diff --git a/Makefile b/Makefile
index 51fcaad..f7dd653 100644
--- a/Makefile
+++ b/Makefile
@@ -124,8 +124,9 @@ SPLAT_YAML      ?= $(TARGET)-$(VERSION).yaml
 
 
 
-IINC := -Iinclude -I.
-IINC += -Ilib/ultralib/include -Ilib/ultralib/include/PR -Ilib/ultralib/include/ido
+IINC := -Iinclude -Iinclude/libc
+IINC += -Ilib/ultralib/include -Ilib/ultralib/include/PR
+IINC += -I.
 
 ifeq ($(KEEP_MDEBUG),0)
   RM_MDEBUG = $(OBJCOPY) --remove-section .mdebug $@
diff --git a/include/gfxprint.h b/include/gfxprint.h
index 226951e..4d92ab4 100644
--- a/include/gfxprint.h
+++ b/include/gfxprint.h
@@ -2,9 +2,11 @@
 #define LIBU64_GFX_PRINT_H
 
 #include "ultra64.h"
-#include "color.h"
+
+#include "stdbool.h"
+
 #include "aprintf.h"
-#include "libc/stdbool.h"
+#include "color.h"
 
 typedef struct gfxprint  {
     /* 0x00 */ PrintCallback proutFunc; /* Current print out func */
diff --git a/include/global.h b/include/global.h
index 92c04e0..d28c29f 100644
--- a/include/global.h
+++ b/include/global.h
@@ -3,9 +3,9 @@
 
 #include "ultra64.h"
 
-#include "libc/stdbool.h"
-#include "libc/stddef.h"
-#include "libc/stdint.h"
+#include "stdbool.h"
+#include "stddef.h"
+#include "stdint.h"
 
 #include "attributes.h"
 #include "eepmgr.h"
diff --git a/include/libc/math.h b/include/libc/math.h
index 8501a66..4b27be5 100644
--- a/include/libc/math.h
+++ b/include/libc/math.h
@@ -1,12 +1,26 @@
-#ifndef MATH_H
-#define MATH_H
-
-#include "PR/ultratypes.h"
-
-float fabsf(float f);
-#pragma intrinsic(fabsf)
-
-double fabs(double f);
-#pragma intrinsic(fabs)
-
-#endif
+#ifndef LIBC_MATH_H
+#define LIBC_MATH_H
+
+#define M_PI 3.14159265358979323846
+#define M_PIf 3.14159265358979323846f
+#define M_SQRT2f 1.41421356237309504880f
+#define M_SQRT1_2f 0.70710678118654752440f /* 1/sqrt(2) */
+
+#define FLT_MAX 3.40282347e+38f
+#define SHRT_MAX 32767.0f
+
+float fabsf(float f);
+#pragma intrinsic(fabsf)
+#ifdef __GNUC__
+#define fabsf(f) __builtin_fabsf((float)(f))
+#endif
+
+double fabs(double f);
+#pragma intrinsic(fabs)
+
+double sqrt(double d);
+#pragma intrinsic(sqrt)
+
+float fmodf(float dividend, float divisor);
+
+#endif
diff --git a/include/libc/stdarg.h b/include/libc/stdarg.h
new file mode 100644
index 0000000..55f6943
--- /dev/null
+++ b/include/libc/stdarg.h
@@ -0,0 +1,44 @@
+#ifndef LIBC_STDARG_H
+#define LIBC_STDARG_H
+
+// When building with GCC, use the official vaarg macros to avoid warnings
+// and possibly bad codegen.
+#ifdef __GNUC__
+#define va_list __builtin_va_list
+#define va_start __builtin_va_start
+#define va_arg __builtin_va_arg
+#define va_end __builtin_va_end
+#else
+
+typedef char *va_list;
+#define _FP 1
+#define _INT 0
+#define _STRUCT 2
+
+#define _VA_FP_SAVE_AREA 0x10
+#define _VA_ALIGN(p, a) (((unsigned int)(((char *)p) + ((a) > 4 ? (a) : 4) - 1)) & -((a) > 4 ? (a) : 4))
+#define va_start(vp, parmN) (vp = ((va_list)&parmN + sizeof(parmN)))
+
+#define __va_stack_arg(list, mode)                          \
+    (                                                       \
+        ((list) = (char *)_VA_ALIGN(list, __builtin_alignof(mode)) + \
+                  _VA_ALIGN(sizeof(mode), 4)),              \
+        (((char *)list) - (_VA_ALIGN(sizeof(mode), 4) - sizeof(mode))))
+
+#define __va_double_arg(list, mode)                                                                    \
+    (                                                                                                  \
+        (((long)list & 0x1) /* 1 byte aligned? */                                                      \
+             ? (list = (char *)((long)list + 7), (char *)((long)list - 6 - _VA_FP_SAVE_AREA))          \
+             : (((long)list & 0x2) /* 2 byte aligned? */                                               \
+                    ? (list = (char *)((long)list + 10), (char *)((long)list - 24 - _VA_FP_SAVE_AREA)) \
+                    : __va_stack_arg(list, mode))))
+
+#define va_arg(list, mode) ((mode *)(((__builtin_classof(mode) == _FP &&          \
+                                       __builtin_alignof(mode) == sizeof(double)) \
+                                          ? __va_double_arg(list, mode)           \
+                                          : __va_stack_arg(list, mode))))[-1]
+#define va_end(__list)
+
+#endif /* __GNUC__ */
+
+#endif /* STDARG_H */
diff --git a/include/libc/stdlib.h b/include/libc/stdlib.h
new file mode 100644
index 0000000..08d313f
--- /dev/null
+++ b/include/libc/stdlib.h
@@ -0,0 +1,28 @@
+#ifndef LIBC_STDLIB_H
+#define LIBC_STDLIB_H
+
+#include "stddef.h"
+
+typedef struct {
+    /* 0x0 */ int quot;
+    /* 0x4 */ int rem;
+} div_t;
+
+typedef struct {
+    /* 0x0 */ long quot;
+    /* 0x4 */ long rem;
+} ldiv_t;
+
+typedef struct {
+    /* 0x0 */ long long quot;
+    /* 0x8 */ long long rem;
+} lldiv_t;
+
+typedef int ssize_t;
+
+typedef long wchar_t;
+
+ldiv_t ldiv(long numer, long denom);
+lldiv_t lldiv(long long numer, long long denom);
+
+#endif /* STDLIB_H */
diff --git a/include/segment_symbols.h b/include/segment_symbols.h
index bb74f1e..d10aa0e 100644
--- a/include/segment_symbols.h
+++ b/include/segment_symbols.h
@@ -1,8 +1,7 @@
 #ifndef SEGMENT_SYMBOLS_H
 #define SEGMENT_SYMBOLS_H
 
