Introduce v8::Exception::GetMessage to find location of an error object.

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 <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
 
 #include "src/v8.h"
@@ skipping 1029 matching lines @@
         !(Script::cast(script)->source()->IsUndefined())) {
       int pos = frame->LookupCode()->SourcePosition(frame->pc());
       // Compute the location from the function and the reloc info.
       Handle<Script> casted_script(Script::cast(script));
       *target = MessageLocation(casted_script, pos, pos + 1);
     }
   }
 }
 
 
+void Isolate::ComputeLocationFromStackTrace(MessageLocation* target,
+                                            Handle<Object> exception) {
+  *target = MessageLocation(Handle<Script>(heap_.empty_script()), -1, -1);
+
+  Handle<Name> key = factory()->stack_trace_symbol();
+  Handle<Object> property = JSObject::GetDataProperty(exception, key);
+  if (!property->IsJSArray()) return;
+  Handle<JSArray> simple_stack_trace = Handle<JSArray>::cast(property);
+
+  Handle<FixedArray> elements(FixedArray::cast(simple_stack_trace->elements()));
+  int elements_limit = Smi::cast(simple_stack_trace->length())->value();
+
+  for (int i = 1; i < elements_limit; i += 4) {
+    Handle<JSFunction> fun =
+        handle(JSFunction::cast(elements->get(i + 1)), this);
+    if (fun->IsFromNativeScript()) continue;
+    Handle<Code> code = handle(Code::cast(elements->get(i + 2)), this);
+    Handle<Smi> offset = handle(Smi::cast(elements->get(i + 3)), this);
+    Address pc = code->address() + offset->value();
+
+    Object* script = fun->shared()->script();
+    if (script->IsScript() &&
+        !(Script::cast(script)->source()->IsUndefined())) {
+      int pos = code->SourcePosition(pc);
+      Handle<Script> casted_script(Script::cast(script));
+      *target = MessageLocation(casted_script, pos, pos + 1);
+      break;
+    }
+  }
+}
+
+
 bool Isolate::ShouldReportException(bool* can_be_caught_externally,
                                     bool catchable_by_javascript) {
   // Find the top-most try-catch handler.
   StackHandler* handler =
       StackHandler::FromAddress(Isolate::handler(thread_local_top()));
   while (handler != NULL && !handler->is_catch()) {
     handler = handler->next();
   }
 
   // Get the address of the external handler so we can compare the address to
@@ skipping 39 matching lines @@
   }
   return false;
 }
 
 static int fatal_exception_depth = 0;
 
 
 Handle<JSMessageObject> Isolate::CreateMessage(Handle<Object> exception,
                                                MessageLocation* location) {
   Handle<JSArray> stack_trace_object;
+  MessageLocation potential_computed_location;
   if (capture_stack_trace_for_uncaught_exceptions_) {
     if (IsErrorObject(exception)) {
       // We fetch the stack trace that corresponds to this error object.
       // If the lookup fails, the exception is probably not a valid Error
       // object. In that case, we fall through and capture the stack trace
       // at this throw site.
       stack_trace_object =
           GetDetailedStackTrace(Handle<JSObject>::cast(exception));
+      if (!location) {
+        ComputeLocationFromStackTrace(&potential_computed_location, exception);
+        location = &potential_computed_location;
+      }
     }
     if (stack_trace_object.is_null()) {
-      // Not an error object, we capture at throw site.
+      // Not an error object, we capture stack and location at throw site.
       stack_trace_object = CaptureCurrentStackTrace(
           stack_trace_for_uncaught_exceptions_frame_limit_,
           stack_trace_for_uncaught_exceptions_options_);
     }
   }
+  if (!location) {
+    ComputeLocation(&potential_computed_location);
+    location = &potential_computed_location;
+  }
 
