diff --git a/Makefile b/Makefile
index 27d77754c0..53a2c7f256 100644
--- a/Makefile
+++ b/Makefile
@@ -67,7 +67,7 @@ OBJ_DIR := build/emerald
 LIBPATH := -L ../../tools/agbcc/lib
 else
 CC1              = $(shell $(CC) --print-prog-name=cc1) -quiet
-override CFLAGS += -mthumb -mthumb-interwork -O2 -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -fno-aggressive-loop-optimizations -Wno-pointer-to-int-cast
+override CFLAGS += -mthumb -mthumb-interwork -O2 -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -Wno-pointer-to-int-cast
 ROM := pokeemerald_modern.gba
 OBJ_DIR := build/modern
 LIBPATH := -L "$(dir $(shell $(CC) -mthumb -print-file-name=libgcc.a))" -L "$(dir $(shell $(CC) -mthumb -print-file-name=libc.a))"
@@ -232,7 +232,7 @@ $(C_BUILDDIR)/record_mixing.o: CFLAGS += -ffreestanding
 $(C_BUILDDIR)/librfu_intr.o: CC1 := tools/agbcc/bin/agbcc_arm
 $(C_BUILDDIR)/librfu_intr.o: CFLAGS := -O2 -mthumb-interwork -quiet
 else
-$(C_BUILDDIR)/librfu_intr.o: CFLAGS := -mthumb-interwork -O2 -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -fno-aggressive-loop-optimizations -Wno-pointer-to-int-cast
+$(C_BUILDDIR)/librfu_intr.o: CFLAGS := -mthumb-interwork -O2 -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -Wno-pointer-to-int-cast
 endif
 
 ifeq ($(NODEP),1)
diff --git a/include/config.h b/include/config.h
index 318ed39d84..4f97a12a3b 100644
--- a/include/config.h
+++ b/include/config.h
@@ -26,4 +26,12 @@
 #define UNITS_METRIC
 #endif
 
+// Various undefined behavior bugs may or may not prevent compilation with
+// newer compilers. So always fix them when using a modern compiler.
+#if MODERN
+#ifndef UBFIX
+#define UBFIX
+#endif
+#endif
+
 #endif // GUARD_CONFIG_H
diff --git a/include/global.tv.h b/include/global.tv.h
index 34791d43c9..ba1c3c37ee 100644
--- a/include/global.tv.h
+++ b/include/global.tv.h
@@ -18,6 +18,13 @@ typedef union // size = 0x24
         /*0x23*/ u8 trainerIdHi;
     } common;
 
+    // Common init (used for initialization loop)
+    struct {
+        /*0x00*/ u8 kind;
+        /*0x01*/ bool8 active;
+        /*0x02*/ u8 pad02[34];
+    } commonInit;
+
     // Local shows
     // TVSHOW_FAN_CLUB_LETTER
     struct {
diff --git a/src/berry_blender.c b/src/berry_blender.c
index 2a122541d4..4d3b7eb6f9 100644
--- a/src/berry_blender.c
+++ b/src/berry_blender.c
@@ -2202,6 +2202,11 @@ static s16 sub_8081BD4(void)
     return sUnknown_03000E06;
 }
 
+#if MODERN
+// TODO remove this as soon as the code below is understood
+// add a UBFIX if required (code buggy?)
+__attribute__((optimize("no-aggressive-loop-optimizations")))
+#endif
 static void Blender_CalculatePokeblock(struct BlenderBerry *berries, struct Pokeblock *pokeblock, u8 playersNo, u8 *flavors, u16 maxRPM)
 {
     s32 i, j;
diff --git a/src/berry_crush.c b/src/berry_crush.c
index 48e4ac4c33..48ad7f4e3c 100755
--- a/src/berry_crush.c
+++ b/src/berry_crush.c
@@ -3209,6 +3209,11 @@ static u32 sub_8024568(__attribute__((unused)) struct BerryCrushGame *r0, __attr
     return 0;
 }
 
+#if MODERN
+// TODO remove this as soon as the code below is understood
+// add a UBFIX if required (code buggy?)
+__attribute__((optimize("no-aggressive-loop-optimizations")))
+#endif
 void sub_8024578(struct BerryCrushGame *r4)
 {
     u8 r5 = 0;
diff --git a/src/easy_chat.c b/src/easy_chat.c
index 1bdb3fdc09..2a4c49213a 100644
--- a/src/easy_chat.c
+++ b/src/easy_chat.c
@@ -5273,12 +5273,17 @@ void InitEasyChatPhrases(void)
             gSaveBlock1Ptr->mail[i].words[j] = 0xFFFF;
     }
 
