On 01/22/2011 11:28 PM, Sergio Belkin wrote: > 2011/1/22 Jason L Tibbitts III<tibbs@xxxxxxxxxxx>: >>>>>>> "SB" == Sergio Belkin<sebelk@xxxxxxxxx> writes: >> >> SB> Is it allowed to override "-O2" and use instead "-O3"? I see that >> SB> those flags overrides those CXXFLAGS from Makefile sources. >> >> Of course for your personal packages you can do whatever you like. In >> Fedora, though, the answer is that you should use the provided optflags >> unless you have specific justification for a change. In order to change >> -O2 to -O3 I'd want to see benchmarking and other such evidence that >> indicates that the change actually makes a difference. Otherwise it's >> just a case of "adding -O99 for uber mega speedz0rs!!!11!!1one". >> >> - J< >> -- >> packaging mailing list > > Thanks for the answer, could you tell me (I'm really no ironic) could > you tell me when I can find that such a evidence. Well, I am not sure if I understand correctly. The problem with -O3 vs. -O2 is -O3 turning on, less-tested agressive features, which * may trip over bugs inside of the compiler (e.g. compiler ICEs). * may cause mis-compiled/defective binaries. * may break interaction with other tools (e.g. break debuginfos) Also, "-O2 vs. -O3" benchmarks are of little significance, because individual upstreams have little possibility to know about the generality and significance of such benchmarks. I.e. though an upstream may be able to prove "-O3 is 5% faster for application XXX on Ubuntu-Y-x86_64", this figure doesn't tell much about the impact of "-O3 on fedora-X-powerpc". > Let's say that I forget the "-O3" issue. Can I use that CXXFLAGS > > "-ansi -Wall -Wno-deprecated" ? -ansi normally doesn't affect code generation, so it's mostly harmless. -ansi however is somewhat problematic when it comes to portability, because the impact of -ansi is not consistent across different OSes. Adding further warning flags (-W*; not -Wno-* == suppressing warnings) is harmless. Ralf -- packaging mailing list packaging@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/packaging
