[gcc r12-5421] libstdc++: One more change for Clang to support constexpr std::string [PR103295]

[gcc r12-5421] libstdc++: One more change for Clang to support constexpr std::string [PR103295]

[Jonathan Wakely]

https://gcc.gnu.org/g:1f8d01eb1476a997eb1fc686b60fccdf97747faa

commit r12-5421-g1f8d01eb1476a997eb1fc686b60fccdf97747faa
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Nov 19 18:27:59 2021 +0000

    libstdc++: One more change for Clang to support constexpr std::string [PR103295]
    
    All writes into the allocated buffer need to be via traits_type::assign
    to begin lifetimes.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/103295
            * include/bits/basic_string.tcc (_M_construct): Use the
            traits assign member to write into allcoated memory.

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

diff --git a/libstdc++-v3/include/bits/basic_string.tcc b/libstdc++-v3/include/bits/basic_string.tcc
index 374406c0e13..6f619a08f70 100644
--- a/libstdc++-v3/include/bits/basic_string.tcc
+++ b/libstdc++-v3/include/bits/basic_string.tcc
@@ -201,7 +201,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		_M_data(__another);
 		_M_capacity(__capacity);
 	      }
-	    _M_data()[__len++] = *__beg;
+	    traits_type::assign(_M_data()[__len++], *__beg);
 	    ++__beg;
 	  }