+#ifndef UBFIX
     // BUG: This is supposed to clear 64 bits, but this loop is clearing 64 bytes.
     // However, this bug has no resulting effect on gameplay because only the
     // Mauville old man data is corrupted, which is initialized directly after
     // this function is called when starting a new game.
     for (i = 0; i < 64; i++)
         gSaveBlock1Ptr->additionalPhrases[i] = 0;
+#else
+    for (i = 0; i < ARRAY_COUNT(gSaveBlock1Ptr->additionalPhrases); i++)
+        gSaveBlock1Ptr->additionalPhrases[i] = 0;
+#endif
 }
 
 static bool8 sub_811F28C(void)
diff --git a/src/fieldmap.c b/src/fieldmap.c
index e953e0f935..25157ebb16 100644
--- a/src/fieldmap.c
+++ b/src/fieldmap.c
@@ -533,9 +533,16 @@ static bool32 SavedMapViewIsEmpty(void)
     u16 i;
     u32 marker = 0;
 
+#ifndef UBFIX
     // BUG: This loop extends past the bounds of the mapView array. Its size is only 0x100.
     for (i = 0; i < 0x200; i++)
         marker |= gSaveBlock1Ptr->mapView[i];
+#else
+    // UBFIX: Only iterate over 0x100
+    for (i = 0; i < ARRAY_COUNT(gSaveBlock1Ptr->mapView); i++)
+        marker |= gSaveBlock1Ptr->mapView[i];
+#endif
+
 
     if (marker == 0)
         return TRUE;
diff --git a/src/image_processing_effects.c b/src/image_processing_effects.c
index 13794faf0b..cbd8b9b374 100644
--- a/src/image_processing_effects.c
+++ b/src/image_processing_effects.c
@@ -5,7 +5,7 @@
 
 // IWRAM common
 u8 gCanvasColumnStart;
-u16 (*gCanvasPixels)[][32];
+u16 *gCanvasPixels;
 u8 gCanvasRowEnd;
 u8 gCanvasHeight;
 u8 gCanvasColumnEnd;
@@ -125,7 +125,7 @@ static void ApplyImageEffect_RedChannelGrayscale(u8 delta)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -150,7 +150,7 @@ static void ApplyImageEffect_RedChannelGrayscaleHighlight(u8 highlight)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -179,7 +179,7 @@ static void ApplyImageEffect_Grayscale(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -195,7 +195,7 @@ static void ApplyImageEffect_Blur(void)
 
     for (i = 0; i < gCanvasColumnEnd; i++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][gCanvasRowStart * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[gCanvasRowStart * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart + i];
         u16 prevPixel = *pixel;
 
@@ -221,7 +221,7 @@ static void ApplyImageEffect_PersonalityColor(u8 personality)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -237,7 +237,7 @@ static void ApplyImageEffect_BlackAndWhite(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -255,7 +255,7 @@ static void ApplyImageEffect_BlackOutline(void)
     // Handle top row of pixels first.
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         pixel = &pixelRow[gCanvasColumnStart];
         *pixel = QuantizePixel_BlackOutline(pixel, pixel + 1);
         for (i = 1, pixel++; i < gCanvasColumnEnd - 1; i++, pixel++)
@@ -270,7 +270,7 @@ static void ApplyImageEffect_BlackOutline(void)
     // Handle each column from left to right.
     for (i = 0; i < gCanvasColumnEnd; i++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][gCanvasRowStart * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[gCanvasRowStart * gCanvasWidth];
         pixel = &pixelRow[gCanvasColumnStart + i];
         *pixel = QuantizePixel_BlackOutline(pixel, pixel + gCanvasWidth);
         for (j = 1, pixel += gCanvasWidth; j < gCanvasRowEnd - 1; j++, pixel += gCanvasWidth)
@@ -289,7 +289,7 @@ static void ApplyImageEffect_Invert(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -306,7 +306,7 @@ static void ApplyImageEffect_Shimmer(void)
     u16 prevPixel;
 
