[Webkit-unassigned] [Bug 212714] Release Assert @ WebCore::RenderTreeBuilder::RenderTreeBuilder

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=212714

Darin Adler <darin at apple.com> changed:

           What    |Removed                     |Added
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                 CC|                            |darin at apple.com

--- Comment #19 from Darin Adler <darin at apple.com> ---
Comment on attachment 401494
  --> https://bugs.webkit.org/attachment.cgi?id=401494
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=401494&action=review

> Source/WebCore/rendering/RenderWidget.cpp:60
> +        auto map = WTFMove(widgetNewParentMap());

In cases like this where we *rely* in the behavior that the source ends up empty afterward, instead of just allowing move as an optimization, we should write using std::exchange instead.

    auto map = std::exchange(widgetNewParentMap(), { });

The WTFMove form allows move as an optimization, but also allows the source map to have a remnant value other than empty. The std::exchange form guarantees that the source map will be empty. Both should generate nearly identical code if all the optimization is working properly.

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