[MacPorts] #70341: g++ fails to compile when -libstd=libc++ is set

[MacPorts]

#70341: g++ fails to compile when -libstd=libc++ is set
--------------------------------+--------------------
  Reporter:  mouse07410         |      Owner:  (none)
      Type:  defect             |     Status:  new
  Priority:  Normal             |  Milestone:
 Component:  ports              |    Version:
Resolution:                     |   Keywords:
      Port:  gcc12 gcc13 gcc14  |
--------------------------------+--------------------

Comment (by mouse07410):

 Here's the next problem that surfaced when I was compiling
 https://github.com/weidai11/cryptopp.git with G++-14, using
 {{{-libstd=libc++}}} (without that flag it builds fine and passes all the
 tests):
 {{{
 .  .  .
 g++ -stdlib=libc++ -pipe -DNDEBUG -g2 -Wa,-q -fPIC -pthread -fno-common
 -pipe -std=gnu++20 -O3 -march=native -isysroot
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
 -c dh2.cpp
 g++ -stdlib=libc++ -pipe -DNDEBUG -g2 -Wa,-q -fPIC -pthread -fno-common
 -pipe -std=gnu++20 -O3 -march=native -isysroot
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
 -c dll.cpp
 In file included from
 /opt/local/libexec/gcc14/libc++/include/c++/v1/__filesystem/filesystem_error.h:15,
                  from
 /opt/local/libexec/gcc14/libc++/include/c++/v1/__filesystem/directory_entry.h:20,
                  from
 /opt/local/libexec/gcc14/libc++/include/c++/v1/filesystem:539,
                  from
 /opt/local/libexec/gcc14/libc++/include/c++/v1/fstream:199,
                  from files.h:16,
                  from dll.h:27,
                  from dll.cpp:6:
 /opt/local/libexec/gcc14/libc++/include/c++/v1/__filesystem/path.h: In
 instantiation of
 'std::__1::__fs::filesystem::path::_EnableIfPathable<_Source>
 std::__1::__fs::filesystem::path::append(const _Source&) [with _Source =
 std::__1::basic_string<char>]':
 /opt/local/libexec/gcc14/libc++/include/c++/v1/__filesystem/path.h:534:52:
 error: use of built-in trait '__remove_pointer(typename
 std::__1::decay<_Tp>::type)' in function signature; use library traits
 instead
   534 |   _LIBCPP_HIDE_FROM_ABI _EnableIfPathable<_Source> append(const
 _Source& __src) {
       |                                                    ^~~~~~
 make: *** [dll.o] Error 1
 }}}

-- 
Ticket URL: <https://trac.macports.org/ticket/70341#comment:8>
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