Don’t use libc’s random/rand

Core/gb.c

@@ -9,8 +9,10 @@
 #include <sys/select.h>
 #include <unistd.h>
 #endif
+#include "random.h"
 #include "gb.h"
 
+
 #ifdef DISABLE_REWIND
 #define GB_rewind_free(...)
 #define GB_rewind_push(...)
@@ -565,7 +567,7 @@ static void reset_ram(GB_gameboy_t *gb)
         case GB_MODEL_CGB_E:
         case GB_MODEL_AGB: /* Unverified */
             for (unsigned i = 0; i < gb->ram_size; i++) {
-                gb->ram[i] = (random() & 0xFF);
+                gb->ram[i] = GB_random();
             }
             break;
             
@@ -573,12 +575,12 @@ static void reset_ram(GB_gameboy_t *gb)
         case GB_MODEL_SGB_NTSC: /* Unverified*/
         case GB_MODEL_SGB_PAL: /* Unverified */
             for (unsigned i = 0; i < gb->ram_size; i++) {
-                gb->ram[i] = (random() & 0xFF);
+                gb->ram[i] = GB_random();
                 if (i & 0x100) {
-                    gb->ram[i] &= random();
+                    gb->ram[i] &= GB_random();
                 }
                 else {
-                    gb->ram[i] |= random();
+                    gb->ram[i] |= GB_random();
                 }
             }
             break;
@@ -586,7 +588,7 @@ static void reset_ram(GB_gameboy_t *gb)
         case GB_MODEL_SGB2:
             for (unsigned i = 0; i < gb->ram_size; i++) {
                 gb->ram[i] = 0x55;
-                gb->ram[i] ^= random() & random() & random();
+                gb->ram[i] ^= GB_random() & GB_random() & GB_random();
             }
             break;
         
@@ -596,7 +598,7 @@ static void reset_ram(GB_gameboy_t *gb)
                     gb->ram[i] = 0;
                 }
                 else {
-                    gb->ram[i] = (random() | random() | random() | random())  & 0xFF;
+                    gb->ram[i] = GB_random() | GB_random() | GB_random() | GB_random();
                 }
             }
             break;
@@ -609,7 +611,7 @@ static void reset_ram(GB_gameboy_t *gb)
         case GB_MODEL_CGB_E:
         case GB_MODEL_AGB:
             for (unsigned i = 0; i < sizeof(gb->hram); i++) {
-                gb->hram[i] = (random() & 0xFF);
+                gb->hram[i] = GB_random();
             }
             break;
             
@@ -619,10 +621,10 @@ static void reset_ram(GB_gameboy_t *gb)
         case GB_MODEL_SGB2:
             for (unsigned i = 0; i < sizeof(gb->hram); i++) {
                 if (i & 1) {
-                    gb->hram[i] = random() | random() | random();
+                    gb->hram[i] = GB_random() | GB_random() | GB_random();
                 }
                 else {
-                    gb->hram[i] = random() & random() & random();
+                    gb->hram[i] = GB_random() & GB_random() & GB_random();
                 }
             }
             break;
@@ -642,10 +644,10 @@ static void reset_ram(GB_gameboy_t *gb)
         case GB_MODEL_SGB2:
             for (unsigned i = 0; i < 8; i++) {
                 if (i & 2) {
-                    gb->oam[i] = random() & random() & random();
+                    gb->oam[i] = GB_random() & GB_random() & GB_random();
                 }
                 else {
-                    gb->oam[i] = random() | random() | random();
+                    gb->oam[i] = GB_random() | GB_random() | GB_random();
                 }
             }
             for (unsigned i = 8; i < sizeof(gb->oam); i++) {
@@ -669,10 +671,10 @@ static void reset_ram(GB_gameboy_t *gb)
             uint8_t temp;
             for (unsigned i = 0; i < GB_IO_WAV_END - GB_IO_WAV_START; i++) {
                 if (i & 1) {
-                    temp = random() & random() & random();
+                    temp = GB_random() & GB_random() & GB_random();
                 }
                 else {
-                    temp = random() | random() | random();
+                    temp = GB_random() | GB_random() | GB_random();
                 }
                 gb->apu.wave_channel.wave_form[i * 2]     = temp >> 4;
                 gb->apu.wave_channel.wave_form[i * 2 + 1] = temp & 0xF;
@@ -684,13 +686,13 @@ static void reset_ram(GB_gameboy_t *gb)
     }
     
