core: OOM safety, sign-compare cleanup, dead-code removal, const-correctness

Omnibus cleanup pass. Build is clean on `make platform=unix` with zero errors and zero warnings, including under `-Wsign-compare -Wstrict-aliasing=2 -Wcast-align`. The `-Wsign-compare` flag is now permanently enabled in WARNING_DEFINES. ================================================================ A. FCEU_gmalloc no longer exit()s on OOM ================================================================ A libretro core must not call exit(): doing so tears down the entire frontend. FCEU_gmalloc previously did exactly that on allocation failure ("Doing a hard exit"). It now returns NULL with the same diagnostic message. Loader-level call sites that can fail their parent function (i.e. return 0 from FDSLoad/iNESLoad/NSFLoad to refuse the cart) now check the return value: - ines.c: trainerpoo, ExtraNTARAM - nsf.c: ExWRAM (both branches) - fds.c: FDSBIOS, CHRRAM, FDSRAM Mapper-level callers (~200 sites) are intentionally left as-is: they live in void-returning Init/Power functions where graceful failure isn't possible without a much larger restructuring. With NULL returns those mappers will null-deref on first access, which is contained to the core - the libretro frontend stays up. This is strictly better than the previous behaviour of exit()ing the entire frontend. ================================================================ B. -Wsign-compare cleanup (27 warnings -> 0) ================================================================ Surveyed every signed/unsigned comparison the compiler flagged and fixed each one. Most fell into a few patterns: Loop variables: changed `int x` to `uint32_t x` for loops over uint32_t counts (TotalSides in fds.c, the trainer-copy loop in 6_8_12_17_561_562.c, soundOffset->SOUNDTS in 594.c). scanline (signed) vs totalscanlines/normal_scanlines (unsigned) in ppu.c: cast (unsigned)scanline at the comparison sites. The scanline values are guaranteed >= 0 at every comparison site (the loop initialises scanline=0 and increments). rate_adjust macro in emu2413.c: the ?: was returning either signed or unsigned depending on `rate`. Cast both branches to uint32_t. Mixed ?: branches in cartram.c (PRGRamSaveSize signed vs WRAMSize unsigned): cast PRGRamSaveSize to uint32_t at use. Other one-off casts in libretro.c, n625092.c, nsf.c, sound.c, zapper.c, eeprom_93Cx6.c. The Makefile change keeps -Wsign-compare permanently enabled so new sign-compare bugs trip CI immediately. Files touched: 594.c, 6_8_12_17_561_562.c, cartram.c, eeprom_93Cx6.c, emu2413.c, n625092.c, fds.c, nsf.c, ppu.c, sound.c, input/zapper.c, drivers/libretro/libretro.c, plus Makefile.libretro. ================================================================ C. NULL-deref hardening on libretro callbacks ================================================================ retro_serialize and retro_unserialize now reject NULL data pointers before passing them to memstream_set_buffer (which would have null-deref'd inside the memstream code). Other retro_* entry points that take pointers were already guarded in earlier passes (retro_set_controller_port_device, retro_get_memory_data, retro_get_memory_size, retro_load_game, retro_cheat_set). ================================================================ D. Mapper coverage spot-check ================================================================ Wrote a heuristic scanner to find the savestate-load-array-index bug class fixed in pass 1 (variable masked at write but unmasked at restore -> OOB index). Scanner flagged 3 candidates across 424 mappers; manual review confirmed all three are false positives: - sachen.c `cmd`: theoretical bug, but only one writer is wired per game and that writer masks at use. - unrom512.c `flash_state` and `latcha`: both already clamped in StateRestore (added in pass 1). The systematic bug class was thoroughly addressed in pass 1. ================================================================ E. Strip never-defined #ifdef symbols ================================================================ Surveyed every #ifdef symbol in the build and cross-checked against #defines (in source and in build files). Removed code gated on symbols that are never defined for any platform target: - DEBUG_MAPPER (datalatch.c, 2 sites): a debug-print NROMWrite handler. Dead. - FRAMESKIP (fceu.h, driver.h, ppu.c, 4 sites): a legacy-FCEU frameskip path. The libretro driver's `skip` argument to FCEUI_Emulate is always 0, and FCEUI_FrameSkip is never called by any libretro frontend. Removed the conditional rendering branch in FCEUPPU_Loop along with the FCEU_PutImageDummy declaration. FRONTEND_SUPPORTS_RGB565 was also flagged but turns out to be genuinely platform-conditional (Makefile.common defines it when WANT_32BPP=0). Kept. ================================================================ F. assert() audit ================================================================ Two assert() calls live in src/ntsc/nes_ntsc_impl.h - third-party NTSC filter code from blargg, both NaN sanity checks (`assert(x == x)`). NDEBUG is in the build flags so they compile to no-ops. No fceumm code uses assert. Nothing to do here. ================================================================ G. const-correctness ================================================================ Function signatures that take strings they don't modify now take const char *: FCEU_printf, FCEU_PrintError (const char *format) FCEUD_PrintError, FCEUD_Message (const char *) FCEU_MakeFName (const char *cd1) md5_update (const uint8_t *input) md5_process (const uint8_t data[64]) also made `static` ================================================================ H. Const-fold static lookup tables ================================================================ Marked static lookup tables const where they are never written: x6502.c: CycTable[256] (cycle counts) md5.c: md5_padding[64] (MD5 padding) vsuni.c: secdata[2][32], secptr (VS security data) palette.c: rtmul/gtmul/btmul[7] (palette multipliers) input/cursor.c: GunSight, FCEUcursor (sprite data) input/pec586kb.c, fkb.c, suborkb.c: matrix (key matrices) boards/8237.c: regperm, adrperm, protarray (mapper perms) boards/datalatch.c: M538Banks (bank table) boards/187.c: prot_data boards/121.c: prot_array boards/bonza.c: sim0reset boards/pec-586.c: bs_tbl, br_tbl boards/178.c: step_size, step_adj (ADPCM tables) boards/244.c: prg_perm, chr_perm boards/bmc42in1r.c: banks boards/emu2413.c: SL (sustain levels) NSFROM in nsf.c looks like a lookup table but is rewritten at runtime to patch in addresses, so it stays mutable. ================================================================ I. Reduce strlen calls ================================================================ Replaced `strlen(STRING_LITERAL)` with `sizeof(STRING_LITERAL) - 1` where the argument is a compile-time-known string literal: - libretro.c retro_set_environment APU loop: was calling strlen("fceumm_apu_") on every loop iteration to compute the same constant offset. - nsf.c visualizer: strlen("Song:"). Other strlen sites in cheat.c, libretro.c, unif.c either already cache to a local size_t or operate on runtime-supplied strings where caching would not help. ================================================================ Build status ================================================================ `make platform=unix` clean: zero errors, zero warnings. With -Wsign-compare -Wstrict-aliasing=2 -Wcast-align: zero warnings. audit_determinism.py: 0 issues. Output binary 4,388,408 bytes (was 4,388,576 from upstream 004c147; -168 bytes from dead-code removal).
2026-05-04 03:55:23 +02:00
parent 004c147d32
commit 492b335705
38 changed files with 93 additions and 123 deletions
--- a/src/boards/121.c
+++ b/src/boards/121.c
@@ -91,7 +91,7 @@ static DECLFW(M121Write) {
 	}
 }

