[Bug libstdc++/79246] New: [C++17] with versioned namespace: FAIL: 27_io/manipulators/standard/wchar_t/2.cc (test for excess errors)

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79246

            Bug ID: 79246
           Summary: [C++17] with versioned namespace: FAIL:
                    27_io/manipulators/standard/wchar_t/2.cc (test for
                    excess errors)
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

This test fails when run with -std=gnu++17 for a
--enable-symvers=gnu-versioned-namespace build

spawn -ignore SIGHUP /home/jwakely/src/gcc/buildso7/./gcc/xg++ -shared-libgcc
-B/home/jwakely/src/gcc/buildso7/./gcc -nostdinc++
-L/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/src
-L/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs
-L/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs
-B/home/jwakely/gcc/so7/x86_64-pc-linux-gnu/bin/
-B/home/jwakely/gcc/so7/x86_64-pc-linux-gnu/lib/ -isystem
/home/jwakely/gcc/so7/x86_64-pc-linux-gnu/include -isystem
/home/jwakely/gcc/so7/x86_64-pc-linux-gnu/sys-include
-B/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/./libstdc++-v3/src/.libs
-fmessage-length=0 -fno-show-column -ffunction-sections -fdata-sections -g -O2
-D_GNU_SOURCE -DLOCALEDIR="." -nostdinc++
-I/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/include/x86_64-pc-linux-gnu
-I/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/include
-I/home/jwakely/src/gcc/gcc/libstdc++-v3/libsupc++
-I/home/jwakely/src/gcc/gcc/libstdc++-v3/include/backward
-I/home/jwakely/src/gcc/gcc/libstdc++-v3/testsuite/util
/home/jwakely/src/gcc/gcc/libstdc++-v3/testsuite/27_io/manipulators/standard/wchar_t/2.cc
-std=c++17 -fno-implicit-templates -fno-diagnostics-show-caret
-fdiagnostics-color=never ./libtestc++.a -Wl,--gc-sections
-L/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/src/filesystem/.libs
-lm -o ./2.exe^M
/tmp/cckkgPOG.o: In function `wchar_t* std::__7::basic_string<wchar_t,
std::__7::char_traits<wchar_t>, std::__7::allocator<wchar_t>
>::_S_construct_aux<wchar_t const*>(wchar_t const*, wchar_t const*,
std::__7::allocator<wchar_t> const&, std::__7::__false_type)':^M
/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:4871:
undefined reference to `wchar_t* std::__7::basic_string<wchar_t,
std::__7::char_traits<wchar_t>, std::__7::allocator<wchar_t>
>::_S_construct<wchar_t const*>(wchar_t const*, wchar_t const*,
std::__7::allocator<wchar_t> const&, std::__7::forward_iterator_tag)'^M
collect2: error: ld returned 1 exit status^M
compiler exited with status 1
FAIL: 27_io/manipulators/standard/wchar_t/2.cc (test for excess errors)
Excess errors:
/home/jwakely/src/gcc/buildso7/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:4871:
undefined reference to `wchar_t* std::__7::basic_string<wchar_t,
std::__7::char_traits<wchar_t>, std::__7::allocator<wchar_t>
>::_S_construct<wchar_t const*>(wchar_t const*, wchar_t const*,
std::__7::allocator<wchar_t> const&, std::__7::forward_iterator_tag)'
collect2: error: ld returned 1 exit status

UNRESOLVED: 27_io/manipulators/standard/wchar_t/2.cc compilation failed to
produce executable


It looks like we need an explicit instantiation of that function in the DSO.