[gcc r12-7734] libstdc++: Work around clang misdesign in time_get<>::get [PR104990]

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:e63ac860afe816fef6b86bee6e47980e1351213c

commit r12-7734-ge63ac860afe816fef6b86bee6e47980e1351213c
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Mar 21 11:02:04 2022 +0100

    libstdc++: Work around clang misdesign in time_get<>::get [PR104990]
    
    Apparently clang has a -fgnuc-version= option which allows it to pretend
    it is any GCC version the user likes.  It is already bad that it claims to
    be GCC 4.2 compatible by default when it is not (various unimplemented
    extensions at least), but this option is a horrible idea.
    
    Anyway, this patch adds a hack for it.
    
    2022-03-21  Jakub Jelinek  <jakub@redhat.com>
    
            PR libstdc++/104990
            * include/bits/locale_facets_nonio.tcc (get): Don't check if do_get
            isn't overloaded if __clang__ is defined.

Diff:
---
 libstdc++-v3/include/bits/locale_facets_nonio.tcc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/locale_facets_nonio.tcc b/libstdc++-v3/include/bits/locale_facets_nonio.tcc
index 8c37a706db8..17a2c8d4486 100644
--- a/libstdc++-v3/include/bits/locale_facets_nonio.tcc
+++ b/libstdc++-v3/include/bits/locale_facets_nonio.tcc
@@ -1465,7 +1465,7 @@ _GLIBCXX_END_NAMESPACE_LDBL_OR_CXX11
       ctype<_CharT> const& __ctype = use_facet<ctype<_CharT> >(__loc);
       __err = ios_base::goodbit;
       bool __use_state = false;
-#if __GNUC__ >= 5
+#if __GNUC__ >= 5 && !defined(__clang__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wpmf-conversions"
       // Nasty hack.  The C++ standard mandates that get invokes the do_get