commit 03af8492bee6243a9d10e78fea1a3e423bd5f9cd
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri May 27 12:43:18 2022 +0100

    libstdc++: Mark non-exported function always_inline [PR105671]
    
    This new function was added for gcc 11.1 but is not exported from the
    shared library. Depending on inlining decisions, its callers might get
    inlined but an external definition be needed for this function. That
    then fails to link.
    
    Since we can't add the export to the gcc-11 release branch now, mark it
    always_inline. We can consider exporting it for gcc-13 if/when we bump
    the shared library version (and maybe also for gcc-12 which is currently
    at the same version as trunk). For now, the attribute will solve the
    problem on all affected branches. The function is small enough that
    force-inlining it shouldn't cause problems.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/105671
            * include/std/sstream (basic_stringbuf::_M_high_mark): Add
            always_inline attribute.
    
    (cherry picked from commit de57440858591a88e8fd7ba2505ca54546c86021)

diff --git a/libstdc++-v3/include/std/sstream b/libstdc++-v3/include/std/sstream
index f21664100ab..56555ecd98a 100644
--- a/libstdc++-v3/include/std/sstream
+++ b/libstdc++-v3/include/std/sstream
@@ -425,6 +425,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       // This might not be the same character as _M_string.end() because
       // basic_stringbuf::overflow might have written to unused capacity
       // in _M_string without updating its length.
+      __attribute__((__always_inline__))
       char_type*
       _M_high_mark() const _GLIBCXX_NOEXCEPT
       {