C 语言 Weak Symbols

1. main.c

#include <stdio.h>
#include "newfun.h"

__attribute__((weak)) void can_be_override(void) {
    printf("default func\n");
}

int main(void) {
    can_be_override();
    return 0;
}

2. newfun.h

#ifndef _NEWFUN_H
#define _NEWFUN_H

void can_be_override(void);

#endif /* _NEWFUN_H */

3. newfun.c

#include <stdio.h>
#include "newfun.h"

void can_be_override(void) {
    printf("new fun\n");
}

4. 编译执行

$ gcc -o test main.c && ./test

default func

$ gcc -o test main.c newfun.c && ./test

new fun