Don't crash on stack overflow entering the debugger.

src/execution.cc

 // 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
@@ skipping 808 matching lines @@
   // Just continue if breaks are disabled.
   if (isolate->debug()->disable_break()) {
     return isolate->heap()->undefined_value();
   }
 
   // Ignore debug break during bootstrapping.
   if (isolate->bootstrapper()->IsActive()) {
     return isolate->heap()->undefined_value();
   }
 
+  StackLimitCheck check(isolate);
+  if (check.HasOverflowed()) {
+    return isolate->heap()->undefined_value();
+  }
+
   {
     JavaScriptFrameIterator it(isolate);
     ASSERT(!it.done());
     Object* fun = it.frame()->function();
     if (fun && fun->IsJSFunction()) {
       // Don't stop in builtin functions.
       if (JSFunction::cast(fun)->IsBuiltin()) {
         return isolate->heap()->undefined_value();
       }
       GlobalObject* global = JSFunction::cast(fun)->context()->global();
@@ skipping 16 matching lines @@
 
   // Return to continue execution.
   return isolate->heap()->undefined_value();
 }
 
 void Execution::ProcessDebugMessages(bool debug_command_only) {
   Isolate* isolate = Isolate::Current();
   // Clear the debug command request flag.
   isolate->stack_guard()->Continue(DEBUGCOMMAND);
 
+  StackLimitCheck check(isolate);
+  if (check.HasOverflowed()) {
+    return;
+  }
+
   HandleScope scope(isolate);
   // Enter the debugger. Just continue if we fail to enter the debugger.
   EnterDebugger debugger;
   if (debugger.FailedToEnter()) {
     return;
   }
 
   // Notify the debug event listeners. Indicate auto continue if the break was
   // a debug command break.
   isolate->debugger()->OnDebugBreak(isolate->factory()->undefined_value(),
@@ skipping 35 matching lines @@
   }
   if (stack_guard->IsInterrupted()) {
     stack_guard->Continue(INTERRUPT);
     return isolate->StackOverflow();
   }
   return isolate->heap()->undefined_value();
 }
 
 
 } }  // namespace v8::internal