Use strerror_r on glibc

include/boost/system/detail/generic_category.hpp

@@ -0,0 +1,69 @@
+// Implementation details of generic_error_category
+//
+// Copyright 2018 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// See library home page at http://www.boost.org/libs/system
+
+#include <cstring>
+
+namespace boost
+{
+
+namespace system
+{
+
+namespace detail
+{
+
+#if defined(__GLIBC__)
+
+// std::strerror is not thread-safe on glibc (for no reason)
+// glibc also has two incompatible strerror_r definitions (for no reason)
+
+inline char const * strerror_r_helper( char const * r, char const * )
+{
+    return r;
+}
+
+inline char const * strerror_r_helper( int r, char const * buffer )
+{
+    return r == 0? buffer: "Unknown error";
+}
+
+inline std::string generic_error_category_message( int ev )
+{
+    char buffer[ 128 ];
+    return strerror_r_helper( strerror_r( ev, buffer, sizeof( buffer ) ), buffer );
+}
+
+#else
+
+// std::strerror is thread-safe on everything else, incl. Windows
+
+inline std::string generic_error_category_message( int ev )
+{
+
+# if defined( BOOST_MSVC )
+#  pragma warning( push )
+#  pragma warning( disable: 4996 )
+# endif
+
+    char const * m = std::strerror( ev );
+
+# if defined( BOOST_MSVC )
+#  pragma warning( pop )
+# endif
+
+    return m? m: "Unknown error";
+
+#endif
+}
+
+} // namespace detail
+
+} // namespace system
+
+} // namespace boost

include/boost/system/error_code.hpp

@@ -17,7 +17,6 @@
 #include <ostream>
 #include <string>
 #include <functional>
-#include <cstring>
 
 // TODO: undef these macros if not already defined
 #include <boost/cerrno.hpp>
@@ -761,38 +760,19 @@ inline bool error_category::equivalent( const error_code & code, int condition )
     return *this == code.category() && code.value() == condition;
 }
 
-// generic_error_category implementation
-
-namespace detail
-{
-
-inline char const * generic_error_category_message( int ev )
-{
-#ifdef BOOST_MSVC
-#pragma warning( push )
-#pragma warning( disable: 4996 )
-#endif
-
-    char const * m = std::strerror( ev );
-
-#ifdef BOOST_MSVC
-#pragma warning( pop )
-#endif
-
-    return m? m: "Unknown error";
-}
-
-inline std::string generic_error_category::message( int ev ) const
-{
-    return generic_error_category_message( ev );
-}
-
-} // namespace detail
-
 } // namespace system
 
 } // namespace boost
 
+// generic_error_category implementation
+
+#include <boost/system/detail/generic_category.hpp>
+
+inline std::string boost::system::detail::generic_error_category::message( int ev ) const
+{
+    return generic_error_category_message( ev );
+}
+
 // system_error_category implementation
 
 #if defined(BOOST_WINDOWS_API)