff --git a/src/apprentice.c b/src/apprentice.c
index 499f85094..faed3756c 100644
--- a/src/apprentice.c
+++ b/src/apprentice.c
@@ -9,7 +9,7 @@
 #include "item.h"
 #include "item_menu.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "new_game.h"
 #include "party_menu.h"
@@ -1079,7 +1079,7 @@ void ResetApprenticeStruct(struct Apprentice *apprentice)
     u8 i;
 
     for (i = 0; i < 6; i++)
-        apprentice->easyChatWords[i] |= 0xFFFF;
+        apprentice->easyChatWords[i] |= INVALID_U16;
 
     apprentice->playerName[0] = EOS;
     apprentice->id = 16;
@@ -1093,7 +1093,7 @@ void ResetAllApprenticeData(void)
     for (i = 0; i < 4; i++)
     {
         for (j = 0; j < 6; j++)
-            gSaveBlock2Ptr->apprentices[i].easyChatWords[j] |= 0xFFFF;
+            gSaveBlock2Ptr->apprentices[i].easyChatWords[j] |= INVALID_U16;
         gSaveBlock2Ptr->apprentices[i].id = 16;
         gSaveBlock2Ptr->apprentices[i].playerName[0] = EOS;
         gSaveBlock2Ptr->apprentices[i].lvlMode = 0;
@@ -1290,7 +1290,7 @@ static u16 sub_819FF98(u8 arg0)
     else
         level = 60;
 
-    for (j = 0; learnset[j] != 0xFFFF; j++)
+    for (j = 0; learnset[j] != INVALID_U16; j++)
     {
         if ((learnset[j] & 0xFE00) > (level << 9))
             break;
@@ -1393,7 +1393,7 @@ static void GetLatestLearnedMoves(u16 species, u16 *moves)
         level = 60;
 
     learnset = gLevelUpLearnsets[species];
-    for (i = 0; learnset[i] != 0xFFFF; i++)
+    for (i = 0; learnset[i] != INVALID_U16; i++)
     {
         if ((learnset[i] & 0xFE00) > (level << 9))
             break;
@@ -2236,7 +2236,7 @@ static void sub_81A1370(void)
     }
 
     r10 = 0xFFFF;
-    r9 = -1;
+    r9 = INVALID_S32;
     for (i = 1; i < 4; i++)
     {
         if (GetTrainerId(gSaveBlock2Ptr->apprentices[i].playerId) == GetTrainerId(gSaveBlock2Ptr->playerTrainerId)
diff --git a/src/bard_music.c b/src/bard_music.c
index 6c2578071..4c28233c2 100644
--- a/src/bard_music.c
+++ b/src/bard_music.c
@@ -54,7 +54,7 @@ void GetWordPhonemes(struct BardSong *song, u16 word)
     for (i = 0; i < 6; i ++)
     {
         sound = &song->sound[i];
-        if (sound->var00 != 0xFF)
+        if (sound->var00 != INVALID_U8)
         {
             song->phonemes[i].length = sound->var01 + gBardSoundLengthTable[sound->var00];
             song->phonemes[i].pitch = CalcWordPitch(word + 30, i);
diff --git a/src/battle_ai_script_commands.c b/src/battle_ai_script_commands.c
index 3e7064eb5..e6c089b1b 100644
--- a/src/battle_ai_script_commands.c
+++ b/src/battle_ai_script_commands.c
@@ -276,7 +276,7 @@ static const u16 sDiscouragedPowerfulMoveEffects[] =
     EFFECT_SUPERPOWER,
     EFFECT_ERUPTION,
     EFFECT_OVERHEAT,
-    0xFFFF
+    INVALID_U16
 };
 
 // code
@@ -463,8 +463,8 @@ static u8 ChooseMoveOrAction_Doubles(void)
     {
         if (i == sBattler_AI || gBattleMons[i].hp == 0)
         {
-            actionOrMoveIndex[i] = -1;
-            bestMovePointsForTarget[i] = -1;
+            actionOrMoveIndex[i] = INVALID_U8;
+            bestMovePointsForTarget[i] = INVALID_S16    ;
         }
         else
         {
@@ -530,7 +530,7 @@ static u8 ChooseMoveOrAction_Doubles(void)
                 // Don't use a move against ally if it has less than 100 points.
                 if (i == (sBattler_AI ^ BIT_FLANK) && bestMovePointsForTarget[i] < 100)
                 {
-                    bestMovePointsForTarget[i] = -1;
+                    bestMovePointsForTarget[i] = INVALID_S16;
                     mostViableMovesScores[0] = mostViableMovesScores[0]; // Needed to match.
                 }
             }
@@ -1003,7 +1003,7 @@ static void BattleAICmd_if_in_bytes(void)
 {
     const u8 *ptr = T1_READ_PTR(gAIScriptPtr + 1);
 
-    while (*ptr != 0xFF)
+    while (*ptr != INVALID_U8)
     {
         if (AI_THINKING_STRUCT->funcResult == *ptr)
         {
@@ -1019,7 +1019,7 @@ static void BattleAICmd_if_not_in_bytes(void)
 {
     const u8 *ptr = T1_READ_PTR(gAIScriptPtr + 1);
 
-    while (*ptr != 0xFF)
+    while (*ptr != INVALID_U8)
     {
         if (AI_THINKING_STRUCT->funcResult == *ptr)
         {
@@ -1035,7 +1035,7 @@ static void BattleAICmd_if_in_hwords(void)
 {
     const u16 *ptr = (const u16 *)T1_READ_PTR(gAIScriptPtr + 1);
 
-    while (*ptr != 0xFFFF)
+    while (*ptr != INVALID_U16)
     {
         if (AI_THINKING_STRUCT->funcResult == *ptr)
         {
@@ -1051,7 +1051,7 @@ static void BattleAICmd_if_not_in_hwords(void)
 {
     const u16 *ptr = (const u16 *)T1_READ_PTR(gAIScriptPtr + 1);
 
-    while (*ptr != 0xFFFF)
+    while (*ptr != INVALID_U16)
     {
         if (AI_THINKING_STRUCT->funcResult == *ptr)
         {
@@ -1167,14 +1167,14 @@ static void BattleAICmd_get_how_powerful_move_is(void)
     s32 i, checkedMove;
     s32 moveDmgs[4];
 
-    for (i = 0; sDiscouragedPowerfulMoveEffects[i] != 0xFFFF; i++)
+    for (i = 0; sDiscouragedPowerfulMoveEffects[i] != INVALID_U16; i++)
     {
         if (gBattleMoves[AI_THINKING_STRUCT->moveConsidered].effect == sDiscouragedPowerfulMoveEffects[i])
             break;
     }
 
     if (gBattleMoves[AI_THINKING_STRUCT->moveConsidered].power > 1
-        && sDiscouragedPowerfulMoveEffects[i] == 0xFFFF)
+        && sDiscouragedPowerfulMoveEffects[i] == INVALID_U16)
     {
         gDynamicBasePower = 0;
         *(&gBattleStruct->dynamicMoveType) = 0;
@@ -1184,14 +1184,14 @@ static void BattleAICmd_get_how_powerful_move_is(void)
 
         for (checkedMove = 0; checkedMove < 4; checkedMove++)
         {
-            for (i = 0; sDiscouragedPowerfulMoveEffects[i] != 0xFFFF; i++)
+            for (i = 0; sDiscouragedPowerfulMoveEffects[i] != INVALID_U16; i++)
             {
                 if (gBattleMoves[gBattleMons[sBattler_AI].moves[checkedMove]].effect == sDiscouragedPowerfulMoveEffects[i])
                     break;
             }
 
             if (gBattleMons[sBattler_AI].moves[checkedMove] != MOVE_NONE
-                && sDiscouragedPowerfulMoveEffects[i] == 0xFFFF
+                && sDiscouragedPowerfulMoveEffects[i] == INVALID_U16
                 && gBattleMoves[gBattleMons[sBattler_AI].moves[checkedMove]].power > 1)
             {
                 gCurrentMove = gBattleMons[sBattler_AI].moves[checkedMove];
diff --git a/src/battle_ai_switch_items.c b/src/battle_ai_switch_items.c
index ad25b483c..d6a8e1336 100644
--- a/src/battle_ai_switch_items.c
+++ b/src/battle_ai_switch_items.c
@@ -126,7 +126,7 @@ static bool8 FindMonThatAbsorbsOpponentsMove(void)
         return FALSE;
     if (gLastLandedMoves[gActiveBattler] == 0)
         return FALSE;
-    if (gLastLandedMoves[gActiveBattler] == 0xFFFF)
+    if (gLastLandedMoves[gActiveBattler] == INVALID_U16)
         return FALSE;
     if (gBattleMoves[gLastLandedMoves[gActiveBattler]].power == 0)
         return FALSE;
@@ -221,7 +221,7 @@ static bool8 ShouldSwitchIfNaturalCure(void)
     if (gBattleMons[gActiveBattler].hp < gBattleMons[gActiveBattler].maxHP / 2)
         return FALSE;
 
-    if ((gLastLandedMoves[gActiveBattler] == 0 || gLastLandedMoves[gActiveBattler] == 0xFFFF) && Random() & 1)
+    if ((gLastLandedMoves[gActiveBattler] == 0 || gLastLandedMoves[gActiveBattler] == INVALID_U16) && Random() & 1)
     {
         *(gBattleStruct->AI_monToSwitchIntoId + gActiveBattler) = PARTY_SIZE;
         BtlController_EmitTwoReturnValues(1, B_ACTION_SWITCH, 0);
@@ -331,9 +331,9 @@ static bool8 FindMonWithFlagsAndSuperEffective(u8 flags, u8 moduloPercent)
 
     if (gLastLandedMoves[gActiveBattler] == 0)
         return FALSE;
-    if (gLastLandedMoves[gActiveBattler] == 0xFFFF)
+    if (gLastLandedMoves[gActiveBattler] == INVALID_U16)
         return FALSE;
-    if (gLastHitBy[gActiveBattler] == 0xFF)
+    if (gLastHitBy[gActiveBattler] == INVALID_U8)
         return FALSE;
     if (gBattleMoves[gLastLandedMoves[gActiveBattler]].power == 0)
         return FALSE;
diff --git a/src/battle_anim.c b/src/battle_anim.c
index e8720fcfb..68ffed834 100644
--- a/src/battle_anim.c
+++ b/src/battle_anim.c
@@ -1452,14 +1452,14 @@ void ClearBattleAnimationVars(void)
 
     // Clear index array.
     for (i = 0; i < ANIM_SPRITE_INDEX_COUNT; i++)
-        sAnimSpriteIndexArray[i] |= 0xFFFF;
+        sAnimSpriteIndexArray[i] |= INVALID_U16;
 
     // Clear anim args.
     for (i = 0; i < ANIM_ARGS_COUNT; i++)
         gBattleAnimArgs[i] = 0;
 
-    sMonAnimTaskIdArray[0] = 0xFF;
-    sMonAnimTaskIdArray[1] = 0xFF;
+    sMonAnimTaskIdArray[0] = INVALID_U8;
+    sMonAnimTaskIdArray[1] = INVALID_U8;
     gAnimMoveTurn = 0;
     sAnimBackgroundFadeState = 0;
     sAnimMoveIndex = 0;
@@ -1505,19 +1505,19 @@ void LaunchBattleAnimation(const u8 *const animsTable[], u16 tableId, bool8 isMo
     for (i = 0; i < ANIM_ARGS_COUNT; i++)
         gBattleAnimArgs[i] = 0;
 
-    sMonAnimTaskIdArray[0] = 0xFF;
-    sMonAnimTaskIdArray[1] = 0xFF;
+    sMonAnimTaskIdArray[0] = INVALID_U8;
+    sMonAnimTaskIdArray[1] = INVALID_U8;
     sBattleAnimScriptPtr = animsTable[tableId];
     gAnimScriptActive = TRUE;
     gAnimFramesToWait = 0;
     gAnimScriptCallback = RunAnimScriptCommand;
 
     for (i = 0; i < ANIM_SPRITE_INDEX_COUNT; i++)
-        sAnimSpriteIndexArray[i] |= 0xFFFF;
+        sAnimSpriteIndexArray[i] |= INVALID_U16;
 
     if (isMoveAnim)
     {
-        for (i = 0; gMovesWithQuietBGM[i] != 0xFFFF; i++)
+        for (i = 0; gMovesWithQuietBGM[i] != INVALID_U16; i++)
         {
             if (tableId == gMovesWithQuietBGM[i])
             {
@@ -1558,7 +1558,7 @@ static void AddSpriteIndex(u16 index)
 
     for (i = 0; i < ANIM_SPRITE_INDEX_COUNT; i++)
     {
-        if (sAnimSpriteIndexArray[i] == 0xFFFF)
+        if (sAnimSpriteIndexArray[i] == INVALID_U16)
         {
             sAnimSpriteIndexArray[i] = index;
             return;
@@ -1574,7 +1574,7 @@ static void ClearSpriteIndex(u16 index)
     {
         if (sAnimSpriteIndexArray[i] == index)
         {
-            sAnimSpriteIndexArray[i] |= 0xFFFF;
+            sAnimSpriteIndexArray[i] |= INVALID_U16;
             return;
         }
     }
@@ -1712,7 +1712,7 @@ static void ScriptCmd_delay(void)
     sBattleAnimScriptPtr++;
     gAnimFramesToWait = sBattleAnimScriptPtr[0];
     if (gAnimFramesToWait == 0)
-        gAnimFramesToWait = -1;
+        gAnimFramesToWait = INVALID_S8;
     sBattleAnimScriptPtr++;
     gAnimScriptCallback = WaitAnimFrameCount;
 }
@@ -1746,7 +1746,7 @@ static void ScriptCmd_end(void)
 
     // Keep waiting as long as there are animations to be done.
     if (gAnimVisualTaskCount != 0 || gAnimSoundTaskCount != 0
-     || sMonAnimTaskIdArray[0] != 0xFF || sMonAnimTaskIdArray[1] != 0xFF)
+     || sMonAnimTaskIdArray[0] != INVALID_U8 || sMonAnimTaskIdArray[1] != INVALID_U8)
     {
         sSoundAnimFramesToWait = 0;
         gAnimFramesToWait = 1;
@@ -1773,11 +1773,11 @@ static void ScriptCmd_end(void)
 
     for (i = 0; i < ANIM_SPRITE_INDEX_COUNT; i++)
     {
-        if (sAnimSpriteIndexArray[i] != 0xFFFF)
+        if (sAnimSpriteIndexArray[i] != INVALID_U16)
         {
             FreeSpriteTilesByTag(gBattleAnimPicTable[sAnimSpriteIndexArray[i]].tag);
             FreeSpritePaletteByTag(gBattleAnimPicTable[sAnimSpriteIndexArray[i]].tag);
-            sAnimSpriteIndexArray[i] |= 0xFFFF; // set terminator.
+            sAnimSpriteIndexArray[i] |= INVALID_U16; // set terminator.
         }
     }
 
@@ -2122,9 +2122,9 @@ static void ScriptCmd_clearmonbg(void)
     else
         battlerId = gBattleAnimTarget;
 
-    if (sMonAnimTaskIdArray[0] != 0xFF)
+    if (sMonAnimTaskIdArray[0] != INVALID_U8)
         gSprites[gBattlerSpriteIds[battlerId]].invisible = FALSE;
-    if (animBattlerId > 1 && sMonAnimTaskIdArray[1] != 0xFF)
+    if (animBattlerId > 1 && sMonAnimTaskIdArray[1] != INVALID_U8)
         gSprites[gBattlerSpriteIds[battlerId ^ BIT_FLANK]].invisible = FALSE;
     else
         animBattlerId = 0;
@@ -2148,17 +2148,17 @@ static void sub_80A4980(u8 taskId)
         else
             to_BG2 = TRUE;
 
-        if (sMonAnimTaskIdArray[0] != 0xFF)
+        if (sMonAnimTaskIdArray[0] != INVALID_U8)
         {
             sub_80A477C(to_BG2);
             DestroyTask(sMonAnimTaskIdArray[0]);
-            sMonAnimTaskIdArray[0] = 0xFF;
+            sMonAnimTaskIdArray[0] = INVALID_U8;
         }
         if (gTasks[taskId].data[0] > 1)
         {
             sub_80A477C(to_BG2 ^ 1);
             DestroyTask(sMonAnimTaskIdArray[1]);
-            sMonAnimTaskIdArray[1] = 0xFF;
+            sMonAnimTaskIdArray[1] = INVALID_U8;
         }
         DestroyTask(taskId);
     }
@@ -2421,7 +2421,7 @@ static void Task_FadeToBg(u8 taskId)
     {
         s16 bgId = gTasks[taskId].tBackgroundId;
 
-        if (bgId == -1)
+        if (bgId == INVALID_S16)
             LoadDefaultBg();
         else
             LoadMoveBg(bgId);
@@ -2477,7 +2477,7 @@ static void ScriptCmd_restorebg(void)
 
     sBattleAnimScriptPtr++;
     taskId = CreateTask(Task_FadeToBg, 5);
-    gTasks[taskId].tBackgroundId = -1;
+    gTasks[taskId].tBackgroundId = INVALID_S16;
     sAnimBackgroundFadeState = 1;
 }
 
@@ -3001,7 +3001,7 @@ static void ScriptCmd_invisible(void)
     u8 spriteId;
 
     spriteId = GetAnimBattlerSpriteId(sBattleAnimScriptPtr[1]);
-    if (spriteId != 0xFF)
+    if (spriteId != INVALID_U8)
         gSprites[spriteId].invisible = TRUE;
 
     sBattleAnimScriptPtr += 2;
@@ -3012,7 +3012,7 @@ static void ScriptCmd_visible(void)
     u8 spriteId;
 
     spriteId = GetAnimBattlerSpriteId(sBattleAnimScriptPtr[1]);
-    if (spriteId != 0xFF)
+    if (spriteId != INVALID_U8)
         gSprites[spriteId].invisible = FALSE;
 
     sBattleAnimScriptPtr += 2;
@@ -3039,7 +3039,7 @@ static void ScriptCmd_doublebattle_2D(void)
             r4 = sub_80A8364(gBattleAnimTarget);
             spriteId = GetAnimBattlerSpriteId(ANIM_TARGET);
         }
-        if (spriteId != 0xFF)
+        if (spriteId != INVALID_U8)
         {
             gSprites[spriteId].invisible = FALSE;
             if (r4 == 2)
@@ -3075,7 +3075,7 @@ static void ScriptCmd_doublebattle_2E(void)
             spriteId = GetAnimBattlerSpriteId(ANIM_TARGET);
         }
 
-        if (spriteId != 0xFF && r4 == 2)
+        if (spriteId != INVALID_U8 && r4 == 2)
             gSprites[spriteId].oam.priority = 2;
     }
 }
diff --git a/src/battle_anim_80A5C6C.c b/src/battle_anim_80A5C6C.c
index 2ac6cca90..1a2c279ec 100644
--- a/src/battle_anim_80A5C6C.c
+++ b/src/battle_anim_80A5C6C.c
@@ -7,7 +7,7 @@
 #include "decompress.h"
 #include "dma3.h"
 #include "gpu_regs.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "pokemon_icon.h"
 #include "sprite.h"
@@ -1590,7 +1590,7 @@ s16 duplicate_obj_of_side_rel2move_in_transparent_mode(u8 whichBattler)
             }
         }
     }
-    return -1;
+    return INVALID_S16;
 }
 
 void obj_delete_but_dont_free_vram(struct Sprite *sprite)
diff --git a/src/battle_anim_80A9C70.c b/src/battle_anim_80A9C70.c
index f1245a032..c329a134d 100644
--- a/src/battle_anim_80A9C70.c
+++ b/src/battle_anim_80A9C70.c
@@ -183,7 +183,7 @@ void sub_80A9EF4(u8 taskId)
     SetGpuReg(REG_OFFSET_BLDCNT, BLDCNT_EFFECT_BLEND | BLDCNT_TGT2_ALL);
     SetGpuReg(REG_OFFSET_BLDALPHA, BLDALPHA_BLEND(0, 16));
     spriteId = CreateSprite(&gUnknown_0853EF48, x, y, 4);
-    if (GetSpriteTileStartByTag(ANIM_TAG_ICE_CUBE) == 0xFFFF)
+    if (GetSpriteTileStartByTag(ANIM_TAG_ICE_CUBE) == INVALID_U16)
         gSprites[spriteId].invisible = TRUE;
     SetSubspriteTables(&gSprites[spriteId], gUnknown_0853EF40);
     gTasks[taskId].data[15] = spriteId;
@@ -315,10 +315,10 @@ void AnimTask_StatsChange(u8 taskId)
     CASE(MINUS2, STAT_ACC):     goesDown = TRUE;   animStatId = 2;     sharply = TRUE;   break;
     CASE(MINUS2, STAT_EVASION): goesDown = TRUE;   animStatId = 4;     sharply = TRUE;   break;
 
-    case STAT_ANIM_MULTIPLE_PLUS1:  goesDown = FALSE;  animStatId = 0xFF;  sharply = FALSE;  break;
-    case STAT_ANIM_MULTIPLE_PLUS2:  goesDown = FALSE;  animStatId = 0xFF;  sharply = TRUE;   break;
-    case STAT_ANIM_MULTIPLE_MINUS1: goesDown = TRUE;   animStatId = 0xFF;  sharply = FALSE;  break;
-    case STAT_ANIM_MULTIPLE_MINUS2: goesDown = TRUE;   animStatId = 0xFF;  sharply = TRUE;   break;
+    case STAT_ANIM_MULTIPLE_PLUS1:  goesDown = FALSE;  animStatId = INVALID_U8;  sharply = FALSE;  break;
+    case STAT_ANIM_MULTIPLE_PLUS2:  goesDown = FALSE;  animStatId = INVALID_U8;  sharply = TRUE;   break;
+    case STAT_ANIM_MULTIPLE_MINUS1: goesDown = TRUE;   animStatId = INVALID_U8;  sharply = FALSE;  break;
+    case STAT_ANIM_MULTIPLE_MINUS2: goesDown = TRUE;   animStatId = INVALID_U8;  sharply = TRUE;   break;
 
     default:
         DestroyAnimVisualTask(taskId);
diff --git a/src/battle_anim_sound_tasks.c b/src/battle_anim_sound_tasks.c
index 07fb604b8..36738d36e 100644
--- a/src/battle_anim_sound_tasks.c
+++ b/src/battle_anim_sound_tasks.c
@@ -214,7 +214,7 @@ void sub_8158E9C(u8 taskId)
 
     if (species != SPECIES_NONE)
     {
-        if (gBattleAnimArgs[1] == 0xFF)
+        if (gBattleAnimArgs[1] == INVALID_U8)
             PlayCry3(species, pan, 9);
         else
             PlayCry3(species, pan, 7);
@@ -238,7 +238,7 @@ static void sub_8158FF4(u8 taskId)
     }
     else
     {
-        if (gTasks[taskId].data[0] == 0xFF)
+        if (gTasks[taskId].data[0] == INVALID_U8)
         {
             if (!IsCryPlaying())
             {
diff --git a/src/battle_anim_utility_funcs.c b/src/battle_anim_utility_funcs.c
index 6dfebe77f..5ed30ddc0 100644
--- a/src/battle_anim_utility_funcs.c
+++ b/src/battle_anim_utility_funcs.c
@@ -3,7 +3,7 @@
 #include "contest.h"
 #include "gpu_regs.h"
 #include "graphics.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "sound.h"
 #include "sprite.h"
@@ -82,7 +82,7 @@ void sub_8116664(u8 taskId)
         animBattlers[1] = gBattleAnimTarget;
         break;
     case 5:
-        animBattlers[0] = 0xFF;
+        animBattlers[0] = INVALID_U8;
         break;
     case 6:
         selectedPalettes = 0;
diff --git a/src/battle_arena.c b/src/battle_arena.c
index cd2c976da..591fc82b9 100644
--- a/src/battle_arena.c
+++ b/src/battle_arena.c
@@ -449,7 +449,7 @@ static const union AnimCmd *const sSpriteAnimTable_8611F4C[] =
 static const struct SpriteTemplate sSpriteTemplate_JudgmentIcon =
 {
     .tileTag = 0x3E8,
-    .paletteTag = 0xFFFF,
+    .paletteTag = INVALID_U16,
     .oam = &sOamData_8611F24,
     .anims = sSpriteAnimTable_8611F4C,
     .images = NULL,
diff --git a/src/battle_controller_link_opponent.c b/src/battle_controller_link_opponent.c
index 8cbc62aab..d65c61884 100644
--- a/src/battle_controller_link_opponent.c
+++ b/src/battle_controller_link_opponent.c
@@ -212,7 +212,7 @@ static void sub_8064470(void)
 
 static void sub_80644D8(void)
 {
-    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == 0xFF)
+    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == INVALID_U8)
     {
         gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 = 0;
         LinkOpponentBufferExecCompleted();
@@ -395,7 +395,7 @@ static void CompleteOnHealthbarDone(void)
 
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
 
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
diff --git a/src/battle_controller_link_partner.c b/src/battle_controller_link_partner.c
index 0cd15f39e..8bbbcbfd1 100644
--- a/src/battle_controller_link_partner.c
+++ b/src/battle_controller_link_partner.c
@@ -203,7 +203,7 @@ static void sub_814AF54(void)
 
 static void sub_814AFBC(void)
 {
-    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == 0xFF)
+    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == INVALID_U8)
     {
         gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 = 0;
         LinkPartnerBufferExecCompleted();
@@ -279,7 +279,7 @@ static void CompleteOnHealthbarDone(void)
 
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
 
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
diff --git a/src/battle_controller_opponent.c b/src/battle_controller_opponent.c
index c057e8575..0aeb24c32 100644
--- a/src/battle_controller_opponent.c
+++ b/src/battle_controller_opponent.c
@@ -220,7 +220,7 @@ static void sub_805F240(void)
 
 static void sub_805F2A8(void)
 {
-    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == 0xFF)
+    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == INVALID_U8)
     {
         gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 = 0;
         OpponentBufferExecCompleted();
@@ -389,7 +389,7 @@ static void CompleteOnHealthbarDone(void)
 {
     s16 hpValue = MoveBattleBar(gActiveBattler, gHealthboxSpriteIds[gActiveBattler], HEALTH_BAR, 0);
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
diff --git a/src/battle_controller_player.c b/src/battle_controller_player.c
index 2bd5ef365..3053e6c37 100644
--- a/src/battle_controller_player.c
+++ b/src/battle_controller_player.c
@@ -635,7 +635,7 @@ u32 sub_8057FBC(void) // unused
         PlaySE(SE_SELECT);
         gBattle_BG0_X = 0;
         gBattle_BG0_Y = 0x140;
-        var = 0xFF;
+        var = INVALID_U8;
     }
     if (gMain.newKeys & DPAD_LEFT && gMoveSelectionCursor[gActiveBattler] & 1)
     {
@@ -936,7 +936,7 @@ static void sub_80588B4(void)
 
 static void sub_8058924(void)
 {
-    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == 0xFF)
+    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == INVALID_U8)
     {
         gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 = 0;
         PlayerBufferExecCompleted();
@@ -1119,7 +1119,7 @@ static void CompleteOnHealthbarDone(void)
 
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
 
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
@@ -1221,7 +1221,7 @@ static void sub_8059400(u8 taskId)
 
         newExpPoints = MoveBattleBar(battlerId, gHealthboxSpriteIds[battlerId], EXP_BAR, 0);
         SetHealthboxSpriteVisible(gHealthboxSpriteIds[battlerId]);
-        if (newExpPoints == -1) // The bar has been filled with given exp points.
+        if (newExpPoints == INVALID_S16) // The bar has been filled with given exp points.
         {
             u8 level;
             s32 currExp;
diff --git a/src/battle_controller_player_partner.c b/src/battle_controller_player_partner.c
index 02dd1383b..775b7676f 100644
--- a/src/battle_controller_player_partner.c
+++ b/src/battle_controller_player_partner.c
@@ -218,7 +218,7 @@ static void sub_81BAE98(void)
 
 static void sub_81BAF00(void)
 {
-    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == 0xFF)
+    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == INVALID_U8)
     {
         gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 = 0;
         PlayerPartnerBufferExecCompleted();
@@ -294,7 +294,7 @@ static void CompleteOnHealthbarDone(void)
 
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
 
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
@@ -397,7 +397,7 @@ static void sub_81BB4E4(u8 taskId)
 
         r4 = MoveBattleBar(battlerId, gHealthboxSpriteIds[battlerId], EXP_BAR, 0);
         SetHealthboxSpriteVisible(gHealthboxSpriteIds[battlerId]);
-        if (r4 == -1)
+        if (r4 == INVALID_S16)
         {
             u8 level;
             s32 currExp;
diff --git a/src/battle_controller_recorded_opponent.c b/src/battle_controller_recorded_opponent.c
index 0cf3634dc..842facd44 100644
--- a/src/battle_controller_recorded_opponent.c
+++ b/src/battle_controller_recorded_opponent.c
@@ -213,7 +213,7 @@ static void sub_81865C8(void)
 
 static void sub_8186630(void)
 {
-    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == 0xFF)
+    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == INVALID_U8)
     {
         gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 = 0;
         RecordedOpponentBufferExecCompleted();
@@ -377,7 +377,7 @@ static void CompleteOnHealthbarDone(void)
 
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
 
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
diff --git a/src/battle_controller_recorded_player.c b/src/battle_controller_recorded_player.c
index 4d7fdc01e..60bec78b1 100644
--- a/src/battle_controller_recorded_player.c
+++ b/src/battle_controller_recorded_player.c
@@ -202,7 +202,7 @@ static void sub_81899F0(void)
 
 static void sub_8189A58(void)
 {
-    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == 0xFF)
+    if (--gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 == INVALID_U8)
     {
         gBattleSpritesDataPtr->healthBoxesData[gActiveBattler].field_9 = 0;
         RecordedPlayerBufferExecCompleted();
@@ -360,7 +360,7 @@ static void CompleteOnHealthbarDone(void)
 
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
 
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
diff --git a/src/battle_controller_wally.c b/src/battle_controller_wally.c
index 5d87c4f90..9078ef577 100644
--- a/src/battle_controller_wally.c
+++ b/src/battle_controller_wally.c
@@ -348,7 +348,7 @@ static void CompleteOnHealthbarDone(void)
 
     SetHealthboxSpriteVisible(gHealthboxSpriteIds[gActiveBattler]);
 
-    if (hpValue != -1)
+    if (hpValue != INVALID_S16)
     {
         UpdateHpTextInHealthbox(gHealthboxSpriteIds[gActiveBattler], hpValue, HP_CURRENT);
     }
diff --git a/src/battle_controllers.c b/src/battle_controllers.c
index a6d6e9294..e24549d82 100644
--- a/src/battle_controllers.c
+++ b/src/battle_controllers.c
@@ -51,7 +51,7 @@ void SetUpBattleVarsAndBirchZigzagoon(void)
     for (i = 0; i < MAX_BATTLERS_COUNT; i++)
     {
         gBattlerControllerFuncs[i] = nullsub_21;
-        gBattlerPositions[i] = 0xFF;
+        gBattlerPositions[i] = INVALID_U8;
         gActionSelectionCursor[i] = 0;
         gMoveSelectionCursor[i] = 0;
     }
diff --git a/src/battle_dome.c b/src/battle_dome.c
index 0f5721fb9..f03de7505 100644
--- a/src/battle_dome.c
+++ b/src/battle_dome.c
@@ -8,7 +8,7 @@
 #include "event_data.h"
 #include "overworld.h"
 #include "util.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "string_util.h"
 #include "random.h"
 #include "task.h"
@@ -3032,7 +3032,7 @@ static s32 GetTypeEffectivenessPoints(s32 move, s32 targetSpecies, s32 arg2)
     s32 i = 0;
     s32 typePower = TYPE_x1;
 
-    if (move == MOVE_NONE || move == 0xFFFF || gBattleMoves[move].power == 0)
+    if (move == MOVE_NONE || move == INVALID_U16 || gBattleMoves[move].power == 0)
         return 0;
 
     defType1 = gBaseStats[targetSpecies].type1;
@@ -3434,14 +3434,14 @@ static s32 TournamentIdOfOpponent(s32 roundId, s32 trainerId)
         if (j != val)
             return gUnknown_0860D14C[j];
         else
-            return 0xFF;
+            return INVALID_U8;
     }
     else
     {
         if (!gSaveBlock2Ptr->frontier.domeTrainers[sIdToOpponentId[i][roundId]].isEliminated)
             return sIdToOpponentId[i][roundId];
         else
-            return 0xFF;
+            return INVALID_U8;
     }
 }
 
@@ -3562,7 +3562,7 @@ static void sub_8190400(u8 taskId)
         SetVBlankCallback(VblankCb0_BattleDome);
         sBattleDomeStruct = AllocZeroed(sizeof(*sBattleDomeStruct));
         for (i = 0; i < DOME_TOURNAMENT_TRAINERS_COUNT; i++)
-            sBattleDomeStruct->arr[i] |= 0xFF;
+            sBattleDomeStruct->arr[i] |= INVALID_U8;
         LoadMonIconPalettes();
         i = CreateTask(sub_8190CD4, 0);
         gTasks[i].data[0] = 0;
@@ -3624,7 +3624,7 @@ static void SpriteCb_TrainerIconCardScrollUp(struct Sprite *sprite)
     {
         if (sprite->pos1.y >= 192)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             FreeAndDestroyTrainerPicSprite(sprite->data[3]);
         }
     }
@@ -3644,7 +3644,7 @@ static void SpriteCb_TrainerIconCardScrollDown(struct Sprite *sprite)
     {
         if (sprite->pos1.y <= -32)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             FreeAndDestroyTrainerPicSprite(sprite->data[3]);
         }
     }
@@ -3664,7 +3664,7 @@ static void SpriteCb_TrainerIconCardScrollLeft(struct Sprite *sprite)
     {
         if (sprite->pos1.x >= 272)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             FreeAndDestroyTrainerPicSprite(sprite->data[3]);
         }
     }
@@ -3684,7 +3684,7 @@ static void SpriteCb_TrainerIconCardScrollRight(struct Sprite *sprite)
     {
         if (sprite->pos1.x <= -32)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             FreeAndDestroyTrainerPicSprite(sprite->data[3]);
         }
     }
@@ -3714,7 +3714,7 @@ static void SpriteCb_MonIconCardScrollUp(struct Sprite *sprite)
     {
         if (sprite->pos1.y >= 176)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             sub_80D2EF8(sprite);
         }
     }
@@ -3736,7 +3736,7 @@ static void SpriteCb_MonIconCardScrollDown(struct Sprite *sprite)
     {
         if (sprite->pos1.y <= -16)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             sub_80D2EF8(sprite);
         }
     }
@@ -3758,7 +3758,7 @@ static void SpriteCb_MonIconCardScrollLeft(struct Sprite *sprite)
     {
         if (sprite->pos1.x >= 256)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             sub_80D2EF8(sprite);
         }
     }
@@ -3780,7 +3780,7 @@ static void SpriteCb_MonIconCardScrollRight(struct Sprite *sprite)
     {
         if (sprite->pos1.x <= -16)
         {
-            sBattleDomeStruct->arr[sprite->data[2]] = 0xFF;
+            sBattleDomeStruct->arr[sprite->data[2]] = INVALID_U8;
             sub_80D2EF8(sprite);
         }
     }
@@ -4005,7 +4005,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 2)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollUp;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4016,7 +4016,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollUp;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4029,7 +4029,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 10)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollUp;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4040,7 +4040,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollUp;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4121,7 +4121,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 2)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollDown;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4132,7 +4132,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollDown;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4145,7 +4145,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 10)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollDown;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4156,7 +4156,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollDown;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4204,7 +4204,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 2)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4215,7 +4215,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4228,7 +4228,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 10)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4239,7 +4239,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4287,7 +4287,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 2)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4298,7 +4298,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4311,7 +4311,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 10)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4322,7 +4322,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollLeft;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4368,7 +4368,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 2)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4379,7 +4379,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4392,7 +4392,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 10)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4403,7 +4403,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4451,7 +4451,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 2)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4462,7 +4462,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2] ^ 1;
@@ -4475,7 +4475,7 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 10)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_TrainerIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4486,7 +4486,7 @@ static void sub_8190CD4(u8 taskId)
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                     {
                         gSprites[sBattleDomeStruct->arr[i]].callback = SpriteCb_MonIconCardScrollRight;
                         gSprites[sBattleDomeStruct->arr[i]].data[0] = gTasks[taskId].data[2];
@@ -4556,12 +4556,12 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 2)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                         FreeAndDestroyTrainerPicSprite(sBattleDomeStruct->arr[i]);
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                         sub_80D2EF8(&gSprites[sBattleDomeStruct->arr[i]]);
                 }
             }
@@ -4569,12 +4569,12 @@ static void sub_8190CD4(u8 taskId)
             {
                 if (i < 10)
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                         FreeAndDestroyTrainerPicSprite(sBattleDomeStruct->arr[i]);
                 }
                 else
                 {
-                    if (sBattleDomeStruct->arr[i] != 0xFF)
+                    if (sBattleDomeStruct->arr[i] != INVALID_U8)
                         sub_80D2EF8(&gSprites[sBattleDomeStruct->arr[i]]);
                 }
             }
@@ -5483,13 +5483,13 @@ static u8 sub_8193BDC(u8 taskId)
     }
     else
     {
-        if (gMain.newKeys == DPAD_UP && gUnknown_0860CBF1[spriteId][roundId][0] != 0xFF)
+        if (gMain.newKeys == DPAD_UP && gUnknown_0860CBF1[spriteId][roundId][0] != INVALID_U8)
             arrId = 0;
-        else if (gMain.newKeys == DPAD_DOWN && gUnknown_0860CBF1[spriteId][roundId][1] != 0xFF)
+        else if (gMain.newKeys == DPAD_DOWN && gUnknown_0860CBF1[spriteId][roundId][1] != INVALID_U8)
             arrId = 1;
-        else if (gMain.newKeys == DPAD_LEFT && gUnknown_0860CBF1[spriteId][roundId][2] != 0xFF)
+        else if (gMain.newKeys == DPAD_LEFT && gUnknown_0860CBF1[spriteId][roundId][2] != INVALID_U8)
             arrId = 2;
-        else if (gMain.newKeys == DPAD_RIGHT && gUnknown_0860CBF1[spriteId][roundId][3] != 0xFF)
+        else if (gMain.newKeys == DPAD_RIGHT && gUnknown_0860CBF1[spriteId][roundId][3] != INVALID_U8)
             arrId = 3;
     }
 
@@ -6314,21 +6314,21 @@ static void DecideRoundWinners(u8 roundId)
         tournamentId1 = i;
         tournamentId2 = TournamentIdOfOpponent(roundId, gSaveBlock2Ptr->frontier.domeTrainers[tournamentId1].trainerId);
         // Frontier Brain always wins, check tournamentId1.
-        if (gSaveBlock2Ptr->frontier.domeTrainers[tournamentId1].trainerId == TRAINER_FRONTIER_BRAIN && tournamentId2 != 0xFF)
+        if (gSaveBlock2Ptr->frontier.domeTrainers[tournamentId1].trainerId == TRAINER_FRONTIER_BRAIN && tournamentId2 != INVALID_U8)
         {
             gSaveBlock2Ptr->frontier.domeTrainers[tournamentId2].isEliminated = 1;
             gSaveBlock2Ptr->frontier.domeTrainers[tournamentId2].eliminatedAt = roundId;
             gSaveBlock2Ptr->frontier.field_EC0[tournamentId2] = GetWinningMove(tournamentId1, tournamentId2, roundId);
         }
         // Frontier Brain always wins, check tournamentId2.
-        else if (gSaveBlock2Ptr->frontier.domeTrainers[tournamentId2].trainerId == TRAINER_FRONTIER_BRAIN && tournamentId1 != 0xFF)
+        else if (gSaveBlock2Ptr->frontier.domeTrainers[tournamentId2].trainerId == TRAINER_FRONTIER_BRAIN && tournamentId1 != INVALID_U8)
         {
             gSaveBlock2Ptr->frontier.domeTrainers[tournamentId1].isEliminated = 1;
             gSaveBlock2Ptr->frontier.domeTrainers[tournamentId1].eliminatedAt = roundId;
             gSaveBlock2Ptr->frontier.field_EC0[tournamentId1] = GetWinningMove(tournamentId2, tournamentId1, roundId);
         }
         // Decide which one of two trainers wins!
-        else if (tournamentId2 != 0xFF)
+        else if (tournamentId2 != INVALID_U8)
         {
             // BUG: points1 and points2 are not cleared at the beginning of the loop resulting in not fair results.
 
diff --git a/src/battle_factory.c b/src/battle_factory.c
index 1d7fbafc9..dd82da746 100644
--- a/src/battle_factory.c
+++ b/src/battle_factory.c
@@ -202,9 +202,9 @@ static void sub_81A5E94(void)
 
     gUnknown_03001288 = FALSE;
     for (i = 0; i < 6; i++)
-        gSaveBlock2Ptr->frontier.field_E70[i].monId |= 0xFFFF;
+        gSaveBlock2Ptr->frontier.field_E70[i].monId |= INVALID_U16;
     for (i = 0; i < 3; i++)
-        gUnknown_03006298[i] |= 0xFFFF;
+        gUnknown_03006298[i] |= INVALID_U16;
 
     saved_warp2_set(0, gSaveBlock1Ptr->location.mapGroup, gSaveBlock1Ptr->location.mapNum, -1);
     gTrainerBattleOpponent_A = 0;
diff --git a/src/battle_factory_screen.c b/src/battle_factory_screen.c
index 42a9b579c..60b233daf 100644
--- a/src/battle_factory_screen.c
+++ b/src/battle_factory_screen.c
@@ -10,7 +10,7 @@
 #include "palette.h"
 #include "task.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "bg.h"
 #include "gpu_regs.h"
 #include "string_util.h"
diff --git a/src/battle_gfx_sfx_util.c b/src/battle_gfx_sfx_util.c
index 6f9d2db80..88dbb5360 100644
--- a/src/battle_gfx_sfx_util.c
+++ b/src/battle_gfx_sfx_util.c
@@ -6,7 +6,7 @@
 #include "constants/battle_anim.h"
 #include "battle_interface.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "graphics.h"
 #include "random.h"
 #include "util.h"
@@ -122,7 +122,7 @@ void FreeBattleSpritesData(void)
 u16 ChooseMoveAndTargetInBattlePalace(void)
 {
     s32 i, var1, var2;
-    s32 chosenMoveId = -1;
+    s32 chosenMoveId = INVALID_S32;
     struct ChooseMoveStruct *moveInfo = (struct ChooseMoveStruct*)(&gBattleBufferA[gActiveBattler][4]);
     u8 unusableMovesBits = CheckMoveLimitations(gActiveBattler, 0, 0xFF);
     s32 percent = Random() % 100;
diff --git a/src/battle_interface.c b/src/battle_interface.c
index c7eb11293..fd6d2a0ab 100644
--- a/src/battle_interface.c
+++ b/src/battle_interface.c
@@ -589,17 +589,17 @@ static void sub_8072308(s16 arg0, u16 *arg1, u8 arg2)
 
     for (; i > -1; i--)
     {
-        array[i] = 0xFF;
+        array[i] = INVALID_U8;
     }
 
