On 10/11/2013 09:50 AM, Francisco Jerez wrote: > Kenneth Graunke <kenn...@whitecape.org> writes: > >> On 10/10/2013 04:27 PM, Alexander von Gluck IV wrote: >>> >>> In llvm.py -fno-rtti is always a build flag if LLVM present >= 3.2 >>> >>> This breaks everything on our end (missing rtti related symbols) in our >>> C++ libGL.so as Haiku uses dynamic casts. >>> >>> We build our LLVM packages with rtti (REQUIRES_RTTI=1). >>> >>> Not 100% sure why we're forcing no-rtti if LLVM >= 3.2. >>> "llvm-config --cxxflags" should always show "-fno-rtti" if REQUIRES_RTTI=1 >>> wasn't set at build time. If REQUIRES_RTTI was set, -fno-rtti is removed >>> from the llvm-config cxxflags. >>> >>> It was originally added here: >>> http://cgit.freedesktop.org/mesa/mesa/commit/scons/llvm.py?id=d37ae642034bcaca39492c1eb75b029fb27ceffb >>> >>> My solutions are either removing the forced -fno-rtti, or wrapping it >>> with a platform != 'Haiku' >>> >>> Thoughts? >>> >>> -- Alex >> >> I would love to see us build with -fno-rtti for all Linux builds. I've >> been meaning to try that and measure the impact. >> > The -fno-rtti option is evil, it changes the C++ ABI in an incompatible > way. As you may have noticed from the build error, in some cases it's > impossible to link normal C++ object files with -fno-rtti object files > if the interface between them exposes polymorphic types. > > That's the reason why some LLVM versions require us to build the > interfacing module with -fno-rtti, and the same versions require us to > build *without* -fno-rtti if RTTI was enabled in the LLVM build, as > might be the case in Haiku and some Linux distributions. > > AFAICT the 'if' statement in scons/llvm.py:198 and the automake > conditional in configure.ac:1953 are broken and should probably be > removed. LLVM doesn't require -fno-rtti unless llvm-config says > otherwise, and if it still does in some case it's an llvm-config bug > that can probably be addressed differently. > > I don't think it's a good idea to enable -fno-rtti except for isolated > modules that can be guaranteed not to expose or use any C++ API. There > are legitimate uses of RTTI, and enabling -fno-rtti means that modules > that use it cannot talk to modules that don't. > > Thanks.
Which would be fine for Mesa (except maybe on Haiku), since all of our usage of C++ is internal and we don't expose /any/ C++ API. Nor should we. It looks like Clover uses RTTI. Nothing else does, and I'd like to keep it that way. --Ken _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
