Add an arena out-of-memory handler

example/arena.c

@@ -9,7 +9,8 @@ typedef struct {
 
 int main(void)
 {
-    Arena arena = gebs_arena_get(4*1024);
+    /* Arena arena = gebs_arena_get(512); */
+    Arena arena = gebs_arena_get(128);
     defer { arena_destroy(&arena); }
 
     Ints ints = {0};

gebs.h

@@ -169,7 +169,7 @@ void gebs_default_allocator_free(void *self, void *memory);
 void *gebs_default_allocator_realloc(void *self, void *memory,
                                      size_t prev_size, size_t new_size);
 
-typedef struct {
+typedef struct Gebs_Arena {
     void *(*malloc)(void *self, size_t size);
     void (*free)(void *self, void *memory);
     void *(*realloc)(void *self, void *memory, size_t prev_size, size_t new_size);
@@ -177,6 +177,8 @@ typedef struct {
     void *buffer;
     void *end;
     size_t capacity;
+
+    void (*out_of_memory_handler)(struct Gebs_Arena *self, size_t requested);
 } Gebs_Arena;
 
 void gebs_arena_reset(Gebs_Arena *a);
@@ -184,6 +186,7 @@ void gebs_arena_destroy(Gebs_Arena *a);
 void *gebs_arena_malloc(void *self, size_t size);
 void gebs_arena_free(void *self, void *memory);
 void *gebs_arena_realloc(void *self, void *memory, size_t prev_size, size_t new_size);
+void gebs_arena_out_of_memory_handler(Gebs_Arena *self, size_t requested);
 
 #define gebs_arena_get(cap) \
 ({ \
@@ -192,6 +195,7 @@ void *gebs_arena_realloc(void *self, void *memory, size_t prev_size, size_t new_
     __arena.realloc = &gebs_arena_realloc; \
     __arena.free = &gebs_arena_free; \
     __arena.capacity = (cap); \
+    __arena.out_of_memory_handler = &gebs_arena_out_of_memory_handler; \
     __arena; \
 })
 
@@ -541,6 +545,15 @@ void *gebs_arena_malloc(void *self, size_t size)
     }
     void *p = a->end;
     a->end = (void *)((uintptr_t)a->end + size);
+
+    size_t requested = (uintptr_t)a->end - (uintptr_t)a->buffer;
+    if (requested > a->capacity) {
+        if (a->out_of_memory_handler == NULL) {
+            abort();
+        }
+        a->out_of_memory_handler(a, requested);
+    }
+
     return p;
 }
 
@@ -572,6 +585,16 @@ void gebs_arena_destroy(Gebs_Arena *a)
 #endif
 }
 
+void gebs_arena_out_of_memory_handler(Gebs_Arena *self, size_t requested)
+{
+    GEBS_LOGE("Arena ran out of memory. capacity = %zu, requested %zu\n",
+        self->capacity, requested);
+    GEBS_LOGI("Arena: buffer %p, end %p, diff %zu\n",
+        self->buffer, self->end,
+        (size_t)((uintptr_t)self->end - (uintptr_t)self->buffer));
+    abort();
+}
+
 // ----------------------------------------------------------------------------
 // Scratch arena
 // ----------------------------------------------------------------------------