On Jul 20, 2004, Archie Cobbs <archie@xxxxxxxxxxxx> wrote: > It appears gcc is completely ignoring the possibility of > "side effects" when it optimizes away the comparison. Oh, rats. That's because the reasoning about dereferencing NULL invoking undefined behavior still applies. Since both arms of the if return the same value, the compare is optimized away, and the dereference of the pointer can be removed because, if it was NULL or any other bad pointer, it would invoke undefined behavior, and otherwise, the dereference would be safe and unused. I think you really need to make the pointer volatile to prevent the dereference from being optimized out. -- Alexandre Oliva http://www.ic.unicamp.br/~oliva/ Red Hat Compiler Engineer aoliva@{redhat.com, gcc.gnu.org} Free Software Evangelist oliva@{lsd.ic.unicamp.br, gnu.org}
