David Brown <david@xxxxxxxxxxxxxxx> writes: >>> but one weird problem is that the following codes compiled with option -O0 >> >> You need to show us a small complete self-contained example. >> >> Normally a program which works at -O0 and fails at -O1 has an >> uninitialized variable somewhere. > > Another common cause is aliasing - using pointer casts to access the > same data in different ways. > > And (especially if this is embedded programming), also check for missing > "volatile" qualifiers. > > Compile your code with lots of warnings - that will help spot > mistakes. The flags I often use are: > > -Wall > -Wextra > -Winit-self > -Wmissing-include-dirs ... ... but be a bit wary of any warning option which isn't included in -Wall or -Wextra -- they're usually omitted for a reason (typically because they yield tons of false positives on reasonable code). -Miles -- Conservative, n. A statesman enamored of existing evils, as opposed to a Liberal, who wants to replace them with new ones.
