On Jan 8, 2016, at 7:50 PM, Duncan P. N. Exon Smith <dexonsm...@apple.com> wrote: > > [re-send to lists.llvm.org] > [necromancy] > > This is causing some strangeness for users of libc++ headers that > ship dylibs and build with -fno-rtti and -fvisibility=hidden. > > Strangely, -fno-rtti does *not* imply -fno-exceptions; the type info > needed for exceptions is generated on-the-fly. This means that each > translation unit generates a linkonce_odr copy of the std::exception > type info -- weird, but kind of reasonable? > > Because of this commit, the (non-canonical) type info from these > other dylibs is getting exported, even though they compile with > -fvisibility=hidden. On Darwin, this means that a link line like > this: > -- > $ ld -o a.out a.o -library-without-rtti -lc++ > -- > will find the type info in libibrary-without-rtti.dylib instead of > libc++.1.dylib. That doesn't seem reasonable. > > The request I've had from such dylib owners is to effectively revert > this commit, so that their copy of std::exception type info isn't > exported when they use -fvisibility=hidden. However, then their > copy of the type info won't get coalesced with libc++.1.dylib's. > > Does anyone have an opinion on this? Should we care about the > visibility of std::exception type info when -fno-rtti? (Note that > when RTTI is on, clang correctly does not generate the type info > for std::exception and friends.) > > Howard, any chance you remember more about the problems this fixed?
Sorry, nope. I have no opinion on this. The only thing I would have to say in this area is that if Nick says it, you can take it to the bank. Howard > >> On 2013-Dec-04, at 13:03, Howard Hinnant <hhinn...@apple.com> wrote: >> >> Author: hhinnant >> Date: Wed Dec 4 15:03:23 2013 >> New Revision: 196411 >> >> URL: http://llvm.org/viewvc/llvm-project?rev=196411&view=rev >> Log: >> Give all members of exception types default visibility. Lack of this is >> causing some illegal code relocations rare and hard to reproduce cases. >> >> Modified: >> libcxx/trunk/include/__config >> >> Modified: libcxx/trunk/include/__config >> URL: >> http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/__config?rev=196411&r1=196410&r2=196411&view=diff >> ============================================================================== >> --- libcxx/trunk/include/__config (original) >> +++ libcxx/trunk/include/__config Wed Dec 4 15:03:23 2013 >> @@ -194,7 +194,7 @@ >> #endif >> >> #ifndef _LIBCPP_EXCEPTION_ABI >> -#define _LIBCPP_EXCEPTION_ABI _LIBCPP_TYPE_VIS >> +#define _LIBCPP_EXCEPTION_ABI __attribute__ ((__visibility__("default"))) >> #endif >> >> #ifndef _LIBCPP_ALWAYS_INLINE >> >> >> _______________________________________________ >> cfe-commits mailing list >> cfe-comm...@cs.uiuc.edu >> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits > > _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
