Fix scoping of v8::HandleScope to prevent use-after-dispose

samples/shell.cc

-// Copyright 2011 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
@@ skipping 48 matching lines @@
 v8::Handle<v8::String> ReadFile(const char* name);
 void ReportException(v8::TryCatch* handler);
 
 
 static bool run_shell;
 
 
 int main(int argc, char* argv[]) {
   v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
   run_shell = (argc == 1);
-  v8::HandleScope handle_scope;
-  v8::Persistent<v8::Context> context = CreateShellContext();
-  if (context.IsEmpty()) {
-    printf("Error creating context\n");
-    return 1;
+  int result;
+  {
+    v8::HandleScope handle_scope;
+    v8::Persistent<v8::Context> context = CreateShellContext();
+    if (context.IsEmpty()) {
+      printf("Error creating context\n");
+      return 1;
+    }
+    context->Enter();
+    result = RunMain(argc, argv);
+    if (run_shell) RunShell(context);
+    context->Exit();
+    context.Dispose();
   }
-  context->Enter();
-  int result = RunMain(argc, argv);
-  if (run_shell) RunShell(context);
-  context->Exit();
-  context.Dispose();
   v8::V8::Dispose();
   return result;
 }
 
 
 // Extracts a C string from a V8 Utf8Value.
 const char* ToCString(const v8::String::Utf8Value& value) {
   return *value ? *value : "<string conversion failed>";
 }
 
@@ skipping 237 matching lines @@
       printf("^");
     }
     printf("\n");
     v8::String::Utf8Value stack_trace(try_catch->StackTrace());
     if (stack_trace.length() > 0) {
       const char* stack_trace_string = ToCString(stack_trace);
       printf("%s\n", stack_trace_string);
     }
   }
 }