GCC warnings for unused global variables

[Gabriel Dos Reis]

Mike Stump <mrs@apple.com> writes:

| On Friday, May 2, 2003, at 07:56 AM, Gabriel Dos Reis wrote:
| > They can be optimized out if the program cannot tell the difference.
| 
| Disagree.  I think the above is probably either confusing, or wrong.
| We can better well what you mean if you tell us if, in:
| 
| Given:
| 
| extern volatile int i;
| int main() {
| 	i = 1;
| 	i = 2;
| }
| 
| can the program tell the difference?

Obviously, with no information about the definition of "i", the
compiler does not have any information necessary to infer that the
optimization is legit.  Where is the problem?

-- Gaby