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

[Stephan Bergmann <sbergman@redhat.com>]

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.

Sorry for the noise.