-    if (arrayPtr[3] == 0xFF)
+    if (arrayPtr[3] == INVALID_U8)
         arrayPtr[3] = 0;
 
     if (arg2 == 0)
     {
         for (i = 0, j = 0; i < 4; i++)
         {
-            if (array[j] == 0xFF)
+            if (array[j] == INVALID_U8)
             {
                 arg1[j] &= 0xFC00;
                 arg1[j] |= 0x1E;
@@ -622,7 +622,7 @@ static void sub_8072308(s16 arg0, u16 *arg1, u8 arg2)
     {
         for (i = 0; i < 4; i++)
         {
-            if (array[i] == 0xFF)
+            if (array[i] == INVALID_U8)
             {
                 arg1[i] &= 0xFC00;
                 arg1[i] |= 0x1E;
@@ -1580,7 +1580,7 @@ u8 CreatePartyStatusSummarySprites(u8 battlerId, struct HpAndStatus *partyInfo,
         {
             for (i = 0; i < PARTY_SIZE; i++)
             {
-                if (partyInfo[i].hp == 0xFFFF) // empty slot or an egg
+                if (partyInfo[i].hp == INVALID_U16) // empty slot or an egg
                 {
                     gSprites[ballIconSpritesIds[i]].oam.tileNum += 1;
                     gSprites[ballIconSpritesIds[i]].data[7] = 1;
@@ -1599,7 +1599,7 @@ u8 CreatePartyStatusSummarySprites(u8 battlerId, struct HpAndStatus *partyInfo,
         {
             for (i = 0, var = 5, j = 0; j < PARTY_SIZE; j++)
             {
-                if (partyInfo[j].hp == 0xFFFF) // empty slot or an egg
+                if (partyInfo[j].hp == INVALID_U16) // empty slot or an egg
                 {
                     gSprites[ballIconSpritesIds[var]].oam.tileNum += 1;
                     gSprites[ballIconSpritesIds[var]].data[7] = 1;
@@ -1628,7 +1628,7 @@ u8 CreatePartyStatusSummarySprites(u8 battlerId, struct HpAndStatus *partyInfo,
         {
             for (var = 5, i = 0; i < PARTY_SIZE; i++)
             {
-                if (partyInfo[i].hp == 0xFFFF) // empty slot or an egg
+                if (partyInfo[i].hp == INVALID_U16) // empty slot or an egg
                 {
                     gSprites[ballIconSpritesIds[var]].oam.tileNum += 1;
                     gSprites[ballIconSpritesIds[var]].data[7] = 1;
@@ -1648,7 +1648,7 @@ u8 CreatePartyStatusSummarySprites(u8 battlerId, struct HpAndStatus *partyInfo,
         {
             for (var = 0, i = 0, j = 0; j < PARTY_SIZE; j++)
             {
-                if (partyInfo[j].hp == 0xFFFF) // empty slot or an egg
+                if (partyInfo[j].hp == INVALID_U16) // empty slot or an egg
                 {
                     gSprites[ballIconSpritesIds[i]].oam.tileNum += 1;
                     gSprites[ballIconSpritesIds[i]].data[7] = 1;
@@ -1765,7 +1765,7 @@ static void sub_8073E64(u8 taskId)
     s32 i;
 
     u8 battlerId = gTasks[taskId].tBattler;
-    if (--gTasks[taskId].tData15 == -1)
+    if (--gTasks[taskId].tData15 == INVALID_S16)
     {
         u8 summaryBarSpriteId = gTasks[taskId].tSummaryBarSpriteId;
 
@@ -1808,7 +1808,7 @@ static void sub_8073F98(u8 taskId)
     {
         SetGpuReg(REG_OFFSET_BLDALPHA, (gTasks[taskId].tData15) | ((16 - gTasks[taskId].tData15) << 8));
     }
-    else if (gTasks[taskId].tData15 == -1)
+    else if (gTasks[taskId].tData15 == INVALID_S16)
     {
         u8 summaryBarSpriteId = gTasks[taskId].tSummaryBarSpriteId;
 
@@ -2289,7 +2289,7 @@ s32 MoveBattleBar(u8 battlerId, u8 healthboxSpriteId, u8 whichBar, u8 unused)
     if (whichBar == EXP_BAR || (whichBar == HEALTH_BAR && !gBattleSpritesDataPtr->battlerData[battlerId].hpNumbersNoBars))
         MoveBattleBarGraphically(battlerId, whichBar);
 
-    if (currentBarValue == -1)
+    if (currentBarValue == INVALID_S32)
         gBattleSpritesDataPtr->battleBars[battlerId].currValue = 0;
 
     return currentBarValue;
@@ -2376,12 +2376,12 @@ static s32 CalcNewBarValue(s32 maxValue, s32 oldValue, s32 receivedValue, s32 *c
     if (maxValue < scale)
     {
         if (newValue == Q_24_8_TO_INT(*currValue) && (*currValue & 0xFF) == 0)
-            return -1;
+            return INVALID_S32;
     }
     else
     {
         if (newValue == *currValue) // we're done, the bar's value has been updated
-            return -1;
+            return INVALID_S32;
     }
 
     if (maxValue < scale) // handle cases of max var having less pixels than the whole bar
@@ -2403,7 +2403,7 @@ static s32 CalcNewBarValue(s32 maxValue, s32 oldValue, s32 receivedValue, s32 *c
             *currValue -= toAdd;
             ret = Q_24_8_TO_INT(*currValue);
             // try round up
-            if ((*currValue & 0xFF) > 0)
+            if ((*currValue & INVALID_U8) > 0)
                 ret++;
             if (ret <= newValue)
             {
diff --git a/src/battle_main.c b/src/battle_main.c
index de0becd2a..19e85f1cf 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -23,7 +23,7 @@
 #include "link_rfu.h"
 #include "load_save.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "m4a.h"
 #include "palette.h"
 #include "party_menu.h"
@@ -500,7 +500,7 @@ const struct TrainerMoney gTrainerMoneyTable[] =
     {TRAINER_CLASS_HIKER, 10},
     {TRAINER_CLASS_YOUNG_COUPLE, 8},
     {TRAINER_CLASS_WINSTRATE, 10},
-    {0xFF, 5},
+    {INVALID_U8, 5},
 };
 
 #include "data/text/abilities.h"
@@ -2251,7 +2251,7 @@ static void sub_8038F34(void)
         ShowBg(0);
         ShowBg(1);
         ShowBg(2);
-        gBattleCommunication[1] = 0xFF;
+        gBattleCommunication[1] = INVALID_U8;
         gBattleCommunication[MULTIUSE_STATE]++;
         break;
     case 1:
@@ -2993,7 +2993,7 @@ static void BattleStartClearSetData(void)
         gLastLandedMoves[i] = 0;
         gLastHitByType[i] = 0;
         gLastResultingMoves[i] = 0;
-        gLastHitBy[i] = 0xFF;
+        gLastHitBy[i] = INVALID_U8;
         gLockedMoves[i] = 0;
         gLastPrintedMoves[i] = 0;
         gBattleResources->flags->flags[i] = 0;
@@ -3161,7 +3161,7 @@ void SwitchInClearSetData(void)
     gLastHitByType[gActiveBattler] = 0;
     gLastResultingMoves[gActiveBattler] = 0;
     gLastPrintedMoves[gActiveBattler] = 0;
-    gLastHitBy[gActiveBattler] = 0xFF;
+    gLastHitBy[gActiveBattler] = INVALID_U8;
 
     *(gBattleStruct->lastTakenMove + gActiveBattler * 2 + 0) = 0;
     *(gBattleStruct->lastTakenMove + gActiveBattler * 2 + 1) = 0;
@@ -3192,7 +3192,7 @@ void SwitchInClearSetData(void)
 
     gBattleResources->flags->flags[gActiveBattler] = 0;
     gCurrentMove = 0;
-    gBattleStruct->field_DA = 0xFF;
+    gBattleStruct->field_DA = INVALID_U8;
 
     ClearBattlerMoveHistory(gActiveBattler);
     ClearBattlerAbilityHistory(gActiveBattler);
@@ -3253,7 +3253,7 @@ void FaintClearSetData(void)
     gLastHitByType[gActiveBattler] = 0;
     gLastResultingMoves[gActiveBattler] = 0;
     gLastPrintedMoves[gActiveBattler] = 0;
-    gLastHitBy[gActiveBattler] = 0xFF;
+    gLastHitBy[gActiveBattler] = INVALID_U8;
 
     *(u8*)((u8*)(&gBattleStruct->choicedMove[gActiveBattler]) + 0) = 0;
     *(u8*)((u8*)(&gBattleStruct->choicedMove[gActiveBattler]) + 1) = 0;
@@ -3440,7 +3440,7 @@ static void BattleIntroDrawPartySummaryScreens(void)
             if (GetMonData(&gEnemyParty[i], MON_DATA_SPECIES2) == SPECIES_NONE
              || GetMonData(&gEnemyParty[i], MON_DATA_SPECIES2) == SPECIES_EGG)
             {
-                hpStatus[i].hp = 0xFFFF;
+                hpStatus[i].hp = INVALID_U16;
                 hpStatus[i].status = 0;
             }
             else
@@ -3458,7 +3458,7 @@ static void BattleIntroDrawPartySummaryScreens(void)
             if (GetMonData(&gPlayerParty[i], MON_DATA_SPECIES2) == SPECIES_NONE
              || GetMonData(&gPlayerParty[i], MON_DATA_SPECIES2) == SPECIES_EGG)
             {
-                hpStatus[i].hp = 0xFFFF;
+                hpStatus[i].hp = INVALID_U16;
                 hpStatus[i].status = 0;
             }
             else
@@ -3484,7 +3484,7 @@ static void BattleIntroDrawPartySummaryScreens(void)
             if (GetMonData(&gPlayerParty[i], MON_DATA_SPECIES2) == SPECIES_NONE
              || GetMonData(&gPlayerParty[i], MON_DATA_SPECIES2) == SPECIES_EGG)
             {
-                hpStatus[i].hp = 0xFFFF;
+                hpStatus[i].hp = INVALID_U16;
                 hpStatus[i].status = 0;
             }
             else
@@ -3991,7 +3991,7 @@ void BattleTurnPassed(void)
         return;
     }
 
-    if (gBattleResults.battleTurnCounter < 0xFF)
+    if (gBattleResults.battleTurnCounter < INVALID_U8)
     {
         gBattleResults.battleTurnCounter++;
         gBattleStruct->field_DA++;
@@ -4375,7 +4375,7 @@ static void HandleTurnActionSelectionState(void)
                         return;
                     default:
                         sub_818603C(2);
-                        if ((gBattleBufferB[gActiveBattler][2] | (gBattleBufferB[gActiveBattler][3] << 8)) == 0xFFFF)
+                        if ((gBattleBufferB[gActiveBattler][2] | (gBattleBufferB[gActiveBattler][3] << 8)) == INVALID_U16)
                         {
                             gBattleCommunication[gActiveBattler] = STATE_BEFORE_ACTION_CHOSEN;
                             RecordedBattle_ClearBattlerAction(gActiveBattler, 1);
@@ -5740,7 +5740,7 @@ static void HandleAction_ThrowPokeblock(void)
     gBattleCommunication[MULTISTRING_CHOOSER] = gBattleBufferB[gBattlerAttacker][1] - 1;
     gLastUsedItem = gBattleBufferB[gBattlerAttacker][2];
 
-    if (gBattleResults.pokeblockThrows < 0xFF)
+    if (gBattleResults.pokeblockThrows < INVALID_U8)
         gBattleResults.pokeblockThrows++;
     if (gBattleStruct->safariPkblThrowCounter < 3)
         gBattleStruct->safariPkblThrowCounter++;
diff --git a/src/battle_message.c b/src/battle_message.c
index 47c4cbe1d..c483740f6 100644
--- a/src/battle_message.c
+++ b/src/battle_message.c
@@ -1156,7 +1156,7 @@ const u16 gCaughtMonStringIds[] =
 
 const u16 gTrappingMoves[] =
 {
-    MOVE_BIND, MOVE_WRAP, MOVE_FIRE_SPIN, MOVE_CLAMP, MOVE_WHIRLPOOL, MOVE_SAND_TOMB, 0xFFFF
+    MOVE_BIND, MOVE_WRAP, MOVE_FIRE_SPIN, MOVE_CLAMP, MOVE_WHIRLPOOL, MOVE_SAND_TOMB, INVALID_U16
 };
 
 const u8 gText_PkmnIsEvolving[] = _("What?\n{STR_VAR_1} is evolving!");
@@ -2967,7 +2967,7 @@ void BattlePutTextOnWindow(const u8 *text, u8 windowId)
     printerTemplate.bgColor = textInfo[windowId].bgColor;
     printerTemplate.shadowColor = textInfo[windowId].shadowColor;
 
-    if (printerTemplate.x == 0xFF)
+    if (printerTemplate.x == INVALID_U8)
     {
         u32 width = sub_80397C4(gBattleScripting.windowsType, windowId);
         s32 alignX = GetStringCenterAlignXOffsetWithLetterSpacing(printerTemplate.fontId, printerTemplate.currentChar, width, printerTemplate.letterSpacing);
diff --git a/src/battle_pike.c b/src/battle_pike.c
index 38d3e7d4a..590fd3d74 100644
--- a/src/battle_pike.c
+++ b/src/battle_pike.c
@@ -9,7 +9,7 @@
 #include "task.h"
 #include "battle_tower.h"
 #include "party_menu.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "script.h"
 #include "battle_setup.h"
@@ -1228,7 +1228,7 @@ static void sub_81A7E60(s16 a0, s16 a1, s16 a2, s16 a3, s16 a4)
 
 static bool8 sub_81A7EC4(void)
 {
-    if (FindTaskIdByFunc(sub_81A7D54) == 0xFF)
+    if (FindTaskIdByFunc(sub_81A7D54) == INVALID_U8)
         return TRUE;
     else
         return FALSE;
@@ -1448,7 +1448,7 @@ static void sub_81A84B4(void)
     u8 i;
 
     for (i = 0; i < 14; i++)
-        gSaveBlock2Ptr->frontier.field_CB4[i] |= 0xFFFF;
+        gSaveBlock2Ptr->frontier.field_CB4[i] |= INVALID_U16;
 }
 
 static void sub_81A84EC(void)
diff --git a/src/battle_pyramid.c b/src/battle_pyramid.c
index 23343ba20..36c757c93 100644
--- a/src/battle_pyramid.c
+++ b/src/battle_pyramid.c
@@ -21,7 +21,7 @@
 #include "main.h"
 #include "load_save.h"
 #include "script.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "overworld.h"
 #include "event_scripts.h"
 #include "constants/battle_frontier.h"
@@ -1541,7 +1541,7 @@ void sub_81AA1D8(void)
     u8 var0, var1;
 
     for (i = 0; i < 8; i++)
-        gSaveBlock2Ptr->frontier.field_CB4[i] |= 0xFFFF;
+        gSaveBlock2Ptr->frontier.field_CB4[i] |= INVALID_U16;
 
     id = sub_81AA9E4();
     sub_81AA33C(&var0, &var1);
diff --git a/src/battle_pyramid_bag.c b/src/battle_pyramid_bag.c
index 2225a3e55..8b3a509b9 100644
--- a/src/battle_pyramid_bag.c
+++ b/src/battle_pyramid_bag.c
@@ -17,7 +17,7 @@
 #include "list_menu.h"
 #include "mail.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "menu_helpers.h"
 #include "overworld.h"
@@ -388,11 +388,11 @@ void sub_81C4F98(u8 a0, void (*callback)(void))
         gPyramidBagCursorData.callback = callback;
 
     gPyramidBagResources->callback2 = NULL;
-    gPyramidBagResources->unk814 = 0xFF;
-    gPyramidBagResources->scrollIndicatorsTaskId = 0xFF;
+    gPyramidBagResources->unk814 = INVALID_U8;
+    gPyramidBagResources->scrollIndicatorsTaskId = INVALID_U8;
 
-    memset(gPyramidBagResources->itemsSpriteIds, 0xFF, sizeof(gPyramidBagResources->itemsSpriteIds));
-    memset(gPyramidBagResources->windowIds, 0xFF, sizeof(gPyramidBagResources->windowIds));
+    memset(gPyramidBagResources->itemsSpriteIds, INVALID_U8, sizeof(gPyramidBagResources->itemsSpriteIds));
+    memset(gPyramidBagResources->windowIds, INVALID_U8, sizeof(gPyramidBagResources->windowIds));
 
     SetMainCallback2(sub_81C504C);
 }
@@ -604,7 +604,7 @@ static void PyramidBagMoveCursorFunc(s32 itemIndex, bool8 onInit, struct ListMen
         PlaySE(SE_SELECT);
         sub_81C6F20();
     }
-    if (gPyramidBagResources->unk814 == 0xFF)
+    if (gPyramidBagResources->unk814 == INVALID_U8)
     {
         sub_81C6FF8(gPyramidBagResources->unk815 ^ 1);
         if (itemIndex != LIST_B_PRESSED)
@@ -622,7 +622,7 @@ static void PrintItemQuantity(u8 windowId, s32 itemIndex, u8 y)
     if (itemIndex == LIST_B_PRESSED)
         return;
 
-    if (gPyramidBagResources->unk814 != 0xFF)
+    if (gPyramidBagResources->unk814 != INVALID_U8)
     {
         if (gPyramidBagResources->unk814 == (u8)(itemIndex))
             sub_81C5AB8(y, 1);
@@ -657,16 +657,16 @@ static void PrintItemDescription(s32 listMenuId)
 
 static void AddScrollArrow(void)
 {
-    if (gPyramidBagResources->scrollIndicatorsTaskId == 0xFF)
+    if (gPyramidBagResources->scrollIndicatorsTaskId == INVALID_U8)
         gPyramidBagResources->scrollIndicatorsTaskId = AddScrollIndicatorArrowPairParameterized(2, 172, 12, 148, gPyramidBagResources->listMenuCount - gPyramidBagResources->listMenuMaxShown, 0xB5E, 0xB5E, &gPyramidBagCursorData.scrollPosition);
 }
 
 static void RemoveScrollArrow(void)
 {
-    if (gPyramidBagResources->scrollIndicatorsTaskId != 0xFF)
+    if (gPyramidBagResources->scrollIndicatorsTaskId != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(gPyramidBagResources->scrollIndicatorsTaskId);
-        gPyramidBagResources->scrollIndicatorsTaskId = 0xFF;
+        gPyramidBagResources->scrollIndicatorsTaskId = INVALID_U8;
     }
 }
 
@@ -803,7 +803,7 @@ static void sub_81C5A98(u8 listMenuTaskId, u8 arg1)
 
 static void sub_81C5AB8(u8 y, u8 arg1)
 {
-    if (arg1 == 0xFF)
+    if (arg1 == INVALID_U8)
         FillWindowPixelRect(0, 0, 0, y, GetMenuCursorDimensionByFont(1, 0), GetMenuCursorDimensionByFont(1, 1));
     else
         PrintOnWindow_Font1(0, gText_SelectorArrow2, 0, y, 0, 0, 0, arg1);
@@ -1323,7 +1323,7 @@ static void PerformItemSwap(u8 taskId)
     else
     {
         MovePyramidBagItemSlotInList(data[1], var);
-        gPyramidBagResources->unk814 = 0xFF;
+        gPyramidBagResources->unk814 = INVALID_U8;
         sub_81C7028(TRUE);
         DestroyListMenuTask(data[0], scrollOffset, selectedRow);
         if (data[1] < var)
@@ -1340,7 +1340,7 @@ static void sub_81C6A14(u8 taskId)
     u16 *scrollOffset = &gPyramidBagCursorData.scrollPosition;
     u16 *selectedRow = &gPyramidBagCursorData.cursorPosition;
 
-    gPyramidBagResources->unk814 = 0xFF;
+    gPyramidBagResources->unk814 = INVALID_U8;
     sub_81C7028(TRUE);
     DestroyListMenuTask(data[0], scrollOffset, selectedRow);
     if (data[1] < *scrollOffset + *selectedRow)
@@ -1427,7 +1427,7 @@ static u8 sub_81C6D08(u8 windowArrayId)
 static u8 sub_81C6D24(u8 windowArrayId)
 {
     u8 *windowId = &gPyramidBagResources->windowIds[windowArrayId];
-    if (*windowId == 0xFF)
+    if (*windowId == INVALID_U8)
     {
         *windowId = AddWindow(&gUnknown_0861F350[windowArrayId]);
         SetWindowBorderStyle(*windowId, FALSE, 1, 0xE);
@@ -1439,13 +1439,13 @@ static u8 sub_81C6D24(u8 windowArrayId)
 static void sub_81C6D6C(u8 windowArrayId)
 {
     u8 *windowId = &gPyramidBagResources->windowIds[windowArrayId];
-    if (*windowId != 0xFF)
+    if (*windowId != INVALID_U8)
     {
         sub_8198070(*windowId, FALSE);
         ClearWindowTilemap(*windowId);
         RemoveWindow(*windowId);
         schedule_bg_copy_tilemap_to_vram(1);
-        *windowId = 0xFF;
+        *windowId = INVALID_U8;
     }
 }
 
@@ -1473,13 +1473,13 @@ static void sub_81C6E1C(void)
 static void sub_81C6E38(u8 itemSpriteArrayId)
 {
     u8 *spriteId = &gPyramidBagResources->itemsSpriteIds[itemSpriteArrayId];
-    if (*spriteId != 0xFF)
+    if (*spriteId != INVALID_U8)
     {
         FreeSpriteTilesByTag(ITEM_IMAGE_TAG + itemSpriteArrayId);
         FreeSpritePaletteByTag(ITEM_IMAGE_TAG + itemSpriteArrayId);
         FreeSpriteOamMatrix(&gSprites[*spriteId]);
         DestroySprite(&gSprites[*spriteId]);
-        *spriteId = 0xFF;
+        *spriteId = INVALID_U8;
     }
 }
 
@@ -1524,7 +1524,7 @@ static void ShowItemImage(u16 itemId, u8 itemSpriteArrayId)
 {
     u8 itemSpriteId;
     u8 *spriteId = &gPyramidBagResources->itemsSpriteIds[itemSpriteArrayId + 1];
-    if (*spriteId == 0xFF)
+    if (*spriteId == INVALID_U8)
     {
         FreeSpriteTilesByTag(ITEM_IMAGE_TAG + 1 + itemSpriteArrayId);
         FreeSpritePaletteByTag(ITEM_IMAGE_TAG + 1 + itemSpriteArrayId);
diff --git a/src/battle_records.c b/src/battle_records.c
index f64b5f494..f9c40d8de 100644
--- a/src/battle_records.c
+++ b/src/battle_records.c
@@ -18,7 +18,7 @@
 #include "international_string_util.h"
 #include "sound.h"
 #include "constants/songs.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "gpu_regs.h"
 #include "constants/game_stat.h"
 
diff --git a/src/battle_script_commands.c b/src/battle_script_commands.c
index 6a7ca1725..53f8defa5 100644
--- a/src/battle_script_commands.c
+++ b/src/battle_script_commands.c
@@ -763,8 +763,8 @@ static const struct SpriteTemplate sSpriteTemplate_MonIconOnLvlUpBox =
 static const u16 sProtectSuccessRates[] = {USHRT_MAX, USHRT_MAX / 2, USHRT_MAX / 4, USHRT_MAX / 8};
 
 #define MIMIC_FORBIDDEN_END             0xFFFE
-#define METRONOME_FORBIDDEN_END         0xFFFF
-#define ASSIST_FORBIDDEN_END            0xFFFF
+#define METRONOME_FORBIDDEN_END         INVALID_U16
+#define ASSIST_FORBIDDEN_END            INVALID_U16
 
 static const u16 sMovesForbiddenToCopy[] =
 {
@@ -822,7 +822,7 @@ static const u16 sWeightToDamageTable[] =
     500, 60,
     1000, 80,
     2000, 100,
-    0xFFFF, 0xFFFF
+    INVALID_U16, INVALID_U16
 };
 
 static const u16 sPickupItems[] =
@@ -1976,7 +1976,7 @@ static void atk0C_datahpupdate(void)
     {
         gActiveBattler = GetBattlerForBattleScript(gBattlescriptCurrInstr[1]);
         if (gSpecialStatuses[gActiveBattler].dmg == 0)
-            gSpecialStatuses[gActiveBattler].dmg = 0xFFFF;
+            gSpecialStatuses[gActiveBattler].dmg = INVALID_U16;
     }
     gBattlescriptCurrInstr += 2;
 }
@@ -2579,7 +2579,7 @@ void SetMoveEffect(bool8 primary, u8 certain)
                     u16 PayDay = gPaydayMoney;
                     gPaydayMoney += (gBattleMons[gBattlerAttacker].level * 5);
                     if (PayDay > gPaydayMoney)
-                        gPaydayMoney = 0xFFFF;
+                        gPaydayMoney = INVALID_U16;
                 }
                 BattleScriptPush(gBattlescriptCurrInstr + 1);
                 gBattlescriptCurrInstr = sMoveEffectBS_Ptrs[gBattleCommunication[MOVE_EFFECT_BYTE]];
@@ -4520,7 +4520,7 @@ static void atk49_moveend(void)
     u8 arg1, arg2;
     u16 originallyUsedMove;
 
-    if (gChosenMove == 0xFFFF)
+    if (gChosenMove == INVALID_U16)
         originallyUsedMove = 0;
     else
         originallyUsedMove = gChosenMove;
@@ -4593,7 +4593,7 @@ static void atk49_moveend(void)
             break;
         case ATK49_CHOICE_MOVE: // update choice band move
             if (!(gHitMarker & HITMARKER_OBEYS) || holdEffectAtk != HOLD_EFFECT_CHOICE_BAND
-                || gChosenMove == MOVE_STRUGGLE || (*choicedMoveAtk != 0 && *choicedMoveAtk != 0xFFFF))
+                || gChosenMove == MOVE_STRUGGLE || (*choicedMoveAtk != 0 && *choicedMoveAtk != INVALID_U16))
                     goto LOOP;
             if (gChosenMove == MOVE_BATON_PASS && !(gMoveResultFlags & MOVE_RESULT_FAILED))
             {
@@ -4708,8 +4708,8 @@ static void atk49_moveend(void)
                 }
                 else
                 {
-                    gLastMoves[gBattlerAttacker] = 0xFFFF;
-                    gLastResultingMoves[gBattlerAttacker] = 0xFFFF;
+                    gLastMoves[gBattlerAttacker] = INVALID_U16;
+                    gLastResultingMoves[gBattlerAttacker] = INVALID_U16;
                 }
 
                 if (!(gHitMarker & HITMARKER_FAINTED(gBattlerTarget)))
@@ -4717,7 +4717,7 @@ static void atk49_moveend(void)
 
                 if (gHitMarker & HITMARKER_OBEYS && !(gMoveResultFlags & MOVE_RESULT_NO_EFFECT))
                 {
-                    if (gChosenMove == 0xFFFF)
+                    if (gChosenMove == INVALID_U16)
                     {
                         gLastLandedMoves[gBattlerTarget] = gChosenMove;
                     }
@@ -4729,7 +4729,7 @@ static void atk49_moveend(void)
                 }
                 else
                 {
-                    gLastLandedMoves[gBattlerTarget] = 0xFFFF;
+                    gLastLandedMoves[gBattlerTarget] = INVALID_U16;
                 }
             }
             gBattleScripting.atk49_state++;
@@ -5662,7 +5662,7 @@ static void atk59_handlelearnnewmove(void)
     {
         gBattlescriptCurrInstr = jumpPtr2;
     }
-    else if (ret == 0xFFFF)
+    else if (ret == INVALID_U16)
     {
         gBattlescriptCurrInstr += 10;
     }
@@ -6015,7 +6015,7 @@ static void atk61_drawpartystatussummary(void)
         if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_NONE
             || GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_EGG)
         {
-            hpStatuses[i].hp = 0xFFFF;
+            hpStatuses[i].hp = INVALID_U16;
             hpStatuses[i].status = 0;
         }
         else
@@ -6930,7 +6930,7 @@ static void atk7C_trymirrormove(void)
             move = *(i * 2 + gBattlerAttacker * 8 + (u8*)(gBattleStruct->lastTakenMoveFrom) + 0)
                 | (*(i * 2 + gBattlerAttacker * 8 + (u8*)(gBattleStruct->lastTakenMoveFrom) + 1) << 8);
 
-            if (move != 0 && move != 0xFFFF)
+            if (move != 0 && move != INVALID_U16)
             {
                 movesArray[validMovesCount] = move;
                 validMovesCount++;
@@ -6941,7 +6941,7 @@ static void atk7C_trymirrormove(void)
     move = *(gBattleStruct->lastTakenMove + gBattlerAttacker * 2 + 0)
         | (*(gBattleStruct->lastTakenMove + gBattlerAttacker * 2 + 1) << 8);
 
-    if (move != 0 && move != 0xFFFF)
+    if (move != 0 && move != INVALID_U16)
     {
         gHitMarker &= ~(HITMARKER_ATTACKSTRING_PRINTED);
         gCurrentMove = move;
@@ -7094,7 +7094,7 @@ bool8 UproarWakeUpCheck(u8 battlerId)
 
         gBattleScripting.battler = i;
 
-        if (gBattlerTarget == 0xFF)
+        if (gBattlerTarget == INVALID_U8)
             gBattlerTarget = i;
         else if (gBattlerTarget == i)
             gBattleCommunication[MULTISTRING_CHOOSER] = 0;
@@ -8008,7 +8008,7 @@ static void atk9A_setfocusenergy(void)
 
 static void atk9B_transformdataexecution(void)
 {
-    gChosenMove = 0xFFFF;
+    gChosenMove = INVALID_U16;
     gBattlescriptCurrInstr++;
     if (gBattleMons[gBattlerTarget].status2 & STATUS2_TRANSFORMED
         || gStatuses3[gBattlerTarget] & STATUS3_SEMI_INVULNERABLE)
@@ -8088,12 +8088,12 @@ static bool8 IsMoveUncopyableByMimic(u16 move)
 
 static void atk9D_mimicattackcopy(void)
 {
-    gChosenMove = 0xFFFF;
+    gChosenMove = INVALID_U16;
 
     if (IsMoveUncopyableByMimic(gLastMoves[gBattlerTarget])
         || gBattleMons[gBattlerAttacker].status2 & STATUS2_TRANSFORMED
         || gLastMoves[gBattlerTarget] == 0
-        || gLastMoves[gBattlerTarget] == 0xFFFF)
+        || gLastMoves[gBattlerTarget] == INVALID_U16)
     {
         gBattlescriptCurrInstr = T1_READ_PTR(gBattlescriptCurrInstr + 1);
     }
@@ -8296,7 +8296,7 @@ static void atkA5_painsplitdmgcalc(void)
         storeLoc[3] = (painSplitHp & 0xFF000000) >> 24;
 
         gBattleMoveDamage = gBattleMons[gBattlerAttacker].hp - hpDiff;
-        gSpecialStatuses[gBattlerTarget].dmg = 0xFFFF;
+        gSpecialStatuses[gBattlerTarget].dmg = INVALID_U16;
 
         gBattlescriptCurrInstr += 5;
     }
@@ -8309,7 +8309,7 @@ static void atkA5_painsplitdmgcalc(void)
 static void atkA6_settypetorandomresistance(void) // conversion 2
 {
     if (gLastLandedMoves[gBattlerAttacker] == 0
-        || gLastLandedMoves[gBattlerAttacker] == 0xFFFF)
+        || gLastLandedMoves[gBattlerAttacker] == INVALID_U16)
     {
         gBattlescriptCurrInstr = T1_READ_PTR(gBattlescriptCurrInstr + 1);
     }
@@ -8376,12 +8376,12 @@ static void atkA7_setalwayshitflag(void)
 
 static void atkA8_copymovepermanently(void) // sketch
 {
-    gChosenMove = 0xFFFF;
+    gChosenMove = INVALID_U16;
 
     if (!(gBattleMons[gBattlerAttacker].status2 & STATUS2_TRANSFORMED)
         && gLastPrintedMoves[gBattlerTarget] != MOVE_STRUGGLE
         && gLastPrintedMoves[gBattlerTarget] != 0
-        && gLastPrintedMoves[gBattlerTarget] != 0xFFFF
+        && gLastPrintedMoves[gBattlerTarget] != INVALID_U16
         && gLastPrintedMoves[gBattlerTarget] != MOVE_SKETCH)
     {
         s32 i;
@@ -8550,7 +8550,7 @@ static void atkAC_remaininghptopower(void)
 static void atkAD_tryspiteppreduce(void)
 {
     if (gLastMoves[gBattlerTarget] != 0
-        && gLastMoves[gBattlerTarget] != 0xFFFF)
+        && gLastMoves[gBattlerTarget] != INVALID_U16)
     {
         s32 i;
 
@@ -9671,13 +9671,13 @@ static void atkDC_trysetgrudge(void)
 static void atkDD_weightdamagecalculation(void)
 {
     s32 i;
-    for (i = 0; sWeightToDamageTable[i] != 0xFFFF; i += 2)
+    for (i = 0; sWeightToDamageTable[i] != INVALID_U16; i += 2)
     {
         if (sWeightToDamageTable[i] > GetPokedexHeightWeight(SpeciesToNationalPokedexNum(gBattleMons[gBattlerTarget].species), 1))
             break;
     }
 
-    if (sWeightToDamageTable[i] != 0xFFFF)
+    if (sWeightToDamageTable[i] != INVALID_U16)
         gDynamicBasePower = sWeightToDamageTable[i + 1];
     else
         gDynamicBasePower = 120;
diff --git a/src/battle_setup.c b/src/battle_setup.c
index 4243d2f3f..0b5cd9e21 100644
--- a/src/battle_setup.c
+++ b/src/battle_setup.c
@@ -1530,7 +1530,7 @@ static s32 FirstBattleTrainerIdToRematchTableId(const struct RematchTrainer *tab
             return i;
     }
 
-    return -1;
+    return INVALID_S32;
 }
 
 static s32 TrainerIdToRematchTableId(const struct RematchTrainer *table, u16 trainerId)
@@ -1548,7 +1548,7 @@ static s32 TrainerIdToRematchTableId(const struct RematchTrainer *table, u16 tra
         }
     }
 
-    return -1;
+    return INVALID_S32;
 }
 
 static bool32 sub_80B1D94(s32 rematchTableId)
@@ -1640,7 +1640,7 @@ static bool8 IsFirstTrainerIdReadyForRematch(const struct RematchTrainer *table,
 {
     s32 tableId = FirstBattleTrainerIdToRematchTableId(table, firstBattleTrainerId);
 
-    if (tableId == -1)
+    if (tableId == INVALID_S32)
         return FALSE;
     if (tableId >= 100)
         return FALSE;
@@ -1654,7 +1654,7 @@ static bool8 IsTrainerReadyForRematch_(const struct RematchTrainer *table, u16 t
 {
     s32 tableId = TrainerIdToRematchTableId(table, trainerId);
 
-    if (tableId == -1)
+    if (tableId == INVALID_S32)
         return FALSE;
     if (tableId >= 100)
         return FALSE;
@@ -1670,7 +1670,7 @@ static u16 GetRematchTrainerIdFromTable(const struct RematchTrainer *table, u16
     s32 i;
     s32 tableId = FirstBattleTrainerIdToRematchTableId(table, firstBattleTrainerId);
 
-    if (tableId == -1)
+    if (tableId == INVALID_S32)
         return FALSE;
 
     trainerEntry = &table[tableId];
@@ -1691,7 +1691,7 @@ static u16 GetLastBeatenRematchTrainerIdFromTable(const struct RematchTrainer *t
     s32 i;
     s32 tableId = FirstBattleTrainerIdToRematchTableId(table, firstBattleTrainerId);
 
-    if (tableId == -1)
+    if (tableId == INVALID_S32)
         return FALSE;
 
     trainerEntry = &table[tableId];
@@ -1710,7 +1710,7 @@ static void ClearTrainerWantRematchState(const struct RematchTrainer *table, u16
 {
     s32 tableId = TrainerIdToRematchTableId(table, firstBattleTrainerId);
 
-    if (tableId != -1)
+    if (tableId != INVALID_S32)
         gSaveBlock1Ptr->trainerRematches[tableId] = 0;
 }
 
@@ -1724,7 +1724,7 @@ static u32 GetTrainerMatchCallFlag(u32 trainerId)
             return FLAG_MATCH_CALL_REGISTERED + i;
     }
 
-    return 0xFFFF;
+    return INVALID_U16;
 }
 
 static void RegisterTrainerInMatchCall(void)
@@ -1732,7 +1732,7 @@ static void RegisterTrainerInMatchCall(void)
     if (FlagGet(FLAG_HAS_MATCH_CALL))
     {
         u32 matchCallFlagId = GetTrainerMatchCallFlag(gTrainerBattleOpponent_A);
-        if (matchCallFlagId != 0xFFFF)
+        if (matchCallFlagId != INVALID_U16)
             FlagSet(matchCallFlagId);
     }
 }
@@ -1741,7 +1741,7 @@ static bool8 WasSecondRematchWon(const struct RematchTrainer *table, u16 firstBa
 {
     s32 tableId = FirstBattleTrainerIdToRematchTableId(table, firstBattleTrainerId);
 
-    if (tableId == -1)
+    if (tableId == INVALID_S32)
         return FALSE;
     if (!HasTrainerBeenFought(table[tableId].trainerIds[1]))
         return FALSE;
diff --git a/src/battle_tent.c b/src/battle_tent.c
index c7e70912c..836b2b6de 100644
--- a/src/battle_tent.c
+++ b/src/battle_tent.c
@@ -364,7 +364,7 @@ static void sub_81BA040(void)
         } while (i != gSaveBlock2Ptr->frontier.curChallengeBattleNum);
 
         gTrainerBattleOpponent_A = trainerId;
-        while (gFacilityTrainers[gTrainerBattleOpponent_A].monSets[setsCount] != 0xFFFF)
+        while (gFacilityTrainers[gTrainerBattleOpponent_A].monSets[setsCount] != INVALID_U16)
             setsCount++;
         if (setsCount > 8)
             break;
diff --git a/src/battle_tower.c b/src/battle_tower.c
index f9dfcabd1..c74cfd9a0 100644
--- a/src/battle_tower.c
+++ b/src/battle_tower.c
@@ -973,7 +973,7 @@ static void FillTrainerParty(u16 trainerId, u8 firstMonId, u8 monCount)
     // Attempt to fill the trainer's party with random Pokemon until 3 have been
     // successfully chosen. The trainer's party may not have duplicate pokemon species
     // or duplicate held items.
-    for (bfMonCount = 0; monSets[bfMonCount] != 0xFFFF; bfMonCount++)
+    for (bfMonCount = 0; monSets[bfMonCount] != INVALID_U16; bfMonCount++)
         ;
     i = 0;
     otID = Random32();
@@ -1081,11 +1081,11 @@ u16 RandomizeFacilityTrainerMonSet(u16 trainerId)
     u8 bfMonCount = 0;
     u32 monSetId = monSets[bfMonCount];
 
-    while (monSetId != 0xFFFF)
+    while (monSetId != INVALID_U16)
     {
         bfMonCount++;
         monSetId = monSets[bfMonCount];
-        if (monSetId == 0xFFFF)
+        if (monSetId == INVALID_U16)
             break;
     }
 
