Re: [committed] libstdc++: Avoid redundant checks in std::use_facet [PR103755]

[Jonathan Wakely <jwakely.gcc@gmail.com>]

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On Sun, 13 Nov 2022, 19:23 Stephan Bergmann via Libstdc++, <
libstdc++@gcc.gnu.org> wrote:

> On 11/12/22 03:47, Jonathan Wakely wrote:
> > On Fri, 11 Nov 2022 at 21:00, Stephan Bergmann <sbergman@redhat.com>
> wrote:
> >>
> >> On 11/11/22 06:30, Jonathan Wakely via Gcc-patches wrote:
> >>> As discussed in the PR, this makes it three times faster to construct
> >>> iostreams objects.
> >>>
> >>> Tested x86_64-linux. Pushed to trunk.
> >>
> >> I haven't yet tried to track down what's going on, but with various
> >> versions of Clang (e.g. clang-15.0.4-1.fc37.x86_64):
> >>
> >>> $ cat test.cc
> >>> #include <regex>
> >>> int main(int, char ** argv) {
> >>>      std::regex_traits<char>().transform(argv[0], argv[0] + 1);
> >>> }
> >>
> >>> $ clang++ --gcc-toolchain=... -fsanitize=undefined -O2 test.cc
> >>> /usr/bin/ld: /tmp/test-c112b1.o: in function
> `std::__cxx11::basic_string<char, std::char_traits<char>,
> std::allocator<char> >
> std::__cxx11::regex_traits<char>::transform<char*>(char*, char*) const':
> >>>
> test.cc:(.text._ZNKSt7__cxx1112regex_traitsIcE9transformIPcEENS_12basic_stringIcSt11char_traitsIcESaIcEEET_S9_[_ZNKSt7__cxx1112regex_traitsIcE9transformIPcEENS_12basic_stringIcSt11char_traitsIcESaIcEEET_S9_]+0x1b):
> undefined reference to `std::__cxx11::collate<char> const*
> std::__try_use_facet<std::__cxx11::collate<char> >(std::locale const&)'
> >>> clang-15: error: linker command failed with exit code 1 (use -v to see
> invocation)
> >
> > That should be present, andis present in my builds:
> >
> > _ZSt15__try_use_facetINSt7__cxx117collateIcEEEPKT_RKSt6locale
> > std::__cxx11::collate<char> const*
> > std::__try_use_facet<std::__cxx11::collate<char> >(std::locale const&)
> > version status: compatible
> > GLIBCXX_3.4.31
> > type: function
> > status: added
> >
> > Was this a clean build, or incremental? I'm guessing the latter.
>
> Yes, indeed.  And a full rebuild fixed the issue for me.
>

Ah good.


> Sorry for the noise.
>

No problem, you do a good job of keeping us working well with clang.