[Bug libstdc++/122172] [16 Regression] 1571 regressions due to std::make_unsigned<_Atomic_word> since r16-3810

[hp at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122172

--- Comment #16 from Hans-Peter Nilsson <hp at gcc dot gnu.org> ---
So, is this too ugly? (Please ignore the whitespace change.)

diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h
b/libstdc++-v3/include/bits/shared_ptr_base.h
index 0c6df64b921f..cd8be8b091fe 100644
--- a/libstdc++-v3/include/bits/shared_ptr_base.h
+++ b/libstdc++-v3/include/bits/shared_ptr_base.h
@@ -267,7 +267,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        // which would cause use_count() to return bogus values.
        constexpr _Atomic_word __max
          = sizeof(long) > sizeof(_Atomic_word)
-             ? -1 : __gnu_cxx::__int_traits<_Atomic_word>::__max;
+            ? -1 : (_Atomic_word_unsigned) -1 / 2;

        if (__count == __max) [[__unlikely__]]
          __builtin_trap();