@@ -2641,11 +2641,11 @@ static void FillTentTrainerParty_(u16 trainerId, u8 firstMonId, u8 monCount)
 
     bfMonCount = 0;
     monSetId = monSets[bfMonCount];
-    while (monSetId != 0xFFFF)
+    while (monSetId != INVALID_U16)
     {
         bfMonCount++;
         monSetId = monSets[bfMonCount];
-        if (monSetId == 0xFFFF)
+        if (monSetId == INVALID_U16)
             break;
     }
 
diff --git a/src/battle_transition.c b/src/battle_transition.c
index 94b9e78f9..f15514f50 100644
--- a/src/battle_transition.c
+++ b/src/battle_transition.c
@@ -7,7 +7,7 @@
 #include "field_effect.h"
 #include "gpu_regs.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "overworld.h"
 #include "palette.h"
 #include "random.h"
@@ -749,7 +749,7 @@ static const union AffineAnimCmd *const sSpriteAffineAnimTable_85C8E60[] =
 
 static const struct SpriteTemplate gUnknown_085C8E68 =
 {
-    .tileTag = 0xFFFF,
+    .tileTag = INVALID_U16,
     .paletteTag = 4105,
     .oam = &gEventObjectBaseOam_32x32,
     .anims = sSpriteAnimTable_85C8E3C,
@@ -798,7 +798,7 @@ static const union AnimCmd *const sSpriteAnimTable_85C8EA0[] =
 
 static const struct SpriteTemplate sSpriteTemplate_85C8EA4 =
 {
-    .tileTag = 0xFFFF,
+    .tileTag = INVALID_U16,
     .paletteTag = 4106,
     .oam = &gOamData_85C8E80,
     .anims = sSpriteAnimTable_85C8EA0,
@@ -809,7 +809,7 @@ static const struct SpriteTemplate sSpriteTemplate_85C8EA4 =
 
 static const struct SpriteTemplate sSpriteTemplate_85C8EBC =
 {
-    .tileTag = 0xFFFF,
+    .tileTag = INVALID_U16,
     .paletteTag = 4106,
     .oam = &gOamData_85C8E80,
     .anims = sSpriteAnimTable_85C8EA0,
@@ -998,7 +998,7 @@ static bool8 Transition_Phase1(struct Task *task)
 
 static bool8 Transition_WaitForPhase1(struct Task *task)
 {
-    if (FindTaskIdByFunc(sPhase1_Tasks[task->tTransitionId]) == 0xFF)
+    if (FindTaskIdByFunc(sPhase1_Tasks[task->tTransitionId]) == INVALID_U8)
     {
         task->tState++;
         return TRUE;
@@ -1019,7 +1019,7 @@ static bool8 Transition_Phase2(struct Task *task)
 static bool8 Transition_WaitForPhase2(struct Task *task)
 {
     task->tTransitionDone = FALSE;
-    if (FindTaskIdByFunc(sPhase2_Tasks[task->tTransitionId]) == 0xFF)
+    if (FindTaskIdByFunc(sPhase2_Tasks[task->tTransitionId]) == INVALID_U8)
         task->tTransitionDone = TRUE;
     return FALSE;
 }
@@ -3605,7 +3605,7 @@ static void CreatePhase1Task(s16 a0, s16 a1, s16 a2, s16 a3, s16 a4)
 
 static bool8 IsPhase1Done(void)
 {
-    if (FindTaskIdByFunc(TransitionPhase1_Task_RunFuncs) == 0xFF)
+    if (FindTaskIdByFunc(TransitionPhase1_Task_RunFuncs) == INVALID_U8)
         return TRUE;
     else
         return FALSE;
diff --git a/src/battle_tv.c b/src/battle_tv.c
index 535046fd1..edd506708 100644
--- a/src/battle_tv.c
+++ b/src/battle_tv.c
@@ -26,9 +26,9 @@ static const u16 sVariableDmgMoves[] =
     MOVE_WATER_SPOUT, MOVE_DREAM_EATER, MOVE_WEATHER_BALL,
     MOVE_SNORE, MOVE_PAIN_SPLIT, MOVE_GUILLOTINE,
     MOVE_FRUSTRATION, MOVE_RETURN, MOVE_ENDEAVOR,
-    MOVE_PRESENT, MOVE_REVENGE, 0xFFFF,
+    MOVE_PRESENT, MOVE_REVENGE, INVALID_U16,
     // those are handled by the function itself
-    MOVE_MAGNITUDE, MOVE_PSYWAVE, 0xFFFF
+    MOVE_MAGNITUDE, MOVE_PSYWAVE, INVALID_U16
 };
 
 static const u16 sUnknown_0860A4E0[] =
@@ -199,7 +199,7 @@ static const u16 sUnknown_0860A8A4[] =
     STRINGID_PKMNAFFLICTEDBYCURSE, STRINGID_PKMNSAPPEDBYLEECHSEED, STRINGID_PKMNLOCKEDINNIGHTMARE,
     STRINGID_PKMNHURTBY, STRINGID_PKMNHURTBYBURN, STRINGID_PKMNHURTBYPOISON,
     STRINGID_PKMNHURTBYSPIKES, STRINGID_ATTACKERFAINTED, STRINGID_TARGETFAINTED,
-    STRINGID_PKMNHITWITHRECOIL, STRINGID_PKMNCRASHED, 0xFFFF
+    STRINGID_PKMNHITWITHRECOIL, STRINGID_PKMNCRASHED, INVALID_U16
 };
 
 // code
@@ -625,9 +625,9 @@ static bool8 sub_817E0B8(u16 stringId)
         if (sUnknown_0860A8A4[i] == stringId)
             break;
         i++;
-    } while (sUnknown_0860A8A4[i] != 0xFFFF);
+    } while (sUnknown_0860A8A4[i] != INVALID_U16);
 
-    if (sUnknown_0860A8A4[i] == 0xFFFF)
+    if (sUnknown_0860A8A4[i] == INVALID_U16)
         return TRUE;
     else
         return FALSE;
@@ -1164,7 +1164,7 @@ static void AddMovePoints(u8 caseId, u16 arg1, u8 arg2, u8 arg3)
                 break;
             }
             i += 2;
-        } while (ptr[i] != 0xFFFF);
+        } while (ptr[i] != INVALID_U16);
         break;
     case 19:
         tvPtr->side[arg2 ^ 1].faintCause = 0;
@@ -1415,9 +1415,9 @@ static void TrySetBattleSeminarShow(void)
         if (currMoveSaved == sVariableDmgMoves[i])
             break;
         i++;
-    } while (sVariableDmgMoves[i] != 0xFFFF);
+    } while (sVariableDmgMoves[i] != INVALID_U16);
 
-    if (sVariableDmgMoves[i] != 0xFFFF)
+    if (sVariableDmgMoves[i] != INVALID_U16)
         return;
 
     dmgByMove[gMoveSelectionCursor[gBattlerAttacker]] = gBattleMoveDamage;
@@ -1490,9 +1490,9 @@ static bool8 ShouldCalculateDamage(u16 moveId, s32 *dmg, u16 *powerOverride)
             if (moveId == sVariableDmgMoves[i])
                 break;
             i++;
-        } while (sVariableDmgMoves[i] != 0xFFFF);
+        } while (sVariableDmgMoves[i] != INVALID_U16);
 
-        if (sVariableDmgMoves[i] != 0xFFFF)
+        if (sVariableDmgMoves[i] != INVALID_U16)
         {
             *dmg = 0;
             return FALSE;
diff --git a/src/battle_util.c b/src/battle_util.c
index 251a545c9..12ca6bc9c 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -29,7 +29,7 @@ extern u8 weather_get_current(void);
 static const u16 sSoundMovesTable[] =
 {
     MOVE_GROWL, MOVE_ROAR, MOVE_SING, MOVE_SUPERSONIC, MOVE_SCREECH, MOVE_SNORE,
-    MOVE_UPROAR, MOVE_METAL_SOUND, MOVE_GRASS_WHISTLE, MOVE_HYPER_VOICE, 0xFFFF
+    MOVE_UPROAR, MOVE_METAL_SOUND, MOVE_GRASS_WHISTLE, MOVE_HYPER_VOICE, INVALID_U16
 };
 
 u8 GetBattlerForBattleScript(u8 caseId)
@@ -382,7 +382,7 @@ u8 TrySetCantSelectMoveBattleScript(void)
 
     gPotentialItemEffectBattler = gActiveBattler;
 
-    if (holdEffect == HOLD_EFFECT_CHOICE_BAND && *choicedMove != 0 && *choicedMove != 0xFFFF && *choicedMove != move)
+    if (holdEffect == HOLD_EFFECT_CHOICE_BAND && *choicedMove != 0 && *choicedMove != INVALID_U16 && *choicedMove != move)
     {
         gCurrentMove = *choicedMove;
         gLastUsedItem = gBattleMons[gActiveBattler].item;
@@ -442,7 +442,7 @@ u8 CheckMoveLimitations(u8 battlerId, u8 unusableMoves, u8 check)
             unusableMoves |= gBitTable[i];
         if (gDisableStructs[battlerId].encoreTimer && gDisableStructs[battlerId].encoredMove != gBattleMons[battlerId].moves[i])
             unusableMoves |= gBitTable[i];
-        if (holdEffect == HOLD_EFFECT_CHOICE_BAND && *choicedMove != 0 && *choicedMove != 0xFFFF && *choicedMove != gBattleMons[battlerId].moves[i])
+        if (holdEffect == HOLD_EFFECT_CHOICE_BAND && *choicedMove != 0 && *choicedMove != INVALID_U16 && *choicedMove != gBattleMons[battlerId].moves[i])
             unusableMoves |= gBitTable[i];
     }
     return unusableMoves;
@@ -451,7 +451,7 @@ u8 CheckMoveLimitations(u8 battlerId, u8 unusableMoves, u8 check)
 bool8 AreAllMovesUnusable(void)
 {
     u8 unusable;
-    unusable = CheckMoveLimitations(gActiveBattler, 0, 0xFF);
+    unusable = CheckMoveLimitations(gActiveBattler, 0, INVALID_U8);
 
     if (unusable == 0xF) // All moves are unusable.
     {
@@ -1137,7 +1137,7 @@ bool8 HandleWishPerishSongOnTurnEnd(void)
                 gBattlerTarget = gActiveBattler;
                 gBattlerAttacker = gWishFutureKnock.futureSightAttacker[gActiveBattler];
                 gBattleMoveDamage = gWishFutureKnock.futureSightDmg[gActiveBattler];
-                gSpecialStatuses[gBattlerTarget].dmg = 0xFFFF;
+                gSpecialStatuses[gBattlerTarget].dmg = INVALID_U16;
                 BattleScriptExecute(BattleScript_MonTookFutureAttack);
 
                 if (gWishFutureKnock.futureSightCounter[gActiveBattler] == 0
@@ -1996,12 +1996,12 @@ u8 AbilityBattleEffects(u8 caseID, u8 battler, u8 ability, u8 special, u16 moveA
         case ABILITYEFFECT_MOVES_BLOCK: // 2
             if (gLastUsedAbility == ABILITY_SOUNDPROOF)
             {
-                for (i = 0; sSoundMovesTable[i] != 0xFFFF; i++)
+                for (i = 0; sSoundMovesTable[i] != INVALID_U16; i++)
                 {
                     if (sSoundMovesTable[i] == move)
                         break;
                 }
-                if (sSoundMovesTable[i] != 0xFFFF)
+                if (sSoundMovesTable[i] != INVALID_U16)
                 {
                     if (gBattleMons[gBattlerAttacker].status2 & STATUS2_MULTIPLETURNS)
                         gHitMarker |= HITMARKER_NO_PPDEDUCT;
@@ -2527,7 +2527,7 @@ u8 AbilityBattleEffects(u8 caseID, u8 battler, u8 ability, u8 special, u16 moveA
             break;
         }
 
-        if (effect && caseID < ABILITYEFFECT_CHECK_OTHER_SIDE && gLastUsedAbility != 0xFF)
+        if (effect && caseID < ABILITYEFFECT_CHECK_OTHER_SIDE && gLastUsedAbility != INVALID_U8)
             RecordAbilityBattle(battler, gLastUsedAbility);
     }
 
@@ -3213,7 +3213,7 @@ u8 ItemBattleEffects(u8 caseID, u8 battlerId, bool8 moveTurn)
             case HOLD_EFFECT_SHELL_BELL:
                 if (!(gMoveResultFlags & MOVE_RESULT_NO_EFFECT)
                     && gSpecialStatuses[gBattlerTarget].dmg != 0
-                    && gSpecialStatuses[gBattlerTarget].dmg != 0xFFFF
+                    && gSpecialStatuses[gBattlerTarget].dmg != INVALID_U16
                     && gBattlerAttacker != gBattlerTarget
                     && gBattleMons[gBattlerAttacker].hp != gBattleMons[gBattlerAttacker].maxHP
                     && gBattleMons[gBattlerAttacker].hp != 0)
@@ -3394,7 +3394,7 @@ u8 IsMonDisobedient(void)
     calc = (gBattleMons[gBattlerAttacker].level + obedienceLevel) * rnd >> 8;
     if (calc < obedienceLevel)
     {
-        calc = CheckMoveLimitations(gBattlerAttacker, gBitTable[gCurrMovePos], 0xFF);
+        calc = CheckMoveLimitations(gBattlerAttacker, gBitTable[gCurrMovePos], INVALID_U8);
         if (calc == 0xF) // all moves cannot be used
         {
             gBattleCommunication[MULTISTRING_CHOOSER] = Random() & 3;
diff --git a/src/battle_util2.c b/src/battle_util2.c
index 5881abf25..a9891814c 100644
--- a/src/battle_util2.c
+++ b/src/battle_util2.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "battle.h"
 #include "battle_controllers.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "pokemon.h"
 #include "event_data.h"
 #include "constants/abilities.h"
diff --git a/src/berry_blender.c b/src/berry_blender.c
index 7320e905f..e977bdbeb 100644
--- a/src/berry_blender.c
+++ b/src/berry_blender.c
@@ -12,7 +12,7 @@
 #include "bg.h"
 #include "palette.h"
 #include "decompress.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "gpu_regs.h"
 #include "text.h"
 #include "text_window.h"
@@ -1455,7 +1455,7 @@ static void sub_808074C(void)
 
     for (i = 0; i < BLENDER_MAX_PLAYERS; i++)
     {
-        sBerryBlenderData->field_96[i] = 0xFF;
+        sBerryBlenderData->field_96[i] = INVALID_U8;
         sBerryBlenderData->field_8E[i] = sUnknown_083399D0[sBerryBlenderData->playersNo - 2][i];
     }
     for (j = 0; j < BLENDER_MAX_PLAYERS; j++)
@@ -1479,7 +1479,7 @@ static void Blender_PrintPlayerNames(void)
 
     for (i = 0; i < BLENDER_MAX_PLAYERS; i++)
     {
-        if (sBerryBlenderData->field_8E[i] != 0xFF)
+        if (sBerryBlenderData->field_8E[i] != INVALID_U8)
         {
             sBerryBlenderData->syncArrowSpriteIds[sBerryBlenderData->field_8E[i]] = sBerryBlenderData->syncArrowSprite2Ids[i];
             StartSpriteAnim(&gSprites[sBerryBlenderData->syncArrowSpriteIds[sBerryBlenderData->field_8E[i]]], i);
diff --git a/src/berry_fix_program.c b/src/berry_fix_program.c
index a90906d05..d87509e10 100644
--- a/src/berry_fix_program.c
+++ b/src/berry_fix_program.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "gpu_regs.h"
 #include "multiboot.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "bg.h"
 #include "graphics.h"
 #include "main.h"
diff --git a/src/berry_tag_screen.c b/src/berry_tag_screen.c
index 39927ab99..22f99a426 100644
--- a/src/berry_tag_screen.c
+++ b/src/berry_tag_screen.c
@@ -21,7 +21,7 @@
 #include "string_util.h"
 #include "strings.h"
 #include "bg.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "scanline_effect.h"
 #include "gpu_regs.h"
 #include "graphics.h"
diff --git a/src/bg.c b/src/bg.c
index a41075ad7..fd6ffca6e 100644
--- a/src/bg.c
+++ b/src/bg.c
@@ -87,37 +87,37 @@ void SetBgControlAttributes(u8 bg, u8 charBaseIndex, u8 mapBaseIndex, u8 screenS
 {
     if (IsInvalidBg(bg) == FALSE)
     {
-        if (charBaseIndex != 0xFF)
+        if (charBaseIndex != INVALID_U8)
         {
             sGpuBgConfigs.configs[bg].charBaseIndex = charBaseIndex & 0x3;
         }
 
-        if (mapBaseIndex != 0xFF)
+        if (mapBaseIndex != INVALID_U8)
         {
             sGpuBgConfigs.configs[bg].mapBaseIndex = mapBaseIndex & 0x1F;
         }
 
-        if (screenSize != 0xFF)
+        if (screenSize != INVALID_U8)
         {
             sGpuBgConfigs.configs[bg].screenSize = screenSize & 0x3;
         }
 
-        if (paletteMode != 0xFF)
+        if (paletteMode != INVALID_U8)
         {
             sGpuBgConfigs.configs[bg].paletteMode = paletteMode;
         }
 
-        if (priority != 0xFF)
+        if (priority != INVALID_U8)
         {
             sGpuBgConfigs.configs[bg].priority = priority & 0x3;
         }
 
-        if (mosaic != 0xFF)
+        if (mosaic != INVALID_U8)
         {
             sGpuBgConfigs.configs[bg].mosaic = mosaic & 0x1;
         }
 
-        if (wraparound != 0xFF)
+        if (wraparound != INVALID_U8)
         {
             sGpuBgConfigs.configs[bg].wraparound = wraparound;
         }
@@ -154,7 +154,7 @@ u16 GetBgControlAttribute(u8 bg, u8 attributeId)
         }
     }
 
-    return 0xFF;
+    return INVALID_U8;
 }
 
 u8 LoadBgVram(u8 bg, const void *src, u16 size, u16 destOffset, u8 mode)
@@ -379,7 +379,7 @@ u16 LoadBgTiles(u8 bg, const void* src, u16 size, u16 destOffset)
 
     cursor = LoadBgVram(bg, src, size, tileOffset, DISPCNT_MODE_1);
 
-    if (cursor == 0xFF)
+    if (cursor == INVALID_U8)
     {
         return -1;
     }
@@ -400,7 +400,7 @@ u16 LoadBgTilemap(u8 bg, const void *src, u16 size, u16 destOffset)
 
     cursor = LoadBgVram(bg, src, size, destOffset * 2, DISPCNT_MODE_2);
 
-    if (cursor == 0xFF)
+    if (cursor == INVALID_U8)
     {
         return -1;
     }
@@ -480,25 +480,25 @@ void SetBgAttribute(u8 bg, u8 attributeId, u8 value)
     switch (attributeId)
     {
     case 1:
-        SetBgControlAttributes(bg, value, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF);
+        SetBgControlAttributes(bg, value, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8);
         break;
     case 2:
-        SetBgControlAttributes(bg, 0xFF, value, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF);
+        SetBgControlAttributes(bg, INVALID_U8, value, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8);
         break;
     case 3:
-        SetBgControlAttributes(bg, 0xFF, 0xFF, value, 0xFF, 0xFF, 0xFF, 0xFF);
+        SetBgControlAttributes(bg, INVALID_U8, INVALID_U8, value, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8);
         break;
     case 4:
-        SetBgControlAttributes(bg, 0xFF, 0xFF, 0xFF, value, 0xFF, 0xFF, 0xFF);
+        SetBgControlAttributes(bg, INVALID_U8, INVALID_U8, INVALID_U8, value, INVALID_U8, INVALID_U8, INVALID_U8);
         break;
     case 7:
-        SetBgControlAttributes(bg, 0xFF, 0xFF, 0xFF, 0xFF, value, 0xFF, 0xFF);
+        SetBgControlAttributes(bg, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, value, INVALID_U8, INVALID_U8);
         break;
     case 5:
-        SetBgControlAttributes(bg, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, value, 0xFF);
+        SetBgControlAttributes(bg, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, value, INVALID_U8);
         break;
     case 6:
-        SetBgControlAttributes(bg, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, value);
+        SetBgControlAttributes(bg, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, INVALID_U8, value);
         break;
     }
 }
@@ -1284,7 +1284,7 @@ u32 GetBgType(u8 bg)
         break;
     }
 
-    return 0xFFFF;
+    return INVALID_U16;
 }
 
 bool32 IsInvalidBg32(u8 bg)
diff --git a/src/blit.c b/src/blit.c
index b4d5f7de5..2ba0e489c 100644
--- a/src/blit.c
+++ b/src/blit.c
@@ -3,7 +3,7 @@
 
 void BlitBitmapRect4BitWithoutColorKey(struct Bitmap *src, struct Bitmap *dst, u16 srcX, u16 srcY, u16 dstX, u16 dstY, u16 width, u16 height)
 {
-    BlitBitmapRect4Bit(src, dst, srcX, srcY, dstX, dstY, width, height, 0xFF);
+    BlitBitmapRect4Bit(src, dst, srcX, srcY, dstX, dstY, width, height, INVALID_U8);
 }
 
 void BlitBitmapRect4Bit(struct Bitmap *src, struct Bitmap *dst, u16 srcX, u16 srcY, u16 dstX, u16 dstY, u16 width, u16 height, u8 colorKey)
@@ -33,7 +33,7 @@ void BlitBitmapRect4Bit(struct Bitmap *src, struct Bitmap *dst, u16 srcX, u16 sr
     multiplierSrcY = (src->width + (src->width & 7)) >> 3;
     multiplierDstY = (dst->width + (dst->width & 7)) >> 3;
 
-    if (colorKey == 0xFF)
+    if (colorKey == INVALID_U8)
     {
         for (loopSrcY = srcY, loopDstY = dstY; loopSrcY < yEnd; loopSrcY++, loopDstY++)
         {
@@ -132,7 +132,7 @@ void BlitBitmapRect4BitTo8Bit(struct Bitmap *src, struct Bitmap *dst, u16 srcX,
     multiplierSrcY = (src->width + (src->width & 7)) >> 3;
     multiplierDstY = (dst->width + (dst->width & 7)) >> 3;
 
-    if (colorKey == 0xFF)
+    if (colorKey == INVALID_U8)
     {
         for (loopSrcY = srcY, loopDstY = dstY; loopSrcY < yEnd; loopSrcY++, loopDstY++)
         {
diff --git a/src/braille_puzzles.c b/src/braille_puzzles.c
index b17ffad33..6a2e42c4e 100644
--- a/src/braille_puzzles.c
+++ b/src/braille_puzzles.c
@@ -465,7 +465,7 @@ bool8 ShouldDoBrailleRegicePuzzle(void)
                 }
 
                 varValue = VarGet(0x403B);
-                if (varValue != 0xFFFF || VarGet(0x403C) != varValue || VarGet(0x403D) != 0xF)
+                if (varValue != INVALID_U16 || VarGet(0x403C) != varValue || VarGet(0x403D) != 0xF)
                     return FALSE;
 
                 if (gSaveBlock1Ptr->pos.x == 8 && gSaveBlock1Ptr->pos.y == 21)
diff --git a/src/cable_club.c b/src/cable_club.c
index 56154d5bf..649534711 100644
--- a/src/cable_club.c
+++ b/src/cable_club.c
@@ -70,7 +70,7 @@ static void sub_80B3220(u8 taskId);
 
 static void sub_80B236C(u8 arg0, u8 arg1)
 {
-    if (FindTaskIdByFunc(sub_80B2634) == 0xFF)
+    if (FindTaskIdByFunc(sub_80B2634) == INVALID_U8)
     {
         u8 taskId1;
 
@@ -604,7 +604,7 @@ void sub_80B2EA8(void)
 {
     u32 taskId = FindTaskIdByFunc(sub_80B2EE4);
 
-    if (taskId == 0xFF)
+    if (taskId == INVALID_U8)
     {
         taskId = CreateTask(sub_80B2EE4, 80);
         gTasks[taskId].data[0] = 0;
@@ -702,7 +702,7 @@ void sub_80B3028(void)
 u8 sub_80B3050(void)
 {
     if (FuncIsActiveTask(sub_80B3144) != FALSE)
-        return 0xFF;
+        return INVALID_U8;
 
     switch (gSpecialVar_0x8004)
     {
diff --git a/src/contest.c b/src/contest.c
index 0c3a041b0..716ed5dfc 100644
--- a/src/contest.c
+++ b/src/contest.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "gpu_regs.h"
 #include "bg.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "constants/items.h"
 #include "constants/event_objects.h"
 #include "constants/moves.h"
@@ -324,7 +324,7 @@ void sub_80D787C(void)
     *gContestResources->field_0 = (struct Contest){};
     for (i = 0; i < 4; i++)
     {
-        gContestResources->field_0->unk19206[i] = 0xFF;
+        gContestResources->field_0->unk19206[i] = INVALID_U8;
     }
     for (i = 0; i < 4; i++)
     {
@@ -344,7 +344,7 @@ void sub_80D787C(void)
         sub_80DCE58(0);
     for (i = 0; i < 4; i++)
     {
-        gContestResources->field_4[i].nextTurnOrder = 0xFF;
+        gContestResources->field_4[i].nextTurnOrder = INVALID_U8;
         gContestResources->field_0->unk19218[i] = gUnknown_02039F26[i];
     }
     sub_80DD590();
@@ -2097,7 +2097,7 @@ void sub_80DAB8C(u8 contestType, u8 rank)
                 opponents[opponentsCount++] = i;
         }
     }
-    opponents[opponentsCount] = 0xFF;
+    opponents[opponentsCount] = INVALID_U8;
 
     // Choose three random opponents from the list
     for (i = 0; i < 3; i++)
@@ -2106,7 +2106,7 @@ void sub_80DAB8C(u8 contestType, u8 rank)
         s32 j;
 
         gContestMons[i] = gContestOpponents[opponents[rnd]];
-        for (j = rnd; opponents[j] != 0xFF; j++)
+        for (j = rnd; opponents[j] != INVALID_U8; j++)
             opponents[j] = opponents[j + 1];
         opponentsCount--;
     }
@@ -2151,7 +2151,7 @@ void sub_80DACBC(u8 contestType, u8 rank, bool32 isPostgame)
         else if (contestType == CONTEST_CATEGORY_TOUGH && gContestOpponents[i].aiPool_Tough)
             opponents[opponentsCount++] = i;
     }
-    opponents[opponentsCount] = 0xFF;
+    opponents[opponentsCount] = INVALID_U8;
     for (i = 0; i < 4 - gUnknown_02039F30; i++)
     {
         u16 rnd = sub_80F903C() % opponentsCount;
@@ -2160,7 +2160,7 @@ void sub_80DACBC(u8 contestType, u8 rank, bool32 isPostgame)
         gContestMons[gUnknown_02039F30 + i] = gContestOpponents[opponents[rnd]];
         sub_80DF9D4(gContestMons[gUnknown_02039F30 + i].trainerName);
         sub_80DF9E0(gContestMons[gUnknown_02039F30 + i].nickname, GAME_LANGUAGE);
-        for (j = rnd; opponents[j] != 0xFF; j++)
+        for (j = rnd; opponents[j] != INVALID_U8; j++)
             opponents[j] = opponents[j + 1];
         opponentsCount--;
     }
@@ -2591,7 +2591,7 @@ void prints_contest_move_description(u16 a)
     ContestBG_FillBoxWithIncrementingTile(0, categoryTile,        0x0b, 0x1f, 0x05, 0x01, 0x11, 0x01);
     ContestBG_FillBoxWithIncrementingTile(0, categoryTile + 0x10, 0x0b, 0x20, 0x05, 0x01, 0x11, 0x01);
 
-    if (gContestEffects[gContestMoves[a].effect].appeal == 0xFF)
+    if (gContestEffects[gContestMoves[a].effect].appeal == INVALID_U8)
         numHearts = 0;
     else
         numHearts = gContestEffects[gContestMoves[a].effect].appeal / 10;
@@ -2600,7 +2600,7 @@ void prints_contest_move_description(u16 a)
     ContestBG_FillBoxWithTile(0, 0x5035, 0x15, 0x1f, 0x08,      0x01, 0x11);
     ContestBG_FillBoxWithTile(0, 0x5012, 0x15, 0x1f, numHearts, 0x01, 0x11);
 
-    if (gContestEffects[gContestMoves[a].effect].jam == 0xFF)
+    if (gContestEffects[gContestMoves[a].effect].jam == INVALID_U8)
         numHearts = 0;
     else
         numHearts = gContestEffects[gContestMoves[a].effect].jam / 10;
diff --git a/src/contest_effect.c b/src/contest_effect.c
index 760d74d69..6f1c19fe2 100644
--- a/src/contest_effect.c
+++ b/src/contest_effect.c
@@ -144,7 +144,7 @@ static void ContestEffect_StartleFrontMon(void)
                 break;
         }
         shared192D0.jamQueue[0] = i;
-        shared192D0.jamQueue[1] = 0xFF;
+        shared192D0.jamQueue[1] = INVALID_U8;
         idx = WasAtLeastOneOpponentJammed();
     }
     if (idx == 0)
@@ -168,7 +168,7 @@ static void ContestEffect_StartlePrevMons(void)
                 shared192D0.jamQueue[j++] = i;
         }
 
-        shared192D0.jamQueue[j] = 0xFF;
+        shared192D0.jamQueue[j] = INVALID_U8;
         idx = WasAtLeastOneOpponentJammed();
     }
     if (idx == 0)
@@ -211,7 +211,7 @@ static void ContestEffect_StartlePrevMons2(void)
                 u8 rval, jam;
 
                 shared192D0.jamQueue[0] = i;
-                shared192D0.jamQueue[1] = 0xFF;
+                shared192D0.jamQueue[1] = INVALID_U8;
                 rval = Random() % 10;
 
                 if (rval == 0)
@@ -288,7 +288,7 @@ static void ContestEffect_StartleMonWithJudgesAttention(void)
                 else
                     shared192D0.jam = 10;
                 shared192D0.jamQueue[0] = i;
-                shared192D0.jamQueue[1] = 0xFF;
+                shared192D0.jamQueue[1] = INVALID_U8;
                 if (WasAtLeastOneOpponentJammed())
                     numStartled++;
             }
@@ -393,7 +393,7 @@ static void ContestEffect_MakeFollowingMonsNervous(void)
     s16 oddsMod[4];
     s16 odds[4];
 
-    memset(contestantIds, 0xFF, ARRAY_COUNT(contestantIds));
+    memset(contestantIds, INVALID_U8, ARRAY_COUNT(contestantIds));
     for (i = 0, numAfter = 0; i < 4; i++)
     {
         if (shared192D0.turnOrder[shared192D0.contestant] < shared192D0.turnOrder[i] &&
@@ -431,7 +431,7 @@ static void ContestEffect_MakeFollowingMonsNervous(void)
     }
     if (odds[0] != 0)
     {
-        for (i = 0; contestantIds[i] != 0xFF; i++)
+        for (i = 0; contestantIds[i] != INVALID_U8; i++)
         {
             if (Random() % 100 < odds[i] + oddsMod[contestantIds[i]])
             {
@@ -504,7 +504,7 @@ static void ContestEffect_BadlyStartlesMonsInGoodCondition(void)
             else
                 shared192D0.jam = 10;
             shared192D0.jamQueue[0] = i;
-            shared192D0.jamQueue[1] = 0xFF;
+            shared192D0.jamQueue[1] = INVALID_U8;
             if (WasAtLeastOneOpponentJammed())
                 numHit++;
         }
@@ -755,7 +755,7 @@ static void ContestEffect_NextAppealEarlier(void)
         for (i = 0; i < 4; i++)
             turnOrder[i] = sContestantStatus[i].nextTurnOrder;
 
-        turnOrder[shared192D0.contestant] = 0xFF;
+        turnOrder[shared192D0.contestant] = INVALID_U8;
 
         for (i = 0; i < 4; i++)
         {
@@ -797,7 +797,7 @@ static void ContestEffect_NextAppealLater(void)
         for (i = 0; i < 4; i++)
             turnOrder[i] = sContestantStatus[i].nextTurnOrder;
 
-        turnOrder[shared192D0.contestant] = 0xFF;
+        turnOrder[shared192D0.contestant] = INVALID_U8;
 
         for (i = 3; i > -1; i--)
         {
@@ -855,12 +855,12 @@ static void ContestEffect_ScrambleNextTurnOrder(void)
 
             for (j = 0; j < 4; j++)
             {
-                if (unselectedContestants[j] != 0xFF)
+                if (unselectedContestants[j] != INVALID_U8)
                 {
                     if (rval == 0)
                     {
                         turnOrder[j] = i;
-                        unselectedContestants[j] = 0xFF;
+                        unselectedContestants[j] = INVALID_U8;
                         break;
                     }
                     else
@@ -906,7 +906,7 @@ static void ContestEffect_BadlyStartleMonsWithGoodAppeals(void)
             else
                 shared192D0.jam = 10;
             shared192D0.jamQueue[0] = i;
-            shared192D0.jamQueue[1] = 0xFF;
+            shared192D0.jamQueue[1] = INVALID_U8;
             if (WasAtLeastOneOpponentJammed())
                 numJammed++;
         }
@@ -974,7 +974,7 @@ static void JamByMoveCategory(u8 category)
             else
                 shared192D0.jam = 10;
             shared192D0.jamQueue[0] = i;
-            shared192D0.jamQueue[1] = 0xFF;
+            shared192D0.jamQueue[1] = INVALID_U8;
             if (WasAtLeastOneOpponentJammed())
                 numJammed++;
         }
@@ -1013,7 +1013,7 @@ static bool8 WasAtLeastOneOpponentJammed(void)
     s16 jamBuffer[4] = {0};
     int i;
 
-    for (i = 0; shared192D0.jamQueue[i] != 0xFF; i++)
+    for (i = 0; shared192D0.jamQueue[i] != INVALID_U8; i++)
     {
         u8 contestant = shared192D0.jamQueue[i];
         if (CanUnnerveContestant(contestant))
diff --git a/src/credits.c b/src/credits.c
index df17ec70b..02b01c072 100644
--- a/src/credits.c
+++ b/src/credits.c
@@ -3,7 +3,7 @@
 #include "main.h"
 #include "task.h"
 #include "bg.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "window.h"
 #include "text.h"
 #include "menu.h"
diff --git a/src/data2b.c b/src/data2b.c
index 022903375..bb1baa266 100644
--- a/src/data2b.c
+++ b/src/data2b.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "data2.h"
 #include "graphics.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "constants/species.h"
 
 const u16 gUnknown_082FF1D8[] = INCBIN_U16("graphics/link/minigame_digits.gbapal");
diff --git a/src/daycare.c b/src/daycare.c
index 2356b36f5..227451f48 100644
--- a/src/daycare.c
+++ b/src/daycare.c
@@ -251,7 +251,7 @@ static void ApplyDaycareExperience(struct Pokemon *mon)
             while ((learnedMove = MonTryLearningNewMove(mon, firstMove)) != 0)
             {
                 firstMove = FALSE;
-                if (learnedMove == 0xFFFF)
+                if (learnedMove == INVALID_U16)
                 {
                     // Mon already knows 4 moves.
                     DeleteFirstMoveAndGiveMoveToMon(mon, gMoveToLearn);
@@ -535,7 +535,7 @@ static void RemoveIVIndexFromList(u8 *ivs, u8 selectedIv)
     s32 i, j;
     u8 temp[NUM_STATS];
 
-    ivs[selectedIv] = 0xff;
+    ivs[selectedIv] = INVALID_U8;
     for (i = 0; i < NUM_STATS; i++)
     {
         temp[i] = ivs[i];
@@ -544,7 +544,7 @@ static void RemoveIVIndexFromList(u8 *ivs, u8 selectedIv)
     j = 0;
     for (i = 0; i < NUM_STATS; i++)
     {
-        if (temp[i] != 0xff)
+        if (temp[i] != INVALID_U8)
             ivs[j++] = temp[i];
     }
 }
@@ -684,7 +684,7 @@ static void BuildEggMoveset(struct Pokemon *egg, struct BoxPokemon *father, stru
             {
                 if (sHatchedEggFatherMoves[i] == sHatchedEggEggMoves[j])
                 {
-                    if (GiveMoveToMon(egg, sHatchedEggFatherMoves[i]) == 0xffff)
+                    if (GiveMoveToMon(egg, sHatchedEggFatherMoves[i]) == INVALID_U16)
                         DeleteFirstMoveAndGiveMoveToMon(egg, sHatchedEggFatherMoves[i]);
                     break;
                 }
@@ -703,7 +703,7 @@ static void BuildEggMoveset(struct Pokemon *egg, struct BoxPokemon *father, stru
             {
                 if (sHatchedEggFatherMoves[i] == ItemIdToBattleMoveId(ITEM_TM01_FOCUS_PUNCH + j) && CanMonLearnTMHM(egg, j))
                 {
-                    if (GiveMoveToMon(egg, sHatchedEggFatherMoves[i]) == 0xffff)
+                    if (GiveMoveToMon(egg, sHatchedEggFatherMoves[i]) == INVALID_U16)
                         DeleteFirstMoveAndGiveMoveToMon(egg, sHatchedEggFatherMoves[i]);
                 }
             }
@@ -728,7 +728,7 @@ static void BuildEggMoveset(struct Pokemon *egg, struct BoxPokemon *father, stru
         {
             if (sHatchedEggLevelUpMoves[j] != MOVE_NONE && sHatchedEggFinalMoves[i] == sHatchedEggLevelUpMoves[j])
             {
-                if (GiveMoveToMon(egg, sHatchedEggFinalMoves[i]) == 0xffff)
+                if (GiveMoveToMon(egg, sHatchedEggFinalMoves[i]) == INVALID_U16)
                     DeleteFirstMoveAndGiveMoveToMon(egg, sHatchedEggFinalMoves[i]);
                 break;
             }
@@ -773,7 +773,7 @@ static void GiveVoltTackleIfLightBall(struct Pokemon *mon, struct DayCare *dayca
 
     if (motherItem == ITEM_LIGHT_BALL || fatherItem == ITEM_LIGHT_BALL)
     {
-        if (GiveMoveToMon(mon, MOVE_VOLT_TACKLE) == 0xFFFF)
+        if (GiveMoveToMon(mon, MOVE_VOLT_TACKLE) == INVALID_U16)
             DeleteFirstMoveAndGiveMoveToMon(mon, MOVE_VOLT_TACKLE);
     }
 }
@@ -909,7 +909,7 @@ static bool8 _DoEggActions_CheckHatch(struct DayCare *daycare)
     }
 
     // try to trigger poke sex
-    if (daycare->offspringPersonality == 0 && validEggs == 2 && (daycare->mons[1].steps & 0xFF) == 0xFF)
+    if (daycare->offspringPersonality == 0 && validEggs == 2 && (daycare->mons[1].steps & 0xFF) == INVALID_U8)
     {
         u8 loveScore = GetDaycareCompatibilityScore(daycare);
         if (loveScore > (Random() * 100u) / USHRT_MAX)
diff --git a/src/decompress.c b/src/decompress.c
index da1df436b..287a03e55 100644
--- a/src/decompress.c
+++ b/src/decompress.c
@@ -2,7 +2,7 @@
 #include "decompress.h"
 #include "constants/species.h"
 #include "text.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "pokemon.h"
 
 EWRAM_DATA ALIGNED(4) u8 gDecompressionBuffer[0x4000] = {0};
diff --git a/src/decoration.c b/src/decoration.c
index eb85b4f5c..11fd59286 100644
--- a/src/decoration.c
+++ b/src/decoration.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "constants/decorations.h"
 #include "decompress.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "text.h"
 #include "string_util.h"
 #include "international_string_util.h"
@@ -312,7 +312,7 @@ const struct SpriteFrameImage sDecorSelectorSpriteFrameImages = {
 };
 
 const struct SpriteTemplate sDecorSelectorSpriteTemplate = {
-    0xffff,
+    INVALID_U16,
     OVERWORLD_PLACE_DECOR_SELECTOR_PAL_TAG,
     &sDecorSelectorOam,
     sDecorSelectorAnims,
@@ -409,7 +409,7 @@ const struct SpriteFrameImage Unknown_085A73FC = {
 };
 
 const struct SpriteTemplate gUnknown_085A7404 = {
-    0xFFFF,
+    INVALID_U16,
     OVERWORLD_PLACE_DECOR_PLAYER_PAL_TAG,
     &Unknown_085A73E8,
     Unknown_085A73F8,
@@ -881,7 +881,7 @@ void sub_81274A0(u8 a0, s32 a1, u8 a2)
 
 void sub_8127500(void)
 {
-    if (sDecorPCBuffer->unk_522 == 0xFF)
+    if (sDecorPCBuffer->unk_522 == INVALID_U8)
     {
         sDecorPCBuffer->unk_522 = AddScrollIndicatorArrowPairParameterized(SCROLL_ARROW_UP, 0x3c, 0x0c, 0x94, sDecorPCBuffer->unk_520 - sDecorPCBuffer->unk_521, 0x6e, 0x6e, &sSecretBasePCSelectDecorPageNo);
     }
@@ -889,10 +889,10 @@ void sub_8127500(void)
 
 void sub_8127554(void)
 {
-    if (sDecorPCBuffer->unk_522 != 0xFF)
+    if (sDecorPCBuffer->unk_522 != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(sDecorPCBuffer->unk_522);
-        sDecorPCBuffer->unk_522 = 0xFF;
+        sDecorPCBuffer->unk_522 = INVALID_U8;
     }
 }
 
@@ -910,7 +910,7 @@ void sub_812759C(u8 taskId)
     sub_81269D4(3);
     sub_8127718(sCurDecorationCategory);
     sDecorPCBuffer = calloc(1, sizeof(struct DecorPCBuffer));
-    sDecorPCBuffer->unk_522 = 0xFF;
+    sDecorPCBuffer->unk_522 = INVALID_U8;
     sub_8127284();
     sub_81272C8();
     sub_81272F8();
@@ -1188,7 +1188,7 @@ void sub_8127B90(u16 mapX, u16 mapY, u8 decWidth, u8 decHeight, u16 decor)
                 v0 = 0;
             }
             v1 = sub_8127B54(gDecorations[decor].id, i * decWidth + j);
-            if (v1 != 0xFFFF)
+            if (v1 != INVALID_U16)
             {
                 MapGridSetMetatileEntryAt(decLeft, decBottom, (gDecorations[decor].tiles[i * decWidth + j] + (0x200 | v0)) | flags | v1);
             }
diff --git a/src/dewford_trend.c b/src/dewford_trend.c
index 3050ebecf..cad5ef9c2 100644
--- a/src/dewford_trend.c
+++ b/src/dewford_trend.c
@@ -3,7 +3,7 @@
 #include "easy_chat.h"
 #include "event_data.h"
 #include "link.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "random.h"
 #include "text.h"
 #include "tv.h"
diff --git a/src/diploma.c b/src/diploma.c
index f8556eb7d..b3d5a48fa 100644
--- a/src/diploma.c
+++ b/src/diploma.c
@@ -5,7 +5,7 @@
 #include "gpu_regs.h"
 #include "scanline_effect.h"
 #include "task.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "decompress.h"
 #include "bg.h"
 #include "window.h"
diff --git a/src/easy_chat.c b/src/easy_chat.c
index e4233fb7f..25ef069e4 100644
--- a/src/easy_chat.c
+++ b/src/easy_chat.c
@@ -1,7 +1,7 @@
 
 // Includes
 #include "global.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "constants/songs.h"
 #include "sound.h"
 #include "overworld.h"
diff --git a/src/egg_hatch.c b/src/egg_hatch.c
index 4b7ee9a61..77296c707 100644
--- a/src/egg_hatch.c
+++ b/src/egg_hatch.c
@@ -17,7 +17,7 @@
 #include "menu.h"
 #include "trig.h"
 #include "random.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "dma3.h"
 #include "gpu_regs.h"
 #include "bg.h"
diff --git a/src/event_object_movement.c b/src/event_object_movement.c
index e509c7738..0606364cd 100644
--- a/src/event_object_movement.c
+++ b/src/event_object_movement.c
@@ -9,7 +9,7 @@
 #include "field_effect_helpers.h"
 #include "field_player_avatar.h"
 #include "fieldmap.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "mauville_old_man.h"
 #include "metatile_behavior.h"
 #include "overworld.h"
@@ -129,7 +129,7 @@ static void UpdateEventObjectSpriteSubpriorityAndVisibility(struct Sprite *);
 
 const u8 gReflectionEffectPaletteMap[] = {1, 1, 6, 7, 8, 9, 6, 7, 8, 9, 11, 11, 0, 0, 0, 0};
 
