1283636 - Use CallbackPreserveColor() less in bindings code

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Andrew McCreight [:mccr8]]

DOM bindings codegen uses CallbackPreserveColor() on callbacks that it knows should be already non-gray. The reason for this is not immediately obvious when looking at the call sites, and nothing actually verifies this property. It seems like there should be some kind of CallbackAlreadyNonGray() method (name suggestions welcome) that is like CallbackPreserveColor(), but asserts that the object is non-gray.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Sure, having a CallbackKnownNotGray() would be fine.

Comment 2

[Andrew McCreight [:mccr8]]

CallbackObject::CallSetup::CallSetup() does this:
  JSObject* realCallback = js::UncheckedUnwrap(aCallback->CallbackPreserveColor());
The callback object is gray here sometimes, for instance during ./mach package, but I think it is okay because the uses of realCallback only grab the C++ native off of the object, AFAICT.  UncheckUnwrap itself can do a write to the gray object, but that should be okay, because we're only trying to avoid black->gray edges. Seems a little fragile but I'll leave it alone.

Comment 3

[Andrew McCreight [:mccr8]]

Attachment: Use CallbackPreserveColor() less.

Some places call CallbackPreserveColor() because they know the object must have already been marked black. This patch replaces those calls with a new function CallbackKnownNotGray() which documents and dynamically checks this assumption.

try: https://treeherder.mozilla.org/#/jobs?repo=try&revision=1204210b2817

Comment 4

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8770702 [details] [diff] [review]
Use CallbackPreserveColor() less.

r=me

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/347b46d43b8b
Use CallbackPreserveColor() less. r=bz

Comment 6

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/347b46d43b8b