C++ 类型转换:将指针从 void 指针转换为类指针 [英] C++ typecast: cast a pointer from void pointer to class pointer

问题描述

如何将指向 void 对象的指针转换为类对象?

How to cast a pointer to void object to class object?

推荐答案

使用 static_cast.请注意，只有在指针确实指向指定类型的对象时才必须这样做；也就是说，指向 void 的指针的值取自指向此类对象的指针.

With a static_cast. Note that you must only do this if the pointer really does point to an object of the specified type; that is, the value of the pointer to void was taken from a pointer to such an object.

thing * p = whatever(); // pointer to object
void * pv = p;          // pointer to void
thing * p2 = static_cast<thing *>(pv); // pointer to the same object

如果您发现自己需要这样做，您可能需要重新考虑您的设计.您正在放弃类型安全，从而很容易编写无效代码:

If you find yourself needing to do this, you may want to rethink your design. You're giving up type safety, making it easy to write invalid code:

something_else * q = static_cast<something_else *>(pv);
q->do_something();  // BOOM! undefined behaviour.

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