-const struct SpriteTemplate gCameraSpriteTemplate = {0, 0xFFFF, &gDummyOamData, gDummySpriteAnimTable, NULL, gDummySpriteAffineAnimTable, ObjectCB_CameraObject};
+const struct SpriteTemplate gCameraSpriteTemplate = {0, INVALID_U16, &gDummyOamData, gDummySpriteAnimTable, NULL, gDummySpriteAffineAnimTable, ObjectCB_CameraObject};
 
 void (*const gCameraObjectFuncs[])(struct Sprite *) = {
     CameraObject_0,
@@ -1093,10 +1093,10 @@ const u8 gUnknown_0850DC3F[][4] = {
 static void ClearEventObject(struct EventObject *eventObject)
 {
     *eventObject = (struct EventObject){};
-    eventObject->localId = 0xFF;
-    eventObject->mapNum = 0xFF;
-    eventObject->mapGroup = 0xFF;
-    eventObject->movementActionId = 0xFF;
+    eventObject->localId = INVALID_U8;
+    eventObject->mapNum = INVALID_U8;
+    eventObject->mapGroup = INVALID_U8;
+    eventObject->movementActionId = INVALID_U8;
 }
 
 static void ClearAllEventObjects(void)
@@ -1537,7 +1537,7 @@ static u8 TrySetupEventObjectSprite(struct EventObjectTemplate *eventObjectTempl
     {
         eventObject->invisible = TRUE;
     }
-    *(u16 *)&spriteTemplate->paletteTag = 0xFFFF;
+    *(u16 *)&spriteTemplate->paletteTag = INVALID_U16;
     spriteId = CreateSprite(spriteTemplate, 0, 0, 0);
     if (spriteId == MAX_SPRITES)
     {
@@ -1666,7 +1666,7 @@ u8 AddPseudoEventObject(u16 graphicsId, void (*callback)(struct Sprite *), s16 x
 
     spriteTemplate = malloc(sizeof(struct SpriteTemplate));
     MakeObjectTemplateFromEventObjectGraphicsInfo(graphicsId, callback, spriteTemplate, &subspriteTables);
-    if (spriteTemplate->paletteTag != 0xFFFF)
+    if (spriteTemplate->paletteTag != INVALID_U16)
     {
         LoadEventObjectPalette(spriteTemplate->paletteTag);
     }
@@ -1692,7 +1692,7 @@ u8 sprite_new(u8 graphicsId, u8 a1, s16 x, s16 y, u8 z, u8 direction)
 
     graphicsInfo = GetEventObjectGraphicsInfo(graphicsId);
     MakeObjectTemplateFromEventObjectGraphicsInfo(graphicsId, UpdateEventObjectSpriteSubpriorityAndVisibility, &spriteTemplate, &subspriteTables);
-    *(u16 *)&spriteTemplate.paletteTag = 0xFFFF;
+    *(u16 *)&spriteTemplate.paletteTag = INVALID_U16;
     x += 7;
     y += 7;
     sub_80930E0(&x, &y, 8, 16);
@@ -1849,7 +1849,7 @@ static void sub_808E1B8(u8 eventObjectId, s16 x, s16 y)
     spriteFrameImage.size = graphicsInfo->size;
     MakeObjectTemplateFromEventObjectGraphicsInfoWithCallbackIndex(eventObject->graphicsId, eventObject->movementType, &spriteTemplate, &subspriteTables);
     spriteTemplate.images = &spriteFrameImage;
-    *(u16 *)&spriteTemplate.paletteTag = 0xFFFF;
+    *(u16 *)&spriteTemplate.paletteTag = INVALID_U16;
     paletteSlot = graphicsInfo->paletteSlot;
     if (paletteSlot == 0)
     {
@@ -1864,7 +1864,7 @@ static void sub_808E1B8(u8 eventObjectId, s16 x, s16 y)
         paletteSlot -= 16;
         sub_808EAB0(graphicsInfo->paletteTag1, paletteSlot);
     }
-    *(u16 *)&spriteTemplate.paletteTag = 0xFFFF;
+    *(u16 *)&spriteTemplate.paletteTag = INVALID_U16;
     spriteId = CreateSprite(&spriteTemplate, 0, 0, 0);
     if (spriteId != MAX_SPRITES)
     {
@@ -2146,9 +2146,9 @@ void Unused_LoadEventObjectPaletteSet(u16 *paletteTags)
 
 static u8 sub_808E8F4(const struct SpritePalette *spritePalette)
 {
-    if (IndexOfSpritePaletteTag(spritePalette->tag) != 0xFF)
+    if (IndexOfSpritePaletteTag(spritePalette->tag) != INVALID_U8)
     {
-        return 0xFF;
+        return INVALID_U8;
     }
     return LoadSpritePalette(spritePalette);
 }
@@ -2181,7 +2181,7 @@ static u8 FindEventObjectPaletteIndexByTag(u16 tag)
             return i;
         }
     }
-    return 0xFF;
+    return INVALID_U8;
 }
 
 void LoadPlayerObjectReflectionPalette(u16 tag, u8 slot)
@@ -2513,7 +2513,7 @@ u8 sub_808F080(u8 localId, u8 mapNum, u8 mapGroup)
 
     if (TryGetEventObjectIdByLocalIdAndMap(localId, mapNum, mapGroup, &eventObjectId))
     {
-        return 0xFF;
+        return INVALID_U8;
     }
     return gEventObjects[eventObjectId].trainerType;
 }
@@ -2529,7 +2529,7 @@ u8 sub_808F0D4(u8 localId, u8 mapNum, u8 mapGroup)
 
     if (TryGetEventObjectIdByLocalIdAndMap(localId, mapNum, mapGroup, &eventObjectId))
     {
-        return 0xFF;
+        return INVALID_U8;
     }
     return gEventObjects[eventObjectId].trainerRange_berryTreeId;
 }
@@ -4374,7 +4374,7 @@ bool8 MovementType_CopyPlayer_Step0(struct EventObject *eventObject, struct Spri
 
 bool8 MovementType_CopyPlayer_Step1(struct EventObject *eventObject, struct Sprite *sprite)
 {
-    if (gEventObjects[gPlayerAvatar.eventObjectId].movementActionId == 0xFF || gPlayerAvatar.tileTransitionState == T_TILE_CENTER)
+    if (gEventObjects[gPlayerAvatar.eventObjectId].movementActionId == INVALID_U8 || gPlayerAvatar.tileTransitionState == T_TILE_CENTER)
     {
         return FALSE;
     }
@@ -4553,7 +4553,7 @@ movement_type_def(MovementType_CopyPlayerInGrass, gMovementTypeFuncs_CopyPlayerI
 
 bool8 MovementType_CopyPlayerInGrass_Step1(struct EventObject *eventObject, struct Sprite *sprite)
 {
-    if (gEventObjects[gPlayerAvatar.eventObjectId].movementActionId == 0xFF || gPlayerAvatar.tileTransitionState == T_TILE_CENTER)
+    if (gEventObjects[gPlayerAvatar.eventObjectId].movementActionId == INVALID_U8 || gPlayerAvatar.tileTransitionState == T_TILE_CENTER)
     {
         return FALSE;
     }
@@ -4699,7 +4699,7 @@ static void ClearEventObjectMovement(struct EventObject *eventObject, struct Spr
     eventObject->singleMovementActive = 0;
     eventObject->heldMovementActive = FALSE;
     eventObject->heldMovementFinished = FALSE;
-    eventObject->movementActionId = 0xFF;
+    eventObject->movementActionId = INVALID_U8;
     sprite->data[1] = 0;
 }
 
@@ -5105,7 +5105,7 @@ bool8 EventObjectIsMovementOverridden(struct EventObject *eventObject)
 
 bool8 EventObjectIsHeldMovementActive(struct EventObject *eventObject)
 {
-    if (eventObject->heldMovementActive && eventObject->movementActionId != 0xFF)
+    if (eventObject->heldMovementActive && eventObject->movementActionId != INVALID_U8)
         return TRUE;
 
     return FALSE;
@@ -5138,7 +5138,7 @@ void EventObjectClearHeldMovementIfActive(struct EventObject *eventObject)
 
 void EventObjectClearHeldMovement(struct EventObject *eventObject)
 {
-    eventObject->movementActionId = 0xFF;
+    eventObject->movementActionId = INVALID_U8;
     eventObject->heldMovementActive = FALSE;
     eventObject->heldMovementFinished = FALSE;
     gSprites[eventObject->spriteId].data[1] = 0;
@@ -5167,7 +5167,7 @@ u8 EventObjectGetHeldMovementActionId(struct EventObject *eventObject)
     if (eventObject->heldMovementActive)
         return eventObject->movementActionId;
 
-    return 0xFF;
+    return INVALID_U8;
 }
 
 void UpdateEventObjectCurrentMovement(struct EventObject *eventObject, struct Sprite *sprite, bool8 (*callback)(struct EventObject *, struct Sprite *))
@@ -5279,7 +5279,7 @@ static bool8 EventObjectExecSingleMovementAction(struct EventObject *eventObject
 {
     if (gMovementActionFuncs[eventObject->movementActionId][sprite->data[2]](eventObject, sprite))
     {
-        eventObject->movementActionId = 0xFF;
+        eventObject->movementActionId = INVALID_U8;
         sprite->data[2] = 0;
         return TRUE;
     }
@@ -5706,7 +5706,7 @@ u8 sub_80940C4(struct EventObject *eventObject, struct Sprite *sprite, u8 callba
         eventObject->triggerGroundEffectsOnMove = TRUE;
         eventObject->disableCoveringGroundEffects = TRUE;
     }
-    else if (result == 0xFF)
+    else if (result == INVALID_U8)
     {
         ShiftStillEventObjectCoords(eventObject);
         eventObject->triggerGroundEffectsOnStop = TRUE;
@@ -5728,7 +5728,7 @@ u8 sub_809419C(struct EventObject *eventObject, struct Sprite *sprite)
 
 bool8 sub_80941B0(struct EventObject *eventObject, struct Sprite *sprite)
 {
-    if (sub_8094188(eventObject, sprite) == 0xFF)
+    if (sub_8094188(eventObject, sprite) == INVALID_U8)
     {
         return TRUE;
     }
@@ -5737,7 +5737,7 @@ bool8 sub_80941B0(struct EventObject *eventObject, struct Sprite *sprite)
 
 bool8 sub_80941C8(struct EventObject *eventObject, struct Sprite *sprite)
 {
-    if (sub_809419C(eventObject, sprite) == 0xFF)
+    if (sub_809419C(eventObject, sprite) == INVALID_U8)
     {
         return TRUE;
     }
@@ -9122,7 +9122,7 @@ void CreateLevitateMovementTask(struct EventObject *eventObject)
 
     StoreWordInTwoHalfwords(&task->data[0], (u32)eventObject);
     eventObject->warpArrowSpriteId = taskId;
-    task->data[3] = 0xFFFF;
+    task->data[3] = INVALID_U16;
 }
 
 static void ApplyLevitateMovement(u8 taskId)
diff --git a/src/evolution_scene.c b/src/evolution_scene.c
index 0d2072a15..25d85a855 100644
--- a/src/evolution_scene.c
+++ b/src/evolution_scene.c
@@ -2,7 +2,7 @@
 #include "evolution_scene.h"
 #include "evolution_graphics.h"
 #include "sprite.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "task.h"
 #include "palette.h"
 #include "main.h"
@@ -748,7 +748,7 @@ static void Task_EvolutionScene(u8 taskID)
                 GetMonData(mon, MON_DATA_NICKNAME, text);
                 StringCopy10(gBattleTextBuff1, text);
 
-                if (var == 0xFFFF) // no place to learn it
+                if (var == INVALID_U16) // no place to learn it
                     gTasks[taskID].tState = 22;
                 else if (var == 0xFFFE) // it already knows that move
                     break;
@@ -1105,7 +1105,7 @@ static void Task_TradeEvolutionScene(u8 taskID)
                 GetMonData(mon, MON_DATA_NICKNAME, text);
                 StringCopy10(gBattleTextBuff1, text);
 
-                if (var == 0xFFFF)
+                if (var == INVALID_U16)
                     gTasks[taskID].tState = 20;
                 else if (var == 0xFFFE)
                     break;
diff --git a/src/field_control_avatar.c b/src/field_control_avatar.c
index c52f5190f..1dce3169e 100644
--- a/src/field_control_avatar.c
+++ b/src/field_control_avatar.c
@@ -266,7 +266,7 @@ const u8 *GetInteractedLinkPlayerScript(struct MapPosition *position, u8 metatil
     else
         eventObjectId = GetEventObjectIdByXYZ(position->x + gDirectionToVectors[direction].x, position->y + gDirectionToVectors[direction].y, position->height);
 
-    if (eventObjectId == 16 || gEventObjects[eventObjectId].localId == 0xFF)
+    if (eventObjectId == 16 || gEventObjects[eventObjectId].localId == INVALID_U8)
         return NULL;
 
     for (i = 0; i < 4; i++)
@@ -287,14 +287,14 @@ static const u8 *GetInteractedEventObjectScript(struct MapPosition *position, u8
     const u8 *script;
 
     eventObjectId = GetEventObjectIdByXYZ(position->x, position->y, position->height);
-    if (eventObjectId == 16 || gEventObjects[eventObjectId].localId == 0xFF)
+    if (eventObjectId == 16 || gEventObjects[eventObjectId].localId == INVALID_U8)
     {
         if (MetatileBehavior_IsCounter(metatileBehavior) != TRUE)
             return NULL;
 
         // Look for an event object on the other side of the counter.
         eventObjectId = GetEventObjectIdByXYZ(position->x + gDirectionToVectors[direction].x, position->y + gDirectionToVectors[direction].y, position->height);
-        if (eventObjectId == 16 || gEventObjects[eventObjectId].localId == 0xFF)
+        if (eventObjectId == 16 || gEventObjects[eventObjectId].localId == INVALID_U8)
             return NULL;
     }
 
diff --git a/src/field_door.c b/src/field_door.c
index c197aca14..a1fe5bb97 100644
--- a/src/field_door.c
+++ b/src/field_door.c
@@ -695,7 +695,7 @@ static void DrawClosedDoorTiles(const struct DoorGraphics *gfx, u32 x, u32 y)
 
 static void DrawDoor(const struct DoorGraphics *gfx, const struct DoorAnimFrame *frame, u32 x, u32 y)
 {
-    if (frame->offset == 0xFFFF)
+    if (frame->offset == INVALID_U16)
     {
         DrawClosedDoorTiles(gfx, x, y);
         if (sub_808A964())
diff --git a/src/field_effect.c b/src/field_effect.c
index 935501130..91d61ef2f 100644
--- a/src/field_effect.c
+++ b/src/field_effect.c
@@ -305,7 +305,7 @@ const union AnimCmd *const gNewGameBirchImageAnimTable[] = {
 };
 
 const struct SpriteTemplate gNewGameBirchObjectTemplate = {
-    .tileTag = 0xffff,
+    .tileTag = INVALID_U16,
     .paletteTag = 4102,
     .oam = &gNewGameBirchOamAttributes,
     .anims = gNewGameBirchImageAnimTable,
@@ -383,7 +383,7 @@ const union AnimCmd *const gSpriteAnimTable_855C300[] = {
 };
 
 const struct SpriteTemplate gSpriteTemplate_855C304 = {
-    .tileTag = 0xffff,
+    .tileTag = INVALID_U16,
     .paletteTag = 4103,
     .oam = &gOamData_855C218,
     .anims = gSpriteAnimTable_855C2F8,
@@ -393,7 +393,7 @@ const struct SpriteTemplate gSpriteTemplate_855C304 = {
 };
 
 const struct SpriteTemplate gSpriteTemplate_855C31C = {
-    .tileTag = 0xffff,
+    .tileTag = INVALID_U16,
     .paletteTag = 4100,
     .oam = &gOamData_855C220,
     .anims = gSpriteAnimTable_855C2F8,
@@ -403,7 +403,7 @@ const struct SpriteTemplate gSpriteTemplate_855C31C = {
 };
 
 const struct SpriteTemplate gSpriteTemplate_855C334 = {
-    .tileTag = 0xffff,
+    .tileTag = INVALID_U16,
     .paletteTag = 4112,
     .oam = &gOamData_855C220,
     .anims = gSpriteAnimTable_855C300,
@@ -413,7 +413,7 @@ const struct SpriteTemplate gSpriteTemplate_855C334 = {
 };
 
 const struct SpriteTemplate gSpriteTemplate_855C34C = {
-    .tileTag = 0xffff,
+    .tileTag = INVALID_U16,
     .paletteTag = 4112,
     .oam = &gOamData_855C26C,
     .anims = gSpriteAnimTable_855C300,
@@ -618,7 +618,7 @@ u32 FieldEffectScript_ReadWord(u8 **script)
 void FieldEffectScript_LoadTiles(u8 **script)
 {
     struct SpriteSheet *sheet = (struct SpriteSheet *)FieldEffectScript_ReadWord(script);
-    if (GetSpriteTileStartByTag(sheet->tag) == 0xFFFF)
+    if (GetSpriteTileStartByTag(sheet->tag) == INVALID_U16)
         LoadSpriteSheet(sheet);
     (*script) += 4;
 }
@@ -665,7 +665,7 @@ void FieldEffectFreeTilesIfUnused(u16 tileStart)
     u8 i;
     u16 tag = GetSpriteTileTagByTileStart(tileStart);
 
-    if (tag != 0xFFFF)
+    if (tag != INVALID_U16)
     {
         for (i = 0; i < MAX_SPRITES; i++)
             if (gSprites[i].inUse && gSprites[i].usingSheet && tileStart == gSprites[i].sheetTileStart)
@@ -679,7 +679,7 @@ void FieldEffectFreePaletteIfUnused(u8 paletteNum)
     u8 i;
     u16 tag = GetSpritePaletteTagByPaletteNum(paletteNum);
 
-    if (tag != 0xFFFF)
+    if (tag != INVALID_U16)
     {
         for (i = 0; i < MAX_SPRITES; i++)
             if (gSprites[i].inUse && gSprites[i].oam.paletteNum == paletteNum)
@@ -761,7 +761,7 @@ u8 CreateMonSprite_PicBox(u16 species, s16 x, s16 y, u8 subpriority)
 {
     s32 spriteId = CreateMonPicSprite_HandleDeoxys(species, 0, 0x8000, 1, x, y, 0, gMonPaletteTable[species].tag);
     PreservePaletteInWeather(IndexOfSpritePaletteTag(gMonPaletteTable[species].tag) + 0x10);
-    if (spriteId == 0xFFFF)
+    if (spriteId == INVALID_U16)
         return MAX_SPRITES;
     else
         return spriteId;
@@ -772,7 +772,7 @@ u8 CreateMonSprite_FieldMove(u16 species, u32 d, u32 g, s16 x, s16 y, u8 subprio
     const struct CompressedSpritePalette *spritePalette = GetMonSpritePalStructFromOtIdPersonality(species, d, g);
     u16 spriteId = CreateMonPicSprite_HandleDeoxys(species, d, g, 1, x, y, 0, spritePalette->tag);
     PreservePaletteInWeather(IndexOfSpritePaletteTag(spritePalette->tag) + 0x10);
-    if (spriteId == 0xFFFF)
+    if (spriteId == INVALID_U16)
         return MAX_SPRITES;
     else
         return spriteId;
@@ -3591,7 +3591,7 @@ const union AnimCmd *const gSpriteAnimTable_855C5DC[] = {
 };
 
 const struct SpriteTemplate gUnknown_0855C5EC = {
-    .tileTag = 0xffff,
+    .tileTag = INVALID_U16,
     .paletteTag = 4378,
     .oam = &gOamData_855C218,
     .anims = gSpriteAnimTable_855C5DC,
diff --git a/src/field_message_box.c b/src/field_message_box.c
index 46da9e9e5..0725ca8c7 100755
--- a/src/field_message_box.c
+++ b/src/field_message_box.c
@@ -53,7 +53,7 @@ void task_add_textbox(void)
 void task_del_textbox(void)
 {
     u8 taskId = FindTaskIdByFunc(sub_8098154);
-    if (taskId != 0xFF)
+    if (taskId != INVALID_U8)
         DestroyTask(taskId);
 }
 
diff --git a/src/field_player_avatar.c b/src/field_player_avatar.c
index a5aa23e32..7da89fe83 100644
--- a/src/field_player_avatar.c
+++ b/src/field_player_avatar.c
@@ -1389,7 +1389,7 @@ void InitPlayerAvatar(s16 x, s16 y, u8 direction, u8 gender)
     u8 eventObjectId;
     struct EventObject *eventObject;
 
-    playerEventObjTemplate.localId = 0xFF;
+    playerEventObjTemplate.localId = INVALID_U8;
     playerEventObjTemplate.graphicsId = GetPlayerAvatarGraphicsIdByStateIdAndGender(PLAYER_AVATAR_STATE_NORMAL, gender);
     playerEventObjTemplate.x = x - 7;
     playerEventObjTemplate.y = y - 7;
diff --git a/src/field_region_map.c b/src/field_region_map.c
index 40f48e668..d49ce3a4e 100644
--- a/src/field_region_map.c
+++ b/src/field_region_map.c
@@ -3,7 +3,7 @@
 #include "gpu_regs.h"
 #include "international_string_util.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "palette.h"
 #include "region_map.h"
diff --git a/src/field_specials.c b/src/field_specials.c
index 4da751b27..629f2d0de 100644
--- a/src/field_specials.c
+++ b/src/field_specials.c
@@ -20,7 +20,7 @@
 #include "link.h"
 #include "list_menu.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "match_call.h"
 #include "menu.h"
 #include "overworld.h"
@@ -1957,12 +1957,12 @@ void sub_8139D98(void)
 
 bool32 warp0_in_pokecenter(void)
 {
-    static const u16 gUnknown_085B2C2A[] = { 0x0202, 0x0301, 0x0405, 0x0504, 0x0604, 0x0700, 0x0804, 0x090b, 0x0a05, 0x0b05, 0x0c02, 0x0d06, 0x0e03, 0x0f02, 0x100c, 0x100a, 0x1a35, 0x193c, 0xffff };
+    static const u16 gUnknown_085B2C2A[] = { 0x0202, 0x0301, 0x0405, 0x0504, 0x0604, 0x0700, 0x0804, 0x090b, 0x0a05, 0x0b05, 0x0c02, 0x0d06, 0x0e03, 0x0f02, 0x100c, 0x100a, 0x1a35, 0x193c, INVALID_U16 };
 
     int i;
     u16 map = (gLastUsedWarp.mapGroup << 8) + gLastUsedWarp.mapNum;
 
-    for (i = 0; gUnknown_085B2C2A[i] != 0xFFFF; i++)
+    for (i = 0; gUnknown_085B2C2A[i] != INVALID_U16; i++)
     {
         if (gUnknown_085B2C2A[i] == map)
             return TRUE;
@@ -2946,10 +2946,10 @@ void sub_813AA44(void)
 
 static void sub_813AA60(u16 a0, u16 a1)
 {
-    static const u16 gUnknown_085B312C[] = { 0x004b, 0x0067, 0x0057, 0x004f, 0x0054, 0x0055, 0x0056, 0x0050, 0x0051, 0x0052, 0xffff };
-    static const u16 gUnknown_085B3142[] = { 0x0071, 0x006f, 0x0072, 0x0073, 0x0074, 0xffff };
-    static const u16 gUnknown_085B314E[] = { 0x0040, 0x0043, 0x0041, 0x0046, 0x0042, 0x003f, 0xffff };
-    static const u16 gUnknown_085B315C[] = { 0x00c8, 0x00b4, 0x00b7, 0x00b9, 0x00b3, 0x00ba, 0x00bb, 0x00c4, 0x00c6, 0xffff };
+    static const u16 gUnknown_085B312C[] = { 0x004b, 0x0067, 0x0057, 0x004f, 0x0054, 0x0055, 0x0056, 0x0050, 0x0051, 0x0052, INVALID_U16 };
+    static const u16 gUnknown_085B3142[] = { 0x0071, 0x006f, 0x0072, 0x0073, 0x0074, INVALID_U16 };
+    static const u16 gUnknown_085B314E[] = { 0x0040, 0x0043, 0x0041, 0x0046, 0x0042, 0x003f, INVALID_U16 };
+    static const u16 gUnknown_085B315C[] = { 0x00c8, 0x00b4, 0x00b7, 0x00b9, 0x00b3, 0x00ba, 0x00bb, 0x00c4, 0x00c6, INVALID_U16 };
 
     static const u8 *const gUnknown_085B3170[] = {
         BattleFrontier_BattlePointExchangeServiceCorner_Text_2601AA,
@@ -3004,7 +3004,7 @@ static void sub_813AA60(u16 a0, u16 a1)
         {
             case 3:
                 AddTextPrinterParameterized2(0, 1, gUnknown_085B3170[a1], 0, NULL, 2, 1, 3);
-                if (gUnknown_085B312C[a1] == 0xFFFF)
+                if (gUnknown_085B312C[a1] == INVALID_U16)
                 {
                     sub_813ABD4(gUnknown_085B312C[a1]);
                 }
@@ -3017,7 +3017,7 @@ static void sub_813AA60(u16 a0, u16 a1)
                 break;
             case 4:
                 AddTextPrinterParameterized2(0, 1, gUnknown_085B319C[a1], 0, NULL, 2, 1, 3);
-                if (gUnknown_085B3142[a1] == 0xFFFF)
+                if (gUnknown_085B3142[a1] == INVALID_U16)
                 {
                     sub_813ABD4(gUnknown_085B3142[a1]);
                 }
@@ -3841,13 +3841,13 @@ bool32 sub_813B9C0(void)
         MAP_TRADE_CENTER,
         MAP_RECORD_CORNER,
         MAP_DOUBLE_BATTLE_COLOSSEUM,
-        0xffff
+        INVALID_U16
     };
 
     int i;
     u16 map = (gSaveBlock1Ptr->location.mapGroup << 8) + gSaveBlock1Ptr->location.mapNum;
 
-    for (i = 0; gUnknown_085B3444[i] != 0xFFFF; i++)
+    for (i = 0; gUnknown_085B3444[i] != INVALID_U16; i++)
     {
         if (gUnknown_085B3444[i] == map)
         {
diff --git a/src/fieldmap.c b/src/fieldmap.c
index 0d8a706b1..aef17d49d 100644
--- a/src/fieldmap.c
+++ b/src/fieldmap.c
@@ -496,7 +496,7 @@ u16 GetBehaviorByMetatileId(u16 metatile)
     }
     else
     {
-        return 0xff;
+        return INVALID_U8;
     }
 }
 
@@ -922,7 +922,7 @@ void sub_8088B94(int x, int y, int a2)
 
 bool8 sub_8088BF0(u16* a0, u16 a1, u8 a2)
 {
-    if (a2 == 0xFF)
+    if (a2 == INVALID_U8)
         return FALSE;
 
     if (a2 == 0)
diff --git a/src/fldeff_cut.c b/src/fldeff_cut.c
index 230a95e0b..2cffd5d41 100644
--- a/src/fldeff_cut.c
+++ b/src/fldeff_cut.c
@@ -6,7 +6,7 @@
 #include "field_player_avatar.h"
 #include "fieldmap.h"
 #include "fldeff_cut.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "metatile_behavior.h"
 #include "overworld.h"
 #include "party_menu.h"
@@ -164,7 +164,7 @@ const struct SpritePalette gFieldEffectObjectPaletteInfo6 = {gFieldEffectObjectP
 
 static const struct SpriteTemplate sSpriteTemplate_CutGrass =
 {
-    .tileTag = 0xFFFF,
+    .tileTag = INVALID_U16,
     .paletteTag = 0x1000,
     .oam = &sOamData_CutGrass,
     .anims = sSpriteAnimTable_CutGrass,
diff --git a/src/fldeff_groundshake.c b/src/fldeff_groundshake.c
index e9a46bb86..3bbc489c1 100644
--- a/src/fldeff_groundshake.c
+++ b/src/fldeff_groundshake.c
@@ -2,7 +2,7 @@
 #include "event_data.h"
 #include "event_object_movement.h"
 #include "field_camera.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "random.h"
 #include "roulette_util.h"
 #include "script.h"
@@ -236,7 +236,7 @@ static void sub_81BE968(void)
     u8 taskId;
 
     taskId = FindTaskIdByFunc(sub_81BE9C0);
-    if(taskId != 0xFF)
+    if(taskId != INVALID_U8)
         gTasks[taskId].data[0]++;
 }
 
diff --git a/src/fossil_specials.c b/src/fossil_specials.c
index 8164a3a78..8f6e38e91 100644
--- a/src/fossil_specials.c
+++ b/src/fossil_specials.c
@@ -8,7 +8,7 @@
 #include "fieldmap.h"
 #include "global.fieldmap.h"
 #include "gpu_regs.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "random.h"
 #include "script.h"
@@ -302,7 +302,7 @@ static void sub_81BED50(u8 taskId)
     case 4:
         UnsetBgTilemapBuffer(0);
         anotherTaskId = FindTaskIdByFunc(sub_81BEBB4);
-        if (anotherTaskId != 0xFF)
+        if (anotherTaskId != INVALID_U8)
             DestroyTask(anotherTaskId);
         sUnknown_0203CF14[1] = sUnknown_0203CF14[0] = 0;
         sub_81BEB90();
diff --git a/src/frontier_util.c b/src/frontier_util.c
index 5af7b3db7..e799f96c8 100644
--- a/src/frontier_util.c
+++ b/src/frontier_util.c
@@ -24,7 +24,7 @@
 #include "data2.h"
 #include "record_mixing.h"
 #include "strings.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "save.h"
 #include "load_save.h"
 #include "battle_dome.h"
@@ -681,7 +681,7 @@ static const u8 sFacilityToBrainEventObjGfx[][2] =
 const u16 gFrontierBannedSpecies[] =
 {
     SPECIES_MEW, SPECIES_MEWTWO, SPECIES_HO_OH, SPECIES_LUGIA, SPECIES_CELEBI,
-    SPECIES_KYOGRE, SPECIES_GROUDON, SPECIES_RAYQUAZA, SPECIES_JIRACHI, SPECIES_DEOXYS, 0xFFFF
+    SPECIES_KYOGRE, SPECIES_GROUDON, SPECIES_RAYQUAZA, SPECIES_JIRACHI, SPECIES_DEOXYS, INVALID_U16
 };
 
 static const u8 *const gUnknown_08611CB0[][2] =
@@ -1829,7 +1829,7 @@ void sub_81A3ACC(void)
     s32 i;
 
     for (i = 0; i < 20; i++)
-        gSaveBlock2Ptr->frontier.field_CB4[i] |= 0xFFFF;
+        gSaveBlock2Ptr->frontier.field_CB4[i] |= INVALID_U16;
 }
 
 static void sub_81A3B00(void)
@@ -1974,10 +1974,10 @@ static void AppendIfValid(u16 species, u16 heldItem, u16 hp, u8 lvlMode, u8 monL
     if (species == SPECIES_EGG || species == SPECIES_NONE)
         return;
 
-    for (i = 0; gFrontierBannedSpecies[i] != 0xFFFF && gFrontierBannedSpecies[i] != species; i++)
+    for (i = 0; gFrontierBannedSpecies[i] != INVALID_U16 && gFrontierBannedSpecies[i] != species; i++)
         ;
 
-    if (gFrontierBannedSpecies[i] != 0xFFFF)
+    if (gFrontierBannedSpecies[i] != INVALID_U16)
         return;
     if (lvlMode == FRONTIER_LVL_50 && monLevel > 50)
         return;
@@ -2060,7 +2060,7 @@ static void sub_81A3FD4(void)
         s32 i;
         s32 caughtBannedMons = 0;
         s32 species = gFrontierBannedSpecies[0];
-        for (i = 0; species != 0xFFFF; i++, species = gFrontierBannedSpecies[i])
+        for (i = 0; species != INVALID_U16; i++, species = gFrontierBannedSpecies[i])
         {
             if (GetSetPokedexFlag(SpeciesToNationalPokedexNum(species), FLAG_GET_CAUGHT))
                 caughtBannedMons++;
@@ -2068,7 +2068,7 @@ static void sub_81A3FD4(void)
         gStringVar1[0] = EOS;
         gSpecialVar_0x8004 = 1;
         count = 0;
-        for (i = 0; gFrontierBannedSpecies[i] != 0xFFFF; i++)
+        for (i = 0; gFrontierBannedSpecies[i] != INVALID_U16; i++)
             count = sub_81A3DD0(gFrontierBannedSpecies[i], count, caughtBannedMons);
 
         if (count == 0)
diff --git a/src/ground.c b/src/ground.c
index 6cb7b8557..abfeb3f3e 100644
--- a/src/ground.c
+++ b/src/ground.c
@@ -588,7 +588,7 @@ void sub_81152DC(u8 taskId)
         break;
     default:
         task->data[9] = GetAnimBattlerSpriteId(gBattleAnimArgs[0]);
-        if (task->data[9] == 0xFF)
+        if (task->data[9] == INVALID_U8)
         {
             DestroyAnimVisualTask(taskId);
         }
diff --git a/src/hall_of_fame.c b/src/hall_of_fame.c
index 315990256..b75243b84 100644
--- a/src/hall_of_fame.c
+++ b/src/hall_of_fame.c
@@ -6,7 +6,7 @@
 #include "pokemon.h"
 #include "text.h"
 #include "text_window.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "gpu_regs.h"
 #include "graphics.h"
 #include "main.h"
@@ -467,11 +467,11 @@ static void Task_Hof_InitMonData(u8 taskId)
 
     sUnknown_0203BCD4 = 0;
     gTasks[taskId].tDisplayedMonId = 0;
-    gTasks[taskId].tPlayerSpriteID = 0xFF;
+    gTasks[taskId].tPlayerSpriteID = INVALID_U8;
 
     for (i = 0; i < PARTY_SIZE; i++)
     {
-        gTasks[taskId].tMonSpriteId(i) = 0xFF;
+        gTasks[taskId].tMonSpriteId(i) = INVALID_U8;
     }
 
     if (gTasks[taskId].tDontSaveData)
@@ -522,7 +522,7 @@ static void Task_Hof_InitTeamSaveData(u8 taskId)
 static void Task_Hof_TrySaveData(u8 taskId)
 {
     gGameContinueCallback = CB2_DoHallOfFameScreenDontSaveData;
-    if (TrySavingData(SAVE_HALL_OF_FAME) == 0xFF && gDamagedSaveSectors != 0)
+    if (TrySavingData(SAVE_HALL_OF_FAME) == INVALID_U8 && gDamagedSaveSectors != 0)
     {
         UnsetBgTilemapBuffer(1);
         UnsetBgTilemapBuffer(3);
@@ -645,7 +645,7 @@ static void Task_Hof_PaletteFadeAndPrintWelcomeText(u8 taskId)
     BeginNormalPaletteFade(0xFFFF0000, 0, 0, 0, RGB_BLACK);
     for (i = 0; i < PARTY_SIZE; i++)
     {
-        if (gTasks[taskId].tMonSpriteId(i) != 0xFF)
+        if (gTasks[taskId].tMonSpriteId(i) != INVALID_U8)
             gSprites[gTasks[taskId].tMonSpriteId(i)].oam.priority = 0;
     }
 
@@ -668,7 +668,7 @@ static void sub_8173DC0(u8 taskId)
         u16 i;
         for (i = 0; i < PARTY_SIZE; i++)
         {
-            if (gTasks[taskId].tMonSpriteId(i) != 0xFF)
+            if (gTasks[taskId].tMonSpriteId(i) != INVALID_U8)
                 gSprites[gTasks[taskId].tMonSpriteId(i)].oam.priority = 1;
         }
         BeginNormalPaletteFade(sUnknown_0203BCD4, 0, 12, 12, RGB(16, 29, 24));
@@ -752,7 +752,7 @@ static void Task_Hof_HandleExit(u8 taskId)
         for (i = 0; i < PARTY_SIZE; i++)
         {
             u8 spriteId = gTasks[taskId].tMonSpriteId(i);
-            if (spriteId != 0xFF)
+            if (spriteId != INVALID_U8)
             {
                 FreeOamMatrix(gSprites[spriteId].oam.matrixNum);
                 FreeAndDestroyMonPicSprite(spriteId);
@@ -847,7 +847,7 @@ void CB2_DoHallOfFamePC(void)
 
             for (i = 0; i < PARTY_SIZE; i++)
             {
-                gTasks[taskId].tMonSpriteId(i) = 0xFF;
+                gTasks[taskId].tMonSpriteId(i) = INVALID_U8;
             }
 
             sHofMonPtr = AllocZeroed(0x2000);
@@ -937,7 +937,7 @@ static void Task_HofPC_DrawSpritesPrintText(u8 taskId)
         }
         else
         {
-            gTasks[taskId].tMonSpriteId(i) = 0xFF;
+            gTasks[taskId].tMonSpriteId(i) = INVALID_U8;
         }
     }
 
@@ -967,7 +967,7 @@ static void Task_HofPC_PrintMonInfo(u8 taskId)
     for (i = 0; i < PARTY_SIZE; i++)
     {
         u16 spriteId = gTasks[taskId].tMonSpriteId(i);
-        if (spriteId != 0xFF)
+        if (spriteId != INVALID_U8)
             gSprites[spriteId].oam.priority = 1;
     }
 
@@ -999,10 +999,10 @@ static void Task_HofPC_HandleInput(u8 taskId)
             for (i = 0; i < 6; i++)
             {
                 u8 spriteId = gTasks[taskId].tMonSpriteId(i);
-                if (spriteId != 0xFF)
+                if (spriteId != INVALID_U8)
                 {
                     FreeAndDestroyMonPicSprite(spriteId);
-                    gTasks[taskId].tMonSpriteId(i) = 0xFF;
+                    gTasks[taskId].tMonSpriteId(i) = INVALID_U8;
                 }
             }
             if (gTasks[taskId].tCurrPageNo != 0)
@@ -1060,10 +1060,10 @@ static void Task_HofPC_HandleExit(u8 taskId)
         for (i = 0; i < PARTY_SIZE; i++)
         {
             u16 spriteId = gTasks[taskId].tMonSpriteId(i);
-            if (spriteId != 0xFF)
+            if (spriteId != INVALID_U8)
             {
                 FreeAndDestroyMonPicSprite(spriteId);
-                gTasks[taskId].tMonSpriteId(i) = 0xFF;
+                gTasks[taskId].tMonSpriteId(i) = INVALID_U8;
             }
         }
 
@@ -1130,7 +1130,7 @@ static void HallOfFame_PrintMonInfo(struct HallofFameMon* currMon, u8 unused1, u
     {
         stringPtr = StringCopy(text, gText_Number);
         dexNumber = SpeciesToPokedexNum(currMon->species);
-        if (dexNumber != 0xFFFF)
+        if (dexNumber != INVALID_U16)
         {
             stringPtr[0] = (dexNumber / 100) + CHAR_0;
             stringPtr++;
@@ -1417,7 +1417,7 @@ void sub_8175280(void)
 
     gSpecialVar_0x8004 = 180;
     taskId = CreateTask(sub_8175364, 0);
-    if (taskId != 0xFF)
+    if (taskId != INVALID_U8)
     {
         gTasks[taskId].data[1] = gSpecialVar_0x8004;
         gSpecialVar_0x8005 = taskId;
@@ -1428,7 +1428,7 @@ static void sub_81752C0(void)
 {
     u8 taskId;
 
-    if ((taskId = FindTaskIdByFunc(sub_8175364)) != 0xFF)
+    if ((taskId = FindTaskIdByFunc(sub_8175364)) != INVALID_U8)
         DestroyTask(taskId);
 
     sub_8152254();
@@ -1473,7 +1473,7 @@ static void sub_8175364(u8 taskId)
         {
             DestroyTask(taskId);
             gSpecialVar_0x8004 = var;
-            gSpecialVar_0x8005 = 0xFFFF;
+            gSpecialVar_0x8005 = INVALID_U16;
         }
         LoadCompressedObjectPic(sHallOfFame_ConfettiSpriteSheet);
         LoadCompressedObjectPalette(sHallOfFame_ConfettiSpritePalette);
@@ -1483,7 +1483,7 @@ static void sub_8175364(u8 taskId)
         if (data[1] != 0 && data[1] % 3 == 0)
         {
             var = sub_81524C4(&sOamData_85E53FC, 0x3E9, 0x3E9, Random() % 240, -(Random() % 8), Random() % 0x11, var);
-            if (var != 0xFF)
+            if (var != INVALID_U8)
             {
                 sub_8152438(var, sub_81752F4);
                 if ((Random() & 3) == 0)
@@ -1496,12 +1496,12 @@ static void sub_8175364(u8 taskId)
         if (data[1] != 0)
             data[1]--;
         else if (data[15] == 0)
-            data[0] = 0xFF;
+            data[0] = INVALID_U8;
         break;
-    case 0xFF:
+    case INVALID_U8:
         sub_81752C0();
         gSpecialVar_0x8004 = var;
-        gSpecialVar_0x8005 = 0xFFFF;
+        gSpecialVar_0x8005 = INVALID_U16;
         break;
     }
 }
diff --git a/src/intro.c b/src/intro.c
index 5a0e13869..44d1c086d 100644
--- a/src/intro.c
+++ b/src/intro.c
@@ -5,7 +5,7 @@
 #include "task.h"
 #include "title_screen.h"
 #include "libgcnmultiboot.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "gpu_regs.h"
 #include "link.h"
 #include "multiboot_pokemon_colosseum.h"
diff --git a/src/intro_credits_graphics.c b/src/intro_credits_graphics.c
index 20a360901..1b4e9e15a 100644
--- a/src/intro_credits_graphics.c
+++ b/src/intro_credits_graphics.c
@@ -58,7 +58,7 @@ static void sub_817B7C4(struct Sprite *sprite);
 static void nullsub_66(struct Sprite *sprite);
 
 static const struct SpriteTemplate gUnknown_085F504C = {
-    2000, 0xFFFF, &gDummyOamData, gDummySpriteAnimTable, NULL, gDummySpriteAffineAnimTable, sub_817B62C
+    2000, INVALID_U16, &gDummyOamData, gDummySpriteAnimTable, NULL, gDummySpriteAffineAnimTable, sub_817B62C
 };
 
 static const struct CompressedSpriteSheet gUnknown_085F5064[] = {
diff --git a/src/item.c b/src/item.c
index 6d2dbd561..e2583ddb1 100644
--- a/src/item.c
+++ b/src/item.c
@@ -4,7 +4,7 @@
 #include "string_util.h"
 #include "text.h"
 #include "event_data.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "secret_base.h"
 #include "item_menu.h"
 #include "strings.h"
diff --git a/src/item_icon.c b/src/item_icon.c
index 41c6589f5..2af938ff8 100644
--- a/src/item_icon.c
+++ b/src/item_icon.c
@@ -2,7 +2,7 @@
 #include "decompress.h"
 #include "graphics.h"
 #include "item_icon.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "sprite.h"
 #include "constants/items.h"
 
