When to use the -g flag to GCC

Question

I'm trying to force ValGrind to tell me what's wrong with my program. Every shred of documentation on the face of the Internet says that you must supply the -g option to GCC, but not one single document says whether you need this flag at compile-time or link-time (or both). So which is it??

Answer 1

The GNU ld documentation says that -g will be ignored, so it doesn't make much sense to pass it. In general you pass -g to gcc (which really is a front-end for the whole compilation process and not just a compiler) and it will take care of it.

Answer 2

GCC provides -g flag to get the debugging, So one you compile the program like Consider a code of example.c like:

#include <stdio.h>
/* Warning: This program is wrong on purpose. */
int main()
{
int age = 10;
int height;
printf("I am %d years old.\n");
printf("I am %d inches tall.\n", height);
return 0;
}

By default if you compile say using make example It will trigger command

cc     example.c   -o example

Now you run command like

cc -g example.c -o example1

then you will find the size of the file example1 is greater than the size of example because -g flag enabled the debugging information.

While running valgrind is -g flag is not required. -g is only required in compilation process.