From e7c1079c4fd48602e80df4a887f50f70115e471c Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Sat, 22 Sep 2018 20:05:31 +0300
Subject: [PATCH] Try to work around g++-5 constexpr issue in failed_impl

---
 include/boost/system/error_code.hpp | 35 ++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/include/boost/system/error_code.hpp b/include/boost/system/error_code.hpp
index 99d23a1..c2b1bc0 100644
--- a/include/boost/system/error_code.hpp
+++ b/include/boost/system/error_code.hpp
@@ -385,7 +385,33 @@ template<class T> struct enable_if<false, T>
 
 // failed_impl
 
-#if defined(BOOST_SYSTEM_HAS_CONSTEXPR)
+#if !defined(BOOST_SYSTEM_HAS_CONSTEXPR)
+
+inline bool failed_impl( int ev, error_category const & cat )
+{
+    return cat.failed( ev );
+}
+
+#elif BOOST_WORKAROUND(BOOST_GCC, < 60000)
+
+inline bool failed2_impl( int ev, error_category const & cat )
+{
+    return cat.failed( ev );
+}
+
+BOOST_SYSTEM_CONSTEXPR inline bool failed_impl( int ev, error_category const & cat )
+{
+    if( cat == system_category() || cat == generic_category() )
+    {
+        return ev != 0;
+    }
+    else
+    {
+        return failed2_impl( ev, cat );
+    }
+}
+
+#else
 
 BOOST_SYSTEM_CONSTEXPR inline bool failed_impl( int ev, error_category const & cat )
 {
@@ -399,13 +425,6 @@ BOOST_SYSTEM_CONSTEXPR inline bool failed_impl( int ev, error_category const & c
     }
 }
 
-#else
-
-inline bool failed_impl( int ev, error_category const & cat )
-{
-    return cat.failed( ev );
-}
-
 #endif
 
 } // namespace detail