@@ -161,7 +161,7 @@ u8 AddCustomItemIconSprite(struct SpriteTemplate *customSpriteTemplate, u16 tile
 
 const void *GetItemIconPicOrPalette(u16 itemId, u8 which)
 {
-    if (itemId == 0xFFFF)
+    if (itemId == INVALID_U16)
         itemId = ITEM_FIELD_ARROW;
     else if (itemId >= ITEMS_COUNT)
         itemId = 0;
diff --git a/src/item_menu.c b/src/item_menu.c
index 1744a1bfa..5b18b06ec 100755
--- a/src/item_menu.c
+++ b/src/item_menu.c
@@ -23,7 +23,7 @@
 #include "link.h"
 #include "mail.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "map_name_popup.h"
 #include "menu.h"
 #include "money.h"
@@ -532,11 +532,11 @@ void GoToBagMenu(u8 bagMenuType, u8 pocketId, void ( *postExitMenuMainCallback2)
         if (temp <= 1)
             gUnknown_0203CE54->unk81B = 1;
         gUnknown_0203CE54->unk0 = 0;
-        gUnknown_0203CE54->unk81A = 0xFF;
+        gUnknown_0203CE54->unk81A = INVALID_U8;
         gUnknown_0203CE54->unk81E = -1;
         gUnknown_0203CE54->unk81F = -1;
-        memset(gUnknown_0203CE54->unk804, 0xFF, sizeof(gUnknown_0203CE54->unk804));
-        memset(gUnknown_0203CE54->unk810, 0xFF, 10);
+        memset(gUnknown_0203CE54->unk804, INVALID_U8, sizeof(gUnknown_0203CE54->unk804));
+        memset(gUnknown_0203CE54->unk810, INVALID_U8, 10);
         SetMainCallback2(CB2_Bag);
     }
 }
@@ -819,7 +819,7 @@ void bag_menu_change_item_callback(s32 a, bool8 b, struct ListMenu *unused)
         PlaySE(SE_SELECT);
         ShakeBagVisual();
     }
-    if (gUnknown_0203CE54->unk81A == 0xFF)
+    if (gUnknown_0203CE54->unk81A == INVALID_U8)
     {
         RemoveBagItemIconSprite(1 ^ gUnknown_0203CE54->unk81B_1);
         if (a != -2)
@@ -840,7 +840,7 @@ void sub_81AB520(u8 rboxId, int item_index_in_pocket, u8 a)
     int offset;
     if (item_index_in_pocket != -2)
     {
-        if (gUnknown_0203CE54->unk81A != 0xFF)
+        if (gUnknown_0203CE54->unk81A != INVALID_U8)
         {
             if (gUnknown_0203CE54->unk81A == (u8)item_index_in_pocket)
                 bag_menu_print_cursor(a, 2);
@@ -897,7 +897,7 @@ void bag_menu_print_cursor_(u8 a, u8 b)
 
 void bag_menu_print_cursor(u8 a, u8 b)
 {
-    if (b == 0xFF)
+    if (b == INVALID_U8)
         FillWindowPixelRect(0, 0, 0, a, GetMenuCursorDimensionByFont(1, 0), GetMenuCursorDimensionByFont(1, 1));
     else
         bag_menu_print(0, 1, gText_SelectorArrow2, 0, a, 0, 0, 0, b);
@@ -906,32 +906,32 @@ void bag_menu_print_cursor(u8 a, u8 b)
 
 void bag_menu_add_pocket_scroll_arrow_indicators_maybe(void)
 {
-    if (gUnknown_0203CE54->unk81E == 0xFF)
+    if (gUnknown_0203CE54->unk81E == INVALID_U8)
         gUnknown_0203CE54->unk81E = AddScrollIndicatorArrowPairParameterized(SCROLL_ARROW_UP, 0xAC, 12, 0x94, gUnknown_0203CE54->unk829[gUnknown_0203CE58.pocket] - gUnknown_0203CE54->unk82E[gUnknown_0203CE58.pocket], 0x6E, 0x6E, &gUnknown_0203CE58.scrollPosition[gUnknown_0203CE58.pocket]);
 }
 
 void sub_81AB824(void)
 {
-    if (gUnknown_0203CE54->unk81E != 0xFF)
+    if (gUnknown_0203CE54->unk81E != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(gUnknown_0203CE54->unk81E);
-        gUnknown_0203CE54->unk81E = 0xFF;
+        gUnknown_0203CE54->unk81E = INVALID_U8;
     }
     sub_81AB89C();
 }
 
 void bag_menu_add_list_scroll_arrow_indicators_maybe(void)
 {
-    if (gUnknown_0203CE54->unk81B != 1 && gUnknown_0203CE54->unk81F == 0xFF)
+    if (gUnknown_0203CE54->unk81B != 1 && gUnknown_0203CE54->unk81F == INVALID_U8)
         gUnknown_0203CE54->unk81F = AddScrollIndicatorArrowPair(&gUnknown_08614094, &gUnknown_0203CE58.unk6);
 }
 
 void sub_81AB89C(void)
 {
-    if (gUnknown_0203CE54->unk81F != 0xFF)
+    if (gUnknown_0203CE54->unk81F != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(gUnknown_0203CE54->unk81F);
-        gUnknown_0203CE54->unk81F = 0xFF;
+        gUnknown_0203CE54->unk81F = INVALID_U8;
     }
 }
 
@@ -2303,7 +2303,7 @@ u8 sub_81AE124(u8 a)
 u8 bag_menu_add_window(u8 a)
 {
     u8 *ptr = &gUnknown_0203CE54->unk810[a];
-    if (*ptr == 0xFF)
+    if (*ptr == INVALID_U8)
     {
         *ptr = AddWindow(&gUnknown_086141AC[a]);
         SetWindowBorderStyle(*ptr, 0, 1, 14);
@@ -2315,20 +2315,20 @@ u8 bag_menu_add_window(u8 a)
 void bag_menu_remove_window(u8 a)
 {
     u8 *ptr = &gUnknown_0203CE54->unk810[a];
-    if (*ptr != 0xFF)
+    if (*ptr != INVALID_U8)
     {
         sub_8198070(*ptr, 0);
         ClearWindowTilemap(*ptr);
         RemoveWindow(*ptr);
         schedule_bg_copy_tilemap_to_vram(1);
-        *ptr = 0xFF;
+        *ptr = INVALID_U8;
     }
 }
 
 u8 AddItemMessageWindow(u8 a)
 {
     u8 *ptr = &gUnknown_0203CE54->unk810[a];
-    if (*ptr == 0xFF)
+    if (*ptr == INVALID_U8)
         *ptr = AddWindow(&gUnknown_086141AC[a]);
     return *ptr;
 }
@@ -2336,13 +2336,13 @@ u8 AddItemMessageWindow(u8 a)
 void bag_menu_RemoveBagItem_message_window(u8 a)
 {
     u8 *ptr = &gUnknown_0203CE54->unk810[a];
-    if (*ptr != 0xFF)
+    if (*ptr != INVALID_U8)
     {
         sub_8197DF8(*ptr, 0);
         ClearWindowTilemap(*ptr);
         RemoveWindow(*ptr);
         schedule_bg_copy_tilemap_to_vram(1);
-        *ptr = 0xFF;
+        *ptr = INVALID_U8;
     }
 }
 
diff --git a/src/item_menu_icons.c b/src/item_menu_icons.c
index 85b42b9b3..67add5926 100644
--- a/src/item_menu_icons.c
+++ b/src/item_menu_icons.c
@@ -301,7 +301,7 @@ static const union AffineAnimCmd *const sSpriteAffineAnimTable_857FC74[] =
 
 static const struct SpriteTemplate gUnknown_0857FC7C =
 {
-    .tileTag = 0xFFFF,
+    .tileTag = INVALID_U16,
     .paletteTag = 0x7544,
     .oam = &sOamData_857FBD0,
     .anims = sSpriteAnimTable_857FBE0,
@@ -410,13 +410,13 @@ static const struct SpriteTemplate gUnknown_0857FE10 =
 void RemoveBagSprite(u8 id)
 {
     u8 *spriteId = &gUnknown_0203CE54->unk804[id];
-    if (*spriteId != 0xFF)
+    if (*spriteId != INVALID_U8)
     {
         FreeSpriteTilesByTag(id + 100);
         FreeSpritePaletteByTag(id + 100);
         FreeSpriteOamMatrix(&gSprites[*spriteId]);
         DestroySprite(&gSprites[*spriteId]);
-        *spriteId = 0xFF;
+        *spriteId = INVALID_U8;
     }
 }
 
@@ -516,7 +516,7 @@ static void SpriteCB_SwitchPocketRotatingBallContinue(struct Sprite *sprite)
 void AddBagItemIconSprite(u16 itemId, u8 id)
 {
     u8 *spriteId = &gUnknown_0203CE54->unk804[id + 2];
-    if (*spriteId == 0xFF)
+    if (*spriteId == INVALID_U8)
     {
         u8 iconSpriteId;
 
diff --git a/src/learn_move.c b/src/learn_move.c
index 7717a5193..cb8bb66ff 100644
--- a/src/learn_move.c
+++ b/src/learn_move.c
@@ -9,7 +9,7 @@
 #include "gpu_regs.h"
 #include "learn_move.h"
 #include "list_menu.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "menu_helpers.h"
 #include "overworld.h"
@@ -381,7 +381,7 @@ static void LearnMoveMain(void)
 
             if (selection == 0)
             {
-                if (GiveMoveToMon(&gPlayerParty[sLearnMoveStruct->partyMon], GetCurrentItemId()) != 0xFFFF)
+                if (GiveMoveToMon(&gPlayerParty[sLearnMoveStruct->partyMon], GetCurrentItemId()) != INVALID_U16)
                 {
                     sub_816084C(gText_PkmnLearnedMove4);
                     gSpecialVar_0x8004 = 1;
@@ -727,12 +727,12 @@ static void CreateHearts(void)
 
 static void AddScrollArrows(void)
 {
-    if (sLearnMoveStruct->scrollArrowTaskId2 == 0xFF)
+    if (sLearnMoveStruct->scrollArrowTaskId2 == INVALID_U8)
     {
         sLearnMoveStruct->scrollArrowTaskId2 = AddScrollIndicatorArrowPair(&gUnknown_085CEBC0, &sLearnMoveStruct->scrollOffset);
     }
 
-    if (sLearnMoveStruct->scrollArrowTaskId1 == 0xFF)
+    if (sLearnMoveStruct->scrollArrowTaskId1 == INVALID_U8)
     {
         gTempScrollArrowTemplate = gUnknown_085CEBD0;
         gTempScrollArrowTemplate.fullyDownThreshold = sLearnMoveStruct->numMenuChoices - sLearnMoveStruct->numToShowAtOnce;
@@ -742,16 +742,16 @@ static void AddScrollArrows(void)
 
 static void RemoveScrollArrows(void)
 {
-    if (sLearnMoveStruct->scrollArrowTaskId2 != 0xFF)
+    if (sLearnMoveStruct->scrollArrowTaskId2 != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(sLearnMoveStruct->scrollArrowTaskId2);
-        sLearnMoveStruct->scrollArrowTaskId2 = 0xFF;
+        sLearnMoveStruct->scrollArrowTaskId2 = INVALID_U8;
     }
 
-    if (sLearnMoveStruct->scrollArrowTaskId1 != 0xFF)
+    if (sLearnMoveStruct->scrollArrowTaskId1 != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(sLearnMoveStruct->scrollArrowTaskId1);
-        sLearnMoveStruct->scrollArrowTaskId1 = 0xFF;
+        sLearnMoveStruct->scrollArrowTaskId1 = INVALID_U8;
     }
 }
 
@@ -792,7 +792,7 @@ void ShowHideHearts(s32 item)
     {
         numHearts = (u8)(gContestEffects[gContestMoves[item].effect].appeal / 10);
         
-        if (numHearts == 0xFF)
+        if (numHearts == INVALID_U8)
         {
             numHearts = 0;
         }
@@ -812,7 +812,7 @@ void ShowHideHearts(s32 item)
 
         numHearts = (u8)(gContestEffects[gContestMoves[item].effect].jam / 10);
         
-        if (numHearts == 0xFF)
+        if (numHearts == INVALID_U8)
         {
             numHearts = 0;
         }
diff --git a/src/librfu_rfu.c b/src/librfu_rfu.c
index c5aa25c10..2f706fcc8 100644
--- a/src/librfu_rfu.c
+++ b/src/librfu_rfu.c
@@ -64,7 +64,7 @@
     v12 = (u16*)((u32)&sub_82E53F4 & ~1);
     v13 = (u16*)gUnknown_03007898->unk_8;
         
-    for (i = 47; i != 0xFFFF; i--)
+    for (i = 47; i != INVALID_U16; i--)
     {
         *v13 = *v12;
         ++v12;
diff --git a/src/librfu_stwi.c b/src/librfu_stwi.c
index 556b79bf8..81363ae0d 100644
--- a/src/librfu_stwi.c
+++ b/src/librfu_stwi.c
@@ -116,7 +116,7 @@ u16 STWI_read_status(u8 index)
     case 3:
         return gRfuState->activeCommand;
     default:
-        return 0xFFFF;
+        return INVALID_U16;
     }
 }
 
diff --git a/src/link.c b/src/link.c
index 687a6c07b..e4bd5053c 100644
--- a/src/link.c
+++ b/src/link.c
@@ -2,7 +2,7 @@
 // Includes
 #include "global.h"
 #include "m4a.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "reset_save_heap.h"
 #include "save.h"
 #include "bg.h"
@@ -2250,7 +2250,7 @@ static bool8 DoHandshake(void)
     u16 minRecv;
 
     playerCount = 0;
-    minRecv = 0xFFFF;
+    minRecv = INVALID_U16;
     if (gLink.handshakeAsMaster == TRUE)
     {
         REG_SIOMLT_SEND = MASTER_HANDSHAKE;
@@ -2274,7 +2274,7 @@ static bool8 DoHandshake(void)
         }
         else
         {
-            if (gLink.tempRecvBuffer[i] != 0xFFFF)
+            if (gLink.tempRecvBuffer[i] != INVALID_U16)
             {
                 playerCount = 0;
             }
diff --git a/src/link_rfu.c b/src/link_rfu.c
index 308ad615c..fe5676770 100644
--- a/src/link_rfu.c
+++ b/src/link_rfu.c
@@ -1,4 +1,5 @@
 #include "global.h"
+#include "alloc.h"
 #include "battle.h"
 #include "berry_blender.h"
 #include "decompress.h"
@@ -7,7 +8,6 @@
 #include "librfu.h"
 #include "link.h"
 #include "link_rfu.h"
-#include "malloc.h"
 #include "overworld.h"
 #include "random.h"
 #include "palette.h"
@@ -276,7 +276,7 @@ const struct {
     { gBlockSendBuffer,  40 }
 };
 const u16 gUnknown_082ED6E0[] = {
-    0x0002, 0x7f7d, 0x0000, 0xffff
+    0x0002, 0x7f7d, 0x0000, INVALID_U16
 };
 
 const char sUnref_082ED6E8[][15] = {
@@ -436,7 +436,7 @@ u8 sub_800C054(u8 r5, u16 r7, u16 r8, const u16 *r6)
     }
     for (i = 0, buffer = r6; i < 16; i++)
     {
-        if (*buffer++ == 0xFFFF)
+        if (*buffer++ == INVALID_U16)
         {
             break;
         }
@@ -754,7 +754,7 @@ void sub_800C54C(u32 a0)
                 switch (gUnknown_03004140.unk_04)
                 {
                     case 23:
-                        r2 = sub_800BEC0() == 0x8001 ? 0x44 : 0xFF;
+                        r2 = sub_800BEC0() == 0x8001 ? 0x44 : INVALID_U8;
                         gUnknown_03004140.unk_04 = gUnknown_03004140.unk_05 = 0;
                         sub_800D30C(r2, 0);
                         break;
@@ -1168,7 +1168,7 @@ static void sub_800C7B4(u16 r8, u16 r6)
                 gUnknown_03004140.unk_00 &= ~gUnknown_03004140.unk_14;
                 if (gUnknown_03004140.unk_07)
                 {
-                    if (gUnknown_03007890->unk_00 == 0xFF)
+                    if (gUnknown_03007890->unk_00 == INVALID_U8)
                     {
                         if (gUnknown_03004140.unk_07 == 8)
                         {
@@ -1183,7 +1183,7 @@ static void sub_800C7B4(u16 r8, u16 r6)
                         }
                     }
                 }
-                if (gUnknown_03007890->unk_00 == 0xFF)
+                if (gUnknown_03007890->unk_00 == INVALID_U8)
                 {
                     if (gUnknown_03004140.unk_04 == 0)
                     {
@@ -1198,7 +1198,7 @@ static void sub_800C7B4(u16 r8, u16 r6)
             break;
         case 38:
             sub_800D20C();
-            if (gUnknown_03007890->unk_00 != 0xFF)
+            if (gUnknown_03007890->unk_00 != INVALID_U8)
             {
                 sub_800D30C(0x50, 0x00);
             }
@@ -1241,7 +1241,7 @@ static void sub_800C7B4(u16 r8, u16 r6)
             sub_800D610();
         }
     }
-    if (r8 == 0xFF)
+    if (r8 == INVALID_U8)
     {
         sub_800D30C(0xf2, 0x00);
         sub_800D610();
@@ -1322,7 +1322,7 @@ static void sub_800CF34(void)
                     if (gUnknown_03007880[i]->unk_61 == 1)
                     {
                         r5 = 0x02;
-                        for (ptr = gUnknown_03004140.unk_20; *ptr != 0xFFFF; ptr++)
+                        for (ptr = gUnknown_03004140.unk_20; *ptr != INVALID_U16; ptr++)
                         {
                             if (gUnknown_03007890->unk_14[i].unk_04 == *ptr)
                             {
@@ -1469,7 +1469,7 @@ static u8 sub_800D294(void)
 
     for (i = 0; i < gUnknown_03007890->unk_08; i++)
     {
-        for (ptr = gUnknown_03004140.unk_20; *ptr != 0xffff; ptr++)
+        for (ptr = gUnknown_03004140.unk_20; *ptr != INVALID_U16; ptr++)
         {
             if (gUnknown_03007890->unk_14[i].unk_04 == *ptr)
             {
@@ -2242,12 +2242,12 @@ void sub_800E084(void)
 
 void sub_800E0E8(void)
 {
-    if (GetSpriteTileStartByTag(sWirelessStatusIndicatorSpriteSheet.tag) == 0xFFFF)
+    if (GetSpriteTileStartByTag(sWirelessStatusIndicatorSpriteSheet.tag) == INVALID_U16)
     {
         LoadCompressedObjectPic(&sWirelessStatusIndicatorSpriteSheet);
     }
     LoadSpritePalette(&sWirelessStatusIndicatorSpritePalette);
-    gWirelessStatusIndicatorSpriteId = 0xFF;
+    gWirelessStatusIndicatorSpriteId = INVALID_U8;
 }
 
 u8 sub_800E124(void)
@@ -2277,7 +2277,7 @@ void sub_800E15C(struct Sprite *sprite, s32 signalStrengthAnimNum)
 
 void sub_800E174(void)
 {
-    if (gWirelessStatusIndicatorSpriteId != 0xFF && gSprites[gWirelessStatusIndicatorSpriteId].data[7] == 0x1234)
+    if (gWirelessStatusIndicatorSpriteId != INVALID_U8 && gSprites[gWirelessStatusIndicatorSpriteId].data[7] == 0x1234)
     {
         struct Sprite *sprite = &gSprites[gWirelessStatusIndicatorSpriteId];
         u8 signalStrength = 255;
@@ -2461,7 +2461,7 @@ void sub_800E604(void)
     u8 unk_ee_bak = gUnknown_03005000.unk_ee;
     CpuFill16(0, &gUnknown_03005000, sizeof gUnknown_03005000);
     gUnknown_03005000.unk_ee = unk_ee_bak;
-    gUnknown_03005000.unk_0c = 0xFF;
+    gUnknown_03005000.unk_0c = INVALID_U8;
     if (gUnknown_03005000.unk_ee != 4)
     {
         gUnknown_03005000.unk_ee = 0;
@@ -3077,7 +3077,7 @@ bool32 sub_800F1E0(void)
                 {
                     if (gUnknown_03005000.unk_14[i][1])
                     {
-                        if (gUnknown_03005000.unk_cee[i] != 0xff && (gUnknown_03005000.unk_14[i][0] >> 5) != ((gUnknown_03005000.unk_cee[i] + 1) & 7))
+                        if (gUnknown_03005000.unk_cee[i] != INVALID_U8 && (gUnknown_03005000.unk_14[i][0] >> 5) != ((gUnknown_03005000.unk_cee[i] + 1) & 7))
                         {
                             if (++gUnknown_03005000.unk_cea[i] > 4)
                                 sub_8011170(0x8100);
@@ -3778,7 +3778,7 @@ bool32 sub_8010454(u32 a0)
     s32 i;
     for (i = 0; gUnknown_082ED6E0[i] != a0; i++)
     {
-        if (gUnknown_082ED6E0[i] == 0xffff)
+        if (gUnknown_082ED6E0[i] == INVALID_U16)
             return FALSE;
     }
     return TRUE;
@@ -3881,7 +3881,7 @@ bool32 sub_80105EC(void)
 bool32 sub_801064C(u16 a0, const u8 *a1)
 {
     u8 r1 = sub_8011CE4(a1, a0);
-    if (r1 == 0xFF)
+    if (r1 == INVALID_U8)
         return TRUE;
     if (gUnknown_03005000.unk_cd1[r1] == 9)
         return TRUE;
@@ -3906,7 +3906,7 @@ void sub_80106D4(void)
 u32 sub_8010714(u16 a0, const u8 *a1)
 {
     u8 r0 = sub_8011CE4(a1, a0);
-    if (r0 == 0xff)
+    if (r0 == INVALID_U8)
         return 2;
     if (gUnknown_03007880[r0]->unk_0 == 0)
         return 1;
diff --git a/src/list_menu.c b/src/list_menu.c
index 6907a75a3..e066d1e9c 100644
--- a/src/list_menu.c
+++ b/src/list_menu.c
@@ -8,7 +8,7 @@
 #include "trig.h"
 #include "decompress.h"
 #include "palette.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "strings.h"
 #include "sound.h"
 #include "constants/songs.h"
@@ -392,7 +392,7 @@ u8 ListMenuInitInRect(struct ListMenuTemplate *listMenuTemplate, struct ListMenu
     s32 i;
 
     u8 taskId = ListMenuInitInternal(listMenuTemplate, scrollOffset, selectedRow);
-    for (i = 0; rect[i].palNum != 0xFF; i++)
+    for (i = 0; rect[i].palNum != INVALID_U8; i++)
     {
         PutWindowRectTilemapOverridePalette(listMenuTemplate->windowId,
                                             rect[i].x,
@@ -465,7 +465,7 @@ s32 ListMenuHandleInputGetItemId(u8 listTaskId)
     }
 }
 
-#define TASK_NONE 0xFF
+#define TASK_NONE INVALID_U8
 
 void DestroyListMenuTask(u8 listTaskId, u16 *scrollOffset, u16 *selectedRow)
 {
@@ -1143,7 +1143,7 @@ static void Task_ScrollIndicatorArrowPair(u8 taskId)
     struct ScrollIndicatorPair *data = (void*) gTasks[taskId].data;
     u16 currItem = (*data->scrollOffset);
 
-    if (currItem == data->fullyUpThreshold && currItem != 0xFFFF)
+    if (currItem == data->fullyUpThreshold && currItem != INVALID_U16)
         gSprites[data->topSpriteId].invisible = TRUE;
     else
         gSprites[data->topSpriteId].invisible = FALSE;
diff --git a/src/load_save.c b/src/load_save.c
index 960a98981..8ecf89959 100644
--- a/src/load_save.c
+++ b/src/load_save.c
@@ -4,7 +4,7 @@
 #include "main.h"
 #include "pokemon.h"
 #include "random.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "item.h"
 #include "overworld.h"
 #include "decoration_inventory.h"
diff --git a/src/mail.c b/src/mail.c
index 513900746..7b096ed00 100644
--- a/src/mail.c
+++ b/src/mail.c
@@ -17,7 +17,7 @@
 #include "bg.h"
 #include "pokemon_icon.h"
 #include "constants/species.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "easy_chat.h"
 
 extern const u16 gMailPalette_Orange[];
diff --git a/src/mail_data.c b/src/mail_data.c
index 809dcc2a8..cf75636b3 100644
--- a/src/mail_data.c
+++ b/src/mail_data.c
@@ -20,7 +20,7 @@ void ClearMailStruct(struct MailStruct *mail)
     s32 i;
 
     for (i = 0; i < MAIL_WORDS_COUNT; i++)
-        mail->words[i] = 0xFFFF;
+        mail->words[i] = INVALID_U16;
 
     for (i = 0; i < PLAYER_NAME_LENGTH + 1; i++)
         mail->playerName[i] = EOS;
@@ -35,7 +35,7 @@ void ClearMailStruct(struct MailStruct *mail)
 bool8 MonHasMail(struct Pokemon *mon)
 {
     u16 heldItem = GetMonData(mon, MON_DATA_HELD_ITEM);
-    if (ItemIsMail(heldItem) && GetMonData(mon, MON_DATA_MAIL) != 0xFF)
+    if (ItemIsMail(heldItem) && GetMonData(mon, MON_DATA_MAIL) != INVALID_U8)
         return TRUE;
     else
         return FALSE;
@@ -56,7 +56,7 @@ u8 GiveMailToMon(struct Pokemon *mon, u16 itemId)
         if (gSaveBlock1Ptr->mail[id].itemId == 0)
         {
             for (i = 0; i < MAIL_WORDS_COUNT; i++)
-                gSaveBlock1Ptr->mail[id].words[i] = 0xFFFF;
+                gSaveBlock1Ptr->mail[id].words[i] = INVALID_U16;
 
             for (i = 0; i < PLAYER_NAME_LENGTH + 1 - 1; i++)
                 gSaveBlock1Ptr->mail[id].playerName[i] = gSaveBlock2Ptr->playerName[i];
@@ -76,7 +76,7 @@ u8 GiveMailToMon(struct Pokemon *mon, u16 itemId)
         }
     }
 
-    return 0xFF;
+    return INVALID_U8;
 }
 
 u16 SpeciesToMailSpecies(u16 species, u32 personality)
@@ -113,8 +113,8 @@ u8 GiveMailToMon2(struct Pokemon *mon, struct MailStruct *mail)
     u16 itemId = mail->itemId;
     u8 mailId = GiveMailToMon(mon, itemId);
 
-    if (mailId == 0xFF)
-        return 0xFF;
+    if (mailId == INVALID_U8)
+        return INVALID_U8;
 
     gSaveBlock1Ptr->mail[mailId] = *mail;
 
@@ -142,7 +142,7 @@ void TakeMailFromMon(struct Pokemon *mon)
     {
         mailId = GetMonData(mon, MON_DATA_MAIL);
         gSaveBlock1Ptr->mail[mailId].itemId = ITEM_NONE;
-        mailId = 0xFF;
+        mailId = INVALID_U8;
         heldItem[0] = ITEM_NONE;
         heldItem[1] = ITEM_NONE << 8;
         SetMonData(mon, MON_DATA_MAIL, &mailId);
@@ -163,7 +163,7 @@ u8 TakeMailFromMon2(struct Pokemon *mon)
 
     newHeldItem[0] = ITEM_NONE;
     newHeldItem[1] = ITEM_NONE << 8;
-    newMailId = 0xFF;
+    newMailId = INVALID_U8;
 
     for (i = PARTY_SIZE; i < MAIL_COUNT; i++)
     {
@@ -177,7 +177,7 @@ u8 TakeMailFromMon2(struct Pokemon *mon)
         }
     }
 
-    return 0xFF;
+    return INVALID_U8;
 }
 
 bool8 ItemIsMail(u16 itemId)
diff --git a/src/main.c b/src/main.c
index d069ab3bc..c4962286c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,6 +1,6 @@
 #include "global.h"
 #include "crt0.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "link.h"
 #include "link_rfu.h"
 #include "librfu.h"
diff --git a/src/malloc.c b/src/malloc.c
deleted file mode 100644
index 1d64351c3..000000000
--- a/src/malloc.c
+++ /dev/null
@@ -1,210 +0,0 @@
-#include "global.h"
-
-static void *sHeapStart;
-static u32 sHeapSize;
-static u32 malloc_c_unused_0300000c; // needed to align dma3_manager.o(.bss)
-
-#define MALLOC_SYSTEM_ID 0xA3A3
-
-struct MemBlock {
-	// Whether this block is currently allocated.
-	bool16 flag;
-
-	// Magic number used for error checking. Should equal MALLOC_SYSTEM_ID.
-	u16 magic;
-
-	// Size of the block (not including this header struct).
-	u32 size;
-
-	// Previous block pointer. Equals sHeapStart if this is the first block.
-	struct MemBlock *prev;
-
-	// Next block pointer. Equals sHeapStart if this is the last block.
-	struct MemBlock *next;
-
-	// Data in the memory block. (Arrays of length 0 are a GNU extension.)
-	u8 data[0];
-};
-
-void PutMemBlockHeader(void *block, struct MemBlock *prev, struct MemBlock *next, u32 size)
-{
-	struct MemBlock *header = (struct MemBlock *)block;
-
-	header->flag = FALSE;
-	header->magic = MALLOC_SYSTEM_ID;
-	header->size = size;
-	header->prev = prev;
-	header->next = next;
-}
-
-void PutFirstMemBlockHeader(void *block, u32 size)
-{
-	PutMemBlockHeader(block, (struct MemBlock *)block, (struct MemBlock *)block, size - sizeof(struct MemBlock));
-}
-
-void *AllocInternal(void *heapStart, u32 size)
-{
-	struct MemBlock *pos = (struct MemBlock *)heapStart;
-	struct MemBlock *head = pos;
-	struct MemBlock *splitBlock;
-	u32 foundBlockSize;
-
-    // Alignment
-	if (size & 3)
-		size = 4 * ((size / 4) + 1);
-
-	for (;;) {
-		// Loop through the blocks looking for unused block that's big enough.
-
-		if (!pos->flag) {
-			foundBlockSize = pos->size;
-
-			if (foundBlockSize >= size) {
-				if (foundBlockSize - size < 2 * sizeof(struct MemBlock)) {
-					// The block isn't much bigger than the requested size,
-					// so just use it.
-					pos->flag = TRUE;
-				} else {
-					// The block is significantly bigger than the requested
-					// size, so split the rest into a separate block.
-					foundBlockSize -= sizeof(struct MemBlock);
-					foundBlockSize -= size;
-
-					splitBlock = (struct MemBlock *)(pos->data + size);
-
-					pos->flag = TRUE;
-					pos->size = size;
-
-					PutMemBlockHeader(splitBlock, pos, pos->next, foundBlockSize);
-
-					pos->next = splitBlock;
-
-					if (splitBlock->next != head)
-						splitBlock->next->prev = splitBlock;
-				}
-
-				return pos->data;
-			}
-		}
-
-		if (pos->next == head)
-			return NULL;
-
-		pos = pos->next;
-	}
-}
-
-void FreeInternal(void *heapStart, void *pointer)
-{
-	if (pointer) {
-		struct MemBlock *head = (struct MemBlock *)heapStart;
-		struct MemBlock *block = (struct MemBlock *)((u8 *)pointer - sizeof(struct MemBlock));
-		block->flag = FALSE;
-
-		// If the freed block isn't the last one, merge with the next block
-		// if it's not in use.
-		if (block->next != head) {
-			if (!block->next->flag) {
-				block->size += sizeof(struct MemBlock) + block->next->size;
-				block->next->magic = 0;
-				block->next = block->next->next;
-				if (block->next != head)
-					block->next->prev = block;
-			}
-		}
-
-		// If the freed block isn't the first one, merge with the previous block
-		// if it's not in use.
-		if (block != head) {
-			if (!block->prev->flag) {
-				block->prev->next = block->next;
-
-				if (block->next != head)
-					block->next->prev = block->prev;
-
-				block->magic = 0;
-				block->prev->size += sizeof(struct MemBlock) + block->size;
-			}
-		}
-	}
-}
-
-void *AllocZeroedInternal(void *heapStart, u32 size)
-{
-	void *mem = AllocInternal(heapStart, size);
-
-	if (mem != NULL) {
-		if (size & 3)
-			size = 4 * ((size / 4) + 1);
-
-		CpuFill32(0, mem, size);
-	}
-
-	return mem;
-}
-
-bool32 CheckMemBlockInternal(void *heapStart, void *pointer)
-{
-	struct MemBlock *head = (struct MemBlock *)heapStart;
-	struct MemBlock *block = (struct MemBlock *)((u8 *)pointer - sizeof(struct MemBlock));
-
-	if (block->magic != MALLOC_SYSTEM_ID)
-		return FALSE;
-
-	if (block->next->magic != MALLOC_SYSTEM_ID)
-		return FALSE;
-
-	if (block->next != head && block->next->prev != block)
-		return FALSE;
-
-	if (block->prev->magic != MALLOC_SYSTEM_ID)
-		return FALSE;
-
-	if (block->prev != head && block->prev->next != block)
-		return FALSE;
-
-	if (block->next != head && block->next != (struct MemBlock *)(block->data + block->size))
-		return FALSE;
-
-	return TRUE;
-}
-
-void InitHeap(void *heapStart, u32 heapSize)
-{
-	sHeapStart = heapStart;
-	sHeapSize = heapSize;
-	PutFirstMemBlockHeader(heapStart, heapSize);
-}
-
-void *Alloc(u32 size)
-{
-	AllocInternal(sHeapStart, size);
-}
-
-void *AllocZeroed(u32 size)
-{
-	AllocZeroedInternal(sHeapStart, size);
-}
-
-void Free(void *pointer)
-{
-	FreeInternal(sHeapStart, pointer);
-}
-
-bool32 CheckMemBlock(void *pointer)
-{
-	return CheckMemBlockInternal(sHeapStart, pointer);
-}
-
-bool32 CheckHeap()
-{
-	struct MemBlock *pos = (struct MemBlock *)sHeapStart;
-
-	do {
-		if (!CheckMemBlockInternal(sHeapStart, pos->data))
-			return FALSE;
-		pos = pos->next;
-	} while (pos != (struct MemBlock *)sHeapStart);
-
-	return TRUE;
-}
diff --git a/src/mauville_old_man.c b/src/mauville_old_man.c
index 110ec068e..2fd60cd5b 100644
--- a/src/mauville_old_man.c
+++ b/src/mauville_old_man.c
@@ -250,7 +250,7 @@ void ScrSpecial_HipsterTeachWord(void)
 {
     u16 var = sub_811F01C();
 
-    if (var == 0xFFFF)
+    if (var == INVALID_U16)
     {
         gSpecialVar_Result = FALSE;
     }
@@ -283,7 +283,7 @@ void ScrSpecial_GenerateGiddyLine(void)
     if (giddy->taleCounter == 0)
         InitGiddyTaleList();
 
-    if (giddy->randomWords[giddy->taleCounter] != 0xFFFF) // is not the last element of the array?
+    if (giddy->randomWords[giddy->taleCounter] != INVALID_U16) // is not the last element of the array?
     {
         u8 *stringPtr;
         u32 adjective = Random();
@@ -348,7 +348,7 @@ static void InitGiddyTaleList(void)
         r1 = Random() % 10;
         if (r1 < 3 && r7 < 8)
         {
-            giddy->randomWords[i] = 0xFFFF;
+            giddy->randomWords[i] = INVALID_U16;
             r7++;
         }
         else
diff --git a/src/menu.c b/src/menu.c
index dde0e0a1a..e1dd136d1 100644
--- a/src/menu.c
+++ b/src/menu.c
@@ -7,7 +7,7 @@
 #include "main.h"
 #include "sound.h"
 #include "menu_helpers.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "task.h"
 #include "dma3.h"
 #include "string_util.h"
@@ -140,8 +140,8 @@ extern void task_free_buf_after_copying_tile_data_to_vram(u8 taskId);
 void sub_81971D0(void)
 {
     InitWindows(gUnknown_0860F098);
-    gStartMenuWindowId = 0xFF;
-    gUnknown_0203CD8D = 0xFF;
+    gStartMenuWindowId = INVALID_U8;
+    gUnknown_0203CD8D = INVALID_U8;
 }
 
 void sub_81971F4(void)
@@ -486,7 +486,7 @@ u8 GetPlayerTextSpeedDelay(void)
 
 u8 sub_81979C4(u8 a1)
 {
-    if (gStartMenuWindowId == 0xFF)
+    if (gStartMenuWindowId == INVALID_U8)
         gStartMenuWindowId = sub_8198AA4(0, 0x16, 1, 7, (a1 * 2) + 2, 0xF, 0x139);
     return gStartMenuWindowId;
 }
@@ -498,10 +498,10 @@ u8 GetStartMenuWindowId(void)
 
 void RemoveStartMenuWindow(void)
 {
-    if (gStartMenuWindowId != 0xFF)
+    if (gStartMenuWindowId != INVALID_U8)
     {
         RemoveWindow(gStartMenuWindowId);
-        gStartMenuWindowId = 0xFF;
+        gStartMenuWindowId = INVALID_U8;
     }
 }
 
@@ -517,7 +517,7 @@ u16 sub_8197A38(void)
 
 u8 AddMapNamePopUpWindow(void)
 {
-    if (gUnknown_0203CD8D == 0xFF)
+    if (gUnknown_0203CD8D == INVALID_U8)
         gUnknown_0203CD8D = sub_8198AA4(0, 1, 1, 10, 3, 14, 0x107);
     return gUnknown_0203CD8D;
 }
@@ -529,10 +529,10 @@ u8 GetMapNamePopUpWindowId(void)
 
 void RemoveMapNamePopUpWindow(void)
 {
-    if (gUnknown_0203CD8D != 0xFF)
+    if (gUnknown_0203CD8D != INVALID_U8)
     {
         RemoveWindow(gUnknown_0203CD8D);
-        gUnknown_0203CD8D = 0xFF;
+        gUnknown_0203CD8D = INVALID_U8;
     }
 }
 
@@ -808,7 +808,7 @@ void sub_8198180(const u8 *string, u8 a2, bool8 copyToVram)
 {
     u16 width = 0;
 
-    if (gUnknown_0203CDA0 != 0xFF)
+    if (gUnknown_0203CDA0 != INVALID_U8)
     {
         PutWindowTilemap(gUnknown_0203CDA0);
         FillWindowPixelBuffer(gUnknown_0203CDA0, 0xFF);
@@ -830,7 +830,7 @@ void sub_8198204(const u8 *string, const u8 *string2, u8 a3, u8 a4, bool8 copyTo
     u8 color[3];
     u16 width = 0;
 
-    if (gUnknown_0203CDA0 != 0xFF)
+    if (gUnknown_0203CDA0 != INVALID_U8)
     {
         if (a3 != 0)
         {
@@ -865,13 +865,13 @@ void sub_8198204(const u8 *string, const u8 *string2, u8 a3, u8 a4, bool8 copyTo
 
 void sub_81982D8(void)
 {
-    if (gUnknown_0203CDA0 != 0xFF)
+    if (gUnknown_0203CDA0 != INVALID_U8)
         CopyWindowToVram(gUnknown_0203CDA0, 3);
 }
 
 void sub_81982F0(void)
 {
-    if (gUnknown_0203CDA0 != 0xFF)
+    if (gUnknown_0203CDA0 != INVALID_U8)
     {
         FillWindowPixelBuffer(gUnknown_0203CDA0, 0xFF);
         CopyWindowToVram(gUnknown_0203CDA0, 3);
@@ -880,13 +880,13 @@ void sub_81982F0(void)
 
 void sub_8198314(void)
 {
-    if (gUnknown_0203CDA0 != 0xFF)
+    if (gUnknown_0203CDA0 != INVALID_U8)
     {
         FillWindowPixelBuffer(gUnknown_0203CDA0, 0);
         ClearWindowTilemap(gUnknown_0203CDA0);
         CopyWindowToVram(gUnknown_0203CDA0, 3);
         RemoveWindow(gUnknown_0203CDA0);
-        gUnknown_0203CDA0 = 0xFF;
+        gUnknown_0203CDA0 = INVALID_U8;
     }
 }
 
diff --git a/src/mossdeep_gym.c b/src/mossdeep_gym.c
index cd377ad83..07920fe4c 100644
--- a/src/mossdeep_gym.c
+++ b/src/mossdeep_gym.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "event_object_movement.h"
 #include "fieldmap.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "mossdeep_gym.h"
 #include "script_movement.h"
 #include "constants/event_object_movement_constants.h"
diff --git a/src/naming_screen.c b/src/naming_screen.c
index 9902df04c..12ff4240f 100644
--- a/src/naming_screen.c
+++ b/src/naming_screen.c
@@ -1,6 +1,6 @@
 #include "global.h"
 #include "naming_screen.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "task.h"
 #include "sprite.h"
@@ -2141,7 +2141,7 @@ static const struct SpriteTemplate sSpriteTemplate_Underscore =
 
 static const struct SpriteTemplate gUnknown_0858C180 =
 {
-    .tileTag = 0xFFFF,
+    .tileTag = INVALID_U16,
     .paletteTag = 0x0000,
     .oam = &gOamData_858BFEC,
     .anims = gSpriteAnimTable_858C0BC,
diff --git a/src/overworld.c b/src/overworld.c
index 3193ec0d3..13c36819f 100644
--- a/src/overworld.c
+++ b/src/overworld.c
@@ -27,7 +27,7 @@
 #include "link_rfu.h"
 #include "load_save.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "m4a.h"
 #include "map_name_popup.h"
 #include "menu.h"
@@ -1110,7 +1110,7 @@ static bool16 IsInflitratedSpaceCenter(struct WarpData *warp)
 u16 GetLocationMusic(struct WarpData *warp)
 {
     if (NoMusicInSotopolisWithLegendaries(warp) == TRUE)
-        return 0xFFFF;
+        return INVALID_U16;
     else if (ShouldLegendaryMusicPlayAtLocation(warp) == TRUE)
         return MUS_OOAME;
     else if (IsInflitratedSpaceCenter(warp) == TRUE)
@@ -1171,7 +1171,7 @@ void Overworld_PlaySpecialMapMusic(void)
 {
     u16 music = GetCurrLocationDefaultMusic();
 
