检查函数是否用 C 预处理器声明? [英] Check whether function is declared with C preprocessor?

问题描述

是否可以告诉 C 预处理器检查是否声明了函数(不是宏)?我尝试了以下方法，但它似乎不起作用:

Is it possible to tell the C preprocessor to check whether a function (not a macro) is declared? I tried the following, but it doesn't appear to work:

#include <stdio.h>

int main(void)
{
#if defined(printf)
    printf("You support printf!
");
#else
    puts("Either you don't support printf, or this test doesn't work.");
#endif
    return 0;
}

推荐答案

没有.预处理器在 C 编译器和 C 编译器处理函数声明之前运行.预处理器仅用于文本处理.

No. Preprocessor runs before the C compiler and the C compiler processes function declarations. The preprocessor is only there for text processing.

但是，大多数头文件都包含诸如 _STDIO_H_ 之类的保护宏，您可以在预处理器阶段对其进行测试.但是，该解决方案不可移植，因为包含保护宏名称未标准化.

However, most header files have include guard macros like _STDIO_H_ that you can test for in the preprocessor stage. However, that solution is not portable as the include guard macro names are not standardized.

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