On Sat, 2014-01-25 at 16:05 +0000, Fraser Adams wrote: > ... > One of my colleagues mentioned to me that he reckons that there was a > performance drop off between (I think) 0.12 and 0.18 but I've got no > evidence other than anecdotal from him and certainly no reproducer.
I doubt this has anything to do with the change of build system. > > It did get me thinking about CMake though (though my colleague insists > he was using automake so there might still be an issue). > > Am I correct in thinking that with CMake there are different "build > types" and that in "idiomatic" CMake usage it's "generally" via the use > of different build types that compiler optimisation flags get set? I think that (too lazy to actually go look) in autotools the build default was -O2 and the Fedora/RHEL packaging set -O3. It is completely true that with cmake we've opted to follow the usual cmake practice (which is standard on Windows too) of having the build configuration dictate the optimisation/debug flags. I think that in the Fedora/RHEL packages we now use the RelWithDebInfo build configuration which corresponds to -O2 -g. It is true that if you specify no CMAKE_BUILD_TYPE then you will get no optimisation or debug flags set which is perhaps a rather bad idea. What do you think the default build type should be? (Out of Debug = -g, Release = -O2 -DNDEBUG, RelWithDebInfo -O2 -DNDEBUG -g, MinSizeRel = -Os -DNDEBUG) It's not clear to me that we should prioritise performance over debugability in our default build. Andrew --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
