编译器警告 - 使用GCC的C函数重载 [英] Function overloading in C using GCC - compiler warnings

问题描述

我试图实现函数重载在 C ，我很接近。我使用C99所以在C11引入了 _Generic 关键字不能提供给我。我已经开发了一些工作code，但是当我编译它，我得到一对夫妇的警告。

I am attempting to implement function overloading in C, and I am very close. I am using C99 so the _Generic keyword introduced in C11 is not available to me. I have developed some working code, but when I compile it I get a couple warnings.

的例子：

#include <stdio.h>

#define print(x)                                                                        \
__builtin_choose_expr(__builtin_types_compatible_p(typeof(x), int   ), print_int(x)   , \
__builtin_choose_expr(__builtin_types_compatible_p(typeof(x), char[]), print_string(x), \
(void)0))


void print_int(int i) {
    printf("int: %d\n", i);
}

void print_string(char* s) {
    printf("char*: %s\n", s);
}

int main(int argc, char* argv[]) {

    print(1);
    print("this");

    return 0;
}

编译生成以下警告：

Compiling creates the following warnings:

gcc overload.c -o main
overload.c: In function 'main':
overload.c:19: warning: passing argument 1 of 'print_string' makes pointer from integer without a cast
overload.c:20: warning: passing argument 1 of 'print_int' makes integer from pointer without a cast

有关更多一点的调试信息，这里是主要的功能是什么样子的preprocessor做工作后：

For a little more debugging information, here is what the main function looks like after the preprocessor does its work:

int main(int argc, char* argv[]) {

 __builtin_choose_expr(__builtin_types_compatible_p(typeof(1), int ), print_int(1) , __builtin_choose_expr(__builtin_types_compatible_p(typeof(1), char[]), print_string(1), (void)0));
 __builtin_choose_expr(__builtin_types_compatible_p(typeof("this"), int ), print_int("this") , __builtin_choose_expr(__builtin_types_compatible_p(typeof("this"), char[]), print_string("this"), (void)0));

 return 0;
}

我怎样才能让编译警告消失，仍然有工作code？

How can I make the compilation warnings go away and still have working code?

推荐答案

在理论上，这应该工作：

In theory, this should work:

#define print(x)                                                                      \
(__builtin_choose_expr(__builtin_types_compatible_p(typeof(x), int   ), print_int   , \
 __builtin_choose_expr(__builtin_types_compatible_p(typeof(x), char[]), print_string, \
(void)0))(x))

它选择为 print_int 或 print_string ，然后应用所选择的功能， X 。

It chooses either print_int or print_string, then applies the chosen function to x.

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