-    if (music != MUS_OOAME && music != 0xFFFF)
+    if (music != MUS_OOAME && music != INVALID_U16)
     {
         if (gSaveBlock1Ptr->savedMusic)
             music = gSaveBlock1Ptr->savedMusic;
@@ -1201,7 +1201,7 @@ static void sub_8085810(void)
     {
         u16 newMusic = GetWarpDestinationMusic();
         u16 currentMusic = GetCurrentMapMusic();
-        if (newMusic != MUS_OOAME && newMusic != 0xFFFF)
+        if (newMusic != MUS_OOAME && newMusic != INVALID_U16)
         {
             if (currentMusic == MUS_DEEPDEEP || currentMusic == MUS_NAMINORI)
                 return;
diff --git a/src/palette.c b/src/palette.c
index 1e92f4bba..3c7485d05 100644
--- a/src/palette.c
+++ b/src/palette.c
@@ -63,7 +63,7 @@ static EWRAM_DATA u32 sPlttBufferTransferPending = 0;
 EWRAM_DATA u8 gPaletteDecompressionBuffer[PLTT_DECOMP_BUFFER_SIZE] = {0};
 
 static const struct PaletteStructTemplate gDummyPaletteStructTemplate = {
-    .uid = 0xFFFF,
+    .uid = INVALID_U16,
     .pst_field_B_5 = 1
 };
 
diff --git a/src/player_pc.c b/src/player_pc.c
index 59ba36350..f42d59147 100644
--- a/src/player_pc.c
+++ b/src/player_pc.c
@@ -15,7 +15,7 @@
 #include "list_menu.h"
 #include "mail.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "menu_helpers.h"
 #include "overworld.h"
diff --git a/src/pokeblock.c b/src/pokeblock.c
index 01343c6eb..41d6dcc8f 100644
--- a/src/pokeblock.c
+++ b/src/pokeblock.c
@@ -13,7 +13,7 @@
 #include "lilycove_lady.h"
 #include "list_menu.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "menu_helpers.h"
 #include "overworld.h"
@@ -435,7 +435,7 @@ void OpenPokeblockCase(u8 caseId, void (*callback)(void))
     sPokeblockMenu = Alloc(sizeof(*sPokeblockMenu));
     sPokeblockMenu->caseId = caseId;
     sPokeblockMenu->callbackOnUse = NULL;
-    sPokeblockMenu->unkTaskId = 0xFF;
+    sPokeblockMenu->unkTaskId = INVALID_U8;
     sPokeblockMenu->isSwapping = FALSE;
     sSavedPokeblockData.callback = callback;
 
@@ -901,7 +901,7 @@ static void sub_8136344(void)
 
 static void sub_81363BC(void)
 {
-    if (sPokeblockMenu->unkTaskId == 0xFF)
+    if (sPokeblockMenu->unkTaskId == INVALID_U8)
     {
         sPokeblockMenu->unkTaskId = AddScrollIndicatorArrowPairParameterized(SCROLL_ARROW_UP, 0xB0, 8, 0x98, sPokeblockMenu->itemsNo - sPokeblockMenu->maxShowed,
                                                                             0x456, 0x456, &sSavedPokeblockData.lastItemPage);
@@ -910,10 +910,10 @@ static void sub_81363BC(void)
 
 static void sub_8136418(void)
 {
-    if (sPokeblockMenu->unkTaskId != 0xFF)
+    if (sPokeblockMenu->unkTaskId != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(sPokeblockMenu->unkTaskId);
-        sPokeblockMenu->unkTaskId = 0xFF;
+        sPokeblockMenu->unkTaskId = INVALID_U8;
     }
 }
 
@@ -1016,7 +1016,7 @@ static void Task_HandlePokeblockMenuInput(u8 taskId)
                 break;
             case LIST_B_PRESSED:
                 PlaySE(SE_SELECT);
-                gSpecialVar_Result = 0xFFFF;
+                gSpecialVar_Result = INVALID_U16;
                 gSpecialVar_ItemId = 0;
                 FadePaletteAndSetTaskToClosePokeblockCase(taskId);
                 break;
diff --git a/src/pokeblock_feed.c b/src/pokeblock_feed.c
index 0a8f1b8c2..91dbd1c99 100644
--- a/src/pokeblock_feed.c
+++ b/src/pokeblock_feed.c
@@ -7,7 +7,7 @@
 #include "gpu_regs.h"
 #include "graphics.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "menu_helpers.h"
 #include "m4a.h"
diff --git a/src/pokedex.c b/src/pokedex.c
index 7578f9687..4e28c8a14 100644
--- a/src/pokedex.c
+++ b/src/pokedex.c
@@ -8,7 +8,7 @@
 #include "graphics.h"
 #include "international_string_util.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "m4a.h"
 #include "overworld.h"
@@ -1271,7 +1271,7 @@ static void ResetPokedexView(struct PokedexView *pokedexView)
     pokedexView->seenCount = 0;
     pokedexView->ownCount = 0;
     for (i = 0; i <= 3; i++)
-        pokedexView->unk61E[i] |= 0xFFFF;
+        pokedexView->unk61E[i] |= INVALID_U16;
     pokedexView->unk628 = 0;
     pokedexView->unk62A = 0;
     pokedexView->unk62C = 0;
@@ -2459,7 +2459,7 @@ u32 sub_80BDACC(u16 num, s16 x, s16 y)
             return spriteId;
         }
     }
-    return 0xFFFF;
+    return INVALID_U16;
 }
 
 static void CreateInterfaceSprites(u8 a)
@@ -2717,8 +2717,8 @@ void sub_80BE4E0(struct Sprite *sprite)
 
         sprite->pos2.y = gSineTable[(u8)sprite->data[5]] * 76 / 256;
         var = 0x10000 / gSineTable[sprite->data[5] + 0x40];
-        if (var > 0xFFFF)
-            var = 0xFFFF;
+        if (var > INVALID_U16)
+            var = INVALID_U16;
         SetOamMatrix(sprite->data[1] + 1, 0x100, 0, 0, var);
         sprite->oam.matrixNum = data1 + 1;
 
@@ -4627,12 +4627,12 @@ u32 sub_80C0E68(u16 a)
 u16 sub_80C0E9C(u16 num, s16 x, s16 y, u16 paletteSlot)
 {
     num = NationalPokedexNumToSpecies(num);
-    return CreateMonPicSprite_HandleDeoxys(num, 8, sub_80C0E68(num), TRUE, x, y, paletteSlot, 0xFFFF);
+    return CreateMonPicSprite_HandleDeoxys(num, 8, sub_80C0E68(num), TRUE, x, y, paletteSlot, INVALID_U16);
 }
 
 u16 sub_80C0EF8(u16 species, s16 x, s16 y, s8 paletteSlot)
 {
-    return CreateTrainerPicSprite(species, TRUE, x, y, paletteSlot, 0xFFFF);
+    return CreateTrainerPicSprite(species, TRUE, x, y, paletteSlot, INVALID_U16);
 }
 
 int sub_80C0F30(u8 dexMode, u8 sortMode, u8 abcGroup, u8 bodyColor, u8 type1, u8 type2)
@@ -4655,7 +4655,7 @@ int sub_80C0F30(u8 dexMode, u8 sortMode, u8 abcGroup, u8 bodyColor, u8 type1, u8
     sPokedexView->pokemonListCount = resultsCount;
 
     // Search by name
-    if (abcGroup != 0xFF)
+    if (abcGroup != INVALID_U8)
     {
         for (i = 0, resultsCount = 0; i < sPokedexView->pokemonListCount; i++)
         {
@@ -4674,7 +4674,7 @@ int sub_80C0F30(u8 dexMode, u8 sortMode, u8 abcGroup, u8 bodyColor, u8 type1, u8
     }
 
     // Search by body color
-    if (bodyColor != 0xFF)
+    if (bodyColor != INVALID_U8)
     {
         for (i = 0, resultsCount = 0; i < sPokedexView->pokemonListCount; i++)
         {
@@ -4690,15 +4690,15 @@ int sub_80C0F30(u8 dexMode, u8 sortMode, u8 abcGroup, u8 bodyColor, u8 type1, u8
     }
 
     // Search by type
-    if (type1 != 0xFF || type2 != 0xFF)
+    if (type1 != INVALID_U8 || type2 != INVALID_U8)
     {
-        if (type1 == 0xFF)
+        if (type1 == INVALID_U8)
         {
             type1 = type2;
-            type2 = 0xFF;
+            type2 = INVALID_U8;
         }
 
-        if (type2 == 0xFF)
+        if (type2 == INVALID_U8)
         {
             for (i = 0, resultsCount = 0; i < sPokedexView->pokemonListCount; i++)
             {
@@ -4987,7 +4987,7 @@ void sub_80C170C(u8 taskId)
         return;
     }
 
-    if ((gMain.newKeys & DPAD_LEFT) && r6[gTasks[taskId].data[1]][0] != 0xFF)
+    if ((gMain.newKeys & DPAD_LEFT) && r6[gTasks[taskId].data[1]][0] != INVALID_U8)
     {
         PlaySE(SE_SELECT);
         gTasks[taskId].data[1] = r6[gTasks[taskId].data[1]][0];
@@ -4995,7 +4995,7 @@ void sub_80C170C(u8 taskId)
         CopyWindowToVram(0, 2);
         CopyBgTilemapBufferToVram(3);
     }
-    if ((gMain.newKeys & DPAD_RIGHT) && r6[gTasks[taskId].data[1]][1] != 0xFF)
+    if ((gMain.newKeys & DPAD_RIGHT) && r6[gTasks[taskId].data[1]][1] != INVALID_U8)
     {
         PlaySE(SE_SELECT);
         gTasks[taskId].data[1] = r6[gTasks[taskId].data[1]][1];
@@ -5003,7 +5003,7 @@ void sub_80C170C(u8 taskId)
         CopyWindowToVram(0, 2);
         CopyBgTilemapBufferToVram(3);
     }
-    if ((gMain.newKeys & DPAD_UP) && r6[gTasks[taskId].data[1]][2] != 0xFF)
+    if ((gMain.newKeys & DPAD_UP) && r6[gTasks[taskId].data[1]][2] != INVALID_U8)
     {
         PlaySE(SE_SELECT);
         gTasks[taskId].data[1] = r6[gTasks[taskId].data[1]][2];
@@ -5011,7 +5011,7 @@ void sub_80C170C(u8 taskId)
         CopyWindowToVram(0, 2);
         CopyBgTilemapBufferToVram(3);
     }
-    if ((gMain.newKeys & DPAD_DOWN) && r6[gTasks[taskId].data[1]][3] != 0xFF)
+    if ((gMain.newKeys & DPAD_DOWN) && r6[gTasks[taskId].data[1]][3] != INVALID_U8)
     {
         PlaySE(SE_SELECT);
         gTasks[taskId].data[1] = r6[gTasks[taskId].data[1]][3];
@@ -5475,12 +5475,12 @@ u8 sub_80C2318(u8 taskId, u8 b)
             return gUnknown_0856EFAE[r2];
         case 0:
             if (r2 == 0)
-                return 0xFF;
+                return INVALID_U8;
             else
                 return r2;
         case 1:
             if (r2 == 0)
-                return 0xFF;
+                return INVALID_U8;
             else
                 return r2 - 1;
         case 2:
diff --git a/src/pokedex_cry_screen.c b/src/pokedex_cry_screen.c
index f3eeeed07..4a9227b99 100755
--- a/src/pokedex_cry_screen.c
+++ b/src/pokedex_cry_screen.c
@@ -2,7 +2,7 @@
 #include "bg.h"
 #include "m4a.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "pokedex_cry_screen.h"
 #include "sound.h"
diff --git a/src/pokemon.c b/src/pokemon.c
index f528ce331..1f8d5339b 100644
--- a/src/pokemon.c
+++ b/src/pokemon.c
@@ -12,7 +12,7 @@
 #include "item.h"
 #include "link.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "m4a.h"
 #include "pokedex.h"
 #include "pokeblock.h"
@@ -2300,7 +2300,7 @@ static const u8 sHoldEffectToType[][2] =
 const struct SpriteTemplate gUnknown_08329D98[MAX_BATTLERS_COUNT] =
 {
     {   // B_POSITION_PLAYER_LEFT
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2309,7 +2309,7 @@ const struct SpriteTemplate gUnknown_08329D98[MAX_BATTLERS_COUNT] =
         .callback = sub_8039BB4,
     },
     {   // B_POSITION_OPPONENT_LEFT
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACA8,
         .anims = NULL,
@@ -2318,7 +2318,7 @@ const struct SpriteTemplate gUnknown_08329D98[MAX_BATTLERS_COUNT] =
         .callback = oac_poke_opponent,
     },
     {   // B_POSITION_PLAYER_RIGHT
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2327,7 +2327,7 @@ const struct SpriteTemplate gUnknown_08329D98[MAX_BATTLERS_COUNT] =
         .callback = sub_8039BB4,
     },
     {   // B_POSITION_OPPONENT_RIGHT
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACA8,
         .anims = NULL,
@@ -2340,7 +2340,7 @@ const struct SpriteTemplate gUnknown_08329D98[MAX_BATTLERS_COUNT] =
 static const struct SpriteTemplate gUnknown_08329DF8[] =
 {
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2349,7 +2349,7 @@ static const struct SpriteTemplate gUnknown_08329DF8[] =
         .callback = sub_8039BB4,
     },
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2358,7 +2358,7 @@ static const struct SpriteTemplate gUnknown_08329DF8[] =
         .callback = sub_8039BB4,
     },
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2367,7 +2367,7 @@ static const struct SpriteTemplate gUnknown_08329DF8[] =
         .callback = sub_8039BB4,
     },
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2376,7 +2376,7 @@ static const struct SpriteTemplate gUnknown_08329DF8[] =
         .callback = sub_8039BB4,
     },
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2385,7 +2385,7 @@ static const struct SpriteTemplate gUnknown_08329DF8[] =
         .callback = sub_8039BB4,
     },
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2394,7 +2394,7 @@ static const struct SpriteTemplate gUnknown_08329DF8[] =
         .callback = sub_8039BB4,
     },
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2403,7 +2403,7 @@ static const struct SpriteTemplate gUnknown_08329DF8[] =
         .callback = sub_8039BB4,
     },
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = 0,
         .oam = &gUnknown_0831ACB0,
         .anims = NULL,
@@ -2450,7 +2450,7 @@ static const s8 gUnknown_08329ECE[][3] =
 static const u16 sHMMoves[] =
 {
     MOVE_CUT, MOVE_FLY, MOVE_SURF, MOVE_STRENGTH, MOVE_FLASH,
-    MOVE_ROCK_SMASH, MOVE_WATERFALL, MOVE_DIVE, 0xFFFF
+    MOVE_ROCK_SMASH, MOVE_WATERFALL, MOVE_DIVE, INVALID_U16
 };
 
 static const struct SpeciesItem sAlteringCaveWildMonHeldItems[] =
@@ -2485,8 +2485,8 @@ static const struct OamData sOamData_8329F20 =
 
 static const struct SpriteTemplate gUnknown_08329F28 =
 {
-    .tileTag = 0xFFFF,
-    .paletteTag = 0xFFFF,
+    .tileTag = INVALID_U16,
+    .paletteTag = INVALID_U16,
     .oam = &sOamData_8329F20,
     .anims = gDummySpriteAnimTable,
     .images = NULL,
@@ -3286,7 +3286,7 @@ u16 GiveMoveToBoxMon(struct BoxPokemon *boxMon, u16 move)
         if (existingMove == move)
             return -2;
     }
-    return -1;
+    return INVALID_U16;
 }
 
 u16 GiveMoveToBattleMon(struct BattlePokemon *mon, u16 move)
@@ -3303,7 +3303,7 @@ u16 GiveMoveToBattleMon(struct BattlePokemon *mon, u16 move)
         }
     }
 
-    return -1;
+    return INVALID_U16;
 }
 
 void SetMonMoveSlot(struct Pokemon *mon, u16 move, u8 slot)
@@ -3341,7 +3341,7 @@ void GiveBoxMonInitialMoveset(struct BoxPokemon *boxMon)
 
         move = (gLevelUpLearnsets[species][i] & 0x1FF);
 
-        if (GiveMoveToBoxMon(boxMon, move) == 0xFFFF)
+        if (GiveMoveToBoxMon(boxMon, move) == INVALID_U16)
             DeleteFirstMoveAndGiveMoveToBoxMon(boxMon, move);
     }
 }
@@ -6495,7 +6495,7 @@ u8 GetMoveRelearnerMoves(struct Pokemon *mon, u16 *moves)
     {
         u16 moveLevel;
 
-        if (gLevelUpLearnsets[species][i] == 0xFFFF)
+        if (gLevelUpLearnsets[species][i] == INVALID_U16)
             break;
 
         moveLevel = gLevelUpLearnsets[species][i] & 0xFE00;
@@ -6524,7 +6524,7 @@ u8 GetLevelUpMovesBySpecies(u16 species, u16 *moves)
     u8 numMoves = 0;
     int i;
 
-    for (i = 0; i < 20 && gLevelUpLearnsets[species][i] != 0xFFFF; i++)
+    for (i = 0; i < 20 && gLevelUpLearnsets[species][i] != INVALID_U16; i++)
          moves[numMoves++] = gLevelUpLearnsets[species][i] & 0x1FF;
 
      return numMoves;
@@ -6549,7 +6549,7 @@ u8 GetNumberOfRelearnableMoves(struct Pokemon *mon)
     {
         u16 moveLevel;
 
-        if (gLevelUpLearnsets[species][i] == 0xFFFF)
+        if (gLevelUpLearnsets[species][i] == INVALID_U16)
             break;
 
         moveLevel = gLevelUpLearnsets[species][i] & 0xFE00;
@@ -6584,7 +6584,7 @@ u16 SpeciesToPokedexNum(u16 species)
         species = SpeciesToHoennPokedexNum(species);
         if (species <= 202)
             return species;
-        return 0xFFFF;
+        return INVALID_U16;
     }
 }
 
@@ -6747,7 +6747,7 @@ const struct CompressedSpritePalette *GetMonSpritePalStructFromOtIdPersonality(u
 bool32 IsHMMove2(u16 move)
 {
     int i = 0;
-    while (sHMMoves[i] != 0xFFFF)
+    while (sHMMoves[i] != INVALID_U16)
     {
         if (sHMMoves[i++] == move)
             return TRUE;
diff --git a/src/pokemon_animation.c b/src/pokemon_animation.c
index 989bce37d..c9a4f5c91 100644
--- a/src/pokemon_animation.c
+++ b/src/pokemon_animation.c
@@ -588,7 +588,7 @@ static const u8 sUnknown_0860AA64[][2] =
     {0, 2},
     {1, 2},
     {0, 2},
-    {0, 0xFF}
+    {0, INVALID_U8}
 };
 
 static const u8 sUnknown_0860AA80[][2] =
@@ -1666,7 +1666,7 @@ static void sub_818031C(struct Sprite *sprite)
     else
         amplitude = 0;
 
-    if (var5 == 0xFF)
+    if (var5 == INVALID_U8)
     {
         sprite->callback = SpriteCB_SetDummyOnAnimEnd;
         sprite->pos2.y = 0;
@@ -2570,7 +2570,7 @@ static void pokemonanimfunc_2C(struct Sprite *sprite)
         sprite->data[4] = 0;
     }
 
-    if (sUnknown_0860AA64[sprite->data[6]][1] == 0xFF)
+    if (sUnknown_0860AA64[sprite->data[6]][1] == INVALID_U8)
     {
         sprite->callback = SpriteCB_SetDummyOnAnimEnd;
     }
@@ -4157,17 +4157,17 @@ static void sub_8183574(struct Sprite *sprite)
     u8 var9 = sprite->data[6];
     u8 var5 = sUnknown_0860AA80[sprite->data[5]][0];
     u8 var2 = var5;
-    if (var5 != 0xFF)
+    if (var5 != INVALID_U8)
         var5 = sprite->data[7];
     else
-        var5 = 0xFF; // needed to match
+        var5 = INVALID_U8; // needed to match
 
     var6 = sUnknown_0860AA80[sprite->data[5]][1];
     var7 = 0;
     if (var2 != 0xFE)
         var7 = (var6 - var9) * var5 / var6;
 
-    if (var5 == 0xFF)
+    if (var5 == INVALID_U8)
     {
         sprite->callback = SpriteCB_SetDummyOnAnimEnd;
         sprite->pos2.y = 0;
@@ -5278,7 +5278,7 @@ static const struct YellowBlendStruct sUnknown_0860ADCC[] =
     {0, 1},
     {1, 1},
     {0, 1},
-    {0, 0xFF}
+    {0, INVALID_U8}
 };
 
 static const struct YellowBlendStruct sUnknown_0860AE1C[] =
@@ -5296,7 +5296,7 @@ static const struct YellowBlendStruct sUnknown_0860AE1C[] =
     {0, 2},
     {1, 2},
     {0, 2},
-    {0, 0xFF}
+    {0, INVALID_U8}
 };
 
 static const struct YellowBlendStruct sUnknown_0860AE54[] =
@@ -5310,7 +5310,7 @@ static const struct YellowBlendStruct sUnknown_0860AE54[] =
     {0, 20},
     {1, 1},
     {0, 1},
-    {0, 0xFF}
+    {0, INVALID_U8}
 };
 
 static const struct YellowBlendStruct *const sUnknown_0860AE7C[] =
@@ -5324,7 +5324,7 @@ static void BackAnimBlendYellow(struct Sprite *sprite)
 {
     const struct YellowBlendStruct *array = sUnknown_0860AE7C[sprite->data[3]];
     sub_8184770(sprite);
-    if (array[sprite->data[6]].field_1 == 0xFF)
+    if (array[sprite->data[6]].field_1 == INVALID_U8)
     {
         sprite->pos2.x = 0;
         sprite->callback = SpriteCB_SetDummyOnAnimEnd;
diff --git a/src/pokemon_icon.c b/src/pokemon_icon.c
index 994cc520e..5926f9513 100644
--- a/src/pokemon_icon.c
+++ b/src/pokemon_icon.c
@@ -1153,14 +1153,14 @@ void SafeLoadMonIconPalette(u16 species)
     if (species > SPECIES_EGG)
         species = 260;
     palIndex = gMonIconPaletteIndices[species];
-    if (IndexOfSpritePaletteTag(gMonIconPaletteTable[palIndex].tag) == 0xFF)
+    if (IndexOfSpritePaletteTag(gMonIconPaletteTable[palIndex].tag) == INVALID_U8)
         LoadSpritePalette(&gMonIconPaletteTable[palIndex]);
 }
 
 void LoadMonIconPalette(u16 species)
 {
     u8 palIndex = gMonIconPaletteIndices[species];
-    if (IndexOfSpritePaletteTag(gMonIconPaletteTable[palIndex].tag) == 0xFF)
+    if (IndexOfSpritePaletteTag(gMonIconPaletteTable[palIndex].tag) == INVALID_U8)
         LoadSpritePalette(&gMonIconPaletteTable[palIndex]);
 }
 
@@ -1287,7 +1287,7 @@ static u8 CreateMonIconSprite(struct MonIconSpriteTemplate *iconTemplate, s16 x,
 
     struct SpriteTemplate spriteTemplate =
     {
-        .tileTag = 0xFFFF,
+        .tileTag = INVALID_U16,
         .paletteTag = iconTemplate->paletteTag,
         .oam = iconTemplate->oam,
         .anims = iconTemplate->anims,
diff --git a/src/pokemon_size_record.c b/src/pokemon_size_record.c
index 2d9a2f08f..f90a6b8c2 100644
--- a/src/pokemon_size_record.c
+++ b/src/pokemon_size_record.c
@@ -109,7 +109,7 @@ static void FormatMonSizeRecord(u8 *string, u32 size)
 
 static u8 CompareMonSize(u16 species, u16 *sizeRecord)
 {
-    if (gSpecialVar_Result == 0xFF)
+    if (gSpecialVar_Result == INVALID_U8)
     {
         return 0;
     }
diff --git a/src/pokemon_storage_system.c b/src/pokemon_storage_system.c
index 465b97da2..30e16da28 100644
--- a/src/pokemon_storage_system.c
+++ b/src/pokemon_storage_system.c
@@ -134,7 +134,7 @@ s16 GetFirstFreeBoxSpot(u8 boxId)
             return i;
     }
 
-    return -1; // all spots are taken
+    return INVALID_S16; // all spots are taken
 }
 
 u8 CountPartyNonEggMons(void)
@@ -426,7 +426,7 @@ s16 StorageSystemGetNextMonIndex(struct BoxPokemon *box, s8 startIdx, u8 stopIdx
                 return i;
         }
     }
-    return -1;
+    return INVALID_S16;
 }
 
 void ResetPokemonStorageSystem(void)
diff --git a/src/pokemon_summary_screen.c b/src/pokemon_summary_screen.c
index f152e70a4..bef127cce 100644
--- a/src/pokemon_summary_screen.c
+++ b/src/pokemon_summary_screen.c
@@ -19,7 +19,7 @@
 #include "item.h"
 #include "link.h"
 #include "m4a.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "menu_helpers.h"
 #include "mon_markings.h"
@@ -1152,7 +1152,7 @@ static bool8 SummaryScreen_LoadGraphics(void)
         break;
     case 17:
         pssData->spriteIds[0] = sub_81C45F4(&pssData->currentMon, &pssData->unk40F0);
-        if (pssData->spriteIds[0] != 0xFF)
+        if (pssData->spriteIds[0] != INVALID_U8)
         {
             pssData->unk40F0 = 0;
             gMain.state++;
@@ -1509,7 +1509,7 @@ static void sub_81C0604(u8 taskId, s8 a)
             r4_2 = sub_81C08F8(a);
         }
 
-        if (r4_2 != -1)
+        if (r4_2 != INVALID_S8)
         {
             PlaySE(SE_SELECT);
             if (pssData->summary.unk7 != 0)
@@ -1564,7 +1564,7 @@ static void sub_81C0704(u8 taskId)
         break;
     case 8:
         pssData->spriteIds[0] = sub_81C45F4(&pssData->currentMon, &data[1]);
-        if (pssData->spriteIds[0] == 0xFF)
+        if (pssData->spriteIds[0] == INVALID_U8)
             return;
         gSprites[pssData->spriteIds[0]].data[2] = 1;
         sub_81C0E24();
@@ -1601,9 +1601,9 @@ static s8 sub_81C08F8(s8 a)
     if (pssData->currPageIndex == PSS_PAGE_INFO)
     {
         if (a == -1 && pssData->curMonIndex == 0)
-            return -1;
+            return INVALID_S8;
         else if (a == 1 && pssData->curMonIndex >= pssData->maxMonIndex)
-            return -1;
+            return INVALID_S8;
         else
             return pssData->curMonIndex + a;
     }
@@ -1615,7 +1615,7 @@ static s8 sub_81C08F8(s8 a)
         {
             index += a;
             if (index < 0 || index > pssData->maxMonIndex)
-                return -1;
+                return INVALID_S8;
         } while (GetMonData(&mon[index], MON_DATA_IS_EGG) != 0);
         return index;
     }
@@ -1643,7 +1643,7 @@ static s8 sub_81C09B4(s8 a)
 
         r5 += a;
         if (r5 < 0 || r5 >= 6)
-            return -1;
+            return INVALID_S8;
         b = c[r5];
         if (sub_81C0A50(&mon[b]) == TRUE)
             return b;
@@ -2341,7 +2341,7 @@ static void sub_81C1DA4(u16 a, s16 b)
     else
     {
         u8 taskId = FindTaskIdByFunc(sub_81C1E20);
-        if (taskId == 0xFF)
+        if (taskId == INVALID_U8)
         {
             taskId = CreateTask(sub_81C1E20, 8);
         }
@@ -2392,7 +2392,7 @@ static void sub_81C1EFC(u16 a, s16 b, u16 move)
     else
     {
         u8 taskId = FindTaskIdByFunc(sub_81C1F80);
-        if (taskId == 0xFF)
+        if (taskId == INVALID_U8)
             taskId = CreateTask(sub_81C1F80, 8);
         gTasks[taskId].data[0] = b;
         gTasks[taskId].data[1] = a;
@@ -2580,12 +2580,12 @@ static void sub_81C240C(u16 move)
     {
         effectValue = gContestEffects[gContestMoves[move].effect].appeal;
 
-        if (effectValue != 0xFF)
+        if (effectValue != INVALID_U8)
             effectValue /= 10;
 
         for (i = 0; i < 8; i++)
         {
-            if (effectValue != 0xFF && i < effectValue)
+            if (effectValue != INVALID_U8 && i < effectValue)
             {
                 tilemap[(i / 4 * 32) + (i & 3) + 0x1E6] = 0x103A;
             }
@@ -2597,12 +2597,12 @@ static void sub_81C240C(u16 move)
 
         effectValue = gContestEffects[gContestMoves[move].effect].jam;
 
-        if (effectValue != 0xFF)
+        if (effectValue != INVALID_U8)
             effectValue /= 10;
 
         for (i = 0; i < 8; i++)
         {
-            if (effectValue != 0xFF && i < effectValue)
+            if (effectValue != INVALID_U8 && i < effectValue)
             {
                 tilemap[(i / 4 * 32) + (i & 3) + 0x226] = 0x103C;
             }
@@ -2634,7 +2634,7 @@ static void sub_81C2554(void)
     }
     for (i = 0; i < 8; i++)
     {
-        pssData->windowIds[i] = 0xFF;
+        pssData->windowIds[i] = INVALID_U8;
     }
 }
 
@@ -2661,7 +2661,7 @@ static void sub_81C2628(void)
     struct Pokemon *mon = &pssData->currentMon;
     struct PokeSummary *summary = &pssData->summary;
     u16 dexNum = SpeciesToPokedexNum(summary->species);
-    if (dexNum != 0xFFFF)
+    if (dexNum != INVALID_U16)
     {
         StringCopy(gStringVar1, &gText_UnkCtrlF908Clear01[0]);
         ConvertIntToDecimalStringN(gStringVar2, dexNum, 2, 3);
@@ -2895,7 +2895,7 @@ static void sub_81C2C38(u8 a)
 static u8 AddWindowFromTemplateList(const struct WindowTemplate *template, u8 templateId)
 {
     u8 *windowIdPtr = &(pssData->windowIds[templateId]);
-    if (*windowIdPtr == 0xFF)
+    if (*windowIdPtr == INVALID_U8)
     {
         *windowIdPtr = AddWindow(&template[templateId]);
         FillWindowPixelBuffer(*windowIdPtr, 0);
@@ -2906,11 +2906,11 @@ static u8 AddWindowFromTemplateList(const struct WindowTemplate *template, u8 te
 static void SummaryScreen_RemoveWindowByIndex(u8 windowIndex)
 {
     u8 *windowIdPtr = &(pssData->windowIds[windowIndex]);
-    if (*windowIdPtr != 0xFF)
+    if (*windowIdPtr != INVALID_U8)
     {
         ClearWindowTilemap(*windowIdPtr);
         RemoveWindow(*windowIdPtr);
-        *windowIdPtr = 0xFF;
+        *windowIdPtr = INVALID_U8;
     }
 }
 
@@ -2919,7 +2919,7 @@ static void sub_81C2D9C(u8 pageIndex)
     u16 i;
     for (i = 0; i < 8; i++)
     {
-        if (pssData->windowIds[i] != 0xFF)
+        if (pssData->windowIds[i] != INVALID_U8)
             FillWindowPixelBuffer(pssData->windowIds[i], 0);
     }
     gUnknown_0861CE54[pageIndex]();
@@ -3651,16 +3651,16 @@ static void sub_81C4190(void)
 
     for (i = 0; i < 28; i++)
     {
-        pssData->spriteIds[i] = 0xFF;
+        pssData->spriteIds[i] = INVALID_U8;
     }
 }
 
 static void DestroySpriteInArray(u8 spriteArrayId)
 {
-    if (pssData->spriteIds[spriteArrayId] != 0xFF)
+    if (pssData->spriteIds[spriteArrayId] != INVALID_U8)
     {
         DestroySprite(&gSprites[pssData->spriteIds[spriteArrayId]]);
-        pssData->spriteIds[spriteArrayId] = 0xFF;
+        pssData->spriteIds[spriteArrayId] = INVALID_U8;
     }
 }
 
@@ -3675,7 +3675,7 @@ static void sub_81C424C(void)
 
     for (i = 3; i < 28; i++)
     {
-        if (pssData->spriteIds[i] != 0xFF)
+        if (pssData->spriteIds[i] != INVALID_U8)
             sub_81C4204(i, TRUE);
     }
 }
@@ -3704,7 +3704,7 @@ static void sub_81C42C8(void)
 
     for (i = 3; i < 8; i++)
     {
-        if (pssData->spriteIds[i] == 0xFF)
+        if (pssData->spriteIds[i] == INVALID_U8)
             pssData->spriteIds[i] = CreateSprite(&sSpriteTemplate_MoveTypes, 0, 0, 2);
 
         sub_81C4204(i, TRUE);
@@ -3851,13 +3851,13 @@ static u8 sub_81C45F4(struct Pokemon *mon, s16 *a1)
                 }
             }
             (*a1)++;
-            return -1;
+            return INVALID_S8;
         case 1:
             pal = GetMonSpritePalStructFromOtIdPersonality(summary->species2, summary->OTID, summary->pid);
             LoadCompressedObjectPalette(pal);
             SetMultiuseSpriteTemplateToPokemon(pal->tag, 1);
             (*a1)++;
-            return -1;
+            return INVALID_S8;
     }
 }
 
@@ -3921,10 +3921,10 @@ void SummaryScreen_SetUnknownTaskId(u8 a0)
 
 void SummaryScreen_DestroyUnknownTask(void)
 {
-    if (sUnknownTaskId != 0xFF)
+    if (sUnknownTaskId != INVALID_U8)
     {
         DestroyTask(sUnknownTaskId);
-        sUnknownTaskId = 0xFF;
+        sUnknownTaskId = INVALID_U8;
     }
 }
 
@@ -3994,7 +3994,7 @@ static void CreateSetStatusSprite(void)
     u8 *spriteId = &pssData->spriteIds[2];
     u8 anim;
 
-    if (*spriteId == 0xFF)
+    if (*spriteId == INVALID_U8)
     {
         *spriteId = CreateSprite(&sSpriteTemplate_StatusCondition, 64, 152, 0);
     }
diff --git a/src/rayquaza_scene.c b/src/rayquaza_scene.c
index 4783f73c0..d0f65c4b0 100644
--- a/src/rayquaza_scene.c
+++ b/src/rayquaza_scene.c
@@ -5,7 +5,7 @@
 #include "graphics.h"
 #include "bg.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "scanline_effect.h"
 #include "menu.h"
diff --git a/src/record_mixing.c b/src/record_mixing.c
index df4a1a720..4a4941294 100644
--- a/src/record_mixing.c
+++ b/src/record_mixing.c
@@ -1,5 +1,5 @@
 #include "global.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "random.h"
 #include "constants/items.h"
 #include "text.h"
@@ -1763,7 +1763,7 @@ static void sub_80E8880(struct RankingHall1P *arg0, struct RankingHall1P *arg1)
     for (i = 0; i < 3; i++)
     {
         s32 highestWinStreak = 0;
-        s32 highestId = -1;
+        s32 highestId = INVALID_S32;
         for (j = 0; j < 6; j++)
         {
             if (arg1[j].winStreak > highestWinStreak)
@@ -1788,7 +1788,7 @@ static void sub_80E88CC(struct RankingHall2P *arg0, struct RankingHall2P *arg1)
     for (i = 0; i < 3; i++)
     {
         s32 highestWinStreak = 0;
-        s32 highestId = -1;
+        s32 highestId = INVALID_S32;
         for (j = 0; j < 6; j++)
         {
             if (arg1[j].winStreak > highestWinStreak)
diff --git a/src/recorded_battle.c b/src/recorded_battle.c
index 5d79cb789..3fc08ff3f 100644
--- a/src/recorded_battle.c
+++ b/src/recorded_battle.c
@@ -9,7 +9,7 @@
 #include "string_util.h"
 #include "palette.h"
 #include "save.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "util.h"
 #include "task.h"
 #include "text.h"
@@ -221,7 +221,7 @@ u8 RecordedBattle_GetBattlerAction(u8 battlerId)
         ResetPaletteFadeControl();
         BeginNormalPaletteFade(0xFFFFFFFF, 0, 0, 0x10, 0);
         SetMainCallback2(CB2_QuitRecordedBattle);
-        return -1;
+        return INVALID_U8;
     }
     else
     {
diff --git a/src/region_map.c b/src/region_map.c
index 262a7d020..d7b53d631 100644
--- a/src/region_map.c
+++ b/src/region_map.c
@@ -2,7 +2,7 @@
 #include "main.h"
 #include "text.h"
 #include "menu.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "gpu_regs.h"
 #include "palette.h"
 #include "party_menu.h"
diff --git a/src/reset_rtc_screen.c b/src/reset_rtc_screen.c
index 34444cbf4..da94c5c46 100644
--- a/src/reset_rtc_screen.c
+++ b/src/reset_rtc_screen.c
@@ -160,7 +160,7 @@ static const union AnimCmd *const sSpriteAnimTable_85104E4[] =
 
 static const struct SpriteTemplate sSpriteTemplate_85104F0 =
 {
-    .tileTag = 0xFFFF,
+    .tileTag = INVALID_U16,
     .paletteTag = 0x1000,
     .oam = &sOamData_08510464,
     .anims = sSpriteAnimTable_85104E4,
diff --git a/src/reset_save_heap.c b/src/reset_save_heap.c
index 1d90448b2..d7c93a75c 100644
--- a/src/reset_save_heap.c
+++ b/src/reset_save_heap.c
@@ -6,7 +6,7 @@
 #include "save.h"
 #include "new_game.h"
 #include "overworld.h"
-#include "malloc.h"
+#include "alloc.h"
 
 void sub_81700F8(void)
 {
diff --git a/src/rock.c b/src/rock.c
index 3b8e505d8..b50ecc155 100644
--- a/src/rock.c
+++ b/src/rock.c
@@ -738,7 +738,7 @@ void sub_811131C(struct Sprite *sprite)
     if (TranslateAnimArc(sprite))
     {
         u8 taskId = FindTaskIdByFunc(sub_81110A4);
-        if (taskId != 0xFF)
+        if (taskId != INVALID_U8)
             gTasks[taskId].data[11]--;
 
         DestroySprite(sprite);
diff --git a/src/rom_8011DC0.c b/src/rom_8011DC0.c
index a197598de..ef82cbf0a 100644
--- a/src/rom_8011DC0.c
+++ b/src/rom_8011DC0.c
@@ -7,7 +7,7 @@
 #include "link.h"
 #include "link_rfu.h"
 #include "librfu.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "list_menu.h"
 #include "menu_helpers.h"
@@ -961,7 +961,7 @@ u8 sub_80132D4(struct UnkStruct_Main0 *arg0)
         if (var == 1)
         {
             id = sub_80176E4(&data->field_0->arr[i], data->field_4->arr);
-            if (id != 0xFF)
+            if (id != INVALID_U8)
             {
                 data->field_0->arr[i].unk = data->field_4->arr[id].unk0;
                 data->field_0->arr[i].field_18 = var;
@@ -1382,7 +1382,7 @@ void sub_8013C7C(u8 taskId)
     case 3:
         if (sub_8013E44() == 1)
             PlaySE(SE_PC_LOGIN);
-        if (gTasks[taskId].data[15] == 0xFF)
+        if (gTasks[taskId].data[15] == INVALID_U8)
             data->state = 10;
         break;
     case 10:
@@ -1401,14 +1401,14 @@ void sub_8013C7C(u8 taskId)
 
 bool32 sub_8013D88(u32 arg0, u32 id)
 {
-    if (id == 0xFF)
+    if (id == INVALID_U8)
         return TRUE;
 
     if (id <= ARRAY_COUNT(gUnknown_082F04D8)) // UB: <= may access data outside the array
     {
         const u8 *bytes = gUnknown_082F04D8[id];
 
-        while ((*(bytes) != 0xFF))
+        while ((*(bytes) != INVALID_U8))
         {
             if ((*bytes) == arg0)
                 return TRUE;
@@ -1454,7 +1454,7 @@ u8 sub_8013E44(void)
         if (data->field_0->arr[i].field_1A_0 != 0)
         {
             id = sub_80176E4(&data->field_0->arr[i], data->field_4->arr);
-            if (id != 0xFF)
+            if (id != INVALID_U8)
             {
                 if (data->field_0->arr[i].field_1A_0 == 1)
                 {
@@ -1500,7 +1500,7 @@ u8 sub_8013E44(void)
 
     for (id = 0; id < 4; id++)
     {
-        if (sub_8017734(data->field_0->arr, &data->field_4->arr[id].unk0, 16) != 0xFF)
+        if (sub_8017734(data->field_0->arr, &data->field_4->arr[id].unk0, 16) != INVALID_U8)
             ret = 1;
     }
 
@@ -2178,7 +2178,7 @@ void sub_8014F48(u8 taskId)
             break;
         case 0:
             id = ListMenuHandleInputGetItemId(data->listTaskId);
-            if (gMain.newKeys & A_BUTTON && id != -1)
+            if (gMain.newKeys & A_BUTTON && id != INVALID_S32)
             {
                 // this unused variable along with the assignment is needed to match
                 u32 unusedVar;
@@ -2732,7 +2732,7 @@ void sub_80156E0(u8 taskId)
         break;
     case 6:
         var5 = sub_8017178(&data->textState, &data->field_1B, &data->field_1C, &gUnknown_082F021C, &gUnknown_082F0244);
-        if (var5 != -1)
+        if (var5 != INVALID_S32)
         {
             if (gReceivedRemoteLinkPlayers == 0)
             {
diff --git a/src/rom_8034C54.c b/src/rom_8034C54.c
index be6d6614a..47d9eaf70 100644
--- a/src/rom_8034C54.c
+++ b/src/rom_8034C54.c
@@ -1,6 +1,6 @@
 #include "global.h"
 #include "rom_8034C54.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "decompress.h"
 #include "main.h"
 
