...
int main(int argc, char *argv[], char *envp[])
{
...
 if ( argc > 1 ) {
    if ( strcmp(argv[1], "-d") == 0 ) {
#define DEBUG 1
   printf("DEBUG value is %d\n", DEBUG);
    }
    else {
#undef DEBUG
    }
 }
...
#ifdef DEBUG
 ...
#endif
...
}