From 2703431699d6c348286614a81107040455c878e4 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Sun, 20 Nov 2022 18:33:13 +0000
Subject: [PATCH] Clang should use _GLIBCXX_RELEASE To determine libstdc++
 version. Fixes https://github.com/boostorg/config/issues/455

---
 include/boost/config/stdlib/libstdcpp3.hpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/boost/config/stdlib/libstdcpp3.hpp b/include/boost/config/stdlib/libstdcpp3.hpp
index 75d33ccc..5a9f444e 100644
--- a/include/boost/config/stdlib/libstdcpp3.hpp
+++ b/include/boost/config/stdlib/libstdcpp3.hpp
@@ -139,6 +139,13 @@
 //
 #ifdef __clang__
 
+#ifdef _GLIBCXX_RELEASE
+#  define BOOST_LIBSTDCXX_VERSION (_GLIBCXX_RELEASE * 10000 + 100)
+#else
+//
+// We figure out which gcc version issued this std lib
+// by checking which headers are available:
+//
 #if __has_include(<expected>)
 #  define BOOST_LIBSTDCXX_VERSION 120100
 #elif __has_include(<source_location>)
@@ -170,6 +177,7 @@
 #elif __has_include(<array>)
 #  define BOOST_LIBSTDCXX_VERSION 40300
 #endif
+#endif
 //
 // If BOOST_HAS_FLOAT128 is set, now that we know the std lib is libstdc++3, check to see if the std lib is
 // configured to support this type.  If not disable it: