[Bug c++/99427] New: [modules] in system headers: non-constant condition for static assertion

["alexander.lelyakin at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99427

            Bug ID: 99427
           Summary: [modules] in system headers: non-constant condition
                    for static assertion
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alexander.lelyakin at googlemail dot com
  Target Milestone: ---

g++ -std=c++20 -fmodules-ts -x c++-system-header optional
g++ -std=c++20 -fmodules-ts -x c++-system-header random
g++ -std=c++20 -fmodules-ts -x c++-system-header memory_resource
g++ -std=c++20 -fmodules-ts -x c++-system-header string_view
g++ -std=c++20 -fmodules-ts -x c++-system-header thread
g++ -std=c++20 -fmodules-ts -x c++-system-header cwchar
g++ -std=c++20 -fmodules-ts -x c++-system-header forward_list
g++ -std=c++20 -fmodules-ts -x c++-system-header unordered_map
g++ -std=c++20 -fmodules-ts -x c++-system-header tuple
g++ -std=c++20 -fmodules-ts -x c++-system-header ios
g++ -std=c++20 -fmodules-ts -x c++-system-header istream
----
/usr/local/include/c++/11.0.1/istream: In function ‘std::basic_istream<_CharT,
_Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT
(&)[_Num])’:
/usr/local/include/c++/11.0.1/istream:840:26: error: non-constant condition for
static assertion
  840 |       static_assert(_Num <=
__gnu_cxx::__numeric_traits<streamsize>::__max);
      |                    
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/c++/11.0.1/istream:840:26: error: the value of
‘__gnu_cxx::__numeric_traits_integer<long int>::__max’ is not usable in a
constant expression
In file included from /usr/local/include/c++/11.0.1/bits/stl_algobase.h:63,
                 from /usr/local/include/c++/11.0.1/bits/char_traits.h:39,
                 from /usr/local/include/c++/11.0.1/string_view:41,
of module /usr/local/include/c++/11.0.1/string_view, imported at
/usr/local/include/c++/11.0.1/bits/basic_string.h:48,
        included from /usr/local/include/c++/11.0.1/string:55,
                 from /usr/local/include/c++/11.0.1/bits/locale_classes.h:40,
                 from /usr/local/include/c++/11.0.1/bits/ios_base.h:41,
                 from /usr/local/include/c++/11.0.1/ios:42,
of module /usr/local/include/c++/11.0.1/ios, imported at
/usr/local/include/c++/11.0.1/istream:38:
/usr/local/include/c++/11.0.1/ext/numeric_traits.h:75:27: note:
‘__gnu_cxx::__numeric_traits_integer<long int>::__max’ was not initialized with
a constant expression
   75 |       static const _Value __max = __is_signed
      |                           ^~~~~
/usr/local/include/c++/11.0.1/istream: At global scope:
/usr/local/include/c++/11.0.1/istream: warning: not writing module
‘/usr/local/include/c++/11.0.1/istream’ due to errors
----
g++ (GCC) 11.0.1 20210305 (experimental)
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