@@ -255,7 +255,7 @@ static void sub_8035164(struct UnkStruct2 *arg0, s32 arg1, bool32 arg2)
     u32 r5 = arg0->field_14;
     gUnknown_03000DD4 = arg0->firstOamId;
     gUnknown_03000DD8 = 0;
-    gUnknown_03000DDC = -1;
+    gUnknown_03000DDC = INVALID_S32;
 
     while (r5 != 0)
     {
@@ -263,12 +263,12 @@ static void sub_8035164(struct UnkStruct2 *arg0, s32 arg1, bool32 arg2)
         arg1 -= (r4 * r5);
         r5 /= 10;
 
-        if (r4 != 0 || gUnknown_03000DDC != -1 || r5 == 0)
+        if (r4 != 0 || gUnknown_03000DDC != INVALID_S32 || r5 == 0)
         {
             gMain.oamBuffer[gUnknown_03000DD4].tileNum = (r4 * arg0->field_9) + arg0->tileStart;
             gMain.oamBuffer[gUnknown_03000DD4].affineMode = 0;
 
-            if (gUnknown_03000DDC == -1)
+            if (gUnknown_03000DDC == INVALID_S32)
                 gUnknown_03000DDC = gUnknown_03000DD8;
         }
         else
diff --git a/src/rom_81520A8.c b/src/rom_81520A8.c
index f6d14d49c..f06823594 100644
--- a/src/rom_81520A8.c
+++ b/src/rom_81520A8.c
@@ -1,6 +1,6 @@
 #include "global.h"
 #include "rom_81520A8.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "main.h"
 #include "rom_8034C54.h"
 
diff --git a/src/rotating_gate.c b/src/rotating_gate.c
index f617321af..395ced06e 100644
--- a/src/rotating_gate.c
+++ b/src/rotating_gate.c
@@ -461,7 +461,7 @@ static const union AffineAnimCmd *const sSpriteAffineAnimTable_RotatingGate[] =
 static const struct SpriteTemplate sSpriteTemplate_RotatingGateLarge =
 {
     .tileTag = ROTATING_GATE_TILE_TAG,
-    .paletteTag = 0xFFFF,
+    .paletteTag = INVALID_U16,
     .oam = &sOamData_RotatingGateLarge,
     .anims = sSpriteAnimTable_RotatingGateLarge,
     .images = NULL,
@@ -472,7 +472,7 @@ static const struct SpriteTemplate sSpriteTemplate_RotatingGateLarge =
 static const struct SpriteTemplate sSpriteTemplate_RotatingGateRegular =
 {
     .tileTag = ROTATING_GATE_TILE_TAG,
-    .paletteTag = 0xFFFF,
+    .paletteTag = INVALID_U16,
     .oam = &sOamData_RotatingGateRegular,
     .anims = sSpriteAnimTable_RotatingGateRegular,
     .images = NULL,
diff --git a/src/rtc.c b/src/rtc.c
index 3f413d0e3..7553d7629 100644
--- a/src/rtc.c
+++ b/src/rtc.c
@@ -46,12 +46,12 @@ void RtcRestoreInterrupts(void)
 u32 ConvertBcdToBinary(u8 bcd)
 {
     if (bcd > 0x9F)
-        return 0xFF;
+        return INVALID_U8;
 
     if ((bcd & 0xF) <= 9)
         return (10 * ((bcd >> 4) & 0xF)) + (bcd & 0xF);
     else
-        return 0xFF;
+        return INVALID_U8;
 }
 
 bool8 IsLeapYear(u32 year)
@@ -166,17 +166,17 @@ u16 RtcCheckInfo(struct SiiRtcInfo *rtc)
 
     year = ConvertBcdToBinary(rtc->year);
 
-    if (year == 0xFF)
+    if (year == INVALID_U8)
         errorFlags |= RTC_ERR_INVALID_YEAR;
 
     month = ConvertBcdToBinary(rtc->month);
 
-    if (month == 0xFF || month == 0 || month > 12)
+    if (month == INVALID_U8 || month == 0 || month > 12)
         errorFlags |= RTC_ERR_INVALID_MONTH;
 
     value = ConvertBcdToBinary(rtc->day);
 
-    if (value == 0xFF)
+    if (value == INVALID_U8)
         errorFlags |= RTC_ERR_INVALID_DAY;
 
     if (month == MONTH_FEB)
diff --git a/src/safari_zone.c b/src/safari_zone.c
index accf94981..69914b565 100644
--- a/src/safari_zone.c
+++ b/src/safari_zone.c
@@ -185,7 +185,7 @@ struct Pokeblock *SafariZoneGetPokeblockInFront(void)
 {
     GetPokeblockFeederInFront();
 
-    if (gSpecialVar_Result == 0xFFFF)
+    if (gSpecialVar_Result == INVALID_U16)
         return NULL;
     else
         return &sPokeblockFeeders[gSpecialVar_Result].pokeblock;
@@ -195,7 +195,7 @@ struct Pokeblock *SafariZoneGetActivePokeblock(void)
 {
     GetPokeblockFeederWithinRange();
 
-    if (gSpecialVar_Result == 0xFFFF)
+    if (gSpecialVar_Result == INVALID_U16)
         return NULL;
     else
         return &sPokeblockFeeders[gSpecialVar_Result].pokeblock;
@@ -245,7 +245,7 @@ bool8 GetInFrontFeederPokeblockAndSteps(void)
 {
     GetPokeblockFeederInFront();
 
-    if (gSpecialVar_Result == 0xFFFF)
+    if (gSpecialVar_Result == INVALID_U16)
     {
         return FALSE;
     }
diff --git a/src/save.c b/src/save.c
index 4ae516fc9..de103864b 100644
--- a/src/save.c
+++ b/src/save.c
@@ -160,7 +160,7 @@ static u8 save_write_to_flash(u16 a1, const struct SaveSectionLocation *location
 
         if (gDamagedSaveSectors != 0) // skip the damaged sector.
         {
-            retVal = 0xFF;
+            retVal = INVALID_U8;
             gLastWrittenSector = gLastKnownGoodSector;
             gSaveCounter = gLastSaveCounter;
         }
@@ -220,7 +220,7 @@ static u8 TryWriteSector(u8 sector, u8 *data)
     if (ProgramFlashSectorAndVerify(sector, data) != 0) // is damaged?
     {
         SetDamagedSectorBits(ENABLE, sector); // set damaged sector bits.
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
@@ -263,14 +263,14 @@ static u8 sub_81529D4(u16 a1, const struct SaveSectionLocation *location)
         gUnknown_03006208++;
         if (gDamagedSaveSectors)
         {
-            retVal = 0xFF;
+            retVal = INVALID_U8;
             gLastWrittenSector = gLastKnownGoodSector;
             gSaveCounter = gLastSaveCounter;
         }
     }
     else
     {
-        retVal = 0xFF;
+        retVal = INVALID_U8;
     }
 
     return retVal;
@@ -284,7 +284,7 @@ static u8 sub_8152A34(u16 a1, const struct SaveSectionLocation *location)
 
     if (gDamagedSaveSectors)
     {
-        retVal = 0xFF;
+        retVal = INVALID_U8;
         gLastWrittenSector = gLastKnownGoodSector;
         gSaveCounter = gLastSaveCounter;
     }
@@ -329,15 +329,15 @@ static u8 ClearSaveData_2(u16 a1, const struct SaveSectionLocation *location)
     {
         if (ProgramFlashByte(sector, i, ((u8 *)gFastSaveSection)[i]))
         {
-            status = 0xFF;
+            status = INVALID_U8;
             break;
         }
     }
 
-    if (status == 0xFF)
+    if (status == INVALID_U8)
     {
         SetDamagedSectorBits(ENABLE, sector);
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
@@ -347,15 +347,15 @@ static u8 ClearSaveData_2(u16 a1, const struct SaveSectionLocation *location)
         {
             if (ProgramFlashByte(sector, 0xFF9 + i, ((u8 *)gFastSaveSection)[0xFF9 + i]))
             {
-                status = 0xFF;
+                status = INVALID_U8;
                 break;
             }
         }
 
-        if (status == 0xFF)
+        if (status == INVALID_U8)
         {
             SetDamagedSectorBits(ENABLE, sector);
-            return 0xFF;
+            return INVALID_U8;
         }
         else
         {
@@ -379,7 +379,7 @@ static u8 sav12_xor_get(u16 a1, const struct SaveSectionLocation *location)
         SetDamagedSectorBits(ENABLE, sector);
         gLastWrittenSector = gLastKnownGoodSector;
         gSaveCounter = gLastSaveCounter;
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
@@ -402,7 +402,7 @@ static u8 sub_8152CAC(u16 a1, const struct SaveSectionLocation *location)
         SetDamagedSectorBits(ENABLE, sector);
         gLastWrittenSector = gLastKnownGoodSector;
         gSaveCounter = gLastSaveCounter;
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
@@ -425,7 +425,7 @@ static u8 sub_8152D44(u16 a1, const struct SaveSectionLocation *location)
         SetDamagedSectorBits(ENABLE, sector);
         gLastWrittenSector = gLastKnownGoodSector;
         gSaveCounter = gLastSaveCounter;
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
@@ -440,7 +440,7 @@ static u8 sub_8152DD0(u16 a1, const struct SaveSectionLocation *location)
     gFastSaveSection = &gSaveDataBuffer;
     if (a1 != 0xFFFF)
     {
-        retVal = 0xFF;
+        retVal = INVALID_U8;
     }
     else
     {
@@ -715,8 +715,8 @@ u8 TrySavingData(u8 saveType)
 {
     if (gFlashMemoryPresent != TRUE)
     {
-        gUnknown_03006294 = 0xFF;
-        return 0xFF;
+        gUnknown_03006294 = INVALID_U8;
+        return INVALID_U8;
     }
 
     HandleSavingData(saveType);
@@ -728,8 +728,8 @@ u8 TrySavingData(u8 saveType)
     else
     {
         DoSaveFailedScreen(saveType);
-        gUnknown_03006294 = 0xFF;
-        return 0xFF;
+        gUnknown_03006294 = INVALID_U8;
+        return INVALID_U8;
     }
 }
 
@@ -748,7 +748,7 @@ bool8 sub_81533AC(void) // trade.s save
     u8 retVal = sub_81529D4(SECTOR_SAVE_SLOT_LENGTH, gRamSaveSectionLocations);
     if (gDamagedSaveSectors)
         DoSaveFailedScreen(0);
-    if (retVal == 0xFF)
+    if (retVal == INVALID_U8)
         return TRUE;
     else
         return FALSE;
@@ -808,7 +808,7 @@ u8 Save_LoadGameData(u8 a1)
     if (gFlashMemoryPresent != TRUE)
     {
         gSaveFileStatus = 4;
-        return 0xFF;
+        return INVALID_U8;
     }
 
     UpdateSaveAddresses();
@@ -861,10 +861,10 @@ u32 TryCopySpecialSaveSection(u8 sector, u8* dst)
     u8* savData;
 
     if (sector != SECTOR_ID_TRAINER_HILL && sector != SECTOR_ID_RECORDED_BATTLE)
-        return 0xFF;
+        return INVALID_U8;
     ReadFlash(sector, 0, (u8 *)&gSaveDataBuffer, sizeof(struct SaveSection));
     if (*(u32*)(&gSaveDataBuffer.data[0]) != 0xB39D)
-        return 0xFF;
+        return INVALID_U8;
     // copies whole save section except u32 counter
     i = 0;
     size = 0xFFB;
@@ -882,7 +882,7 @@ u32 sub_8153634(u8 sector, u8* src)
     void* savDataBuffer;
 
     if (sector != 30 && sector != 31)
-        return 0xFF;
+        return INVALID_U8;
 
     savDataBuffer = &gSaveDataBuffer;
     *(u32*)(savDataBuffer) = 0xB39D;
@@ -894,7 +894,7 @@ u32 sub_8153634(u8 sector, u8* src)
     for (; i <= size; i++)
         savData[i] = src[i];
     if (ProgramFlashSectorAndVerify(sector, savDataBuffer) != 0)
-        return 0xFF;
+        return INVALID_U8;
     return 1;
 }
 
diff --git a/src/save_location.c b/src/save_location.c
index d49afa736..f7d3aa60b 100644
--- a/src/save_location.c
+++ b/src/save_location.c
@@ -12,7 +12,7 @@ static bool32 IsCurMapInLocationList(const u16 *list)
     s32 i;
     u16 locSum = (gSaveBlock1Ptr->location.mapGroup << 8) + (gSaveBlock1Ptr->location.mapNum);
 
-    for (i = 0; list[i] != 0xFFFF; i++)
+    for (i = 0; list[i] != INVALID_U16; i++)
     {
         if (list[i] == locSum)
             return TRUE;
@@ -61,7 +61,7 @@ static const u16 sSaveLocationPokeCenterList[] =
     MAP_TRADE_CENTER,
     MAP_RECORD_CORNER,
     MAP_DOUBLE_BATTLE_COLOSSEUM,
-    0xFFFF,
+    INVALID_U16,
 };
 
 static bool32 IsCurMapPokeCenter(void)
@@ -72,7 +72,7 @@ static bool32 IsCurMapPokeCenter(void)
 static const u16 sSaveLocationReloadLocList[] = // There's only 1 location, and it's presumed its for the save reload feature for battle tower.
 {
     MAP_BATTLE_FRONTIER_BATTLE_TOWER_LOBBY,
-    0xFFFF,
+    INVALID_U16,
 };
 
 static bool32 IsCurMapReloadLocation(void)
@@ -83,7 +83,7 @@ static bool32 IsCurMapReloadLocation(void)
 // Nulled out list. Unknown what this would have been.
 static const u16 sUnknown_0861440E[] =
 {
-    0xFFFF,
+    INVALID_U16,
 };
 
 static bool32 sub_81AFCEC(void)
diff --git a/src/scanline_effect.c b/src/scanline_effect.c
index a9ae9427b..2e264ee29 100644
--- a/src/scanline_effect.c
+++ b/src/scanline_effect.c
@@ -22,10 +22,10 @@ void ScanlineEffect_Stop(void)
 {
     gScanlineEffect.state = 0;
     DmaStop(0);
-    if (gScanlineEffect.waveTaskId != 0xFF)
+    if (gScanlineEffect.waveTaskId != INVALID_U8)
     {
         DestroyTask(gScanlineEffect.waveTaskId);
-        gScanlineEffect.waveTaskId = 0xFF;
+        gScanlineEffect.waveTaskId = INVALID_U8;
     }
 }
 
@@ -40,7 +40,7 @@ void ScanlineEffect_Clear(void)
     gScanlineEffect.state = 0;
     gScanlineEffect.unused16 = 0;
     gScanlineEffect.unused17 = 0;
-    gScanlineEffect.waveTaskId = 0xFF;
+    gScanlineEffect.waveTaskId = INVALID_U8;
 }
 
 void ScanlineEffect_SetParams(struct ScanlineEffectParams params)
@@ -132,7 +132,7 @@ static void TaskFunc_UpdateWavePerFrame(u8 taskId)
     if (sShouldStopWaveTask)
     {
         DestroyTask(taskId);
-        gScanlineEffect.waveTaskId = 0xFF;
+        gScanlineEffect.waveTaskId = INVALID_U8;
     }
     else
     {
diff --git a/src/scrcmd.c b/src/scrcmd.c
index 310387337..4217f7237 100644
--- a/src/scrcmd.c
+++ b/src/scrcmd.c
@@ -790,7 +790,7 @@ bool8 ScrCmd_warphole(struct ScriptContext *ctx)
     u16 y;
 
     PlayerGetDestCoords(&x, &y);
-    if (mapGroup == 0xFF && mapNum == 0xFF)
+    if (mapGroup == INVALID_U8 && mapNum == INVALID_U8)
         SetFixedHoleWarpAsDestination(x - 7, y - 7);
     else
         Overworld_SetWarpDestination(mapGroup, mapNum, -1, x - 7, y - 7);
@@ -1491,7 +1491,7 @@ bool8 ScrCmd_braillemessage(struct ScriptContext *ctx)
     if (width > 0x1C)
         width = 0x1C;
 
-    for (i = 0, height = 4; gStringVar4[i] != 0xFF;)
+    for (i = 0, height = 4; gStringVar4[i] != INVALID_U8;)
     {
         if (gStringVar4[i++] == 0xFE)
             height += 3;
diff --git a/src/script.c b/src/script.c
index c61ae7183..4e133a188 100644
--- a/src/script.c
+++ b/src/script.c
@@ -391,11 +391,11 @@ bool32 sub_80991F8(void)
     struct RamScriptData *scriptData = &gSaveBlock1Ptr->ramScript.data;
     if (scriptData->magic != RAM_SCRIPT_MAGIC)
         return FALSE;
-    if (scriptData->mapGroup != 0xFF)
+    if (scriptData->mapGroup != INVALID_U8)
         return FALSE;
-    if (scriptData->mapNum != 0xFF)
+    if (scriptData->mapNum != INVALID_U8)
         return FALSE;
-    if (scriptData->objectId != 0xFF)
+    if (scriptData->objectId != INVALID_U8)
         return FALSE;
     if (CalculateRamScriptChecksum() != gSaveBlock1Ptr->ramScript.checksum)
         return FALSE;
@@ -409,11 +409,11 @@ u8 *sub_8099244(void)
         return NULL;
     if (scriptData->magic != RAM_SCRIPT_MAGIC)
         return NULL;
-    if (scriptData->mapGroup != 0xFF)
+    if (scriptData->mapGroup != INVALID_U8)
         return NULL;
-    if (scriptData->mapNum != 0xFF)
+    if (scriptData->mapNum != INVALID_U8)
         return NULL;
-    if (scriptData->objectId != 0xFF)
+    if (scriptData->objectId != INVALID_U8)
         return NULL;
     if (CalculateRamScriptChecksum() != gSaveBlock1Ptr->ramScript.checksum)
     {
diff --git a/src/script_menu.c b/src/script_menu.c
index 2aa546288..fcb2d17a2 100644
--- a/src/script_menu.c
+++ b/src/script_menu.c
@@ -1040,7 +1040,7 @@ bool8 ScriptMenu_Multichoice(u8 left, u8 top, u8 multichoiceId, u8 ignoreBPress)
     }
     else
     {
-        gSpecialVar_Result = 0xFF;
+        gSpecialVar_Result = INVALID_U8;
         DrawMultichoiceMenu(left, top, multichoiceId, ignoreBPress, 0);
         return TRUE;
     }
@@ -1054,7 +1054,7 @@ bool8 ScriptMenu_MultichoiceWithDefault(u8 left, u8 top, u8 multichoiceId, bool8
     }
     else
     {
-        gSpecialVar_Result = 0xFF;
+        gSpecialVar_Result = INVALID_U8;
         DrawMultichoiceMenu(left, top, multichoiceId, ignoreBPress, defaultChoice);
         return TRUE;
     }
@@ -1201,7 +1201,7 @@ bool8 ScriptMenu_YesNo(u8 left, u8 top)
     }
     else
     {
-        gSpecialVar_Result = 0xFF;
+        gSpecialVar_Result = INVALID_U8;
         DisplayYesNoMenu();
         taskId = CreateTask(Task_HandleYesNoInput, 0x50);
         return TRUE;
@@ -1211,7 +1211,7 @@ bool8 ScriptMenu_YesNo(u8 left, u8 top)
 // unused
 bool8 IsScriptActive(void)
 {
-    if (gSpecialVar_Result == 0xFF)
+    if (gSpecialVar_Result == INVALID_U8)
         return FALSE;
     else
         return TRUE;
@@ -1261,7 +1261,7 @@ bool8 ScriptMenu_MultichoiceGrid(u8 left, u8 top, u8 multichoiceId, u8 ignoreBPr
         int i;
         u8 newWidth;
 
-        gSpecialVar_Result = 0xFF;
+        gSpecialVar_Result = INVALID_U8;
         width = 0;
 
         for (i = 0; i < gMultichoiceLists[multichoiceId].count; i++)
@@ -1320,7 +1320,7 @@ bool8 ScrSpecial_CreatePCMenu(void)
     }
     else
     {
-        gSpecialVar_Result = 0xFF;
+        gSpecialVar_Result = INVALID_U8;
         CreatePCMenu();
         return TRUE;
     }
@@ -1389,7 +1389,7 @@ bool8 sub_80E2548(void)
     }
     else
     {
-        gSpecialVar_Result = 0xFF;
+        gSpecialVar_Result = INVALID_U8;
         sub_80E2578();
         return TRUE;
     }
@@ -1407,7 +1407,7 @@ static void sub_80E2578(void)
 
     for (i = 0; i < ARRAY_COUNT(gUnknown_03001124); i++)
     {
-        gUnknown_03001124[i] |= 0xFF;
+        gUnknown_03001124[i] |= INVALID_U8;
     }
 
     GetFontAttribute(1, FONTATTR_MAX_LETTER_WIDTH);
@@ -1508,7 +1508,7 @@ static void sub_80E2578(void)
         for (j = 0; j < ARRAY_COUNT(gUnknown_0858BB80); j++)
         {
             u8 test = gUnknown_03001124[j];
-            if (test != 0xFF)
+            if (test != INVALID_U8)
             {
                 pixelWidth = display_text_and_get_width(gUnknown_0858BB80[test], pixelWidth);
             }
@@ -1520,7 +1520,7 @@ static void sub_80E2578(void)
 
         for (temp = 0, i = 0; i < ARRAY_COUNT(gUnknown_0858BB80); i++)
         {
-            if (gUnknown_03001124[i] != 0xFF)
+            if (gUnknown_03001124[i] != INVALID_U8)
             {
                 AddTextPrinterParameterized(windowId, 1, gUnknown_0858BB80[gUnknown_03001124[i]], 8, temp * 16 + 1, TEXT_SPEED_FF, NULL);
                 temp++;
@@ -1575,7 +1575,7 @@ bool8 ScriptMenu_ShowPokemonPic(u16 species, u8 x, u8 y)
     u8 taskId;
     u8 spriteId;
 
-    if (FindTaskIdByFunc(Task_PokemonPicWindow) != 0xFF)
+    if (FindTaskIdByFunc(Task_PokemonPicWindow) != INVALID_U8)
     {
         return FALSE;
     }
@@ -1599,7 +1599,7 @@ bool8 (*ScriptMenu_GetPicboxWaitFunc(void))(void)
 {
     u8 taskId = FindTaskIdByFunc(Task_PokemonPicWindow);
 
-    if (taskId == 0xFF)
+    if (taskId == INVALID_U8)
         return NULL;
     gTasks[taskId].tState++;
     return IsPicboxClosed;
@@ -1607,7 +1607,7 @@ bool8 (*ScriptMenu_GetPicboxWaitFunc(void))(void)
 
 static bool8 IsPicboxClosed(void)
 {
-    if (FindTaskIdByFunc(Task_PokemonPicWindow) == 0xFF)
+    if (FindTaskIdByFunc(Task_PokemonPicWindow) == INVALID_U8)
         return TRUE;
     else
         return FALSE;
@@ -1672,7 +1672,7 @@ bool16 sp106_CreateStartMenu(void)
         return FALSE;
     }
 
-    gSpecialVar_Result = 0xFF;
+    gSpecialVar_Result = INVALID_U8;
     CreateStartMenu();
     return TRUE;
 }
diff --git a/src/script_movement.c b/src/script_movement.c
index 9fee9e060..54e6f9995 100644
--- a/src/script_movement.c
+++ b/src/script_movement.c
@@ -50,7 +50,7 @@ void sub_80D338C(void)
     u8 taskId;
 
     taskId = sub_80D33F4();
-    if (taskId != 0xFF)
+    if (taskId != INVALID_U8)
     {
         UnfreezeObjects(taskId);
         DestroyTask(taskId);
@@ -65,7 +65,7 @@ static void sub_80D33AC(u8 priority)
 
     taskId = CreateTask(sub_80D3660, priority);
     for (i = 1; i < 16; i++)
-        gTasks[taskId].data[i] = 0xFFFF;
+        gTasks[taskId].data[i] = INVALID_U16;
 }
 
 static u8 sub_80D33F4(void)
@@ -188,7 +188,7 @@ static void UnfreezeObjects(u8 taskId)
     pEventObjId = (u8 *)&gTasks[taskId].data[1];
     for (i = 0; i < 16; i++, pEventObjId++)
     {
-        if (*pEventObjId != 0xFF)
+        if (*pEventObjId != INVALID_U8)
             UnfreezeEventObject(&gEventObjects[*pEventObjId]);
     }
 }
@@ -201,7 +201,7 @@ static void sub_80D3660(u8 taskId)
     for (i = 0; i < 16; i++)
     {
         sub_80D3508(taskId, i, &var);
-        if (var != 0xFF)
+        if (var != INVALID_U8)
             sub_80A2490(taskId, i, var, sub_80D35CC(i));
     }
 }
diff --git a/src/script_pokemon_util_80F87D8.c b/src/script_pokemon_util_80F87D8.c
index 7fc61f953..77c1a88e0 100755
--- a/src/script_pokemon_util_80F87D8.c
+++ b/src/script_pokemon_util_80F87D8.c
@@ -318,7 +318,7 @@ void ShowContestEntryMonPic(void)
     u8 taskId;
     u8 left, top;
 
-    if (FindTaskIdByFunc(sub_80F8EE8) == 0xFF)
+    if (FindTaskIdByFunc(sub_80F8EE8) == INVALID_U8)
     {
         AllocateMonSpritesGfx();
         left = 10;
@@ -361,7 +361,7 @@ void ShowContestEntryMonPic(void)
 void sub_80F8EB8(void)
 {
     u8 taskId = FindTaskIdByFunc(sub_80F8EE8);
-    if (taskId != 0xFF)
+    if (taskId != INVALID_U8)
     {
         gTasks[taskId].data[0]++;
         FreeMonSpritesGfx();
diff --git a/src/secret_base.c b/src/secret_base.c
index 8436d8520..78e6bd7d0 100644
--- a/src/secret_base.c
+++ b/src/secret_base.c
@@ -3,7 +3,7 @@
 #include "global.h"
 #include "constants/bg_event_constants.h"
 #include "constants/decorations.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "main.h"
 #include "task.h"
 #include "palette.h"
@@ -1385,7 +1385,7 @@ s16 sub_80EA990(u8 secretBaseRecordId)
             return i;
         }
     }
-    return -1;
+    return INVALID_S16;
 }
 
 u8 sub_80EA9D8(void)
@@ -1427,7 +1427,7 @@ u8 sub_80EAA64(struct SecretBaseRecord *base, u32 version, u32 language)
     secretBaseRecordId = sub_80EA990(base->secretBaseId);
     if (secretBaseRecordId != 0)
     {
-        if (secretBaseRecordId != -1)
+        if (secretBaseRecordId != INVALID_S16)
         {
             if (gSaveBlock1Ptr->secretBases[secretBaseRecordId].sbr_field_1_0 == 1)
             {
@@ -1757,7 +1757,7 @@ void ReceiveSecretBasesData(void *records, size_t recordSize, u8 linkIdx)
                 gSaveBlock1Ptr->secretBases[i].sbr_field_1_6 = 0;
             }
         }
-        if (gSaveBlock1Ptr->secretBases[0].secretBaseId != 0 && gSaveBlock1Ptr->secretBases[0].sbr_field_e != 0xFFFF)
+        if (gSaveBlock1Ptr->secretBases[0].secretBaseId != 0 && gSaveBlock1Ptr->secretBases[0].sbr_field_e != INVALID_U16)
         {
             gSaveBlock1Ptr->secretBases[0].sbr_field_e ++;
         }
diff --git a/src/shop.c b/src/shop.c
index a0eddee01..c0359bda0 100755
--- a/src/shop.c
+++ b/src/shop.c
@@ -17,7 +17,7 @@
 #include "item_menu.h"
 #include "list_menu.h"
 #include "main.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "menu.h"
 #include "menu_helpers.h"
 #include "money.h"
@@ -446,9 +446,9 @@ static void CB2_InitBuyMenu(void)
         ResetTasks();
         clear_scheduled_bg_copies_to_vram();
         gShopDataPtr = AllocZeroed(sizeof(struct ShopData));
-        gShopDataPtr->scrollIndicatorsTaskId = 0xFF;
-        gShopDataPtr->itemSpriteIds[0] = -1;
-        gShopDataPtr->itemSpriteIds[1] = -1;
+        gShopDataPtr->scrollIndicatorsTaskId = INVALID_U8;
+        gShopDataPtr->itemSpriteIds[0] = INVALID_U8;
+        gShopDataPtr->itemSpriteIds[1] = INVALID_U8;
         BuyMenuBuildListMenuTemplate();
         BuyMenuInitBgs();
         FillBgTilemapBufferRect_Palette0(0, 0, 0, 0, 0x20, 0x20);
@@ -580,7 +580,7 @@ static void BuyMenuPrintPriceInList(u8 windowId, int item, u8 y)
 
 static void BuyMenuAddScrollIndicatorArrows(void)
 {
-    if (gShopDataPtr->scrollIndicatorsTaskId == 0xFF && gMartInfo.itemCount + 1 > 8)
+    if (gShopDataPtr->scrollIndicatorsTaskId == INVALID_U8 && gMartInfo.itemCount + 1 > 8)
     {
         gShopDataPtr->scrollIndicatorsTaskId = AddScrollIndicatorArrowPairParameterized(
             SCROLL_ARROW_UP,
@@ -596,10 +596,10 @@ static void BuyMenuAddScrollIndicatorArrows(void)
 
 static void BuyMenuRemoveScrollIndicatorArrows(void)
 {
-    if (gShopDataPtr->scrollIndicatorsTaskId != 0xFF)
+    if (gShopDataPtr->scrollIndicatorsTaskId != INVALID_U8)
     {
         RemoveScrollIndicatorArrowPair(gShopDataPtr->scrollIndicatorsTaskId);
-        gShopDataPtr->scrollIndicatorsTaskId = 0xFF;
+        gShopDataPtr->scrollIndicatorsTaskId = INVALID_U8;
     }
 }
 
@@ -613,10 +613,10 @@ static void BuyMenuAddItemIcon(u16 item, u8 iconSlot)
 {
     u8 spriteId;
     u8 *spriteIdPtr = &gShopDataPtr->itemSpriteIds[iconSlot];
-    if (*spriteIdPtr != 0xFF)
+    if (*spriteIdPtr != INVALID_U8)
         return;
 
-    if (gMartInfo.martType == MART_TYPE_0 || item == 0xFFFF)
+    if (gMartInfo.martType == MART_TYPE_0 || item == INVALID_U16)
     {
         spriteId = AddItemIconSprite(iconSlot + 2110, iconSlot + 2110, item);
         if (spriteId != MAX_SPRITES)
@@ -637,13 +637,13 @@ static void BuyMenuAddItemIcon(u16 item, u8 iconSlot)
 static void BuyMenuRemoveItemIcon(u16 item, u8 iconSlot)
 {
     u8 *spriteIdPtr = &gShopDataPtr->itemSpriteIds[iconSlot];
-    if (*spriteIdPtr == 0xFF)
+    if (*spriteIdPtr == INVALID_U8)
         return;
 
     FreeSpriteTilesByTag(iconSlot + 2110);
     FreeSpritePaletteByTag(iconSlot + 2110);
     DestroySprite(&gSprites[*spriteIdPtr]);
-    *spriteIdPtr = 0xFF;
+    *spriteIdPtr = INVALID_U8;
 }
 
 static void BuyMenuInitBgs(void)
diff --git a/src/slot_machine.c b/src/slot_machine.c
index 01ef6d85c..97fe0b146 100644
--- a/src/slot_machine.c
+++ b/src/slot_machine.c
@@ -14,7 +14,7 @@
 #include "util.h"
 #include "text.h"
 #include "menu.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "bg.h"
 #include "gpu_regs.h"
 #include "coins.h"
@@ -1637,7 +1637,7 @@ void PlaySlotMachine(u8 arg0, MainCallback cb)
 
 /*static */bool8 sub_8102A44(void)
 {
-    if (FindTaskIdByFunc(sub_8102A64) == 0xff)
+    if (FindTaskIdByFunc(sub_8102A64) == INVALID_U8)
         return TRUE;
     else
         return FALSE;
@@ -2672,7 +2672,7 @@ s16 sub_8102D5C(s16 a0)
 
 /*static */bool8 sub_810432C(void)
 {
-    if (FindTaskIdByFunc(sub_810434C) == 0xFF)
+    if (FindTaskIdByFunc(sub_810434C) == INVALID_U8)
         return TRUE;
     return FALSE;
 }
@@ -3007,7 +3007,7 @@ s16 sub_8102D5C(s16 a0)
 
 /*static */bool8 sub_8104AEC(void)
 {
-    if (FindTaskIdByFunc(sub_8104B0C) == 0xFF)
+    if (FindTaskIdByFunc(sub_8104B0C) == INVALID_U8)
         return TRUE;
     else
         return FALSE;
@@ -3108,7 +3108,7 @@ s16 sub_8102D5C(s16 a0)
     task = gTasks + sSlotMachine->unk3D;
     task->data[1] = arg0;
 
-    for (i = 0; gUnknown_083ED048[arg0][i].unk00 != 0xFF; i++)
+    for (i = 0; gUnknown_083ED048[arg0][i].unk00 != INVALID_U8; i++)
     {
         u8 spriteId;
         spriteId = sub_8105BB4(
@@ -3138,7 +3138,7 @@ s16 sub_8102D5C(s16 a0)
 {
     u8 i;
     struct Task *task = gTasks + sSlotMachine->unk3D;
-    if ((u16)task->data[1] != 0xFFFF)
+    if ((u16)task->data[1] != INVALID_U16)
         gUnknown_083ED064[task->data[1]]();
     for (i = 4; i < 16; i++)
     {
diff --git a/src/smokescreen.c b/src/smokescreen.c
index 9b37cd234..1119e9e90 100644
--- a/src/smokescreen.c
+++ b/src/smokescreen.c
@@ -12,7 +12,7 @@ u8 sub_807521C(s16 x, s16 y, u8 a3)
     u8 spriteId1, spriteId2, spriteId3, spriteId4;
     struct Sprite *mainSprite;
 
-    if (GetSpriteTileStartByTag(gUnknown_0831C620.tag) == 0xFFFF)
+    if (GetSpriteTileStartByTag(gUnknown_0831C620.tag) == INVALID_U16)
     {
         LoadCompressedObjectPicUsingHeap(&gUnknown_0831C620);
         LoadCompressedObjectPaletteUsingHeap(&gUnknown_0831C628);
diff --git a/src/sound.c b/src/sound.c
index ba3f659cc..7798700c3 100644
--- a/src/sound.c
+++ b/src/sound.c
@@ -247,7 +247,7 @@ void FadeInNewBGM(u16 songNum, u8 speed)
 {
     if (gDisableMusic)
         songNum = 0;
-    if (songNum == 0xFFFF)
+    if (songNum == INVALID_U16)
         songNum = 0;
     m4aSongNumStart(songNum);
     m4aMPlayImmInit(&gMPlayInfo_BGM);
@@ -544,7 +544,7 @@ void PlayBGM(u16 songNum)
 {
     if (gDisableMusic)
         songNum = 0;
-    if (songNum == 0xFFFF)
+    if (songNum == INVALID_U16)
         songNum = 0;
     m4aSongNumStart(songNum);
 }
diff --git a/src/sprite.c b/src/sprite.c
index 4087dd8c4..3f0223dee 100644
--- a/src/sprite.c
+++ b/src/sprite.c
@@ -108,7 +108,7 @@ typedef void (*AffineAnimCmdFunc)(u8 matrixNum, struct Sprite *);
     0                         \
 }
 
-#define ANIM_END        0xFFFF
+#define ANIM_END        INVALID_U16
 #define AFFINE_ANIM_END 0x7FFF
 
 // forward declarations
@@ -204,7 +204,7 @@ const union AffineAnimCmd * const gDummySpriteAffineAnimTable[] = { &sDummyAffin
 const struct SpriteTemplate gDummySpriteTemplate =
 {
     .tileTag = 0,
-    .paletteTag = 0xFFFF,
+    .paletteTag = INVALID_U16,
     .oam = &gDummyOamData,
     .anims = gDummySpriteAnimTable,
     .images = NULL,
@@ -572,12 +572,12 @@ u8 CreateSpriteAt(u8 index, const struct SpriteTemplate *template, s16 x, s16 y,
 
     CalcCenterToCornerVec(sprite, sprite->oam.shape, sprite->oam.size, sprite->oam.affineMode);
 
-    if (template->tileTag == 0xFFFF)
+    if (template->tileTag == INVALID_U16)
     {
         s16 tileNum;
         sprite->images = template->images;
         tileNum = AllocSpriteTiles((u8)(sprite->images->size / TILE_SIZE_4BPP));
-        if (tileNum == -1)
+        if (tileNum == INVALID_S16)
         {
             ResetSprite(sprite);
             return MAX_SPRITES;
@@ -595,7 +595,7 @@ u8 CreateSpriteAt(u8 index, const struct SpriteTemplate *template, s16 x, s16 y,
     if (sprite->oam.affineMode & ST_OAM_AFFINE_ON_MASK)
         InitSpriteAffineAnim(sprite);
 
-    if (template->paletteTag != 0xFFFF)
+    if (template->paletteTag != INVALID_U16)
         sprite->oam.paletteNum = IndexOfSpritePaletteTag(template->paletteTag);
 
     return index;
@@ -740,7 +740,7 @@ s16 AllocSpriteTiles(u16 tileCount)
             i++;
 
             if (i == TOTAL_OBJ_TILE_COUNT)
-                return -1;
+                return INVALID_S16;
         }
 
         start = i;
@@ -751,7 +751,7 @@ s16 AllocSpriteTiles(u16 tileCount)
             i++;
 
             if (i == TOTAL_OBJ_TILE_COUNT)
-                return -1;
+                return INVALID_S16;
 
             if (!SPRITE_TILE_IS_ALLOCATED(i))
                 numTilesFound++;
@@ -877,7 +877,7 @@ void ResetAllSprites(void)
 
 void FreeSpriteTiles(struct Sprite *sprite)
 {
-    if (sprite->template->tileTag != 0xFFFF)
+    if (sprite->template->tileTag != INVALID_U16)
         FreeSpriteTilesByTag(sprite->template->tileTag);
 }
 
@@ -923,7 +923,7 @@ void BeginAnim(struct Sprite *sprite)
     sprite->animLoopCounter = 0;
     imageValue = sprite->anims[sprite->animNum][sprite->animCmdIndex].frame.imageValue;
 
-    if (imageValue != -1)
+    if (imageValue != INVALID_S16)
     {
         sprite->animBeginning = FALSE;
         duration = sprite->anims[sprite->animNum][sprite->animCmdIndex].frame.duration;
@@ -1441,7 +1441,7 @@ u8 AllocOamMatrix(void)
         bit <<= 1;
     }
 
-    return 0xFF;
+    return INVALID_U8;
 }
 
 void FreeOamMatrix(u8 matrixNum)
@@ -1462,7 +1462,7 @@ void FreeOamMatrix(u8 matrixNum)
 void InitSpriteAffineAnim(struct Sprite *sprite)
 {
     u8 matrixNum = AllocOamMatrix();
-    if (matrixNum != 0xFF)
+    if (matrixNum != INVALID_U8)
     {
         CalcCenterToCornerVec(sprite, sprite->oam.shape, sprite->oam.size, sprite->oam.affineMode);
         sprite->oam.matrixNum = matrixNum;
@@ -1508,7 +1508,7 @@ void LoadSpriteSheets(const struct SpriteSheet *sheets)
 void FreeSpriteTilesByTag(u16 tag)
 {
     u8 index = IndexOfSpriteTileTag(tag);
-    if (index != 0xFF)
+    if (index != INVALID_U8)
     {
         u16 i;
         u16 *rangeStarts;
@@ -1523,7 +1523,7 @@ void FreeSpriteTilesByTag(u16 tag)
         for (i = start; i < start + count; i++)
             FREE_SPRITE_TILE(i);
 
-        sSpriteTileRangeTags[index] = 0xFFFF;
+        sSpriteTileRangeTags[index] = INVALID_U16;
     }
 }
 
@@ -1533,7 +1533,7 @@ void FreeSpriteTileRanges(void)
 
     for (i = 0; i < MAX_SPRITES; i++)
     {
-        sSpriteTileRangeTags[i] = 0xFFFF;
+        sSpriteTileRangeTags[i] = INVALID_U16;
         SET_SPRITE_TILE_RANGE(i, 0, 0);
     }
 }
@@ -1541,8 +1541,8 @@ void FreeSpriteTileRanges(void)
 u16 GetSpriteTileStartByTag(u16 tag)
 {
     u8 index = IndexOfSpriteTileTag(tag);
-    if (index == 0xFF)
-        return 0xFFFF;
+    if (index == INVALID_U8)
+        return INVALID_U16;
     return sSpriteTileRanges[index * 2];
 }
 
@@ -1554,7 +1554,7 @@ u8 IndexOfSpriteTileTag(u16 tag)
         if (sSpriteTileRangeTags[i] == tag)
             return i;
 
-    return 0xFF;
+    return INVALID_U8;
 }
 
 u16 GetSpriteTileTagByTileStart(u16 start)
@@ -1563,16 +1563,16 @@ u16 GetSpriteTileTagByTileStart(u16 start)
 
     for (i = 0; i < MAX_SPRITES; i++)
     {
-        if (sSpriteTileRangeTags[i] != 0xFFFF && sSpriteTileRanges[i * 2] == start)
+        if (sSpriteTileRangeTags[i] != INVALID_U16 && sSpriteTileRanges[i * 2] == start)
             return sSpriteTileRangeTags[i];
     }
 
-    return 0xFFFF;
+    return INVALID_U16;
 }
 
 void AllocSpriteTileRange(u16 tag, u16 start, u16 count)
 {
-    u8 freeIndex = IndexOfSpriteTileTag(0xFFFF);
+    u8 freeIndex = IndexOfSpriteTileTag(INVALID_U16);
     sSpriteTileRangeTags[freeIndex] = tag;
     SET_SPRITE_TILE_RANGE(freeIndex, start, count);
 }
@@ -1582,21 +1582,21 @@ void FreeAllSpritePalettes(void)
     u8 i;
     gReservedSpritePaletteCount = 0;
     for (i = 0; i < 16; i++)
-        sSpritePaletteTags[i] = 0xFFFF;
+        sSpritePaletteTags[i] = INVALID_U16;
 }
 
 u8 LoadSpritePalette(const struct SpritePalette *palette)
 {
     u8 index = IndexOfSpritePaletteTag(palette->tag);
 