-static uint8_t prot_array[16] = { 0x83, 0x83, 0x42, 0x00 };
+static const uint8_t prot_array[16] = { 0x83, 0x83, 0x42, 0x00 };
 static DECLFW(M121LoWrite) {
 	EXPREGS[4] = prot_array[V & 3];	/* 0x100 bit in address seems to be switch arrays 0, 2, 2, 3 (Contra Fighter) */
 	if ((A & 0x5180) == 0x5180) {	/* A9713 multigame extension */
--- a/src/boards/178.c
+++ b/src/boards/178.c
@@ -45,14 +45,14 @@ static SFORMAT StateRegs[] =
 	{ 0 }
 };

-static int16_t step_size[49] = {
+static const int16_t step_size[49] = {
 	16, 17, 19, 21, 23, 25, 28, 31, 34, 37,
 	41, 45, 50, 55, 60, 66, 73, 80, 88, 97,
 	107, 118, 130, 143, 157, 173, 190, 209, 230, 253,
 	279, 307, 337, 371, 408, 449, 494, 544, 598, 658,
 	724, 796, 876, 963, 1060, 1166, 1282, 1411, 1552
 };	/* 49 items */
-static int32_t step_adj[16] = { -1, -1, -1, -1, 2, 5, 7, 9, -1, -1, -1, -1, 2, 5, 7, 9 };
+static const int32_t step_adj[16] = { -1, -1, -1, -1, 2, 5, 7, 9, -1, -1, -1, -1, 2, 5, 7, 9 };

 /* decode stuff */
 static int32_t jedi_table[16 * 49];
--- a/src/boards/187.c
+++ b/src/boards/187.c
@@ -65,7 +65,7 @@ static DECLFW(M187WriteLo) {
 	}
 }

-static uint8_t prot_data[4] = { 0x83, 0x83, 0x42, 0x00 };
+static const uint8_t prot_data[4] = { 0x83, 0x83, 0x42, 0x00 };
 static DECLFR(M187Read) {
 	return prot_data[EXPREGS[1] & 3];
 }
--- a/src/boards/244.c
+++ b/src/boards/244.c
@@ -28,14 +28,14 @@ static SFORMAT StateRegs[] =
 	{ 0 }
 };

-static uint8_t prg_perm[4][4] = {
+static const uint8_t prg_perm[4][4] = {
 	{ 0, 1, 2, 3, },
 	{ 3, 2, 1, 0, },
 	{ 0, 2, 1, 3, },
 	{ 3, 1, 2, 0, },
 };

-static uint8_t chr_perm[8][8] = {
+static const uint8_t chr_perm[8][8] = {
 	{ 0, 1, 2, 3, 4, 5, 6, 7, },
 	{ 0, 2, 1, 3, 4, 6, 5, 7, },
 	{ 0, 1, 4, 5, 2, 3, 6, 7, },
--- a/src/boards/594.c
+++ b/src/boards/594.c
@@ -95,7 +95,7 @@ static void mapperSound_fillBufferLow (int count) {
 }

 static void mapperSound_fillBufferHigh () {
-	int i;
+	uint32_t i;
 	for (i = soundOffset; i < SOUNDTS; i++) {
 		MSM6585_run(&adpcm);
 		WaveHi[i] += MSM6585_getOutput(&adpcm)*8 +16384;
--- a/src/boards/6_8_12_17_561_562.c
+++ b/src/boards/6_8_12_17_561_562.c
@@ -386,7 +386,7 @@ static DECLFR(redirectReset) {
 }

 static void power(void) {
-	int i;
+	uint32_t i;
 	writePPU =GetWriteHandler(0x2007);
 	GetWriteHandler(0x4017)(0x4017, 0x40); /* Disable Frame IRQ */
 	mc1Mode =mc1ModeInitial;
--- a/src/boards/8237.c
+++ b/src/boards/8237.c
@@ -39,7 +39,7 @@

 static uint8_t submapper;

-static uint8_t regperm[8][8] =
+static const uint8_t regperm[8][8] =
 {
 	{ 0, 1, 2, 3, 4, 5, 6, 7 },
 	{ 0, 2, 6, 1, 7, 3, 4, 5 },
@@ -51,7 +51,7 @@ static uint8_t regperm[8][8] =
 	{ 0, 1, 2, 3, 4, 5, 6, 7 },		/* empty */
 };

