On Tue, 6 Oct 2020 13:29:56 -0000 (UTC)
Stuart Henderson <s...@spacehopper.org> wrote:
> On 2020-10-05, Julian Smith <ju...@op59.net> wrote:
> > It looks like OpenBSD's cmake port patches cmake to remove the use
> > of -O2 in Release and RelWithDebInfo builds -
> > /usr/ports/devel/cmake/patches/patch-Modules_Compiler_GNU_cmake has:
> >
> > - string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os
> > -DNDEBUG")
> > - string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3 -DNDEBUG")
> > - string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g
> > -DNDEBUG")
> > + string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
> > + string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -DNDEBUG")
> > + string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -g
> > -DNDEBUG")
> >
> > Does anyone know why things are patched in this way?
> >
> >
> > [I think one can force optimisation with (for example):
> >
> > cmake -DCMAKE_CXX_FLAGS_RELWITHDEBINFO="-O2 -g -DNDEBUG" ...
> > ]
> >
> >
> > Thanks,
> >
> > - Jules
> >
>
> It's setup to work with builds done from ports, which should not
> override whatever optimization level is set by either the user or the
> build infrastructure.
>
> The downside is that you need to add this yourself for builds from
> outside ports.
Thanks for the explanation.
Would it be worth documenting this in the cmake(1) manpage? If so, i'll
submit a patch.
It's quite confusing to have cmake not optimise by default for Release
or RelWithDeb builds - i built OpenSceneGraph-3.6 while working on
Flightgear and it took a rather long time to figure out why i was
getting such a reduced frame rate.
Thanks,
- Jules
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