Tighten integration with Ruby exceptions by tying in Exception#message

For Thrift exceptions that contain only a single string field, integrate
these even more tightly with Ruby exceptions by aliasing Ruby's
Exception#message field with the Thrift field.

Ruby exception objects created by Thrift will now display properly in
Ruby backtraces, etc. without any special handling by client code.


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665503 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/compiler/cpp/src/generate/t_rb_generator.cc b/compiler/cpp/src/generate/t_rb_generator.cc
index 7faa736..bb9c4d1 100644
--- a/compiler/cpp/src/generate/t_rb_generator.cc
+++ b/compiler/cpp/src/generate/t_rb_generator.cc
@@ -303,12 +303,18 @@
     vector<t_field*>::const_iterator m_iter = members.begin();
 
     if ((*m_iter)->get_type()->is_string()) {
+      string name = (*m_iter)->get_name();
+
       indent(out) << "def initialize(message=nil)" << endl;
       indent_up();
       indent(out) << "super()" << endl;
-      indent(out) << "self." << (*m_iter)->get_name() << " = message" << endl;
+      indent(out) << "self." << name << " = message" << endl;
       indent_down();
       indent(out) << "end" << endl << endl;
+
+      if (name != "message") {
+        indent(out) << "def message; " << name << " end" << endl << endl;
+      }
     }
   }
 }