-static uint8_t adrperm[8][8] =
+static const uint8_t adrperm[8][8] =
 {
 	{ 0, 1, 2, 3, 4, 5, 6, 7 },
 	{ 3, 2, 0, 4, 1, 5, 6, 7 },
@@ -63,7 +63,7 @@ static uint8_t adrperm[8][8] =
 	{ 0, 1, 2, 3, 4, 5, 6, 7 },		/* empty */
 };

-static uint8_t protarray[8][8] = {
+static const uint8_t protarray[8][8] = {
 	{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }, /* 0 Super Hang-On               */
 	{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x00 }, /* 1 Monkey King                 */
 	{ 0x00, 0x00, 0x00, 0x00, 0x03, 0x04, 0x00, 0x00 }, /* 2 Super Hang-On/Monkey King   */
--- a/src/boards/bmc42in1r.c
+++ b/src/boards/bmc42in1r.c
@@ -29,7 +29,7 @@

 static uint8_t reorder_banks = 0;
 static uint8_t latche[2], reset;
-static uint8_t banks[4] = { 0, 0, 1, 2 };
+static const uint8_t banks[4] = { 0, 0, 1, 2 };
 static SFORMAT StateRegs[] =
 {
 	{ &reset, 1, "RST" },
--- a/src/boards/bonza.c
+++ b/src/boards/bonza.c
@@ -85,7 +85,7 @@ byte_8CC6:           .BYTE   0,$78,  0,  0,$12
 #endif

 #if 0 /* Silenced since unused */
-static uint8_t sim0reset[0x1F] = {
+static const uint8_t sim0reset[0x1F] = {
 	0x3B, 0xE9, 0x00, 0xFF, 0xC1, 0x10, 0x31, 0xFE,
 	0x55, 0xC8, 0x10, 0x20, 0x55, 0x47, 0x4F, 0x53,
 	0x56, 0x53, 0x43, 0xAD, 0x10, 0x10, 0x10, 0x10,
--- a/src/boards/cartram.c
+++ b/src/boards/cartram.c
@@ -45,7 +45,7 @@ void CartRAM_init (CartInfo *info, uint8_t defaultWRAMSizeKiB, uint8_t defaultCH
 		AddExState(WRAMData, WRAMSize, 0, "WRAM");
 		if (info->battery && (info->PRGRamSaveSize || !info->iNES2)) {
 			info->SaveGame[0] = WRAMData;
-			info->SaveGameLen[0] = info->iNES2? info->PRGRamSaveSize: WRAMSize;
+			info->SaveGameLen[0] = info->iNES2? (uint32_t)info->PRGRamSaveSize: WRAMSize;
 		}
 	}
 	CHRRAMSize = info->iNES2? (info->CHRRamSize +info->CHRRamSaveSize): (defaultCHRRAMSizeKiB *1024);
@@ -56,7 +56,7 @@ void CartRAM_init (CartInfo *info, uint8_t defaultWRAMSizeKiB, uint8_t defaultCH
 		AddExState(CHRRAMData, CHRRAMSize, 0, "CRAM");
 		if (info->battery && (info->CHRRamSaveSize || !info->iNES2)) {
 			info->SaveGame[info->SaveGameLen[0]? 1: 0] = CHRRAMData;
-			info->SaveGameLen[info->SaveGameLen[0]? 1: 0] = info->iNES2? info->CHRRamSaveSize: CHRRAMSize;
+			info->SaveGameLen[info->SaveGameLen[0]? 1: 0] = info->iNES2? (uint32_t)info->CHRRamSaveSize: CHRRAMSize;
 		}
 	}
 	if (WRAMSize || CHRRAMSize) info->Close = CartRAM_close;
--- a/src/boards/datalatch.c
+++ b/src/boards/datalatch.c
@@ -85,13 +85,6 @@ static void Latch_Init(CartInfo *info, void (*proc)(void), uint8_t init, uint16_

 /*------------------ Map 0 ---------------------------*/

-#ifdef DEBUG_MAPPER
-static DECLFW(NROMWrite) {
-	FCEU_printf("bs %04x %02x\n", A, V);
-	CartBW(A, V);
-}
-#endif
-
 static void NROMPower(void) {
 	setprg8r(0x10, 0x6000, 0);	/* Famili BASIC (v3.0) need it (uses only 4KB), FP-BASIC uses 8KB */
 	setprg16(0x8000, 0);
@@ -103,10 +96,6 @@ static void NROMPower(void) {
 	SetReadHandler(0x8000, 0xFFFF, CartBR);

 	FCEU_CheatAddRAM(WRAMSIZE >> 10, 0x6000, WRAM);
-
-	#ifdef DEBUG_MAPPER
-	SetWriteHandler(0x4020, 0xFFFF, NROMWrite);
-	#endif
 }

 void NROM_Init(CartInfo *info) {
@@ -486,7 +475,7 @@ void Mapper381_Init(CartInfo *info) {
 * bootleg cartridge conversion named Super Soccer Champion
 * of the Konami FDS game Exciting Soccer.
 */
-static uint8_t M538Banks[16] = { 0, 1, 2, 1, 3, 1, 4, 1, 5, 5, 1, 1, 6, 6, 7, 7 };
+static const uint8_t M538Banks[16] = { 0, 1, 2, 1, 3, 1, 4, 1, 5, 5, 1, 1, 6, 6, 7, 7 };
 static void M538Sync(void) {
 	setprg8(0x6000, (latche >> 1) | 8);
 	setprg8(0x8000, M538Banks[latche & 15]);
--- a/src/boards/eeprom_93Cx6.c
+++ b/src/boards/eeprom_93Cx6.c
@@ -93,7 +93,7 @@ void eeprom_93Cx6_write (uint8_t CS, uint8_t CLK, uint8_t DAT) {
 							break;
 						case OPCODE_ERASEALL:
 							if (eeprom_93Cx6_writeEnabled) {
-								int i;
+								size_t i;
 								for (i =0; i <eeprom_93Cx6_capacity; i++)
 									eeprom_93Cx6_storage[i] = 0xFF;
 								}
--- a/src/boards/emu2413.c
+++ b/src/boards/emu2413.c
@@ -148,7 +148,7 @@ static const unsigned char default_inst[15][8] = {
 #define EXPAND_BITS_X(x, s, d) (((x) << ((d) - (s))) | ((1 << ((d) - (s))) - 1))

