http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46680
--- Comment #2 from Adriano Rezende <adriano.rezende at openbossa dot org> 2010-11-27 12:10:21 UTC --- >> Am I missing something? > -O1 / -O2 / -O3 / -Os option. I know about these optimization flags :). My suggestion is directed specifically to -O0. I would not rest knowing that it generates 4 instructions per comparison, while it could use 2 instructions, reducing my code size and my compilation time while using -O0, which is the default one. >> but I think this is a strange behavior >> even for non-initialized variables. > http://en.wikipedia.org/wiki/Undefined_behavior I also know about UB. The strange behavior I'm referring to regards the compiler implementation rather than the language specification. I just looked for this, because I expected a consistent behavior in gcc for non-initialized bool values in that matter. For example, for char types it wouldn't make sense a == !a, for whatever value randomly placed in those 8 bits. For the 'if' statements, I expected a mutual exclusive operation, like [if(a) - cmpb/je] and [if(!a) - cmpb/jne], and that wasn't happening for bool comparisons. Well, I'm not an asm programmer nor a gcc contributor, so I may be wrong. But unless those 4 instructions make some sense, there is no purpose in keeping them.
