Fixed infinite growth of arena allocator

src/arena_allocator.c

@@ -6,14 +6,14 @@
 #define DEFAUL_REGION_SIZE 1048576 /* 8 * 1024 * 1024 = 8MB */
 
 Region *new_region(size_t capacity) {
-  if (capacity == 0) {
+  if (capacity < DEFAUL_REGION_SIZE) {
     capacity = DEFAUL_REGION_SIZE;
   }
-  Region *region = malloc(capacity);
+  Region *region = malloc(capacity + sizeof(Region));
   assert(region != NULL);
   *region = (Region){.next = NULL,
-                     .capacity = capacity + sizeof(Region),
-                     .cursor = sizeof(Region) - 1};
+                     .capacity = capacity,
+                     .cursor = 0};
   return region;
 }
 
@@ -39,8 +39,6 @@ void *arena_alloc(Arena *arena, size_t size) {
   assert(region != NULL);
 
   if (region->cursor + size > region->capacity) {
-    if (size < DEFAUL_REGION_SIZE)
-      size = DEFAUL_REGION_SIZE;
     region->next = new_region(size);
     arena->end = region->next;
     region = region->next;
@@ -51,7 +49,7 @@ void *arena_alloc(Arena *arena, size_t size) {
   return result;
 }
 
-//void *arena_clear(Arena *arena) {
-//  arena->size = 0;
-//  return arena->data;
-//}
+// void *arena_clear(Arena *arena) {
+//   arena->size = 0;
+//   return arena->data;
+// }

src/arena_allocator.h

@@ -8,7 +8,7 @@ struct Region_s {
   Region *next;
   size_t capacity;
   size_t cursor;
-  uintptr_t data[];
+  unsigned char data[];
 };
 
 typedef struct {

src/main.c

@@ -8,6 +8,17 @@
 #include "shader.h"
 #include "window.h"
 
+#include "arena_allocator.h"
+
+/*int main(int argc, char *argv[]) {
+  Arena global_arena = arena_init(0);
+  for (int i = 0; i <= 1048576+100; i++) {
+    int *number = arena_alloc(&global_arena, sizeof(int));
+    *number = 42;
+  }
+  arena_deinit(&global_arena);
+}*/
+
 int main(int argc, char *argv[]) {
   wn_window window = {0};
   if (!wn_window_init(&window)) {