Simplify DOM wrapper destruction, don't deref() in finalizers.

• Component: WebCore JavaScript
• Status: RESOLVED FIXED

[Andreas Kling]

Finalizers are not guaranteed to run for a Weak if its WeakImpl has been replaced by another (through use of Weak::operator=(Weak&&)) before the GC's incremental sweeper has swept the containing WeakBlock.

Let's settle on a single way of invoking deref() on the DOM object.

[Andreas Kling]

Created attachment 251609 [details]
Proposed patch

[Darin Adler]

Comment on attachment 251609 [details]
Proposed patch

View in context: https://bugs.webkit.org/attachment.cgi?id=251609&action=review

> Source/WebCore/bindings/scripts/CodeGeneratorJS.pm:1089
> +        push(@headerContent, "    void releaseImpl() { m_impl->deref(); m_impl = nullptr; }\n\n");

Could consider the suggestion Oliver Hunt made for the smart pointer classes:

    void releaseImpl() { std::exchange(m_impl, nullptr)->deref(); }

That would mean that m_impl would be null if something happened to run in the destructor and turn around and see this object.

[Andreas Kling]

Created attachment 251899 [details]
Patch for landing

With std::exchange like darin suggested.

[Andreas Kling]

Comment on attachment 251899 [details]
Patch for landing

Holding cq+ while I check on a potential issue locally.

[Andreas Kling]

Comment on attachment 251899 [details]
Patch for landing

Local issue was something else entirely. Resuming commit queue.

[WebKit Commit Bot]

Comment on attachment 251899 [details]
Patch for landing

Clearing flags on attachment: 251899

Committed r183523: <http://trac.webkit.org/changeset/183523>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.