c - getchar 是否定义为宏？

Question

这个问题已经有答案了:

Are getchar() and putchar() functions or macros? (3 个回答)

已关闭 5 年前。

我在 K&R 第 90 页读到 getchar 通常被定义为宏。

那么，为什么这段代码实际上有效:

#include <stdio.h>

#undef getchar

int main()
{
    char c;
    c= getchar();
    printf("%c\n",c);

    return 0;
}

Answer 1

不。它是一个类似宏的函数。

C99 7.1.4(P1):

Any function declared in a header may be additionally implemented as a function-like macro defined in the header,so if a library function is declared explicitly when its header is included, one of the techniques shown below can be used to ensure the declaration is not affected by such a macro.