From fc0c70ad611dab564bf13a24e8e32cfda81ab044 Mon Sep 17 00:00:00 2001
From: igor <igor@kolokolnikov.dev>
Date: Thu, 19 Mar 2026 15:54:13 -0700
Subject: [PATCH] Date 22 complete.

---
 Makefile         |  3 +++
 sdl_handmade.cpp | 69 +++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 63 insertions(+), 9 deletions(-)

diff --git a/Makefile b/Makefile
index 02a1b55..5be5b21 100644
--- a/Makefile
+++ b/Makefile
@@ -47,6 +47,9 @@ libhandmade: handmade.cpp
 $(EXE): sdl_handmade.cpp libhandmade
 	$(CC) $(FLAGS) $(UFLAGS) $(INCLUDE) sdl_handmade.cpp $(LIBS) $(FRAMEWORKS) -o $@
 
+run:
+	./$(EXE)
+
 tags: $(OBJS)
 	ctags -R *.h *.c
 
diff --git a/sdl_handmade.cpp b/sdl_handmade.cpp
index 4232287..dacbb82 100644
--- a/sdl_handmade.cpp
+++ b/sdl_handmade.cpp
@@ -11,8 +11,12 @@
 
 #include <sys/stat.h> // fstat
 #include <fcntl.h>    // open
-#include <unistd.h>   // close, read
+#include <unistd.h>   // close, read, readlink
 #include <dlfcn.h>    // dlopen
+#include <sys/stat.h> // stat
+#if __APPLE__ && __MACH__
+#include <mach-o/dyld.h>
+#endif
 
 // NOTE: This is so it compiles on ARM.
 #if __x86_64__ || __i386__
@@ -326,17 +330,34 @@ static F32 SDLGetSecondsElapsed(U64 Start, U64 End)
 
 typedef struct sdl_game_code {
     void *GameCodeDLL;
+    U32 DLLLastWriteTime;
+
     void (*UpdateAndRender)(game_memory *, game_input *, game_offscreen_buffer *, game_sound_output_buffer *);
 
     B32 IsValid;
 } sdl_game_code;
 
-static sdl_game_code SDLLoadGameCode()
+static U32 GetLastWriteTime(const char *FileName)
+{
+    struct stat file_info = {0};
+
+    if(stat(FileName, &file_info) != 0) {
+        // TODO: Diagnostic. perror("stat failed");
+    }
+
+    return (U32)file_info.st_mtime;
+}
+
+#define GAME_DLL_NAME "libhandmade.so"
+
+static sdl_game_code SDLLoadGameCode(char *DLLPath)
 {
     sdl_game_code Result = {0};
 
-    Result.GameCodeDLL = dlopen("./libhandmade.so", RTLD_NOW);
+    Result.GameCodeDLL = dlopen(DLLPath, RTLD_NOW);
     if(Result.GameCodeDLL) {
+        Result.DLLLastWriteTime = GetLastWriteTime(DLLPath);
+
         Result.UpdateAndRender = (void(*)(game_memory *, game_input *, game_offscreen_buffer *, game_sound_output_buffer *))dlsym(Result.GameCodeDLL, "UpdateAndRender");
         if(!Result.UpdateAndRender) {
             // TODO: Diagnostic. dlerror()
@@ -362,8 +383,40 @@ static void SDLUnloadGameCode(sdl_game_code *GameCode)
     GameCode->UpdateAndRender = NULL;
 }
 
+char *GetExecutablePath()
+{
+    static char path[1024] = ""; // NOTE: We choose 1024 only because MacOS's MAXPATHLEN says such a value.
+    ssize_t size = (ssize_t)sizeof(path); // WARNING: size_t is usually an unsigned integer, whilst ssize_t is signed. We don't care because the path is not long.
+
+#if __APPLE__ && __MACH__
+    if(_NSGetExecutablePath(path, &size) != 0) { // NOTE: Not an absolute path.
+        // TODO: Diagnostics.
+    }
+#else
+    size = readlink("/proc/self/exe", path, size - 1);
+    if(size != -1) {
+        path[size] = '\0';
+    } else {
+        // TODO: Diagnostics.
+    }
+#endif
+
+    return path;
+}
+
 S32 main(S32 argc, char *argv[])
 {
+    char *path = GetExecutablePath();
+    U32 len = strlen(path);
+    U32 i = len;
+    while(path[i] != '/' || i == 0) {
+        i--;
+    }
+    path[i+1] = '\0';
+
+    char game_dll_path[1024];
+    snprintf(game_dll_path, sizeof(game_dll_path), "%s%s", path, GAME_DLL_NAME);
+
     if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_GAMECONTROLLER | SDL_INIT_AUDIO)) {
         /* TODO: This didn't work . . . */
     }
@@ -431,8 +484,7 @@ S32 main(S32 argc, char *argv[])
                 U64 LastCycleCount;
 #endif
 
-                sdl_game_code Game = SDLLoadGameCode();
-                U32 LoadCounter = 0;
+                sdl_game_code Game = SDLLoadGameCode(game_dll_path);
 
                 while(GlobalRunning) {
                     LastCounter = SDLGetWallClock();
@@ -445,12 +497,11 @@ S32 main(S32 argc, char *argv[])
                     S32 GameUpdateHz = MonitorRefreshHz / 2;
                     F32 TargetSecondsPerFrame = 1.0f / (F32)GameUpdateHz;
 
-                    if(LoadCounter > (U32)(GameUpdateHz * 2)) {
+                    U32 NewDLLWriteTime = GetLastWriteTime(game_dll_path);
+                    if(NewDLLWriteTime > Game.DLLLastWriteTime) {
                         SDLUnloadGameCode(&Game);
-                        Game = SDLLoadGameCode();
-                        LoadCounter = 0;
+                        Game = SDLLoadGameCode(game_dll_path);
                     }
-                    LoadCounter++;
 
                     game_controller_input *OldKeyboardController = GetController(OldInput, 0);
                     game_controller_input *NewKeyboardController = GetController(NewInput, 0);