uint32_t Wasm::allocContextId() {
  while (true) {
    auto id = next_context_id_++;
    // Prevent reuse.
    if (contexts_.find(id) == contexts_.end()) {
      return id;
    }
  }
}
uint32_t Wasm::allocContextId() {
  while (true) {
    auto id = next_context_id_++;
     
    if (contexts_.find(id) == contexts_.end()) {
      return id;
    }
  }
}