从构造函数抛出异常 [英] Throwing exceptions from constructors

问题描述

我与同事讨论关于从构造函数抛出异常的问题，我想要一些反馈。

是否可以抛出异常构造函数，从设计的角度？

假设我在一个类中包装一个posix mutex，它看起来像这样：

> class Mutex {
public：
Mutex（）{
if（pthread_mutex_init（& mutex_，0）！ = 0）{
throw MutexInitException（）;
}
}

〜Mutex（）{
pthread_mutex_destroy（& mutex_）;
}

void lock（）{
if（pthread_mutex_lock（& mutex_）！= 0）{
throw MutexLockException
}
}

void unlock（）{
if（pthread_mutex_unlock（& mutex_）！= 0）{
throw MutexUnlockException
}
}

private：
pthread_mutex_t mutex_;
};


我的问题是，这是标准的做法吗？因为如果pthread mutex_init调用失败，互斥对象是不可用的，所以抛出异常确保不会创建互斥。

我应该创建一个成员函数init Mutex类并调用pthread mutex_init，在其中将返回一个基于pthread的bool mutex_init的返回？这种方式我不必为这样的低级对象使用异常。

解决方案

是的，构造函数是这样做的标准方式。有关详细信息，请参阅有关处理失败的构造函数的常见问题。有一个init（）方法也可以工作，但是每个创建mutex对象的人都必须记住必须调用init（）。我认为这违反了 RAII 原则。

I'm having a debate with a co-worker about throwing exceptions from constructors, and thought I would like some feedback.

Is it ok to throw exceptions from constructors, from a design point of view?

Lets say I'm wrapping a posix mutex in a class, it would look something like this:

class Mutex {
public:
  Mutex() {
    if (pthread_mutex_init(&mutex_, 0) != 0) {
      throw MutexInitException();
    }
  }

  ~Mutex() {
    pthread_mutex_destroy(&mutex_);
  }

  void lock() {
    if (pthread_mutex_lock(&mutex_) != 0) {
      throw MutexLockException();
    }
  }

  void unlock() {
    if (pthread_mutex_unlock(&mutex_) != 0) {
      throw MutexUnlockException();
    }
  }

private:
  pthread_mutex_t mutex_;
};

My question is, is this the standard way to do it? Because if the pthread mutex_init call fails the mutex object is unusable so throwing an exception ensures that the mutex won't be created.

Should I rather create a member function init for the Mutex class and call pthread mutex_init within which would return a bool based on pthread mutex_init's return? This way I don't have to use exceptions for such a low level object.

解决方案

Yes, throwing an exception from the failed constructor is the standard way of doing this. Read this FAQ about Handling a constructor that fails for more information. Having a init() method will also work, but everybody who creates the object of mutex has to remember that init() has to be called. I feel it goes against the RAII principle.

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