gcc -Wpadded does not provide any warning

Question

I am trying to use gcc's -Wpadded option to know if gcc can help me in finding out whether a structure is padded or not. This is the following code.

#include<stdio.h>

struct my {
    char *name;
    int age;
} my_details;

int main() {
    struct my person1;
    return 0;
}

I complied the code using the following. gcc -Wpadded alignment_demo.c. It did not return any warnings. So is my structure not padded or I am missing something? man gcc however shows it supports an option called -Wpadded. Kindly help

Thanks Chidambaram

Answer 1

Seems that pack struct default is - 4. (gcc -fpack-struct=4)
If it so - than this structure is already aligned.
Because

char* - 4 or 8 bytes
int - 4 bytes

If you run this, you will have warning:

azat:~$ gcc -Wpadded -fpack-struct=8 -o test /tmp/test.c
/tmp/test.c:6:1: warning: padding struct size to alignment boundary [-Wpadded]

Because of the int.