// ---- arena constants
enum{big_arena_size=1024*1024, std_arena_size=64*1024};

#define MAKE_ARENA(name, size) \
  uint8_t name##_buf[size]; \
  arena name; \
  arena_init(&name, name##_buf, sizeof(name##_buf))

#define MAKE_STD_ARENA(name) MAKE_ARENA(name, std_arena_size)