-    if (index != 0xFF)
+    if (index != INVALID_U8)
         return index;
 
-    index = IndexOfSpritePaletteTag(0xFFFF);
+    index = IndexOfSpritePaletteTag(INVALID_U16);
 
-    if (index == 0xFF)
+    if (index == INVALID_U8)
     {
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
@@ -1610,7 +1610,7 @@ void LoadSpritePalettes(const struct SpritePalette *palettes)
 {
     u8 i;
     for (i = 0; palettes[i].data != NULL; i++)
-        if (LoadSpritePalette(&palettes[i]) == 0xFF)
+        if (LoadSpritePalette(&palettes[i]) == INVALID_U8)
             break;
 }
 
@@ -1621,10 +1621,10 @@ void DoLoadSpritePalette(const u16 *src, u16 paletteOffset)
 
 u8 AllocSpritePalette(u16 tag)
 {
-    u8 index = IndexOfSpritePaletteTag(0xFFFF);
-    if (index == 0xFF)
+    u8 index = IndexOfSpritePaletteTag(INVALID_U16);
+    if (index == INVALID_U8)
     {
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
@@ -1640,7 +1640,7 @@ u8 IndexOfSpritePaletteTag(u16 tag)
         if (sSpritePaletteTags[i] == tag)
             return i;
 
-    return 0xFF;
+    return INVALID_U8;
 }
 
 u16 GetSpritePaletteTagByPaletteNum(u8 paletteNum)
@@ -1651,8 +1651,8 @@ u16 GetSpritePaletteTagByPaletteNum(u8 paletteNum)
 void FreeSpritePaletteByTag(u16 tag)
 {
     u8 index = IndexOfSpritePaletteTag(tag);
-    if (index != 0xFF)
-        sSpritePaletteTags[index] = 0xFFFF;
+    if (index != INVALID_U8)
+        sSpritePaletteTags[index] = INVALID_U16;
 }
 
 void SetSubspriteTables(struct Sprite *sprite, const struct SubspriteTable *subspriteTables)
diff --git a/src/task.c b/src/task.c
index f067e21b4..2a77b8a9b 100644
--- a/src/task.c
+++ b/src/task.c
@@ -19,7 +19,7 @@ void ResetTasks(void)
         gTasks[i].func = TaskDummy;
         gTasks[i].prev = i;
         gTasks[i].next = i + 1;
-        gTasks[i].priority = -1;
+        gTasks[i].priority = INVALID_S8;
         memset(gTasks[i].data, 0, sizeof(gTasks[i].data));
     }
 
@@ -186,7 +186,7 @@ u8 FindTaskIdByFunc(TaskFunc func)
         if (gTasks[i].isActive == TRUE && gTasks[i].func == func)
             return (u8)i;
 
-    return -1;
+    return INVALID_U8;
 }
 
 u8 GetTaskCount(void)
diff --git a/src/text.c b/src/text.c
index 07c15596e..44895722d 100644
--- a/src/text.c
+++ b/src/text.c
@@ -1877,7 +1877,7 @@ u32 GetStringWidth(u8 fontId, const u8 *str, s16 letterSpacing)
     if (func == NULL)
         return 0;
 
-    if (letterSpacing == -1)
+    if (letterSpacing == INVALID_S16)
         localLetterSpacing = GetFontAttribute(fontId, FONTATTR_LETTER_SPACING);
     else
         localLetterSpacing = letterSpacing;
@@ -1953,7 +1953,7 @@ u32 GetStringWidth(u8 fontId, const u8 *str, s16 letterSpacing)
                 func = GetFontWidthFunc(*++str);
                 if (func == NULL)
                     return 0;
-                if (letterSpacing == -1)
+                if (letterSpacing == INVALID_S16)
                     localLetterSpacing = GetFontAttribute(*str, FONTATTR_LETTER_SPACING);
                 break;
             case 0x11:
diff --git a/src/trader.c b/src/trader.c
index e23efb4ce..afb0cca48 100644
--- a/src/trader.c
+++ b/src/trader.c
@@ -155,7 +155,7 @@ void ScrSpecial_IsDecorationFull(void)
 {
     gSpecialVar_Result = FALSE;
     if (gDecorations[gSpecialVar_0x8004].category != gDecorations[gSpecialVar_0x8006].category
-        && GetFirstEmptyDecorSlot(gDecorations[gSpecialVar_0x8004].category) == -1)
+        && GetFirstEmptyDecorSlot(gDecorations[gSpecialVar_0x8004].category) == INVALID_S8)
     {
         sub_8127250(gStringVar2, gDecorations[gSpecialVar_0x8004].category);
         gSpecialVar_Result = TRUE;
diff --git a/src/trainer_pokemon_sprites.c b/src/trainer_pokemon_sprites.c
index 040310901..fd97623fe 100644
--- a/src/trainer_pokemon_sprites.c
+++ b/src/trainer_pokemon_sprites.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "sprite.h"
 #include "window.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "constants/species.h"
 #include "palette.h"
 #include "decompress.h"
@@ -107,9 +107,9 @@ static void LoadPicPaletteByTagOrSlot(u16 species, u32 otId, u32 personality, u8
 {
     if (!isTrainer)
     {
-        if (paletteTag == 0xFFFF)
+        if (paletteTag == INVALID_U16)
         {
-            sCreatingSpriteTemplate.paletteTag |= 0xFFFF;
+            sCreatingSpriteTemplate.paletteTag |= INVALID_U16;
             LoadCompressedPalette(GetFrontSpritePalFromSpeciesAndPersonality(species, otId, personality), 0x100 + paletteSlot * 0x10, 0x20);
         }
         else
@@ -120,9 +120,9 @@ static void LoadPicPaletteByTagOrSlot(u16 species, u32 otId, u32 personality, u8
     }
     else
     {
-        if (paletteTag == 0xFFFF)
+        if (paletteTag == INVALID_U16)
         {
-            sCreatingSpriteTemplate.paletteTag |= 0xFFFF;
+            sCreatingSpriteTemplate.paletteTag |= INVALID_U16;
             LoadCompressedPalette(gTrainerFrontPicPaletteTable[species].data, 0x100 + paletteSlot * 0x10, 0x20);
         }
         else
@@ -166,30 +166,30 @@ static u16 CreatePicSprite(u16 species, u32 otId, u32 personality, bool8 isFront
     }
     if (i == PICS_COUNT)
     {
-        return 0xFFFF;
+        return INVALID_U16;
     }
     framePics = Alloc(4 * 0x800);
     if (!framePics)
     {
-        return 0xFFFF;
+        return INVALID_U16;
     }
     images = Alloc(4 * sizeof(struct SpriteFrameImage));
     if (!images)
     {
         Free(framePics);
-        return 0xFFFF;
+        return INVALID_U16;
     }
     if (DecompressPic(species, personality, isFrontPic, framePics, isTrainer, ignoreDeoxys))
     {
         // debug trap?
-        return 0xFFFF;
+        return INVALID_U16;
     }
     for (j = 0; j < 4; j ++)
     {
         images[j].data = framePics + 0x800 * j;
         images[j].size = 0x800;
     }
-    sCreatingSpriteTemplate.tileTag = 0xFFFF;
+    sCreatingSpriteTemplate.tileTag = INVALID_U16;
     sCreatingSpriteTemplate.oam = &gUnknown_0860B064;
     AssignSpriteAnimsTable(isTrainer);
     sCreatingSpriteTemplate.images = images;
@@ -197,7 +197,7 @@ static u16 CreatePicSprite(u16 species, u32 otId, u32 personality, bool8 isFront
     sCreatingSpriteTemplate.callback = DummyPicSpriteCallback;
     LoadPicPaletteByTagOrSlot(species, otId, personality, paletteSlot, paletteTag, isTrainer);
     spriteId = CreateSprite(&sCreatingSpriteTemplate, x, y, 0);
-    if (paletteTag == 0xFFFF)
+    if (paletteTag == INVALID_U16)
     {
         gSprites[spriteId].oam.paletteNum = paletteSlot;
     }
@@ -232,12 +232,12 @@ u16 CreatePicSprite2(u16 species, u32 otId, u32 personality, u8 flags, s16 x, s1
     }
     if (i == PICS_COUNT)
     {
-        return 0xFFFF;
+        return INVALID_U16;
     }
     framePics = Alloc(4 * 0x800);
     if (!framePics)
     {
-        return 0xFFFF;
+        return INVALID_U16;
     }
     if (flags & 0x80)
     {
@@ -252,19 +252,19 @@ u16 CreatePicSprite2(u16 species, u32 otId, u32 personality, u8 flags, s16 x, s1
     if (!images)
     {
         Free(framePics);
-        return 0xFFFF;
+        return INVALID_U16;
     }
     if (DecompressPic(species, personality, flags, framePics, FALSE, FALSE))
     {
         // debug trap?
-        return 0xFFFF;
+        return INVALID_U16;
     }
     for (j = 0; j < 4; j ++)
     {
         images[j].data = framePics + 0x800 * j;
         images[j].size = 0x800;
     }
-    sCreatingSpriteTemplate.tileTag = 0xFFFF;
+    sCreatingSpriteTemplate.tileTag = INVALID_U16;
     sCreatingSpriteTemplate.anims = gMonAnimationsSpriteAnimsPtrTable[species];
     sCreatingSpriteTemplate.images = images;
     if (flags2 == 0x01)
@@ -285,7 +285,7 @@ u16 CreatePicSprite2(u16 species, u32 otId, u32 personality, u8 flags, s16 x, s1
     sCreatingSpriteTemplate.callback = DummyPicSpriteCallback;
     LoadPicPaletteByTagOrSlot(species, otId, personality, paletteSlot, paletteTag, FALSE);
     spriteId = CreateSprite(&sCreatingSpriteTemplate, x, y, 0);
-    if (paletteTag == 0xFFFF)
+    if (paletteTag == INVALID_U16)
     {
         gSprites[spriteId].oam.paletteNum = paletteSlot;
     }
@@ -312,11 +312,11 @@ static u16 FreeAndDestroyPicSpriteInternal(u16 spriteId)
     }
     if (i == PICS_COUNT)
     {
-        return 0xFFFF;
+        return INVALID_U16;
     }
     framePics = sSpritePics[i].frames;
     images = sSpritePics[i].images;
-    if (sSpritePics[i].paletteTag != 0xFFFF)
+    if (sSpritePics[i].paletteTag != INVALID_U16)
     {
         FreeSpritePaletteByTag(GetSpritePaletteTagByPaletteNum(gSprites[spriteId].oam.paletteNum));
     }
@@ -331,7 +331,7 @@ static u16 sub_818D65C(u16 species, u32 otId, u32 personality, bool8 isFrontPic,
 {
     if (DecompressPic_HandleDeoxys(species, personality, isFrontPic, (u8 *)GetWindowAttribute(windowId, WINDOW_TILE_DATA), FALSE))
     {
-        return 0xFFFF;
+        return INVALID_U16;
     }
     LoadPicPaletteBySlot(species, otId, personality, paletteSlot, isTrainer);
     return 0;
@@ -349,7 +349,7 @@ static u16 sub_818D6CC(u16 species, u32 otId, u32 personality, bool8 isFrontPic,
         Free(framePics);
         return 0;
     }
-    return 0xFFFF;
+    return INVALID_U16;
 }
 
 static u16 CreateMonPicSprite(u16 species, u32 otId, u32 personality, bool8 isFrontPic, s16 x, s16 y, u8 paletteSlot, u16 paletteTag, bool8 ignoreDeoxys)
diff --git a/src/tv.c b/src/tv.c
index d3d1e797b..0c5c3f564 100644
--- a/src/tv.c
+++ b/src/tv.c
@@ -30,7 +30,7 @@
 #include "text.h"
 #include "script_menu.h"
 #include "naming_screen.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "region_map.h"
 #include "constants/region_map_sections.h"
 #include "decoration.h"
@@ -799,7 +799,7 @@ u8 special_0x44(void)
             j --;
         }
     } while (j != selIdx);
-    return 0xFF;
+    return INVALID_U8;
 }
 
 u8 FindAnyTVShowOnTheAir(void)
@@ -807,9 +807,9 @@ u8 FindAnyTVShowOnTheAir(void)
     u8 response;
 
     response = special_0x44();
-    if (response == 0xFF)
+    if (response == INVALID_U8)
     {
-        return 0xFF;
+        return INVALID_U8;
     }
     if (gSaveBlock1Ptr->outbreakPokemonSpecies != SPECIES_NONE && gSaveBlock1Ptr->tvShows[response].common.kind == TVSHOW_MASS_OUTBREAK)
     {
@@ -833,7 +833,7 @@ void UpdateTVScreensOnMap(int width, int height)
             {
                 SetTVMetatilesOnMap(width, height, 0x3);
             }
-            else if (FlagGet(FLAG_SYS_TV_START) && (FindAnyTVShowOnTheAir() != 0xff || FindAnyTVNewsOnTheAir() != 0xff || IsTVShowInSearchOfTrainersAiring()))
+            else if (FlagGet(FLAG_SYS_TV_START) && (FindAnyTVShowOnTheAir() != INVALID_U8 || FindAnyTVNewsOnTheAir() != INVALID_U8 || IsTVShowInSearchOfTrainersAiring()))
             {
                 FlagClear(FLAG_SYS_TV_WATCH);
                 SetTVMetatilesOnMap(width, height, 0x3);
@@ -887,7 +887,7 @@ u8 FindFirstActiveTVShowThatIsNotAMassOutbreak(void)
             return i;
         }
     }
-    return 0xFF;
+    return INVALID_U8;
 }
 
 u8 special_0x4a(void)
@@ -932,7 +932,7 @@ void GabbyAndTyBeforeInterview(void)
     gSaveBlock1Ptr->gabbyAndTyData.mon1 = gBattleResults.playerMon1Species;
     gSaveBlock1Ptr->gabbyAndTyData.mon2 = gBattleResults.playerMon2Species;
     gSaveBlock1Ptr->gabbyAndTyData.lastMove = gBattleResults.lastUsedMovePlayer;
-    if (gSaveBlock1Ptr->gabbyAndTyData.battleNum != 0xFF)
+    if (gSaveBlock1Ptr->gabbyAndTyData.battleNum != INVALID_U8)
     {
         gSaveBlock1Ptr->gabbyAndTyData.battleNum ++;
     }
@@ -1007,7 +1007,7 @@ bool8 IsTVShowInSearchOfTrainersAiring(void)
 
 bool8 GabbyAndTyGetLastQuote(void)
 {
-    if (gSaveBlock1Ptr->gabbyAndTyData.quote[0] == 0xFFFF)
+    if (gSaveBlock1Ptr->gabbyAndTyData.quote[0] == INVALID_U16)
     {
         return FALSE;
     }
@@ -1125,7 +1125,7 @@ void PutPokemonTodayCaughtOnAir(void)
         if (!rbernoulli(1, 1) && StringCompare(gSpeciesNames[gBattleResults.caughtMonSpecies], gBattleResults.caughtMonNick))
         {
             sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-            if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_POKEMON_TODAY_CAUGHT, FALSE) != TRUE)
+            if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_POKEMON_TODAY_CAUGHT, FALSE) != TRUE)
             {
                 for (i = 0; i < 11; i ++)
                 {
@@ -1206,7 +1206,7 @@ void PutPokemonTodayFailedOnTheAir(void)
         if (ct > 2 && (gBattleOutcome == B_OUTCOME_MON_FLED || gBattleOutcome == B_OUTCOME_WON))
         {
             sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-            if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_POKEMON_TODAY_FAILED, FALSE) != TRUE)
+            if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_POKEMON_TODAY_FAILED, FALSE) != TRUE)
             {
                 show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
                 show->pokemonTodayFailed.kind = TVSHOW_POKEMON_TODAY_FAILED;
@@ -1282,7 +1282,7 @@ void PutBattleUpdateOnTheAir(u8 opponentLinkPlayerId, u16 move, u16 speciesPlaye
     u8 name[32];
 
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         FindActiveBroadcastByShowType_SetScriptResult(TVSHOW_BATTLE_UPDATE);
         if (gSpecialVar_Result != 1)
@@ -1329,7 +1329,7 @@ bool8 Put3CheersForPokeblocksOnTheAir(const u8 *partnersName, u8 flavor, u8 unus
     u8 name[32];
 
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot == -1)
+    if (sCurTVShowSlot == INVALID_S8)
     {
         return FALSE;
     }
@@ -1396,7 +1396,7 @@ void ContestLiveUpdates_BeforeInterview_1(u8 a0)
 
     DeleteTVShowInArrayByIdx(gSaveBlock1Ptr->tvShows, 24);
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show = &gSaveBlock1Ptr->tvShows[24];
         show->contestLiveUpdates.round1Rank = a0;
@@ -1410,7 +1410,7 @@ void ContestLiveUpdates_BeforeInterview_2(u8 a0)
 
     show = &gSaveBlock1Ptr->tvShows[24];
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show->contestLiveUpdates.round2Rank = a0;
     }
@@ -1422,7 +1422,7 @@ void ContestLiveUpdates_BeforeInterview_3(u8 a0)
 
     show = &gSaveBlock1Ptr->tvShows[24];
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show->contestLiveUpdates.appealFlags1 = a0;
     }
@@ -1434,7 +1434,7 @@ void ContestLiveUpdates_BeforeInterview_4(u16 a0)
 
     show = &gSaveBlock1Ptr->tvShows[24];
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show->contestLiveUpdates.move = a0;
     }
@@ -1446,7 +1446,7 @@ void ContestLiveUpdates_BeforeInterview_5(u8 a0, u8 a1)
 
     show = &gSaveBlock1Ptr->tvShows[24];
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show->contestLiveUpdates.winningSpecies = gContestMons[a1].species;
         StringCopy(show->contestLiveUpdates.winningTrainerName, gContestMons[a1].trainerName);
@@ -1507,7 +1507,7 @@ void BravoTrainerPokemonProfile_BeforeInterview1(u16 a0)
     show = &gSaveBlock1Ptr->tvShows[24];
     InterviewBefore_BravoTrainerPkmnProfile();
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         DeleteTVShowInArrayByIdx(gSaveBlock1Ptr->tvShows, 24);
         show->bravoTrainer.move = a0;
@@ -1521,7 +1521,7 @@ void BravoTrainerPokemonProfile_BeforeInterview2(u8 a0)
 
     show = &gSaveBlock1Ptr->tvShows[24];
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show->bravoTrainer.contestResult = a0;
         show->bravoTrainer.contestCategory = gSpecialVar_ContestCategory;
@@ -1577,7 +1577,7 @@ void SaveRecordedItemPurchasesForTVShow(void)
      && !rbernoulli(1, 3))
     {
         sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-        if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_SMART_SHOPPER, FALSE) != TRUE)
+        if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_SMART_SHOPPER, FALSE) != TRUE)
         {
             TV_SortPurchasesByQuantity();
             if (gMartPurchaseHistory[0].quantity >= 20)
@@ -1742,7 +1742,7 @@ static void sub_80ED718(void)
         if (!rbernoulli(1, 200))
         {
             sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-            if (sCurTVShowSlot != -1)
+            if (sCurTVShowSlot != INVALID_S8)
             {
                 outbreakIdx = Random() % ARRAY_COUNT(sPokeOutbreakSpeciesList);
                 show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
@@ -1843,7 +1843,7 @@ void sub_80ED950(bool8 flag)
             PutFishingAdviceShowOnTheAir();
         }
         sPokemonAnglerAttemptCounters &= 0xFF;
-        if (sPokemonAnglerAttemptCounters != 0xFF)
+        if (sPokemonAnglerAttemptCounters != INVALID_U8)
         {
             sPokemonAnglerAttemptCounters += 0x01;
         }
@@ -1855,7 +1855,7 @@ void sub_80ED950(bool8 flag)
             PutFishingAdviceShowOnTheAir();
         }
         sPokemonAnglerAttemptCounters &= 0xFF00;
-        if (sPokemonAnglerAttemptCounters >> 8 != 0xFF)
+        if (sPokemonAnglerAttemptCounters >> 8 != INVALID_U8)
         {
             sPokemonAnglerAttemptCounters += 0x0100;
         }
@@ -1867,7 +1867,7 @@ void PutFishingAdviceShowOnTheAir(void)
     TVShow *show;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_FISHING_ADVICE, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_FISHING_ADVICE, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->pokemonAngler.kind = TVSHOW_FISHING_ADVICE;
@@ -1910,7 +1910,7 @@ void sub_80EDA80(void)
     if (!rbernoulli(1, 1))
     {
         sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-        if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_WORLD_OF_MASTERS, FALSE) != TRUE)
+        if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_WORLD_OF_MASTERS, FALSE) != TRUE)
         {
             show2 = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
             show2->worldOfMasters.kind = TVSHOW_WORLD_OF_MASTERS;
@@ -1936,7 +1936,7 @@ void sub_80EDB44(void)
 
     HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_TODAYS_RIVAL_TRAINER, TRUE);
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->rivalTrainer.kind = TVSHOW_TODAYS_RIVAL_TRAINER;
@@ -1984,7 +1984,7 @@ void sub_80EDC60(const u16 *words)
     TVShow *show;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_TREND_WATCHER, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_TREND_WATCHER, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->trendWatcher.kind = TVSHOW_TREND_WATCHER;
@@ -2003,7 +2003,7 @@ void sub_80EDCE8(void)
     TVShow *show;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_TREASURE_INVESTIGATORS, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_TREASURE_INVESTIGATORS, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->treasureInvestigators.kind = TVSHOW_TREASURE_INVESTIGATORS;
@@ -2024,7 +2024,7 @@ void sub_80EDD78(u16 nCoinsPaidOut)
     u16 nCoinsWon;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_FIND_THAT_GAMER, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_FIND_THAT_GAMER, FALSE) != TRUE)
     {
         flag = FALSE;
         switch (sFindThatGamerWhichGame)
@@ -2207,7 +2207,7 @@ void TV_PutSecretBaseVisitOnTheAir(void)
 
     HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_SECRET_BASE_VISIT, TRUE);
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->secretBaseVisit.kind = TVSHOW_SECRET_BASE_VISIT;
@@ -2227,7 +2227,7 @@ void sub_80EE184(void)
     u16 balls;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_BREAKING_NEWS, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_BREAKING_NEWS, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->breakingNews.kind = TVSHOW_BREAKING_NEWS;
@@ -2298,7 +2298,7 @@ void sub_80EE2CC(void)
     TVShow *show;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_LOTTO_WINNER, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_LOTTO_WINNER, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->lottoWinner.kind = TVSHOW_LOTTO_WINNER;
@@ -2318,7 +2318,7 @@ void sub_80EE35C(u16 foeSpecies, u16 species, u8 moveIdx, const u16 *movePtr, u1
     u8 j;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_BATTLE_SEMINAR, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_BATTLE_SEMINAR, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->battleSeminar.kind = TVSHOW_BATTLE_SEMINAR;
@@ -2347,7 +2347,7 @@ void sub_80EE44C(u8 nMonsCaught, u8 nPkblkUsed)
     TVShow *show;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_SAFARI_FAN_CLUB, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_SAFARI_FAN_CLUB, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->safariFanClub.kind = TVSHOW_SAFARI_FAN_CLUB;
@@ -2365,7 +2365,7 @@ void sub_80EE4DC(struct Pokemon *pokemon, u8 ribbonMonDataIdx)
     TVShow *show;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_CUTIES, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_CUTIES, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->cuties.kind = TVSHOW_CUTIES;
@@ -2440,7 +2440,7 @@ void sub_80EE72C(void)
     TVShow *show;
 
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_TRAINER_FAN_CLUB, FALSE) != TRUE)
+    if (sCurTVShowSlot != INVALID_S8 && HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_TRAINER_FAN_CLUB, FALSE) != TRUE)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->trainerFanClub.kind = TVSHOW_TRAINER_FAN_CLUB;
@@ -2456,7 +2456,7 @@ void sub_80EE72C(void)
 bool8 sub_80EE7C0(void)
 {
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot == -1)
+    if (sCurTVShowSlot == INVALID_S8)
     {
         return TRUE;
     }
@@ -2493,7 +2493,7 @@ bool8 sub_80EE818(void)
         }
     }
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot == -1)
+    if (sCurTVShowSlot == INVALID_S8)
     {
         return FALSE;
     }
@@ -2557,7 +2557,7 @@ void sub_80EEA70(void)
     if (HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_SECRET_BASE_SECRETS, FALSE) != TRUE)
     {
         sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-        if (sCurTVShowSlot != -1)
+        if (sCurTVShowSlot != INVALID_S8)
         {
             show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
             show->secretBaseSecrets.kind = TVSHOW_SECRET_BASE_SECRETS;
@@ -2608,7 +2608,7 @@ static void sub_80EEBF4(u8 actionIdx)
 
     HasMixableShowAlreadyBeenSpawnedWithPlayerID(TVSHOW_NUMBER_ONE, TRUE);
     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
-    if (sCurTVShowSlot != -1)
+    if (sCurTVShowSlot != INVALID_S8)
     {
         show = &gSaveBlock1Ptr->tvShows[sCurTVShowSlot];
         show->numberOne.kind = TVSHOW_NUMBER_ONE;
@@ -2665,7 +2665,7 @@ static void sub_80EED88(void)
     if (FlagGet(FLAG_SYS_GAME_CLEAR))
     {
         sCurTVShowSlot = sub_80EEE30(gSaveBlock1Ptr->pokeNews);
-        if (sCurTVShowSlot != -1 && rbernoulli(1, 100) != TRUE)
+        if (sCurTVShowSlot != INVALID_S8 && rbernoulli(1, 100) != TRUE)
         {
             newsKind = (Random() % 4) + POKENEWS_SLATEPORT;
             if (sub_80EF0E4(newsKind) != TRUE)
@@ -2689,7 +2689,7 @@ s8 sub_80EEE30(PokeNews *pokeNews)
             return i;
         }
     }
-    return -1;
+    return INVALID_S8;
 }
 
 void ClearPokemonNews(void)
@@ -2742,7 +2742,7 @@ u8 FindAnyTVNewsOnTheAir(void)
             return i;
         }
     }
-    return -1;
+    return INVALID_U8;
 }
 
 void DoPokeNews(void)
@@ -2751,7 +2751,7 @@ void DoPokeNews(void)
     u16 n;
 
     i = FindAnyTVNewsOnTheAir();
-    if (i == 0xFF)
+    if (i == INVALID_U8)
     {
         gSpecialVar_Result = FALSE;
     }
@@ -3252,7 +3252,7 @@ static void sub_80EFA88(void)
 {
     sCurTVShowSlot = FindEmptyTVSlotWithinFirstFiveShowsOfArray(gSaveBlock1Ptr->tvShows);
     gSpecialVar_0x8006 = sCurTVShowSlot;
-    if (sCurTVShowSlot == -1)
+    if (sCurTVShowSlot == INVALID_S8)
     {
         gSpecialVar_Result = TRUE;
     }
@@ -3273,7 +3273,7 @@ s8 FindEmptyTVSlotWithinFirstFiveShowsOfArray(TVShow *shows)
             return i;
         }
     }
-    return -1;
+    return INVALID_S8;
 }
 
 s8 FindEmptyTVSlotBeyondFirstFiveShowsOfArray(TVShow *shows)
@@ -3287,7 +3287,7 @@ s8 FindEmptyTVSlotBeyondFirstFiveShowsOfArray(TVShow *shows)
             return i;
         }
     }
-    return -1;
+    return INVALID_S8;
 }
 
 bool8 TV_BernoulliTrial(u16 ratio)
@@ -3310,7 +3310,7 @@ void TV_FanClubLetter_RandomWordToStringVar3(TVShow *show)
         {
             i = 0;
         }
-        if (show->fanclubLetter.words[i] != 0xFFFF)
+        if (show->fanclubLetter.words[i] != INVALID_U16)
         {
             break;
         }
@@ -3677,7 +3677,7 @@ static void sub_80F0358(TVShow player1[25], TVShow player2[25], TVShow player3[2
                 sRecordMixingPartnersWithoutShowsToShare = i;
             }
             sTVShowMixingCurSlot = sub_80F06D0(argslist[i][0]);
-            if (sTVShowMixingCurSlot == -1)
+            if (sTVShowMixingCurSlot == INVALID_S8)
             {
                 sRecordMixingPartnersWithoutShowsToShare ++;
                 if (sRecordMixingPartnersWithoutShowsToShare == sTVShowMixingNumPlayers)
@@ -3690,7 +3690,7 @@ static void sub_80F0358(TVShow player1[25], TVShow player2[25], TVShow player3[2
                 for (j = 0; j < sTVShowMixingNumPlayers - 1; j ++)
                 {
                     sCurTVShowSlot = FindEmptyTVSlotBeyondFirstFiveShowsOfArray(argslist[(i + j + 1) % sTVShowMixingNumPlayers][0]);
-                    if (sCurTVShowSlot != -1
+                    if (sCurTVShowSlot != INVALID_S8
                         && sub_80F049C(&argslist[(i + j + 1) % sTVShowMixingNumPlayers][0], &argslist[i][0], (i + j + 1) % sTVShowMixingNumPlayers) == 1)
                     {
                         break;
@@ -3801,7 +3801,7 @@ static s8 sub_80F06D0(TVShow *tvShows)
             return i;
         }
     }
-    return -1;
+    return INVALID_S8;
 }
 
 #ifdef NONMATCHING
@@ -4486,12 +4486,12 @@ static void sub_80F0D60(PokeNews player1[16], PokeNews player2[16], PokeNews pla
         for (j = 0; j < sTVShowNewsMixingNumPlayers; j ++)
         {
             sTVShowMixingCurSlot = sub_80F0ECC(*argslist[j], i);
-            if (sTVShowMixingCurSlot != -1)
+            if (sTVShowMixingCurSlot != INVALID_S8)
             {
                 for (k = 0; k < sTVShowNewsMixingNumPlayers - 1; k++)
                 {
                     sCurTVShowSlot = sub_80EEE30(*argslist[(j + k + 1) % sTVShowNewsMixingNumPlayers]);
-                    if (sCurTVShowSlot != -1)
+                    if (sCurTVShowSlot != INVALID_S8)
                     {
                         sub_80F0E58(argslist[(j + k + 1) % sTVShowNewsMixingNumPlayers], argslist[j]);
                     }
@@ -4538,7 +4538,7 @@ static s8 sub_80F0ECC(PokeNews *pokeNews, u8 idx)
 {
     if (pokeNews[idx].kind == POKENEWS_NONE)
     {
-        return -1;
+        return INVALID_S8;
     }
     return idx;
 }
@@ -7425,7 +7425,7 @@ static void DoTVShowSecretBaseSecrets(void)
                     }
                     break;
                 default:
-                    for (i = 0; i < 0xFFFF; i ++)
+                    for (i = 0; i < INVALID_U16; i ++)
                     {
                         sTVSecretBaseSecretsRandomValues[1] = Random() % bitCount;
                         if (sTVSecretBaseSecretsRandomValues[1] != sTVSecretBaseSecretsRandomValues[0])
@@ -7447,7 +7447,7 @@ static void DoTVShowSecretBaseSecrets(void)
             }
             else
             {
-                for (i = 0; i < 0xFFFF; i ++)
+                for (i = 0; i < INVALID_U16; i ++)
                 {
                     sTVSecretBaseSecretsRandomValues[2] = Random() % bitCount;
                     if (sTVSecretBaseSecretsRandomValues[2] != sTVSecretBaseSecretsRandomValues[0] && sTVSecretBaseSecretsRandomValues[2] != sTVSecretBaseSecretsRandomValues[1])
diff --git a/src/unk_pokedex_area_screen_helper.c b/src/unk_pokedex_area_screen_helper.c
index 6b88069bb..67fd52cb5 100644
--- a/src/unk_pokedex_area_screen_helper.c
+++ b/src/unk_pokedex_area_screen_helper.c
@@ -2,7 +2,7 @@
 #include "main.h"
 #include "menu.h"
 #include "bg.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "unk_pokedex_area_screen_helper.h"
 
diff --git a/src/use_pokeblock.c b/src/use_pokeblock.c
index 72c33100f..762019ecd 100644
--- a/src/use_pokeblock.c
+++ b/src/use_pokeblock.c
@@ -1,7 +1,7 @@
 #include "global.h"
 #include "main.h"
 #include "pokeblock.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "palette.h"
 #include "pokenav.h"
 #include "scanline_effect.h"
diff --git a/src/walda_phrase.c b/src/walda_phrase.c
index ff2ee7399..44da22f31 100644
--- a/src/walda_phrase.c
+++ b/src/walda_phrase.c
@@ -176,7 +176,7 @@ static void sub_81D9C90(u8 *array, s32 arg1, s32 arg2)
     s32 i, j;
     u8 var1, var2;
 
-    for (i = arg2 - 1; i != -1; i--)
+    for (i = arg2 - 1; i != INVALID_S32; i--)
     {
         var1 = (array[0] & 0x80) >> 7;
 
diff --git a/src/wild_encounter.c b/src/wild_encounter.c
index 9b3c70ad7..8fb7d08d6 100644
--- a/src/wild_encounter.c
+++ b/src/wild_encounter.c
@@ -4825,7 +4825,7 @@ static u16 GetCurrentMapWildMonHeaderId(void)
     for (i = 0; ; i++)
     {
         const struct WildPokemonHeader *wildHeader = &gWildMonHeaders[i];
-        if (wildHeader->mapGroup == 0xFF)
+        if (wildHeader->mapGroup == INVALID_U8)
             break;
 
         if (gWildMonHeaders[i].mapGroup == gSaveBlock1Ptr->location.mapGroup &&
@@ -4845,7 +4845,7 @@ static u16 GetCurrentMapWildMonHeaderId(void)
         }
     }
 
-    return -1;
+    return INVALID_S16;
 }
 
 static u8 PickWildMonNature(void)
@@ -5079,7 +5079,7 @@ bool8 StandardWildEncounter(u16 currMetaTileBehavior, u16 previousMetaTileBehavi
         return FALSE;
 
     headerId = GetCurrentMapWildMonHeaderId();
-    if (headerId == 0xFFFF) // invalid
+    if (headerId == INVALID_U16)
     {
         if (gMapHeader.mapLayoutId == 0x166)
         {
@@ -5190,7 +5190,7 @@ void RockSmashWildEncounter(void)
 {
     u16 headerId = GetCurrentMapWildMonHeaderId();
 
-    if (headerId != 0xFFFF)
+    if (headerId != INVALID_U16)
     {
         const struct WildPokemonInfo *wildPokemonInfo = gWildMonHeaders[headerId].rockSmashMonsInfo;
 
@@ -5222,7 +5222,7 @@ bool8 SweetScentWildEncounter(void)
 
     PlayerGetDestCoords(&x, &y);
     headerId = GetCurrentMapWildMonHeaderId();
-    if (headerId == 0xFFFF) // invalid
+    if (headerId == INVALID_U16)
     {
         if (gMapHeader.mapLayoutId == 0x166)
         {
@@ -5292,7 +5292,7 @@ bool8 DoesCurrentMapHaveFishingMons(void)
 {
     u16 headerId = GetCurrentMapWildMonHeaderId();
 
-    if (headerId != 0xFFFF && gWildMonHeaders[headerId].fishingMonsInfo != NULL)
+    if (headerId != INVALID_U16 && gWildMonHeaders[headerId].fishingMonsInfo != NULL)
         return TRUE;
     else
         return FALSE;
@@ -5326,7 +5326,7 @@ u16 GetLocalWildMon(bool8 *isWaterMon)
 
     *isWaterMon = FALSE;
     headerId = GetCurrentMapWildMonHeaderId();
-    if (headerId == 0xFFFF)
+    if (headerId == INVALID_U16)
         return SPECIES_NONE;
     landMonsInfo = gWildMonHeaders[headerId].landMonsInfo;
     waterMonsInfo = gWildMonHeaders[headerId].waterMonsInfo;
@@ -5358,7 +5358,7 @@ u16 GetLocalWaterMon(void)
 {
     u16 headerId = GetCurrentMapWildMonHeaderId();
 
-    if (headerId != 0xFFFF)
+    if (headerId != INVALID_U16)
     {
         const struct WildPokemonInfo *waterMonsInfo = gWildMonHeaders[headerId].waterMonsInfo;
 
diff --git a/src/window.c b/src/window.c
index 8efd1c281..d5b996df1 100644
--- a/src/window.c
+++ b/src/window.c
@@ -1,6 +1,6 @@
 #include "global.h"
 #include "window.h"
-#include "malloc.h"
+#include "alloc.h"
 #include "bg.h"
 #include "blit.h"
 
@@ -52,12 +52,12 @@ bool16 InitWindows(const struct WindowTemplate *templates)
         gWindows[i].tileData = NULL;
     }
 
-    for (i = 0, allocatedBaseBlock = 0, bgLayer = templates[i].bg; bgLayer != 0xFF && i < 0x20; ++i, bgLayer = templates[i].bg)
+    for (i = 0, allocatedBaseBlock = 0, bgLayer = templates[i].bg; bgLayer != INVALID_U8 && i < 0x20; ++i, bgLayer = templates[i].bg)
     {
         if (gUnneededFireRedVariable == 1)
         {
             allocatedBaseBlock = DummiedOutFireRedLeafGreenTileAllocFunc(bgLayer, 0, templates[i].width * templates[i].height, 0);
-            if (allocatedBaseBlock == -1)
+            if (allocatedBaseBlock == INVALID_S32)
                 return FALSE;
         }
 
@@ -65,7 +65,7 @@ bool16 InitWindows(const struct WindowTemplate *templates)
         {
             attrib = GetBgAttribute(bgLayer, 0x8);
 
-            if (attrib != 0xFFFF)
+            if (attrib != INVALID_U16)
             {
                 allocatedTilemapBuffer = AllocZeroed(attrib);
 
@@ -121,12 +121,12 @@ u16 AddWindow(const struct WindowTemplate *template)
 
     for (win = 0; win < WINDOWS_MAX; ++win)
     {
-        if ((bgLayer = gWindows[win].window.bg) == 0xFF)
+        if ((bgLayer = gWindows[win].window.bg) == INVALID_U8)
             break;
     }
 
     if (win == WINDOWS_MAX)
-        return 0xFF;
+        return INVALID_U8;
 
     bgLayer = template->bg;
     allocatedBaseBlock = 0;
@@ -135,20 +135,20 @@ u16 AddWindow(const struct WindowTemplate *template)
     {
         allocatedBaseBlock = DummiedOutFireRedLeafGreenTileAllocFunc(bgLayer, 0, template->width * template->height, 0);
 
-        if (allocatedBaseBlock == -1)
-            return 0xFF;
+        if (allocatedBaseBlock == INVALID_S32)
+            return INVALID_U8;
     }
 
     if (gUnknown_03002F70[bgLayer] == NULL)
     {
         attrib = GetBgAttribute(bgLayer, 0x8);
 
-        if (attrib != 0xFFFF)
+        if (attrib != INVALID_U16)
         {
             allocatedTilemapBuffer = AllocZeroed(attrib);
 
             if (allocatedTilemapBuffer == NULL)
-                return 0xFF;
+                return INVALID_U8;
 
             for (i = 0; i < attrib; ++i)
                 allocatedTilemapBuffer[i] = 0;
@@ -167,7 +167,7 @@ u16 AddWindow(const struct WindowTemplate *template)
             Free(gUnknown_03002F70[bgLayer]);
             gUnknown_03002F70[bgLayer] = allocatedTilemapBuffer;
         }
-        return 0xFF;
+        return INVALID_U8;
     }
 
     gWindows[win].tileData = allocatedTilemapBuffer;
@@ -190,12 +190,12 @@ int AddWindowWithoutTileMap(const struct WindowTemplate *template)
 
     for (win = 0; win < WINDOWS_MAX; ++win)
     {
-        if (gWindows[win].window.bg == 0xFF)
+        if (gWindows[win].window.bg == INVALID_U8)
             break;
     }
 
     if (win == WINDOWS_MAX)
-        return 0xFF;
+        return INVALID_U8;
 
     bgLayer = template->bg;
     allocatedBaseBlock = 0;
@@ -204,8 +204,8 @@ int AddWindowWithoutTileMap(const struct WindowTemplate *template)
     {
         allocatedBaseBlock = DummiedOutFireRedLeafGreenTileAllocFunc(bgLayer, 0, template->width * template->height, 0);
 
-        if (allocatedBaseBlock == -1)
-            return 0xFF;
+        if (allocatedBaseBlock == INVALID_S32)
+            return INVALID_U8;
     }
 
     gWindows[win].window = *template;
@@ -609,21 +609,21 @@ u16 AddWindow8Bit(struct WindowTemplate *template)
 
     for (windowId = 0; windowId < 32; windowId++)
     {
-        if (gWindows[windowId].window.bg == 0xFF)
+        if (gWindows[windowId].window.bg == INVALID_U8)
             break;
     }
     if (windowId == WINDOWS_MAX)
-        return 0xFF;
+        return INVALID_U8;
     bgLayer = template->bg;
     if (gUnknown_03002F70[bgLayer] == 0)
     {
         u16 attribute = GetBgAttribute(bgLayer, 8);
-        if (attribute != 0xFFFF)
+        if (attribute != INVALID_U16)
         {
             s32 i;
             memAddress = Alloc(attribute);
             if (memAddress == NULL)
-                return 0xFF;
+                return INVALID_U8;
             for (i = 0; i < attribute; i++) // if we're going to zero out the memory anyway, why not call AllocZeroed?
                 memAddress[i] = 0;
             gUnknown_03002F70[bgLayer] = memAddress;
@@ -638,7 +638,7 @@ u16 AddWindow8Bit(struct WindowTemplate *template)
             Free(gUnknown_03002F70[bgLayer]);
             gUnknown_03002F70[bgLayer] = NULL;
         }
-        return 0xFF;
+        return INVALID_U8;
     }
     else
     {
diff --git a/sym_bss.txt b/sym_bss.txt
index d006e1364..996187c26 100644
--- a/sym_bss.txt
+++ b/sym_bss.txt
@@ -1,5 +1,5 @@
 	.include "src/main.o"
-	.include "src/malloc.o"
+	.include "src/alloc.o"
 	.include "src/dma3_manager.o"
 	.include "src/gpu_regs.o"
 	.include "src/bg.o"