Only use GNU cxxabi demangler for debug printing

Unfortunately, the cxxabi demangler utility causes an error in
the serialization code. Until that is resolved (see also issue #811)
use the normal typeid string for serialization and cxxabi
for debug printing.

hpx/util/debug/demangle_helper.hpp

@@ -10,25 +10,42 @@
 #include <hpx/config.hpp>
 #include <string>
 #include <type_traits>
+#include <typeinfo>
+
+// --------------------------------------------------------------------
+// Always present regardless of compiler : used by serialization code
+// --------------------------------------------------------------------
+namespace hpx { namespace util { namespace debug
+{
+    template <typename T>
+    struct demangle_helper
+    {
+        char const* type_id() const
+        {
+            return typeid(T).name();
+        }
+    };
+}}}
+
+#if defined(__GNUG__)
 
-#if defined(__GNUC__)
 #include <cxxabi.h>
 #include <stdlib.h>
 
+// --------------------------------------------------------------------
+// if available : demangle an arbitrary c++ type using gnu utility
+// --------------------------------------------------------------------
 namespace hpx { namespace util { namespace debug
 {
-    // --------------------------------------------------------------------
-    // demangle an arbitrary c++ type using gnu utility
-    // --------------------------------------------------------------------
     template <typename T>
-    class demangle_helper
+    class cxxabi_demangle_helper
     {
     public:
-        demangle_helper()
+        cxxabi_demangle_helper()
           : demangled_(abi::__cxa_demangle(typeid(T).name(), 0, 0, 0))
         {}
 
-        ~demangle_helper()
+        ~cxxabi_demangle_helper()
         {
             free(demangled_);
         }
@@ -46,18 +63,10 @@ namespace hpx { namespace util { namespace debug
 
 #else
 
-#include <typeinfo>
-
 namespace hpx { namespace util { namespace debug
 {
     template <typename T>
-    struct demangle_helper
-    {
-        char const* type_id() const
-        {
-            return typeid(T).name();
-        }
-    };
+    using cxxabi_demangle_helper = demangle_helper<T>;
 }}}
 
 #endif
@@ -74,6 +83,20 @@ namespace hpx { namespace util { namespace debug
     template <typename T>
     demangle_helper<T> type_id<T>::typeid_ = demangle_helper<T>();
 
+#if defined(__GNUG__)
+    template <typename T>
+    struct cxx_type_id
+    {
+        static cxxabi_demangle_helper<T> typeid_;
+    };
+
+    template <typename T>
+    cxxabi_demangle_helper<T> cxx_type_id<T>::typeid_ = cxxabi_demangle_helper<T>();
+#else
+    template <typename T>
+    using cxx_type_id = type_id<T>;
+#endif
+
     // --------------------------------------------------------------------
     // print type information
     // usage : std::cout << print_type<args...>("separator")
@@ -82,7 +105,7 @@ namespace hpx { namespace util { namespace debug
     template <typename T=void>
     inline std::string print_type(const char *delim="")
     {
-        return std::string(hpx::util::debug::type_id<T>::typeid_.type_id());
+        return std::string(cxx_type_id<T>::typeid_.type_id());
     }
 
     template <>
@@ -95,7 +118,7 @@ namespace hpx { namespace util { namespace debug
     inline typename std::enable_if<sizeof...(Args)!=0, std::string>::type
     print_type(const char *delim="")
     {
-        std::string temp(hpx::util::debug::type_id<T>::typeid_.type_id());
+        std::string temp(cxx_type_id<T>::typeid_.type_id());
         return temp + delim + print_type<Args...>(delim);
     }
 }}}