[gcc r13-8310] libstdc++: Do not use assume attribute for Clang [PR112467]

[Torbjorn Svensson]

https://gcc.gnu.org/g:adef1e0ebeb5055ed4e8776fd3f73c9d84821eaa

commit r13-8310-gadef1e0ebeb5055ed4e8776fd3f73c9d84821eaa
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Nov 10 21:06:15 2023 +0000

    libstdc++: Do not use assume attribute for Clang [PR112467]
    
    Clang has an 'assume' attribute, but it's a function attribute not a
    statement attribute. The recently-added use of the statement form causes
    an error with Clang.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/112467
            * include/bits/stl_bvector.h (_M_assume_normalized): Do not use
            statement form of assume attribute for Clang.
    
    (cherry picked from commit 807f47497f17ed50be91f0f879308cb6fa063966)

Diff:
---
 libstdc++-v3/include/bits/stl_bvector.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h
index 2b91af2005f2..64f04c1f4f59 100644
--- a/libstdc++-v3/include/bits/stl_bvector.h
+++ b/libstdc++-v3/include/bits/stl_bvector.h
@@ -185,8 +185,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
     void
     _M_assume_normalized() const
     {
+#if __has_attribute(__assume__) && !defined(__clang__)
       unsigned int __ofst = _M_offset;
       __attribute__ ((__assume__ (__ofst < unsigned(_S_word_bit))));
+#endif
     }
 
     _GLIBCXX20_CONSTEXPR