[Bug libstdc++/78627] New: [7 Regression] r243036 causes Firefox build failure

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78627

            Bug ID: 78627
           Summary: [7 Regression] r243036 causes Firefox build failure
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
                CC: ville at gcc dot gnu.org
  Target Milestone: ---

Since r243036:

trippels@gcc2-power8 thebes % g++ -w -c Unified_cpp_gfx_thebes0.ii
In file included from ../../dist/system_wrappers/ostream:4:0,
                 from ../../dist/stl_wrappers/ostream:55,
                 from
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/istream:39,
                 from
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/sstream:38,
                 from ../../dist/system_wrappers/sstream:4,
                 from ../../dist/include/mozilla/ToString.h:13,
                 from ../../dist/include/mozilla/gfx/BasePoint.h:11,
                 from /home/trippels/gecko-dev/gfx/thebes/gfxPoint.h:11,
                 from /home/trippels/gecko-dev/gfx/thebes/gfxMatrix.h:9,
                 from /home/trippels/gecko-dev/gfx/thebes/gfx3DMatrix.cpp:6,
                 from
/home/trippels/moz-build-dir/gfx/thebes/Unified_cpp_gfx_thebes0.cpp:2:
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream: In instantiation
of ‘struct std::__is_convertible_to_basic_ostream<const mozilla::EmptyLog&>’:
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:656:5:   required
by substitution of ‘template<class _Ostream, class _Tp> typename
std::enable_if<std::__and_<std::__not_<std::is_lvalue_reference<_Tp> >,
std::__is_convertible_to_basic_ostream<_Ostream>,
std::__is_insertable<_Ostream&, const _Tp&, void> >::value, typename
std::__is_convertible_to_basic_ostream<_Tp>::ostream_type>::type
std::operator<<(_Ostream&&, const _Tp&) [with _Ostream = const
mozilla::EmptyLog&; _Tp = unsigned int]’
/home/trippels/gecko-dev/ipc/chromium/src/chrome/common/ipc_message_utils.h:1055:94:
  required from here
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:625:23: error: no
matching function for call to ‘std::__is_convertible_to_basic_ostream<const
mozilla::EmptyLog&>::__check(const mozilla::EmptyLog*)’
       decltype(__check(declval<typename remove_reference<_Tp>::type*>()));
                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:620:37: note:
candidate: template<class _Ch, class _Up> static std::basic_ostream<_Ch, _Up>&
std::__is_convertible_to_basic_ostream<_Tp>::__check(std::basic_ostream<_Ch,
_Up>*) [with _Ch = _Ch; _Up = _Up; _Tp = const mozilla::EmptyLog&]
     static basic_ostream<_Ch, _Up>& __check(basic_ostream<_Ch, _Up>*);
                                     ^~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:620:37: note:  
template argument deduction/substitution failed:
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:625:23: note:  
types ‘std::basic_ostream<_CharT, _Traits>’ and ‘const mozilla::EmptyLog’ have
incompatible cv-qualifiers
       decltype(__check(declval<typename remove_reference<_Tp>::type*>()));
                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:622:23: note:
candidate: static const void
std::__is_convertible_to_basic_ostream<_Tp>::__check(void*) [with _Tp = const
mozilla::EmptyLog&] <near match>
     static void __check(void*);
                       ^~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:622:23: note:  
conversion of argument 1 would be ill-formed:
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:625:23: error:
invalid conversion from ‘const void*’ to ‘void*’ [-fpermissive]
       decltype(__check(declval<typename remove_reference<_Tp>::type*>()));
                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:625:23: error: no
matching function for call to ‘std::__is_convertible_to_basic_ostream<const
mozilla::EmptyLog&>::__check(const mozilla::EmptyLog*)’
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:620:37: note:
candidate: template<class _Ch, class _Up> static std::basic_ostream<_Ch, _Up>&
std::__is_convertible_to_basic_ostream<_Tp>::__check(std::basic_ostream<_Ch,
_Up>*) [with _Ch = _Ch; _Up = _Up; _Tp = const mozilla::EmptyLog&]
     static basic_ostream<_Ch, _Up>& __check(basic_ostream<_Ch, _Up>*);
                                     ^~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:620:37: note:  
template argument deduction/substitution failed:
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:625:23: note:  
types ‘std::basic_ostream<_CharT, _Traits>’ and ‘const mozilla::EmptyLog’ have
incompatible cv-qualifiers
       decltype(__check(declval<typename remove_reference<_Tp>::type*>()));
                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:622:23: note:
candidate: static const void
std::__is_convertible_to_basic_ostream<_Tp>::__check(void*) [with _Tp = const
mozilla::EmptyLog&] <near match>
     static void __check(void*);
                       ^~~~~~~
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:622:23: note:  
conversion of argument 1 would be ill-formed:
/home/trippels/gcc_test/usr/local/include/c++/7.0.0/ostream:625:23: error:
invalid conversion from ‘const void*’ to ‘void*’ [-fpermissive]
       decltype(__check(declval<typename remove_reference<_Tp>::type*>()));
                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~