指针到功能和指针到对象C和C之间投下++ [英] Casts between pointer-to-function and pointer-to-object in C and C++

问题描述

我错了有关以下内容？

C ++标准说，指针到函数和指针到对象的（反面）之间的转换是conditionnaly支持与实现定义的语义，而所有的C标准说，这是在任何情况下非法的，对吧？

C++ standards says that conversion between pointer-to-function and pointer-to-object (and back) is conditionnaly-supported with implementation-defined semantics, while all C standards says that this is illegal in all cases, right?

void foo() {}

int main(void)
{
    void (*fp)() = foo;
    void* ptr = (void*)fp;
    return 0;
}

ISO / IEC 14882：2011

5.2.10 Reinter preT施放[expr.reinter pret.cast]

5.2.10 Reinterpret cast [expr.reinterpret.cast]

8转换函数指针，指向一个对象的指针型或副
  有条件支持反之亦然。这种转换的意思是
  实现定义的，但如果实现支持
  转换在两个方向上，一种类型的一个prvalue转换为
  其他类型和背面，可能具有不同cvqualification，
  应产生原始指针值。

8 Converting a function pointer to an object pointer type or vice versa is conditionally-supported. The meaning of such a conversion is implementation-defined, except that if an implementation supports conversions in both directions, converting a prvalue of one type to the other type and back, possibly with different cvqualification, shall yield the original pointer value.

我现在不能找到它在C标准什么...

I can't find anything about it in C standard right now...

推荐答案

你是对的，C（99）标准只字未提从指针到函数指针到对象的转换，所以这是不确定的行为。 ^*

You're right, the C(99) standard says nothing about conversion from pointer-to-function to pointer-to-object, therefore it's undefined behaviour.^*

---

<子> *注意，但是，它确实定义指针到函数类型之间的行为。

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