"Felix J. Ogris" <fjo-lists@xxxxxxxx> writes: > On Apr 20, 2011, at 2:29 AM, Ian Lance Taylor wrote: > > [...] > >> This code is accessing values of type int using a pointer of type >> short*. That is invalid aliasing and your program uses undefined >> behaviour. Your suggested workarounds are the right one. >> >> To get a warning, you could try the -Wstrict-aliasing option. I don't >> think it exists in gcc 4.2, though. > > I tried with -Wstrict-aliasing, -Wstrict-aliasing=1..2 and -Wstrict-aliasing=3 with gcc 4.6, but didn't get a warning. This is a little bit annoying as it just happens after the implicit optimization/inlining. Declaring struct s as volatile or compiling with -fno-inline-functions helps, too. However, I'll stick with -fno-strict-aliasing. I'm sorry that -Wstrict-aliasing does not detect this case. You may want to report that as a bug. For your program, you could also consider rewriting it in valid C. Ian
