Function _mi_is_main_thread

3rd/mimalloc-2.0.9/src/init.c:418–420

bool _mi_is_main_thread(void) {
  return (_mi_heap_main.thread_id==0 || _mi_heap_main.thread_id == _mi_thread_id());
}

static _Atomic(size_t) thread_count = MI_ATOMIC_VAR_INIT(1);