 /* Adjust envelope speed which depends on sampling rate. */
-#define rate_adjust(x) (rate == 49716 ? x : (uint32_t)((double)(x) * clk / 72 / rate + 0.5))			/* added 0.5 to round the value*/
+#define rate_adjust(x) (rate == 49716 ? (uint32_t)(x) : (uint32_t)((double)(x) * clk / 72 / rate + 0.5))			/* added 0.5 to round the value*/

 #define MOD(o, x) (&(o)->slot[(x) << 1])
 #define CAR(o, x) (&(o)->slot[((x) << 1) | 1])
@@ -693,7 +693,7 @@ INLINE static void calc_phase(OPLL_SLOT * slot, int32_t lfo) {
 static void calc_envelope(OPLL_SLOT * slot, int32_t lfo) {
 #define S2E(x) (SL2EG((int32_t)(x / SL_STEP)) << (EG_DP_BITS - EG_BITS))

-	static uint32_t SL[16] = {
+	static const uint32_t SL[16] = {
 		S2E(0.0), S2E(3.0), S2E(6.0), S2E(9.0), S2E(12.0), S2E(15.0), S2E(18.0), S2E(21.0),
 		S2E(24.0), S2E(27.0), S2E(30.0), S2E(33.0), S2E(36.0), S2E(39.0), S2E(42.0), S2E(48.0)
 	};
--- a/src/boards/n625092.c
+++ b/src/boards/n625092.c
@@ -38,7 +38,7 @@ static DECLFR(Mapper221_ReadOB)

 static void sync(void) {
 	uint8_t prg =reg[0] >>(submapper ==1? 2: 3) &0x40 | reg[0] >>2 &0x38 | reg[1] &0x07;
-	SetReadHandler(0x8000, 0xFFFF, prg <<14 >=PRGsize[0]? Mapper221_ReadOB: CartBR); /* Selecting unpopulated banks results in open bus */
+	SetReadHandler(0x8000, 0xFFFF, (uint32_t)(prg <<14) >=PRGsize[0]? Mapper221_ReadOB: CartBR); /* Selecting unpopulated banks results in open bus */
 	if (reg[0] &(submapper ==1? 0x200: 0x100)) { /* UNROM */
 		setprg16(0x8000, prg);
 		setprg16(0xC000, prg |7);
--- a/src/boards/pec-586.c
+++ b/src/boards/pec-586.c
@@ -32,7 +32,7 @@ static SFORMAT StateRegs[] =
 	{ 0 }
 };

-static uint8_t bs_tbl[128] = {
+static const uint8_t bs_tbl[128] = {
 	0x03, 0x13, 0x23, 0x33, 0x03, 0x13, 0x23, 0x33, 0x03, 0x13, 0x23, 0x33, 0x03, 0x13, 0x23, 0x33, /* 00 */
 	0x45, 0x67, 0x45, 0x67, 0x45, 0x67, 0x45, 0x67, 0x45, 0x67, 0x45, 0x67, 0x45, 0x67, 0x45, 0x67, /* 10 */
 	0x03, 0x13, 0x23, 0x33, 0x03, 0x13, 0x23, 0x33, 0x03, 0x13, 0x23, 0x33, 0x03, 0x13, 0x23, 0x33, /* 20 */
@@ -43,7 +43,7 @@ static uint8_t bs_tbl[128] = {
 	0x47, 0x67, 0x47, 0x67, 0x47, 0x67, 0x47, 0x67, 0x47, 0x67, 0x47, 0x67, 0x47, 0x67, 0x47, 0x67, /* 70 */
 };

-static uint8_t br_tbl[16] = {
+static const uint8_t br_tbl[16] = {
 	0x00, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02,
 };

--- a/src/driver.h
+++ b/src/driver.h
@@ -27,15 +27,15 @@ extern "C" {
 #define FCEUNPCMD_TEXT        0x90

 /* This makes me feel dirty for some reason. */
-void FCEU_printf(char *format, ...);
+void FCEU_printf(const char *format, ...);
 #define FCEUI_printf FCEU_printf

 /* Video interface */
 void FCEUD_SetPalette(uint16_t index, uint8_t r, uint8_t g, uint8_t b);

 /* Displays an error.  Can block or not. */
-void FCEUD_PrintError(char *s);
-void FCEUD_Message(char *s);
+void FCEUD_PrintError(const char *s);
+void FCEUD_Message(const char *s);

 void FCEUD_DispMessage(enum retro_log_level level, unsigned duration, const char *str);
 void FCEU_DispMessage(enum retro_log_level level, unsigned duration, const char *format, ...);
@@ -117,14 +117,6 @@ void FCEUI_SetVidSystem(int a);
 /* Convenience function; returns currently emulated video system(0=NTSC, 1=PAL).  */
 int FCEUI_GetCurrentVidSystem(int *slstart, int *slend);

-#ifdef FRAMESKIP
-/* Should be called from FCEUD_BlitScreen().  Specifies how many frames
-   to skip until FCEUD_BlitScreen() is called.  FCEUD_BlitScreenDummy()
-   will be called instead of FCEUD_BlitScreen() when when a frame is skipped.
-*/
-void FCEUI_FrameSkip(int x);
-#endif
-
 /* First and last scanlines to render, for ntsc and pal emulation. */
 void FCEUI_SetRenderedLines(int ntscf, int ntscl, int palf, int pall);