     // First, invert all of the colors.
-    pixel = (*gCanvasPixels)[0];
+    pixel = gCanvasPixels;
     for (i = 0; i < 64; i++)
     {
         for (j = 0; j < 64; j++, pixel++)
@@ -319,7 +319,7 @@ static void ApplyImageEffect_Shimmer(void)
     // Blur the pixels twice.
     for (j = 0; j < 64; j++)
     {
-        pixel = &(*gCanvasPixels)[0][j];
+        pixel = &gCanvasPixels[j];
         prevPixel = *pixel;
         *pixel = 0x8000;
         for (i = 1, pixel += 64; i < 63; i++, pixel += 64)
@@ -332,7 +332,7 @@ static void ApplyImageEffect_Shimmer(void)
         }
 
         *pixel = 0x8000;
-        pixel = &(*gCanvasPixels)[0][j];
+        pixel = &gCanvasPixels[j];
         prevPixel = *pixel;
         *pixel = 0x8000;
         for (i = 1, pixel += 64; i < 63; i++, pixel += 64)
@@ -350,7 +350,7 @@ static void ApplyImageEffect_Shimmer(void)
     // Finally, invert colors back to the original color space.
     // The above blur causes the outline areas to darken, which makes
     // this inversion give the effect of light outlines.
-    pixel = (*gCanvasPixels)[0];
+    pixel = gCanvasPixels;
     for (i = 0; i < 64; i++)
     {
         for (j = 0; j < 64; j++, pixel++)
@@ -367,7 +367,7 @@ static void ApplyImageEffect_BlurRight(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         u16 prevPixel = *pixel;
         for (i = 1, pixel++; i < gCanvasColumnEnd - 1; i++, pixel++)
@@ -387,7 +387,7 @@ static void ApplyImageEffect_BlurDown(void)
 
     for (i = 0; i < gCanvasColumnEnd; i++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][gCanvasRowStart * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[gCanvasRowStart * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart + i];
         u16 prevPixel = *pixel;
         for (j = 1, pixel += gCanvasWidth; j < gCanvasRowEnd - 1; j++, pixel += gCanvasWidth)
@@ -445,7 +445,7 @@ static void AddPointillismPoints(u16 arg0)
 
     for (i = 0; i < points[0].delta; i++)
     {
-        u16 *pixel = &(*gCanvasPixels)[points[i].row * 2][points[i].column];
+        u16 *pixel = &gCanvasPixels[points[i].row * 64] + points[i].column;
 
         if (!(0x8000 & *pixel))
         {
@@ -910,7 +910,7 @@ static void QuantizePalette_Standard(bool8 useLimitedPalette)
     gCanvasPalette[maxIndex] = RGB2(15, 15, 15);
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -978,7 +978,7 @@ static void QuantizePalette_BlackAndWhite(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -1009,7 +1009,7 @@ static void QuantizePalette_GrayscaleSmall(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -1027,7 +1027,7 @@ static void QuantizePalette_Grayscale(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
@@ -1045,7 +1045,7 @@ static void QuantizePalette_PrimaryColors(void)
 
     for (j = 0; j < gCanvasRowEnd; j++)
     {
-        u16 *pixelRow = &(*gCanvasPixels)[0][(gCanvasRowStart + j) * gCanvasWidth];
+        u16 *pixelRow = &gCanvasPixels[(gCanvasRowStart + j) * gCanvasWidth];
         u16 *pixel = &pixelRow[gCanvasColumnStart];
         for (i = 0; i < gCanvasColumnEnd; i++, pixel++)
         {
diff --git a/src/slot_machine.c b/src/slot_machine.c
index 9e94d11f02..d1cb05b180 100644
--- a/src/slot_machine.c
+++ b/src/slot_machine.c
@@ -384,7 +384,7 @@ static const u16 gSlotPayouts[];
 static const u8 *const gUnknown_083EDCE4;
 static const u8 *const gUnknown_083EDCDC;
 static const u32 gReelTimeGfx[];
-static const struct SpriteSheet gSlotMachineSpriteSheets[];
+static const struct SpriteSheet gSlotMachineSpriteSheets[22];
 static const struct SpritePalette gSlotMachineSpritePalettes[];
 static const u16 *const gUnknown_083EDE20;
 static const s16 gInitialReelPositions[][2];
@@ -4171,8 +4171,8 @@ static void sub_81063C0(void)
     LZDecompressWram(gSlotMachineReelTime_Gfx, sUnknown_0203AAD4);
     sUnknown_0203AAD8 = Alloc(0x3600);
     LZDecompressWram(gReelTimeGfx, sUnknown_0203AAD8);
-    sUnknown_0203AB30 = AllocZeroed(sizeof(struct SpriteSheet) * 22);
-    for (i = 0; i < 22; i++)
+    sUnknown_0203AB30 = AllocZeroed(sizeof(struct SpriteSheet) * ARRAY_COUNT(gSlotMachineSpriteSheets));
+    for (i = 0; i < ARRAY_COUNT(gSlotMachineSpriteSheets); i++)
     {
         sUnknown_0203AB30[i].data = gSlotMachineSpriteSheets[i].data;
         sUnknown_0203AB30[i].size = gSlotMachineSpriteSheets[i].size;
@@ -6708,7 +6708,7 @@ static const struct SubspriteTable *const gUnknown_083EDBC4[] =
     NULL
 };
 
