Re: [libvirt] [PATCH 3/3] qemu: Split if condition in qemuDomainSnapshotUndoSingleDiskActive

On Fri, Apr 13, 2012 at 11:12:54AM +0200, Michal Privoznik wrote: > Since compilers are trying to optimize code they are allowed to > reorder evaluation of conditions in if statement (okay, not in all > cases, but they can in this one). Therefore if we do: > if (stat(file, &st) == 0 && unlink(file) < 0) > after compiler chews this it may get feeling that swapping order > is a good idea. However, we obviously don't want to call stat() > on just unlink()-ed file. Really ? I'm not sure I believe that. IIRC in-order short-circuit evaluation is a part of the C standard. Compilers can't do any optimization which changes the order of evalation without breaking countless C programs.