Question

Can you add more than one attribute to an identifier in C with gcc?
Here is what I have now. I left out the include statements because they get scramble in the post.
If there is a way to add two, what is the general syntax, and how can I do it both with the defintion, and with a prototype? Thank you. 🙂

main() {  
    printf("In Main\n");  
}  
__attribute__ ((constructor)) void beforeMain(void)  
{  
    printf("Before Main\n");  
}  

Answer 1

There are two different ways of specifying multiple attributes in C with GCC:

#include <stdio.h>

// Attributes in prototypes:
__attribute__((constructor, weak)) void beforeMain(void);
__attribute__((constructor)) __attribute__((weak)) void beforeMain2(void);

int main(){
    printf("In Main\n");
    return 0;
}

// Attributes in definitions:
__attribute__((constructor, weak)) void beforeMain(void){
    printf("Before Main 1\n");
}

__attribute__((constructor)) __attribute__((weak)) void beforeMain2(void){
    printf("Before Main 2\n");
}

The code above compiles and runs correctly for me under GCC versions 4.4.3 and 12.3.0.