Tested on gcc 4.0.2 20050808 and gcc 4.0.3 20051013 

I don't know if this is a bug or a feature : this code, also
compiled without optimization, doesn't check if the address of
the variable is zero.

extern unsigned long int __spm_addr;
int main(void)
{
     return &__spm_addr ? __spm_addr + 1 : -1;
}

gcc 3.x checks the variable address.