Reduce boilerplace for common pattern to return MaybeHandle.

src/isolate.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include <queue>
 #include <set>
 
@@ skipping 106 matching lines @@
     Isolate* __isolate__ = (isolate);                       \
     if (__isolate__->has_scheduled_exception()) {           \
       __isolate__->PromoteScheduledException();             \
       return value;                                         \
     }                                                       \
   } while (false)
 
 #define RETURN_EXCEPTION_IF_SCHEDULED_EXCEPTION(isolate, T) \
   RETURN_VALUE_IF_SCHEDULED_EXCEPTION(isolate, MaybeHandle<T>())
 
+#define RETURN_RESULT_OR_FAILURE(isolate, call)   \
+  do {                                            \
+    Handle<Object> __result__;                    \
+    if (!(call).ToHandle(&__result__)) {          \
+      DCHECK((isolate)->has_pending_exception()); \
+      return isolate->heap()->exception();        \

[Jakob Kummerow, 2016/05/24 09:16:21]

It seems inconsistent that the DCHECK line puts parentheses around (isolate) but
this line doesn't. If we want to be robust against funky expressions being used
as inputs we should be so everywhere.

[Yang, 2016/05/24 11:07:21]

you are right. We actually have this problem below as well. Will fix.

+    }                                             \
+    return *__result__;                           \
+  } while (false)
+
 #define ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, dst, call, value)  \
   do {                                                               \
     if (!(call).ToHandle(&dst)) {                                    \
       DCHECK((isolate)->has_pending_exception());                    \
       return value;                                                  \
     }                                                                \
   } while (false)
 
 #define ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, dst, call)  \
   ASSIGN_RETURN_ON_EXCEPTION_VALUE(                             \
@@ skipping 1477 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_