C函数名称或函数指针? [英] C function name or function pointer?

问题描述

让我们看一下这段代码:

Let's see this code:

#include <stdio.h>

typedef int (*callback) (void *arg);
callback world = NULL;

int f(void *_) {
    printf("World!");
    return 0;
}

int main() {
    printf("Hello, ");
    // world = f;
    world = &f; // both works
    if (world != NULL) {
        world(NULL);
    }
}

设置 world 变量时，两者 world = f; 和 world =& f; 有效.

When setting world variable, both world = f; and world = &f; works.

我应该使用哪个?它取决于编译器还是C版本?

Which should I use? Does it depend on the compiler or C version?

% gcc -v
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 8.0.0 (clang-800.0.38)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

推荐答案

world = f; 和 world =& f; 均有效，因为两者之间没有区别将 f 和& f 作为参数传递时.

Both world = f; and world = &f; works because there is no difference between f and &f when passing it as an argument.

请参见 C99 规范(第6.7节).5.3.8).

See C99 specification (section 6.7.5.3.8).

将参数声明为函数返回类型"声明调整为指向函数返回类型的指针"，如6.3.2.1.所示.

A declaration of a parameter as ‘‘function returning type’’ shall be adjusted to ‘‘pointer to function returning type’’, as in 6.3.2.1.

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