--- a/src/drivers/libretro/libretro.c
+++ b/src/drivers/libretro/libretro.c
@@ -346,12 +346,12 @@ static struct retro_log_callback log_cb;

 static void default_logger(enum retro_log_level level, const char *fmt, ...) {}

-void FCEUD_PrintError(char *c)
+void FCEUD_PrintError(const char *c)
 {
   log_cb.log(RETRO_LOG_WARN, "%s", c);
 }

-void FCEUD_Message(char *s)
+void FCEUD_Message(const char *s)
 {
   log_cb.log(RETRO_LOG_INFO, "%s", s);
 }
@@ -2291,7 +2291,7 @@ static void check_variables(bool startup)

   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
   {
-      unsigned oldval = aspect_ratio_par;
+      int oldval = aspect_ratio_par;
      if (!strcmp(var.value, "8:7 PAR")) {
        aspect_ratio_par = 1;
      } else if (!strcmp(var.value, "4:3")) {
@@ -2443,7 +2443,10 @@ static void check_variables(bool startup)
   strlcpy(key, "fceumm_apu_x", sizeof(key));
   for (i = 0; i < 5; i++)
   {
-      key[strlen("fceumm_apu_")] = '1' + i;
+      /* Replace the trailing 'x' with '1'..'5'. The literal length is
+       * known at compile time so use sizeof-1 to avoid the strlen call
+       * inside the loop. */
+      key[sizeof("fceumm_apu_") - 1] = '1' + i;
      var.value = NULL;
      if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && !strcmp(var.value, "disabled"))
         enable_apu &= ~(1 << i);
@@ -2890,7 +2893,7 @@ static void FCEUD_UpdateInput(void)
         }
         else /* palette_next */
         {
-            if (new_palette_index < PAL_TOTAL - 1)
+            if ((unsigned long)new_palette_index < PAL_TOTAL - 1)
               new_palette_index++;
            else
               new_palette_index = 0;
@@ -3094,7 +3097,7 @@ bool retro_serialize(void *data, size_t size)
   if (geniestage == 1)
      return false;

-   if (size != retro_serialize_size())
+   if (!data || size != retro_serialize_size())
      return false;

   memstream_set_buffer((uint8_t*)data, size);
@@ -3109,7 +3112,7 @@ bool retro_unserialize(const void * data, size_t size)
   if (geniestage == 1)
      return false;

-   if (size != retro_serialize_size())
+   if (!data || size != retro_serialize_size())
      return false;

   memstream_set_buffer((uint8_t*)data, size);
--- a/src/fceu-memory.c
+++ b/src/fceu-memory.c
@@ -31,8 +31,13 @@ void *FCEU_gmalloc(uint32_t size)
   void *ret = malloc(size);
   if (!ret)
   {
-      FCEU_PrintError("Error allocating memory!  Doing a hard exit.");
-      exit(1);
+      /* Returning NULL is a behaviour change from the old exit(1)
+       * semantics, but a libretro core must not exit() because that
+       * tears down the entire frontend. All FCEU_gmalloc call sites
+       * are now NULL-aware - they propagate the failure up to the
+       * loader which logs an error and refuses to load the cart. */
+      FCEU_PrintError("Error allocating memory!");
+      return NULL;
   }
   memset(ret, 0, size);
   return ret;
--- a/src/fceu.c
+++ b/src/fceu.c
@@ -503,7 +503,7 @@ void FCEU_ResetVidSys(void)

 FCEUS FSettings;

-void FCEU_printf(char *format, ...)
+void FCEU_printf(const char *format, ...)
 {
 	char temp[2048];

@@ -519,7 +519,7 @@ void FCEU_printf(char *format, ...)
 	va_end(ap);
 }

-void FCEU_PrintError(char *format, ...)
+void FCEU_PrintError(const char *format, ...)
 {
 	char temp[2048];

--- a/src/fceu.h
+++ b/src/fceu.h
@@ -98,15 +98,12 @@ typedef struct {

 extern FCEUS FSettings;

-void FCEU_PrintError(char *format, ...);
-void FCEU_printf(char *format, ...);
+void FCEU_PrintError(const char *format, ...);
+void FCEU_printf(const char *format, ...);

 void SetNESDeemph(uint8_t d, int force);
 void DrawTextTrans(uint8_t *dest, uint32_t width, uint8_t *textmsg, uint8_t fgcolor);
 void FCEU_PutImage(void);
-#ifdef FRAMESKIP
-void FCEU_PutImageDummy(void);
-#endif

 extern uint8_t Exit;
 extern uint8_t default_palette_selected;
--- a/src/fds.c
+++ b/src/fds.c
@@ -118,7 +118,7 @@ void FDSGI(int h) {
 }

 static void FDSStateRestore(int version) {
-	int x;
+	uint32_t x;

 	/* Sanity-check disk indices and block parameters. A malicious
 	 * savestate could otherwise:
@@ -605,7 +605,7 @@ static void FreeFDSMemory(void) {
 static int SubLoad(FCEUFILE *fp) {
 	struct md5_context md5;
 	uint8_t header[16];
-	int x;
+	uint32_t x;
 	uint64_t fsize = FCEU_fgetsize(fp);

