Fixed demangle bug

include/boost/leaf/detail/demangle.hpp

@@ -6,7 +6,7 @@
 // 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)
 
-// core::demangle
+// This file is based on boost::core::demangle
 //
 // Copyright 2014 Peter Dimov
 // Copyright 2014 Andrey Semashev
@@ -61,22 +61,26 @@ char const * t =
 
 ////////////////////////////////////////
 
-#if defined(__has_include) && ((__GNUC__ + 0) >= 5)
+// __has_include is currently supported by GCC and Clang. However GCC 4.9 may have issues and
+// returns 1 for 'defined( __has_include )', while '__has_include' is actually not supported:
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63662
+#if defined(__has_include) && (!defined(__GNUC__) || defined(__clang__) || (__GNUC__ + 0) >= 5)
 #   if __has_include(<cxxabi.h>)
 #       define BOOST_LEAF_HAS_CXXABI_H
 #   endif
-#elif defined(__GLIBCXX__) || defined(__GLIBCPP__)
+#elif defined( __GLIBCXX__ ) || defined( __GLIBCPP__ )
 #   define BOOST_LEAF_HAS_CXXABI_H
 #endif
 
 #if defined( BOOST_LEAF_HAS_CXXABI_H )
 #   include <cxxabi.h>
-// For some architectures (mips, mips64, x86, x86_64) cxxabi.h in Android NDK is implemented by gabi++ library
-// (https://android.googlesource.com/platform/ndk/+/master/sources/cxx-stl/gabi++/), which does not implement
-// abi::__cxa_demangle(). We detect this implementation by checking the include guard here.
+//  For some archtectures (mips, mips64, x86, x86_64) cxxabi.h in Android NDK is implemented by gabi++ library
+//  (https://android.googlesource.com/platform/ndk/+/master/sources/cxx-stl/gabi++/), which does not implement
+//  abi::__cxa_demangle(). We detect this implementation by checking the include guard here.
 #   if defined( __GABIXX_CXXABI_H__ )
 #       undef BOOST_LEAF_HAS_CXXABI_H
 #   else
+#       include <cstdlib>
 #       include <cstddef>
 #   endif
 #endif