[debug] use catch prediction flag for promise rejections.

src/isolate.cc

 // 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.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 1260 matching lines @@
       entry_handler = frame->top_handler()->next()->address();
     }
 
     // For JavaScript frames we perform a lookup in the handler table.
     if (frame->is_java_script()) {
       JavaScriptFrame* js_frame = static_cast<JavaScriptFrame*>(frame);
       HandlerTable::CatchPrediction prediction;
       if (js_frame->LookupExceptionHandlerInTable(nullptr, &prediction) > 0) {
         // We are conservative with our prediction: try-finally is considered
         // to always rethrow, to meet the expectation of the debugger.
-        if (prediction == HandlerTable::CAUGHT) return CAUGHT_BY_JAVASCRIPT;
+        if (prediction != HandlerTable::UNCAUGHT) return CAUGHT_BY_JAVASCRIPT;

[Dan Ehrenberg, 2016/07/21 21:07:33]

This is big--it deserves a comment mentioning the implications for Promises.

[Dan Ehrenberg, 2016/07/21 21:08:51]

Sorry, please ignore this comment; I wrote it while in the process of
understanding the code and forgot to delete it.

       }
     }
 
     // The exception has been externally caught if and only if there is an
     // external handler which is on top of the top-most JS_ENTRY handler.
     if (external_handler != nullptr && !try_catch_handler()->is_verbose_) {
       if (entry_handler == nullptr || entry_handler > external_handler) {
         return CAUGHT_BY_EXTERNAL;
       }
     }
@@ skipping 364 matching lines @@
     clear_pending_exception();
     return false;
   }
 
   // Reschedule the exception.
   thread_local_top()->scheduled_exception_ = pending_exception();
   clear_pending_exception();
   return true;
 }
 
-
-void Isolate::PushPromise(Handle<JSObject> promise,
-                          Handle<JSFunction> function) {
+void Isolate::PushPromise(Handle<JSObject> promise) {
   ThreadLocalTop* tltop = thread_local_top();
   PromiseOnStack* prev = tltop->promise_on_stack_;
   Handle<JSObject> global_promise =
       Handle<JSObject>::cast(global_handles()->Create(*promise));
-  Handle<JSFunction> global_function =
-      Handle<JSFunction>::cast(global_handles()->Create(*function));
-  tltop->promise_on_stack_ =
-      new PromiseOnStack(global_function, global_promise, prev);
+  tltop->promise_on_stack_ = new PromiseOnStack(global_promise, prev);
 }
 
 
 void Isolate::PopPromise() {
   ThreadLocalTop* tltop = thread_local_top();
   if (tltop->promise_on_stack_ == NULL) return;
   PromiseOnStack* prev = tltop->promise_on_stack_->prev();
-  Handle<Object> global_function = tltop->promise_on_stack_->function();
   Handle<Object> global_promise = tltop->promise_on_stack_->promise();
   delete tltop->promise_on_stack_;
   tltop->promise_on_stack_ = prev;
-  global_handles()->Destroy(global_function.location());
   global_handles()->Destroy(global_promise.location());
 }
 
 
 Handle<Object> Isolate::GetPromiseOnStackOnThrow() {
   Handle<Object> undefined = factory()->undefined_value();
   ThreadLocalTop* tltop = thread_local_top();
   if (tltop->promise_on_stack_ == NULL) return undefined;
-  Handle<JSFunction> promise_function = tltop->promise_on_stack_->function();
   // Find the top-most try-catch or try-finally handler.
   if (PredictExceptionCatcher() != CAUGHT_BY_JAVASCRIPT) return undefined;
   for (JavaScriptFrameIterator it(this); !it.done(); it.Advance()) {
     JavaScriptFrame* frame = it.frame();
-    if (frame->LookupExceptionHandlerInTable(nullptr, nullptr) > 0) {
+    HandlerTable::CatchPrediction prediction;
+    if (frame->LookupExceptionHandlerInTable(nullptr, &prediction) > 0) {
       // Throwing inside a Promise only leads to a reject if not caught by an
       // inner try-catch or try-finally.
-      if (frame->function() == *promise_function) {
+      if (prediction == HandlerTable::PROMISE) {

[Dan Ehrenberg, 2016/07/21 21:07:33]

Beautiful

         return tltop->promise_on_stack_->promise();
       }
       return undefined;
     }
   }
   return undefined;
 }
 
 
 void Isolate::SetCaptureStackTraceForUncaughtExceptions(
@@ skipping 1379 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8