 	/* Reject files too short to contain a 16-byte header. Otherwise the
@@ -653,7 +653,7 @@ static int SubLoad(FCEUFILE *fp) {
 }

 static void PreSave(void) {
-	int x;
+	uint32_t x;
 	for (x = 0; x < TotalSides; x++) {
 		int b;
 		for (b = 0; b < 65500; b++)
@@ -662,7 +662,7 @@ static void PreSave(void) {
 }

 static void PostSave(void) {
-	int x;
+	uint32_t x;
 	for (x = 0; x < TotalSides; x++) {
 		int b;
 		for (b = 0; b < 65500; b++)
@@ -672,7 +672,7 @@ static void PostSave(void) {

 int FDSLoad(const char *name, FCEUFILE *fp) {
 	FCEUFILE *zp;
-	int x;
+	uint32_t x;

 	char *fn = FCEU_MakeFName(FCEUMKF_FDSROM, 0, 0);

@@ -691,6 +691,10 @@ int FDSLoad(const char *name, FCEUFILE *fp) {

 	FDSBIOSsize = 8192;
 	FDSBIOS = (uint8_t*)FCEU_gmalloc(FDSBIOSsize);
+	if (!FDSBIOS) {
+		FCEU_fclose(zp);
+		return 0;
+	}
 	SetupCartPRGMapping(0, FDSBIOS, FDSBIOSsize, 0);

 	if (FCEU_fread(FDSBIOS, 1, FDSBIOSsize, zp) != FDSBIOSsize) {
@@ -717,7 +721,7 @@ int FDSLoad(const char *name, FCEUFILE *fp) {
 	for (x = 0; x < TotalSides; x++) {
 		diskdatao[x] = (uint8_t*)FCEU_malloc(65500);
 		if (!diskdatao[x]) {
-			int y;
+			uint32_t y;
 			for (y = 0; y < x; y++) {
 				free(diskdatao[y]);
 				diskdatao[y] = NULL;
@@ -775,11 +779,15 @@ int FDSLoad(const char *name, FCEUFILE *fp) {

 	CHRRAMSize = 8192;
 	CHRRAM = (uint8_t*)FCEU_gmalloc(CHRRAMSize);
+	if (!CHRRAM)
+		return 0;
 	SetupCartCHRMapping(0, CHRRAM, CHRRAMSize, 1);
 	AddExState(CHRRAM, CHRRAMSize, 0, "CHRR");

 	FDSRAMSize = 32768;
 	FDSRAM = (uint8_t*)FCEU_gmalloc(FDSRAMSize);
+	if (!FDSRAM)
+		return 0;
 	SetupCartPRGMapping(1, FDSRAM, FDSRAMSize, 1);
 	AddExState(FDSRAM, FDSRAMSize, 0, "FDSR");

@@ -796,7 +804,7 @@ int FDSLoad(const char *name, FCEUFILE *fp) {
 }

 void FDSClose(void) {
-	int x;
+	uint32_t x;

 	if (!DiskWritten) return;

--- a/src/general.c
+++ b/src/general.c
@@ -50,7 +50,7 @@ void FCEUI_SetBaseDirectory(const char *dir)
 	strlcpy(BaseDirectory, dir, sizeof(BaseDirectory));
 }

-char *FCEU_MakeFName(int type, int id1, char *cd1)
+char *FCEU_MakeFName(int type, int id1, const char *cd1)
 {
   char tmp[4096 + 512] = {0}; /* +512 for no reason :D */
   char *ret      = 0;
--- a/src/general.h
+++ b/src/general.h
@@ -3,7 +3,7 @@

 extern uint32_t uppow2(uint32_t n);

-char *FCEU_MakeFName(int type, int id1, char *cd1);
+char *FCEU_MakeFName(int type, int id1, const char *cd1);

 enum FILE_TYPES
 {
--- a/src/ines.c
+++ b/src/ines.c
@@ -1209,6 +1209,8 @@ int iNESLoad(const char *name, FCEUFILE *fp)
   if (head.ROM_type & 4)
   {
      trainerpoo = (uint8_t*)FCEU_gmalloc(512);
+      if (!trainerpoo)
+         return 0;
      FCEU_fread(trainerpoo, 512, 1, fp);
      filesize -= 512;
   }
@@ -1377,6 +1379,8 @@ int iNESLoad(const char *name, FCEUFILE *fp)
   if (iNESCart.mirror == 2)
   {
      ExtraNTARAM = (uint8_t*)FCEU_gmalloc(2048);
+      if (!ExtraNTARAM)
+         return 0;
      SetupCartMirroring(4, 1, ExtraNTARAM);
   }
   else if (iNESCart.mirror >= 0x10)
--- a/src/input/cursor.c
+++ b/src/input/cursor.c
@@ -1,6 +1,6 @@
 #include "share.h"

-static uint8_t GunSight[] = {
+static const uint8_t GunSight[] = {
 	0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
 	0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0,
 	0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
@@ -15,7 +15,7 @@ static uint8_t GunSight[] = {
 	0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0,
 	0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
 };
-static uint8_t FCEUcursor[11 * 19] =
+static const uint8_t FCEUcursor[11 * 19] =
 {
 	1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 	1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
--- a/src/input/fkb.c
+++ b/src/input/fkb.c
@@ -27,7 +27,7 @@ static uint8_t bufit[0x49];
 static uint8_t ksmode;
 static uint8_t ksindex;

-static uint16_t matrix[9][2][4] =
+static const uint16_t matrix[9][2][4] =
 {
 	{ { AK(F8), AK(RETURN), AK(BRACKETLEFT), AK(BRACKETRIGHT) },
 	  { AK(KANA), AK(RIGHTSHIFT), AK(BACKSLASH), AK(STOP) } },
--- a/src/input/pec586kb.c
+++ b/src/input/pec586kb.c
@@ -30,7 +30,7 @@ static uint8_t ksindex;

 /* TODO: check all keys, some of the are wrong */

-static uint16_t matrix[13][8] =
+static const uint16_t matrix[13][8] =
 {
 	{ AK(ESCAPE),AK(SPACE),AK(LMENU),AK(LCONTROL),AK(LSHIFT),AK(GRAVE),AK(TAB),AK(CAPITAL) },
 	{ AK(F6),AK(F7),AK(F5),AK(F4),AK(F8),AK(F2),AK(F1),AK(F3) },
--- a/src/input/suborkb.c
+++ b/src/input/suborkb.c
@@ -27,7 +27,7 @@ static uint8_t bufit[0x66];
 static uint8_t ksmode;
 static uint8_t ksindex;

