Added subarenas but currently run into memory alignment issues

src/arena_allocator.c

@@ -11,19 +11,49 @@ Region *new_region(size_t capacity) {
   }
   Region *region = malloc(capacity + sizeof(Region));
   assert(region != NULL);
-  *region = (Region){.next = NULL,
-                     .capacity = capacity,
-                     .cursor = 0};
+  *region = (Region){.next = NULL, .capacity = capacity, .cursor = 0};
   return region;
 }
 
-Arena arena_init(size_t capacity) {
+Arena arena_init(Arena *parent, size_t capacity) {
   Region *region = new_region(capacity);
-  Arena arena = {.begin = region, .end = region};
+
+  if (parent != NULL) {
+    // Allocate new arena in parent to reduce likelyhood of loss
+    Arena *current_arena = arena_alloc(parent, sizeof(Arena));
+    *current_arena = (Arena){
+        .begin = region, .end = region, .child = NULL, .sibling = NULL};
+
+    // if parent has no children this arena is now it's child
+    if (parent->child == NULL) {
+      parent->child = current_arena;
+      return *current_arena;
+    }
+
+    // Push the arena onto the first childs sibling list
+    current_arena->sibling = parent->child;
+    parent->child = current_arena;
+    return *current_arena;
+  }
+
+  // This is the root of the arena tree
+  Arena arena = {
+      .begin = region, .end = region, .child = NULL, .sibling = NULL};
   return arena;
 }
 
 void arena_deinit(Arena *arena) {
+  if (arena == NULL) {
+    return;
+  }
+  // Recursively deinit children
+  while (arena->child != NULL) {
+    Arena *current_child = arena->child;
+    arena->child = current_child->sibling;
+    arena_deinit(current_child);
+  }
+
+  // actually free the data
   assert(arena->begin != NULL && arena->end != NULL);
   Region *region = arena->begin;
   while (region != NULL) {
@@ -31,6 +61,7 @@ void arena_deinit(Arena *arena) {
     free(region);
     region = next_region;
   }
+
   *arena = (Arena){.begin = NULL, .end = NULL};
 }
 

src/arena_allocator.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #include <stddef.h>
-#include <stdint.h>
 
 typedef struct Region_s Region;
 struct Region_s {
@@ -11,12 +10,15 @@ struct Region_s {
   unsigned char data[];
 };
 
-typedef struct {
+typedef struct Arena_s Arena;
+struct Arena_s {
+  Arena *child;
+  Arena *sibling;
   Region *begin;
   Region *end;
-} Arena;
+};
 
-Arena arena_init(size_t capacity);
+Arena arena_init(Arena *parent, size_t capacity);
 void arena_deinit(Arena *arena);
 
 void *arena_alloc(Arena *arena, size_t size);

src/main.c

@@ -1,5 +1,6 @@
 #include <GL/glew.h>
 #include <SDL3/SDL.h>
+#include <stdio.h>
 #include <stdlib.h>
 
 #include "SDL3/SDL_events.h"
@@ -10,16 +11,28 @@
 
 #include "arena_allocator.h"
 
-/*int main(int argc, char *argv[]) {
-  Arena global_arena = arena_init(0);
+int main(int argc, char *argv[]) {
+  // arena allocation test
+  printf("Allocation test");
+  Arena global_arena = arena_init(NULL, 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[]) {
+  printf("children test");
+
+  // arena children test
+  Arena child_arena = arena_init(&global_arena, 0);
+  //Arena sibling_arena = arena_init(&global_arena, 0);
+  //Arena grandchild_arena = arena_init(&child_arena, 0);
+
+  arena_deinit(&global_arena);
+
+  
+}
+
+/*int main(int argc, char *argv[]) {
   wn_window window = {0};
   if (!wn_window_init(&window)) {
     SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't initialize wn_window");
@@ -132,4 +145,4 @@ int main(int argc, char *argv[]) {
   wn_window_deinit(&window);
 
   return EXIT_SUCCESS;
-}
+}*/