Do sanity check of exception state when returning from native to JS.

src/ia32/code-stubs-ia32.cc

 // Copyright 2011 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 4705 matching lines @@
   }
 
   // Check for failure result.
   Label failure_returned;
   STATIC_ASSERT(((kFailureTag + 1) & kFailureTagMask) == 0);
   __ lea(ecx, Operand(eax, 1));
   // Lower 2 bits of ecx are 0 iff eax has failure tag.
   __ test(ecx, Immediate(kFailureTagMask));
   __ j(zero, &failure_returned, not_taken);
 
+  ExternalReference pending_exception_address(Top::k_pending_exception_address);
+
+  // Check that there is no pending exception, otherwise we
+  // should have returned some failure value.
+  if (FLAG_debug_code) {
+    __ push(edx);
+    __ mov(edx, Operand::StaticVariable(
+           ExternalReference::the_hole_value_location()));
+    NearLabel okay;
+    __ cmp(edx, Operand::StaticVariable(pending_exception_address));
+    // Cannot use check here as it attempts to generate call into runtime.
+    __ j(equal, &okay);
+    __ int3();
+    __ bind(&okay);
+    __ pop(edx);
+  }
+
   // Exit the JavaScript to C++ exit frame.
   __ LeaveExitFrame(save_doubles_);
   __ ret(0);
 
   // Handling of failure.
   __ bind(&failure_returned);
 
   Label retry;
   // If the returned exception is RETRY_AFTER_GC continue at retry label
   STATIC_ASSERT(Failure::RETRY_AFTER_GC == 0);
   __ test(eax, Immediate(((1 << kFailureTypeTagSize) - 1) << kFailureTagSize));
   __ j(zero, &retry, taken);
 
   // Special handling of out of memory exceptions.
   __ cmp(eax, reinterpret_cast<int32_t>(Failure::OutOfMemoryException()));
   __ j(equal, throw_out_of_memory_exception);
 
   // Retrieve the pending exception and clear the variable.
-  ExternalReference pending_exception_address(Top::k_pending_exception_address);
   __ mov(eax, Operand::StaticVariable(pending_exception_address));
   __ mov(edx,
          Operand::StaticVariable(ExternalReference::the_hole_value_location()));
   __ mov(Operand::StaticVariable(pending_exception_address), edx);
 
   // Special handling of termination exceptions which are uncatchable
   // by javascript code.
   __ cmp(eax, Factory::termination_exception());
   __ j(equal, throw_termination_exception);
 
@@ skipping 1802 matching lines @@
   __ SmiTag(result);
   __ ret(0);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32