Bug 145753 – DeferredWrapper should clear its JS strong references once its promise is resolved/rejected

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[youenn fablet]

Clearing strong references would lower the chances to get stuck in a retain cycle.

[youenn fablet]

Created attachment 254566 [details]
Patch

[Darin Adler]

Comment on attachment 254566 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=254566&action=review

> Source/WebCore/ChangeLog:12
> +        Removed DeferredWrapper constructor that creates internally its promise.
> +        Reason is DeferredWrapper should be moved and we would loose access to its promise.

I don’t understand this. I don’t see DeferredWrapper being moved! It seems to be captured by lambda, which makes copies and doesn’t move. Is this a statement of future intent?

> Source/WebCore/bindings/js/JSDOMPromise.cpp:43
> +    // FIXME: Remove this accessor once ReadableStreamReader custom binding do not need it.

Grammar mistake: should be "does not need it".

> Source/WebCore/bindings/js/JSDOMPromise.h:62
> +    ASSERT(m_deferred && m_globalObject);

A rule of thumb in WebKit is that we never use && in the top level expression in an ASSERT, because we’d like to know which clause failed. So this should be written in two lines:

    ASSERT(m_deferred);
    ASSERT(m_globalObject);

[youenn fablet]

Comment on attachment 254566 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=254566&action=review

>> Source/WebCore/ChangeLog:12
>> +        Reason is DeferredWrapper should be moved and we would loose access to its promise.
> 
> I don’t understand this. I don’t see DeferredWrapper being moved! It seems to be captured by lambda, which makes copies and doesn’t move. Is this a statement of future intent?

The log states 'DeferredWrapper should be moved', not that it is actually moved.
This migration is done in bug 145223 patch for AudioPromise, 
Once all promise binding code is moved to direct use of DOMPromise/DeferredWrapper, promise() accessor and copy constructors of DeferredWrapper could be also removed.

I will clarify this in a new version of the patch.

>> Source/WebCore/bindings/js/JSDOMPromise.cpp:43
>> +    // FIXME: Remove this accessor once ReadableStreamReader custom binding do not need it.
> 
> Grammar mistake: should be "does not need it".

I thought I fixed it...
Will do in next patch.

>> Source/WebCore/bindings/js/JSDOMPromise.h:62
>> +    ASSERT(m_deferred && m_globalObject);
> 
> A rule of thumb in WebKit is that we never use && in the top level expression in an ASSERT, because we’d like to know which clause failed. So this should be written in two lines:
> 
>     ASSERT(m_deferred);
>     ASSERT(m_globalObject);

OK

[youenn fablet]

Created attachment 254589 [details]
Fixed according review

[Darin Adler]

Comment on attachment 254589 [details]
Fixed according review

View in context: https://bugs.webkit.org/attachment.cgi?id=254589&action=review

> Source/WebCore/bindings/js/JSDOMPromise.h:84
> +    ASSERT(m_deferred && m_globalObject);

Oops, left this one in by accident.

[youenn fablet]

Created attachment 254594 [details]
Removed redundant assert

[Build Bot]

Comment on attachment 254594 [details]
Removed redundant assert

Attachment 254594 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://webkit-queues.appspot.com/results/5766373422661632

New failing tests:
platform/mac-wk2/tiled-drawing/scrolling/scroll-snap/scroll-snap-mandatory-mainframe-slow-vertical.html

[Build Bot]

Created attachment 254607 [details]
Archive of layout-test-results from ews104 for mac-mavericks-wk2

The attached test failures were seen while running run-webkit-tests on the mac-wk2-ews.
Bot: ews104  Port: mac-mavericks-wk2  Platform: Mac OS X 10.9.5

[youenn fablet]

Comment on attachment 254594 [details]
Removed redundant assert

Let's try cq+. The failing test might be unrelated.

[WebKit Commit Bot]

Comment on attachment 254594 [details]
Removed redundant assert

Clearing flags on attachment: 254594

Committed r185404: <http://trac.webkit.org/changeset/185404>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.