> -----Original Message----- > From: Szabolcs Nagy via Phabricator [mailto:revi...@reviews.llvm.org] > Sent: Friday, January 12, 2018 3:18 PM > > nsz added a comment. > > > it is not clear to me from the original bug report what "fedora 27 workloads" > break because of the lack of _Float128 type on x86. The glibc headers refer > to > _Float128, but normal include should not break unless the compiler claims to > be > >=gcc-7 or somebody explicitly requested the _Float128 support. [Blower, Melanie] I was building open source projects like ffmpeg, linux from scratch, and others. I was incorrect in my original post, I was using a patched compiler which led to _Float128 being exposed. In an unpatched clang this problem doesn't arise. I regret the lack of care taken in my analysis of the problem. > > if clang defines _Float128 then the headers "work" on x86 as in simple math.h > include is not broken, but some macro definitions will use the f128 const > suffix > (e.g. FLT128_MAX) which won't cause much breakage now but in the future > users will want to know whether they can use these macros or not. > > so either clang have to introduce all these features that are used by glibc > together or provide ways for users (and glibc) to figure out what is supported > and what isn't. > > on non-x86 targets a glibc fix can solve the problem such that they "work" on > the same level as x86, i.e. no immediate build breakage on most code, but some > features are not supported. i think that's the right way forward, but it's > not clear > if anybody has time to do the header changes in glibc before release (it has > to be > tested on several targets). > > if glibc is released as is today then those non-x86 targets don't want a > _Float128 > definition in clang-6 that breaks any math.h include on a glibc-2.27 system. > > > (We have a bit of time before the 6.0 release, so we can adjust the behavior > here to make it work. We probably don't want to try to add full _Float128 > support on the branch, though.) > > > > > Repository: > rC Clang > > https://reviews.llvm.org/D40673 > >
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