-#include "ultra64.h"
-#include "libc/stdint.h"
+#include "stdint.h"
 
 #define DECLARE_VRAM_SEGMENT(name) \
     extern u8 name ## _VRAM[]; \
diff --git a/src/main/O2/65430.c b/src/main/O2/65430.c
index 7bc7227..5628e0b 100644
--- a/src/main/O2/65430.c
+++ b/src/main/O2/65430.c
@@ -231,20 +231,19 @@ void Idle_ThreadEntry(void* arg) {
 void Idle_ThreadEntry(void* arg);
 #pragma GLOBAL_ASM("asm/us/nonmatchings/main/O2/65430/Idle_ThreadEntry.s")
 #endif
-#undef NON_MATCHING
 
 void Idle_InitVideo(void) {
     switch (osTvType) {
         case OS_TV_TYPE_PAL:
-            osViSetMode(&osViModeTable[16]);
+            osViSetMode(&osViModeTable[OS_VI_PAL_LAN1]);
             break;
 
         case OS_TV_TYPE_NTSC:
-            osViSetMode(&osViModeTable[2]);
+            osViSetMode(&osViModeTable[OS_VI_NTSC_LAN1]);
             break;
 
         case OS_TV_TYPE_MPAL:
-            osViSetMode(&osViModeTable[30]);
+            osViSetMode(&osViModeTable[OS_VI_MPAL_LAN1]);
             break;
     }
 }
diff --git a/src/main/O2/math64.c b/src/main/O2/math64.c
index db64233..89d88f5 100644
--- a/src/main/O2/math64.c
+++ b/src/main/O2/math64.c
@@ -1,7 +1,9 @@
-#include "global.h"
 #include "math64.h"
-#include "libc/math.h"
+
+#include "math.h"
+
 #include "fp.h"
+#include "macros.h"
 
 f32 Math_FTanF(f32 x) {
     return sinf(x) / cosf(x);
@@ -61,9 +63,9 @@ f32 Math_FAtanContFracF(f32 x) {
     }
 
