On Tue, Jun 7, 2011 at 16:05, David Brown <david@xxxxxxxxxxxxxxx> wrote: > On 07/06/2011 15:38, Albert ARIBAUD wrote: >> >> Hi all, >> >> First of all, apologies if this is not the right list, or the correct >> way, to ask -- just point me in the right direction. >> >> We have encountered a weird case of gcc C code generation when >> compiling an if statement with a compound condition under -Os -O2; we >> suspect that the generated code is wrong, and we would like to make >> sure before we report a compiler bug... >> > > The options "-Os -O2" are contradictory. "-Os" enables most of the same > optimisations as "-O2" except those that are expected to increase code size, > and it also makes the compiler pick smaller code on some occasions. Thanks for pointing this out > > The key issue is documented here : > > <http://gcc.gnu.org/onlinedocs/gcc-4.3.5/gcc/Optimize-Options.html#index-fdelete_002dnull_002dpointer_002dchecks-658> > > Disable this optimisation and you'll get the "correct" result for your > "incorrect" C code. > > mvh., > > David Thanks David. I wanted to make sure whether we'd uncovered a compiler bug (and thus had to report it) or not, but anyway, as I admitted up front our C code is obviously bad here and will be fixed anyway. Regards, -- Albert ARIBAUD - Motorola Mobility France SAS