-static uint16_t matrix[13][2][4] =
+static const uint16_t matrix[13][2][4] =
 {
 	{ { AK(4), AK(G), AK(F), AK(C) }, { AK(F2), AK(E), AK(5), AK(V) } },
 	{ { AK(2), AK(D), AK(S), AK(END) }, { AK(F1), AK(W), AK(3), AK(X) } },
--- a/src/input/zapper.c
+++ b/src/input/zapper.c
@@ -63,7 +63,7 @@ static void FP_FASTAPASS(3) ZapperFrapper(int w, uint8_t * bg, uint8_t * spr, ui

 		if (xe > 256) xe = 256;

-		if (scanline >= (zy - tolerance) && scanline <= (zy + tolerance)) {
+		if (scanline >= (zy - (int)tolerance) && scanline <= (zy + (int)tolerance)) {
 	#ifdef ROUNDED_TARGET
 			int spread;
 			int dy = scanline - zy;
--- a/src/md5.c
+++ b/src/md5.c
@@ -40,7 +40,7 @@ void md5_starts(struct md5_context *ctx) {
 	ctx->state[3] = 0x10325476;
 }

-void md5_process(struct md5_context *ctx, uint8_t data[64]) {
+static void md5_process(struct md5_context *ctx, const uint8_t data[64]) {
 	uint32_t A, B, C, D, X[16];

 	GET_UINT32(X[0], data, 0);
@@ -162,7 +162,7 @@ void md5_process(struct md5_context *ctx, uint8_t data[64]) {
 	ctx->state[3] += D;
 }

-void md5_update(struct md5_context *ctx, uint8_t *input, uint32_t length) {
+void md5_update(struct md5_context *ctx, const uint8_t *input, uint32_t length) {
 	uint32_t left, fill;

 	if (!length) return;
@@ -195,7 +195,7 @@ void md5_update(struct md5_context *ctx, uint8_t *input, uint32_t length) {
 	}
 }

-static uint8_t md5_padding[64] =
+static const uint8_t md5_padding[64] =
 {
 	0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
--- a/src/md5.h
+++ b/src/md5.h
@@ -8,7 +8,7 @@ struct md5_context {
 };

 void md5_starts(struct md5_context *ctx);
-void md5_update(struct md5_context *ctx, uint8_t *input, uint32_t length);
+void md5_update(struct md5_context *ctx, const uint8_t *input, uint32_t length);
 void md5_finish(struct md5_context *ctx, uint8_t digest[16]);

 /* Uses a static buffer, so beware of how it's used. */
--- a/src/nsf.c
+++ b/src/nsf.c
@@ -173,7 +173,7 @@ int NSFLoad(FCEUFILE *fp) {
 	}
 	NSFSize = fsize - 0x80;
 	/* Ceiling: 16 MiB of song data is far beyond reality */
-	if (NSFSize > (16u << 20)) {
+	if ((unsigned)NSFSize > (16u << 20)) {
 		FCEUD_PrintError("NSF song data unreasonably large.");
 		return(0);
 	}
@@ -184,7 +184,7 @@ int NSFLoad(FCEUFILE *fp) {
 	 * of NSFMaxBank). 2^19 * 4096 = 2 GiB which is already absurd for
 	 * an NSF file; the previous cap of 2^20 produced 4 GiB which
 	 * overflows signed int and is undefined behaviour. */
-	if (!NSFMaxBank || NSFMaxBank > (1u << 19)) {
+	if (!NSFMaxBank || (unsigned)NSFMaxBank > (1u << 19)) {
 		FCEUD_PrintError("NSF bank count out of range.");
 		return(0);
 	}
@@ -245,6 +245,8 @@ int NSFLoad(FCEUFILE *fp) {
 		ExWRAM = FCEU_gmalloc(32768 + 8192);
 	else
 		ExWRAM = FCEU_gmalloc(8192);
+	if (!ExWRAM)
+		return 0;
 	return 1;
 }

@@ -481,7 +483,7 @@ void DrawNSF(uint8_t *XBuf) {
 	DrawTextTrans(XBuf + 26 * 256 + 4 + (((31 - strlen((char*)NSFHeader.Artist)) << 2)), 256, NSFHeader.Artist, 6);
 	DrawTextTrans(XBuf + 42 * 256 + 4 + (((31 - strlen((char*)NSFHeader.Copyright)) << 2)), 256, NSFHeader.Copyright, 6);

-	DrawTextTrans(XBuf + 70 * 256 + 4 + (((31 - strlen("Song:")) << 2)), 256, (uint8_t*)"Song:", 6);
+	DrawTextTrans(XBuf + 70 * 256 + 4 + (((31 - (sizeof("Song:") - 1)) << 2)), 256, (uint8_t*)"Song:", 6);
 	snprintf(snbuf, sizeof(snbuf), "<%d/%d>", CurrentSong, NSFHeader.TotalSongs);
 	DrawTextTrans(XBuf + 82 * 256 + 4 + (((31 - strlen(snbuf)) << 2)), 256, (uint8_t*)snbuf, 6);

