Test hot reloading

.gitignore

@@ -1,3 +1,5 @@
 .cache
 compile_commands.json
 main
+*.so
+*.o

compile

@@ -1,9 +1,46 @@
 #!/bin/bash
 
-CC=clang
-CFLAGS="-g -Wall $(pkg-config --cflags sdl2)"
-LIBS="$(pkg-config --libs sdl2)"
-SRC=src/*.c
-OUT=main
+BUILD_TYPE="debug"
 
-(set -x ; $CC $CFLAGS $LIBS $SRC -o $OUT)
+while [[ $# > 0 ]];do
+  case $1 in
+    --release)
+      BUILD_TYPE="release"
+      shift
+      ;;
+    *|-*|--*)
+      echo "Unknown option $1"
+      exit 1
+      ;;
+  esac
+done
+
+CC=clang
+CFLAGS="-Wall $(pkg-config --cflags sdl2)"
+LIBS="$(pkg-config --libs sdl2)"
+MAIN=src/main.c
+MAIN_FLAGS=""
+GAME=src/game.c
+GAME_FLAGS="-DNDEBUG"
+OUT=main
+GAME_OUT=""
+
+if [[ $BUILD_TYPE == "debug" ]]; then
+	CFLAGS+=" -g"
+	MAIN_FLAGS="-ldl -Wl,-rpath,\$ORIGIN"
+	GAME_FLAGS+=" -fPIC -shared"
+	GAME_OUT="-o game.so"
+	MAIN+=" src/game.c"
+else
+	CFLAGS+=" -O3"
+	MAIN_FLAGS="-DNDEBUG"
+	GAME_FLAGS+=" -c"
+	MAIN+=" game.o"
+fi
+
+LOCKFILE="game.so.lock"
+touch $LOCKFILE && (set -x ; $CC $CFLAGS $GAME_FLAGS $LIBS $GAME $GAME_OUT)
+if [[ -f $LOCKFILE ]];then
+	rm $LOCKFILE
+fi
+(set -x ; $CC $CFLAGS $MAIN_FLAGS $LIBS $MAIN -o $OUT)

src/game.c

@@ -0,0 +1,102 @@
+#include "game.h"
+
+#if DEBUG
+#include <dlfcn.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <time.h>
+
+#define LIB "game.so"
+#define LOCKFILE "game.so.lock"
+
+static void *handle = NULL;
+static long int last_mtime;
+void (*update_character)(int window_height) = NULL;
+void (*render_character)(SDL_Renderer *renderer) = NULL;
+
+bool load_symbols(void) {
+  struct stat st;
+  if (stat(LOCKFILE, &st) == 0) {
+    // If lock file exists, don't reload the library
+    return true;
+  }
+
+  if (stat(LIB, &st) != 0) {
+    perror("Error checking library stat: ");
+    return false;
+  }
+
+  long int mtime = st.st_mtim.tv_sec * 1000000000 + st.st_mtim.tv_nsec;
+  if (mtime == last_mtime) {
+    return true;
+  }
+
+  last_mtime = mtime;
+
+  if (handle) {
+    close_library();
+  }
+
+  handle = dlopen(LIB, RTLD_NOW | RTLD_GLOBAL);
+  if (!handle) {
+    fprintf(stderr, "Failed to load library: %s\n", dlerror());
+    return false;
+  }
+
+  dlerror(); // Clear errors
+
+  *(void **)(&update_character) = dlsym(handle, "update_character");
+  *(void **)(&render_character) = dlsym(handle, "render_character");
+
+  char *error = dlerror();
+  if (error != NULL) {
+    fprintf(stderr, "Failed to load function symbol: %s", error);
+    return false;
+  }
+
+  return true;
+}
+
+void close_library(void) {
+  if (handle) {
+    dlclose(handle);
+    handle = NULL;
+  }
+}
+#else
+#include "SDL_rect.h"
+#include "SDL_render.h"
+
+typedef struct state State;
+struct state {
+  float delta;
+  float speed;
+  SDL_Rect character;
+};
+
+static State game = {
+    .delta = 1.f / 60.f,
+    .speed = 1600.f,
+    .character = {.x = 375, .y = 0, .w = 50, .h = 50},
+};
+
+void update_character(int window_height) {
+  game.character.y += game.speed * game.delta;
+  if (game.character.y < 0 ||
+      game.character.y + game.character.h > window_height) {
+    game.speed *= -1.f;
+
+    if (game.character.y < 0) {
+      game.character.y = 0;
+    } else {
+      game.character.y = window_height - game.character.h;
+    }
+  }
+}
+
+void render_character(SDL_Renderer *renderer) {
+  SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+  SDL_RenderFillRect(renderer, &game.character);
+}
+#endif

src/game.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "SDL_render.h"
+
+#ifdef NDEBUG
+#define DEBUG 0
+#else
+#define DEBUG 1
+#endif
+
+#if DEBUG
+#include <stdbool.h>
+
+bool load_symbols(void);
+void close_library(void);
+
+extern void (*update_character)(int window_height);
+extern void (*render_character)(SDL_Renderer *renderer);
+#else
+void update_character(int window_height);
+void render_character(SDL_Renderer *renderer);
+#endif

src/main.c

@@ -1,9 +1,16 @@
+#include "game.h"
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_events.h>
 #include <SDL2/SDL_render.h>
 #include <SDL2/SDL_video.h>
 #include <stdbool.h>
 
+#ifdef NDEBUG
+#define DEBUG 0
+#else
+#define DEBUG 1
+#endif
+
 #define WINDOW_WIDTH 800
 #define WINDOW_HEIGHT 600
 
@@ -21,6 +28,13 @@ int main(void) {
 
   SDL_Event event = {0};
 
+#if DEBUG
+  if (!load_symbols()) {
+    fprintf(stderr, "Failed to load game library\n");
+    return 1;
+  }
+#endif
+
   while (running) {
     while (SDL_PollEvent(&event)) {
       switch (event.type) {
@@ -30,13 +44,28 @@ int main(void) {
       }
     }
 
+#if DEBUG
+    if (!load_symbols()) {
+      fprintf(stderr, "Failed to load game library\n");
+      return 1;
+    }
+#endif
+
+    update_character(WINDOW_HEIGHT);
+
     SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
 
     SDL_RenderClear(renderer);
 
+    render_character(renderer);
+
     SDL_RenderPresent(renderer);
   }
 
+#if DEBUG
+  close_library();
+#endif
+
   SDL_DestroyRenderer(renderer);
 
   SDL_DestroyWindow(window);