[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):

 Well, this is an annoyingly stupid problem - and I came up with an equally
 stupid workaround:
 {{{
 --- /opt/local/libexec/gcc14/libc++/include/c++/v1/cstdlib.orig 2024-07-09
 13:43:11
 +++ /opt/local/libexec/gcc14/libc++/include/c++/v1/cstdlib      2024-07-09
 13:42:41
 @@ -142,7 +142,7 @@
  using ::mbstowcs _LIBCPP_USING_IF_EXISTS;
  using ::wcstombs _LIBCPP_USING_IF_EXISTS;
  #endif
 -#if !defined(_LIBCPP_CXX03_LANG)
 +#if !defined(_LIBCPP_CXX03_LANG) && 0
  using ::at_quick_exit _LIBCPP_USING_IF_EXISTS;
  using ::quick_exit _LIBCPP_USING_IF_EXISTS;
  #endif
 }}}

 With it, {{{-libstd=libc++}}} mostly works:
 {{{
 $ cat t-sstream.cpp
 #include <string>
 #include <iostream>
 #include <sstream>

 int main () {

   std::ostringstream foo;
   std::stringstream boo;

   foo.str("Test string");
   boo.str("Example string");

   //std::cout << foo << std::endl;
   std::cout << foo.str() << std::endl;

   foo << boo.str();

   //std::cout << foo << std::endl;
   std::cout << foo.str() << std::endl;

   return 0;
 }
 $ g++-mp-14 -pipe -stdlib=libc++ -std=gnu++20 -o t t-sstream.cpp
 $ ./t
 Test string
 Example string
 $
 }}}

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Ticket URL: <https://trac.macports.org/ticket/70341#comment:7>
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