gistfile1.h

static void *
alloc_ruby_heap_with_file(size_t size)
{
    FileHeapAllocatorMetaData meta;
    meta.fd = open("/dev/zero", O_RDONLY);
    meta.size = size;
    if (meta.fd == -1) {
	return NULL;
    } else {
	void *memory = mmap(NULL, size + sizeof(meta), PROT_READ | PROT_WRITE,
	                    MAP_PRIVATE, meta.fd, 0);
	if (memory == NULL) {
	    return NULL;
	} else {
	    memcpy(memory, &meta, sizeof(meta));
	    return memory + sizeof(meta);
	}
    }
}

static void *
alloc_ruby_heap(size_t size)
{
    if (debug_options.alloc_heap_with_file) {
	return alloc_ruby_heap_with_file(size);
    } else {
	return malloc(size);
    }
}

static void
free_ruby_heap_with_file(void *heap)
{
    FileHeapAllocatorMetaData *meta = (FileHeapAllocatorMetaData *)
        (heap - sizeof(FileHeapAllocatorMetaData));
    close(meta->fd);
    munmap(heap, meta->size + sizeof(FileHeapAllocatorMetaData));
}