-static const struct SpriteSheet gSlotMachineSpriteSheets[] =
+static const struct SpriteSheet gSlotMachineSpriteSheets[22] =
 {
     { .data = gSlotMachineReelSymbol1Tiles, .size = 0x200, .tag = 0 },
     { .data = gSlotMachineReelSymbol2Tiles, .size = 0x200, .tag = 1 },
@@ -6727,15 +6727,12 @@ static const struct SpriteSheet gSlotMachineSpriteSheets[] =
     { .data = gSlotMachineNumber7Tiles, .size = 0x40, .tag = 14 },
     { .data = gSlotMachineNumber8Tiles, .size = 0x40, .tag = 15 },
     { .data = gSlotMachineNumber9Tiles, .size = 0x40, .tag = 16 },
-};
-
-static const u8 sUnused1[][8] = 
-{
-    {0, 0, 0, 0, 0, 2, 18},
-    {0, 0, 0, 0, 0, 2, 19}, 
-    {0, 0, 0, 0, 0, 3, 20}, 
-    {0, 0, 0, 0, 0, 3, 21}, 
-    {0, 0, 0, 0, 0, 0,  0}
+    // the data for these sheets is determined at runtime
+    { .data = NULL, .size = 0x200, .tag = 18 },
+    { .data = NULL, .size = 0x200, .tag = 19 },
+    { .data = NULL, .size = 0x300, .tag = 20 },
+    { .data = NULL, .size = 0x300, .tag = 21 },
+    {},
 };
 
 static const u8 *const gUnknown_083EDCDC = gUnknown_08DD19F8;
diff --git a/src/tv.c b/src/tv.c
index eaf30f82b8..b3722e87a2 100644
--- a/src/tv.c
+++ b/src/tv.c
@@ -764,11 +764,11 @@ void ClearTVShowData(void)
 
     for (i = 0; i < ARRAY_COUNT(gSaveBlock1Ptr->tvShows); i ++)
     {
-        gSaveBlock1Ptr->tvShows[i].common.kind = 0;
-        gSaveBlock1Ptr->tvShows[i].common.active = 0;
-        for (j = 0; j < sizeof(TVShow) - 2; j ++)
+        gSaveBlock1Ptr->tvShows[i].commonInit.kind = 0;
+        gSaveBlock1Ptr->tvShows[i].commonInit.active = 0;
+        for (j = 0; j < ARRAY_COUNT(gSaveBlock1Ptr->tvShows[i].commonInit.pad02); j ++)
         {
-            gSaveBlock1Ptr->tvShows[i].common.pad02[j] = 0;
+            gSaveBlock1Ptr->tvShows[i].commonInit.pad02[j] = 0;
         }
     }
     ClearPokemonNews();
@@ -3167,11 +3167,11 @@ void DeleteTVShowInArrayByIdx(TVShow *shows, u8 idx)
 {
     u8 i;
 
-    shows[idx].common.kind = TVSHOW_OFF_AIR;
-    shows[idx].common.active = FALSE;
-    for (i = 0; i < 34; i ++)
+    shows[idx].commonInit.kind = TVSHOW_OFF_AIR;
+    shows[idx].commonInit.active = FALSE;
+    for (i = 0; i < ARRAY_COUNT(shows[idx].commonInit.pad02); i++)
     {
-        shows[idx].common.pad02[i] = 0;
+        shows[idx].commonInit.pad02[i] = 0;
     }
 }