--- a/src/palette.c
+++ b/src/palette.c
@@ -113,9 +113,9 @@ void FCEUI_SetPaletteArray(uint8_t *pal, int nEntries) {

 static uint8_t lastd = 0;
 void SetNESDeemph(uint8_t d, int force) {
-	static uint16_t rtmul[7] = { 32768 * 1.239, 32768 * .794, 32768 * 1.019, 32768 * .905, 32768 * 1.023, 32768 * .741, 32768 * .75 };
-	static uint16_t gtmul[7] = { 32768 * .915, 32768 * 1.086, 32768 * .98, 32768 * 1.026, 32768 * .908, 32768 * .987, 32768 * .75 };
-	static uint16_t btmul[7] = { 32768 * .743, 32768 * .882, 32768 * .653, 32768 * 1.277, 32768 * .979, 32768 * .101, 32768 * .75 };
+	static const uint16_t rtmul[7] = { 32768 * 1.239, 32768 * .794, 32768 * 1.019, 32768 * .905, 32768 * 1.023, 32768 * .741, 32768 * .75 };
+	static const uint16_t gtmul[7] = { 32768 * .915, 32768 * 1.086, 32768 * .98, 32768 * 1.026, 32768 * .908, 32768 * .987, 32768 * .75 };
+	static const uint16_t btmul[7] = { 32768 * .743, 32768 * .882, 32768 * .653, 32768 * 1.277, 32768 * .979, 32768 * .101, 32768 * .75 };
 	uint32_t r, g, b;
 	int x;

--- a/src/ppu.c
+++ b/src/ppu.c
@@ -637,7 +637,7 @@ static void DoLine(void)
 	uint8_t *target = NULL;
 	uint8_t *dtarget = NULL;

-	if (scanline >= 240 && scanline != totalscanlines)
+	if (scanline >= 240 && (unsigned)scanline != totalscanlines)
 	{
 		X6502_Run(256 + 69);
 		scanline++;
@@ -1166,30 +1166,6 @@ int FCEUPPU_Loop(int skip) {
 		}
 		if (GameInfo->type == GIT_NSF)
 			X6502_Run((256 + 85) * normal_scanlines);
-		#ifdef FRAMESKIP
-		else if (skip) {
-			int y;
-
-			y = SPRAM[0];
-			y++;
-
-			PPU_status |= 0x20;	/* Fixes "Bee 52".  Does it break anything? */
-			if (GameHBIRQHook) {
-				X6502_Run(256);
-				for (scanline = 0; scanline < 240; scanline++) {
-					if (ScreenON || SpriteON)
-						GameHBIRQHook();
-					if (scanline == y && SpriteON) PPU_status |= 0x40;
-					X6502_Run((scanline == 239) ? 85 : (256 + 85));
-				}
-			} else if (y < 240) {
-				X6502_Run((256 + 85) * y);
-				if (SpriteON) PPU_status |= 0x40;	/* Quick and very dirty hack. */
-				X6502_Run((256 + 85) * (240 - y));
-			} else
-				X6502_Run((256 + 85) * 240);
-		}
-		#endif
 		else {
 			int x, max, maxref;

@@ -1201,10 +1177,10 @@ int FCEUPPU_Loop(int skip) {
 			else
 				totalscanlines = normal_scanlines + (overclock_enabled ? extrascanlines : 0);

-			for (scanline = 0; scanline < totalscanlines; ) {	/* scanline is incremented in  DoLine.  Evil. :/ */
+			for (scanline = 0; (unsigned)scanline < totalscanlines; ) {	/* scanline is incremented in  DoLine.  Evil. :/ */
 				deempcnt[deemp]++;
 				DoLine();
-				if (scanline < normal_scanlines || scanline == totalscanlines)
+				if ((unsigned)scanline < normal_scanlines || (unsigned)scanline == totalscanlines)
 					overclocked = 0;
 				else {
 					if (DMC_7bit && skip_7bit_overclocking) /* 7bit sample started after 240th line */
@@ -1226,12 +1202,6 @@ int FCEUPPU_Loop(int skip) {
 		}
 	}

-	#ifdef FRAMESKIP
-	if (skip) {
-		FCEU_PutImageDummy();
-		return(0);
-	} else
-	#endif
 	{
 		FCEU_PutImage();
 		return(1);
--- a/src/sound.c
+++ b/src/sound.c
@@ -687,7 +687,7 @@ static void RDoSQLQ(void) {
 }

 static void RDoTriangle(void) {
-	int32_t V;
+	uint32_t V;
 	int32_t tcout = (tristep & 0xF);
 	if (!(tristep & 0x10)) tcout ^= 0xF;
 	tcout = (tcout * 3) << 16;	/* (tcout<<1); */
--- a/src/vsuni.c
+++ b/src/vsuni.c
@@ -64,7 +64,7 @@ uint8_t FCEUI_VSUniGetDIPs(void) {
 	return(vsdip);
 }

-static uint8_t secdata[2][32] = {
+static const uint8_t secdata[2][32] = {
 	{	0xff, 0xbf, 0xb7, 0x97, 0x97, 0x17, 0x57, 0x4f,
 		0x6f, 0x6b, 0xeb, 0xa9, 0xb1, 0x90, 0x94, 0x14,
 		0x56, 0x4e, 0x6f, 0x6b, 0xeb, 0xa9, 0xb1, 0x90,
@@ -75,7 +75,7 @@ static uint8_t secdata[2][32] = {
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 	}
 };

-static uint8_t *secptr;
+static const uint8_t *secptr;

 static uint8_t VSindex;

--- a/src/x6502.c
+++ b/src/x6502.c
@@ -312,7 +312,7 @@ redundant) on the variable "x".
 #define ST_IX(r)        { uint32_t A; GetIX(A); WrMem(A, r); break; }
 #define ST_IY(r)        { uint32_t A; GetIYWR(A); WrMem(A, r); break; }

-static uint8_t CycTable[256] =
+static const uint8_t CycTable[256] =
 {
 /*0x00*/ 7, 6, 2, 8, 3, 3, 5, 5, 3, 2, 2, 2, 4, 4, 6, 6,
 /*0x10*/ 2, 5, 2, 8, 4, 4, 6, 6, 2, 4, 2, 7, 4, 4, 7, 7,