c - 当我们将 "if(ptr==NULL)"用作整数指针 ptr 时，NULL 指针是否隐式转换为类型 (int*)？

Question

我知道 NULL 指针是 (void*)0。但是当我们使用如下语句时会发生什么:

  if(ptr==NULL)

ptr可以是char、float或int指针？是NULL 保证被隐式转换为左边的类型，例如，在 C 中，malloc() 返回的类型是 void* 但被隐式转换到左值的类型？

Answer 1

Is NULL guaranteed to be implicitly converted to the type on the left? [...]

是的。

根据 ISO/IEC 9899:2011 C programming language standard 的第 6.3.2.3.4 节:

Conversion of a null pointer to another pointer type yields a null pointer of that type. Any two null pointers shall compare equal.

和第 6.3.2.3.1 节

A pointer to void may be converted to or from a pointer to any object type. A pointer to any object type may be converted to a pointer to void and back again; the result shall compare equal to the original pointer.