   // If the exception argument is a custom object, turn it into a string
   // before throwing as uncaught exception.  Note that the pending
   // exception object to be set later must not be turned into a string.
   if (exception->IsJSObject() && !IsErrorObject(exception)) {
     MaybeHandle<Object> maybe_exception =
         Execution::ToDetailString(this, exception);
     if (!maybe_exception.ToHandle(&exception)) {
       exception =
           factory()->InternalizeOneByteString(STATIC_CHAR_VECTOR("exception"));
@@ skipping 72 matching lines @@
   // Notify debugger of exception.
   if (catchable_by_javascript) {
     debug()->OnThrow(exception_handle, report_exception);
   }
 
   // Generate the message if required.
   if (!rethrowing_message && (report_exception || try_catch_needs_message)) {
     MessageLocation potential_computed_location;
     if (location == NULL) {
       // If no location was specified we use a computed one instead.
       ComputeLocation(&potential_computed_location);

[Yang, 2014/10/30 12:32:38]

If you are going to compute the location in CreateMessage anyways, can we omit
it here and put a call to ComputeLocation in ReportBootstrapingException?

[aandrey, 2014/10/30 12:47:11]

But we need it below also to assign pending_message_script_ and etc.

       location = &potential_computed_location;
     }
 
     if (bootstrapper()->IsActive()) {
       // It's not safe to try to make message objects or collect stack traces
       // while the bootstrapper is active since the infrastructure may not have
       // been properly initialized.
       ReportBootstrappingException(exception_handle, location);
     } else {
       Handle<Object> message_obj = CreateMessage(exception_handle, location);
 
       thread_local_top()->pending_message_obj_ = *message_obj;
-      if (location != NULL) {
-        thread_local_top()->pending_message_script_ = *location->script();
-        thread_local_top()->pending_message_start_pos_ = location->start_pos();
-        thread_local_top()->pending_message_end_pos_ = location->end_pos();
-      }
+      thread_local_top()->pending_message_script_ = *location->script();

[Yang, 2014/10/30 12:32:38]

This can't work, if the location is &potential_computed_location in
CreateMessage, since it's stack allocated and already torn down.

I don't think CreateMessage and ComputeLocation guarantee to successfully
compute the location, so I think the check is still necessary.

[aandrey, 2014/10/30 12:47:11]

The "location" variable here is not changed by CreateMessage.

[aandrey, 2014/10/30 12:47:11]

The "location" variable here is not altered by CreateMessage().

+      thread_local_top()->pending_message_start_pos_ = location->start_pos();
+      thread_local_top()->pending_message_end_pos_ = location->end_pos();
 
       // If the abort-on-uncaught-exception flag is specified, abort on any
       // exception not caught by JavaScript, even when an external handler is
       // present.  This flag is intended for use by JavaScript developers, so
       // print a user-friendly stack trace (not an internal one).
       if (fatal_exception_depth == 0 && FLAG_abort_on_uncaught_exception &&
           (report_exception || can_be_caught_externally)) {
         fatal_exception_depth++;
         PrintF(stderr, "%s\n\nFROM\n",
                MessageHandler::GetLocalizedMessage(this, message_obj).get());
@@ skipping 82 matching lines @@
   }
   if (can_clear_message) clear_pending_message();
 }
 
 
 MessageLocation Isolate::GetMessageLocation() {
   DCHECK(has_pending_exception());
 
   if (thread_local_top_.pending_exception_ != heap()->termination_exception() &&
       thread_local_top_.has_pending_message_ &&
-      !thread_local_top_.pending_message_obj_->IsTheHole() &&
       !thread_local_top_.pending_message_obj_->IsTheHole()) {
     Handle<Script> script(
         Script::cast(thread_local_top_.pending_message_script_));
     int start_pos = thread_local_top_.pending_message_start_pos_;
     int end_pos = thread_local_top_.pending_message_end_pos_;
     return MessageLocation(script, start_pos, end_pos);
   }
 
   return MessageLocation();
 }
@@ skipping 1148 matching lines @@
   if (prev_ && prev_->Intercept(flag)) return true;
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 } }  // namespace v8::internal