     for (unsigned i = 0; i < sizeof(gb->extra_oam); i++) {
-        gb->extra_oam[i] = (random() & 0xFF);
+        gb->extra_oam[i] = GB_random();
     }
     
     if (GB_is_cgb(gb)) {
         for (unsigned i = 0; i < 64; i++) {
-            gb->background_palettes_data[i] = random() & 0xFF; /* Doesn't really matter as the boot ROM overrides it anyway*/
+            gb->background_palettes_data[i] = GB_random(); /* Doesn't really matter as the boot ROM overrides it anyway*/
-            gb->sprite_palettes_data[i] = random() & 0xFF;
+            gb->sprite_palettes_data[i] = GB_random();
         }
         for (unsigned i = 0; i < 32; i++) {
             GB_palette_changed(gb, true, i * 2);

Core/random.c

@@ -0,0 +1,38 @@
+#include "random.h"
+#include <time.h>
+
+static uint64_t seed;
+static bool enabled = true;
+
+uint8_t GB_random(void)
+{
+    if (!enabled) return 0;
+    
+    seed *= 0x27BB2EE687B0B0FDL;
+    seed += 0xB504F32D;
+    return seed >> 56;
+}
+
+uint32_t GB_random32(void)
+{
+    GB_random();
+    return seed >> 32;
+}
+
+void GB_random_seed(uint64_t new_seed)
+{
+    seed = new_seed;
+}
+
+void GB_random_set_enabled(bool enable)
+{
+    enabled = enable;
+}
+
+static void __attribute__((constructor)) init_seed(void)
+{
+    seed = time(NULL);
+    for (unsigned i = 64; i--;) {
+        GB_random();
+    }
+}

Core/random.h

@@ -0,0 +1,12 @@
+#ifndef random_h
+#define random_h
+
+#include <stdint.h>
+#include <stdbool.h>
+
+uint8_t GB_random(void);
+uint32_t GB_random32(void);
+void GB_random_seed(uint64_t seed);
+void GB_random_set_enabled(bool enable);
+
+#endif /* random_h */

Core/sgb.c

@@ -1,4 +1,5 @@
 #include "gb.h"
+#include "random.h"
 #include <math.h>
 
 #define INTRO_ANIMATION_LENGTH 200
@@ -682,7 +683,7 @@ static double fm_sweep(double phase)
 }
 static double random_double(void)
 {
-    return ((random() % 0x10001) - 0x8000) / (double) 0x8000;
+    return ((signed)(GB_random32() % 0x10001) - 0x8000) / (double) 0x8000;
 }
 
 bool GB_sgb_render_jingle(GB_gameboy_t *gb, GB_sample_t *dest, size_t count)

Tester/main.c

@@ -16,12 +16,7 @@
 #endif
 
 #include <Core/gb.h>
-
+#include <Core/random.h>
-/* Disable all randomness during automatic tests */
-long random(void)
-{
-    return 0;
-}
 
 static bool running = false;
 static char *filename;
@@ -263,6 +258,8 @@ int main(int argc, char **argv)
     bool dmg = false;
     const char *boot_rom_path = NULL;
     
+    GB_random_set_enabled(false);
+
     for (unsigned i = 1; i < argc; i++) {
         if (strcmp(argv[i], "--dmg") == 0) {
             fprintf(stderr, "Using DMG mode\n");

libretro/Makefile

@@ -243,7 +243,6 @@ else
    CC = gcc
    TARGET := $(TARGET_NAME)_libretro.dll
    SHARED := -shared -static-libgcc -static-libstdc++ -s -Wl,--version-script=$(CORE_DIR)/libretro/link.T -Wl,--no-undefined
-   CFLAGS += -Drandom=rand
 endif
 
 TARGET := $(CORE_DIR)/build/bin/$(TARGET)