     if (sector > 0) {
-        return ((f32)M_PI / 2) - (x / (1.0f + conv));
+        return (M_PIf / 2) - (x / (1.0f + conv));
     } else if (sector < 0) {
-        return -((f32)M_PI / 2) - (x / (1.0f + conv));
+        return -(M_PIf / 2) - (x / (1.0f + conv));
     } else {
         return x / (1.0f + conv);
     }
@@ -74,15 +76,15 @@ f32 fatan2(f32 y, f32 x) {
         return 0.0f;
     } else if (x == 0.0f) {
         if (y < 0.0f) {
-            return -((f32)M_PI / 2);
+            return -(M_PIf / 2);
         } else {
-            return (f32)M_PI / 2;
+            return M_PIf / 2;
         }
     } else if (x < 0.0f) {
         if (y < 0.0f) {
-            return -((f32)M_PI - Math_FAtanContFracF(fabs((f64)(y / x))));
+            return -(M_PIf - Math_FAtanContFracF(fabs((f64)(y / x))));
         } else {
-            return (f32)M_PI - Math_FAtanContFracF(fabs((f64)(y / x)));
+            return M_PIf - Math_FAtanContFracF(fabs((f64)(y / x)));
         }
     } else {
         return Math_FAtanContFracF(y / x);
@@ -94,5 +96,5 @@ f32 Math_FAsinF(f32 x) {
 }
 
 f32 Math_FAcosF(f32 x) {
-    return ((f32)M_PI / 2) - Math_FAsinF(x);
+    return (M_PIf / 2) - Math_FAsinF(x);
 }
diff --git a/src/main/O2/stackcheck.c b/src/main/O2/stackcheck.c
index 80f8a42..7e1d233 100644
--- a/src/main/O2/stackcheck.c
+++ b/src/main/O2/stackcheck.c
@@ -1,7 +1,9 @@
 #include "stackcheck.h"
+
+#include "stdbool.h"
+#include "stdint.h"
+
 #include "terminal.h"
-#include "libc/stdbool.h"
-#include "libc/stdint.h"
 
 StackEntry* sStackInfoListStart = NULL;
 StackEntry* sStackInfoListEnd = NULL;
diff --git a/src/main/dmamgr.c b/src/main/dmamgr.c
index 8b5386a..facfcd5 100644
--- a/src/main/dmamgr.c
+++ b/src/main/dmamgr.c
@@ -151,6 +151,6 @@ void DmaMgr_Init(void) {
     osCreateMesgQueue(&D_8010ED10, D_8010ED28, ARRAY_COUNT(D_8010ED28));
     osCreateMesgQueue(&D_8010ED50, D_8010ED68, ARRAY_COUNT(D_8010ED68));
     StackCheck_Init(&sDmaStackInfo, sDmaStack, STACK_TOP(sDmaStack), 0, 0x100, "dmamgr");
-    osCreateThread(&sDmaThread, Y_THREAD_ID_DMA, DmaMgr_ThreadEntry, NULL, &sDmaStackInfo, Y_PRIORITY_DMA);
+    osCreateThread(&sDmaThread, Y_THREAD_ID_DMA, DmaMgr_ThreadEntry, NULL, STACK_TOP(sDmaStack), Y_PRIORITY_DMA);
     osStartThread(&sDmaThread);
 }
diff --git a/src/main/fault.c b/src/main/fault.c
index 5df6f9c..525432a 100644
--- a/src/main/fault.c
+++ b/src/main/fault.c
@@ -1,10 +1,10 @@
 #include "fault.h"
 
-#include "lib/ultralib/src/libc/xstdio.h"
-#include "libc/stdbool.h"
-#include "libc/stddef.h"
-#include "libc/stdint.h"
+#include "stdbool.h"
+#include "stddef.h"
+#include "stdint.h"
 #include "PR/os_internal.h"
+#include "lib/ultralib/src/libc/xstdio.h"
 
 #include "global.h"
 
@@ -740,7 +740,8 @@ void Fault_Init(void) {
     debugger.depth = 16;
     osCreateMesgQueue(&debugger.queue, debugger.msg, ARRAY_COUNT(debugger.msg));
     StackCheck_Init(&sFaultStackInfo, sFaultStack, STACK_TOP(sFaultStack), 0, 0x100, "fault");
-    osCreateThread(&debugger.thread, Y_THREAD_ID_FAULT, Fault_ThreadEntry, NULL, &sFaultStackInfo, Y_PRIORITY_FAULT);
+    osCreateThread(&debugger.thread, Y_THREAD_ID_FAULT, Fault_ThreadEntry, NULL, STACK_TOP(sFaultStack),
+                   Y_PRIORITY_FAULT);
     osStartThread(&debugger.thread);
 }
 
diff --git a/src/main/vimode.c b/src/main/vimode.c
index cabdecc..cf47f4d 100644
--- a/src/main/vimode.c
+++ b/src/main/vimode.c
@@ -1,8 +1,10 @@
 #include "vimode.h"
+
+#include "stdbool.h"
+#include "lib/ultralib/src/io/viint.h"
+
 #include "attributes.h"
 #include "macros.h"
-#include "libc/stdbool.h"
-#include "lib/ultralib/src/io/viint.h"
 #include "pad.h"
 
 void ViMode_LogPrint(UNUSED OSViMode* osViMode) {