Question

I would like to suppress a particular warning issued by gcc caused by returning the address of a local variable.

#include <stdio.h>
#pragma GCC diagnostic ignored "-Waddress"
void *get_stack() {
  unsigned long v;
  return &v;
}

int main()
{
  void *p = get_stack();
  printf("stack is %p\n",p);
  return 0;
}

>gcc -fdiagnostics-show-option p.c
p.c: In function ‘get_stack’:
p.c:5: warning: function returns address of local variable

Platform: this issue exists at least on MacOSX 10.5 Snow Leopard,
I haven’t tried on Linux yet.

In case you’re wondering why: I would like to run with warnings turned into errors
to halt a long winded build process so I can actually SEE problems and be forced
to fix them.

This particular code isn’t a bug, it is a “portable” technique for finding a
the stack pointer (which works on MSVC too). [Actually it won’t work on the
Itanium which has two stack pointers]

The stack pointer is required for use by a garbage collection routine
(to search for pointers on the stacks of suspended threads).

Answer 1

This appears to make the warning go away for me:

void *get_stack(void) {
  void *v = &v;
  return v;
}