[webkit-reviews] review granted: [Bug 224179] BidiContext caching is not thread-safe : [Attachment 425144] Patch

[bugzilla-daemon at webkit.org]

Darin Adler <darin at apple.com> has granted Chris Lord <clord at igalia.com>'s
request for review:
Bug 224179: BidiContext caching is not thread-safe
https://bugs.webkit.org/show_bug.cgi?id=224179

Attachment 425144: Patch

https://bugs.webkit.org/attachment.cgi?id=425144&action=review




--- Comment #2 from Darin Adler <darin at apple.com> ---
Comment on attachment 425144
  --> https://bugs.webkit.org/attachment.cgi?id=425144
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=425144&action=review

> Source/WebCore/platform/text/BidiContext.cpp:65
> +	       static BidiContext* ltrContext;
> +	       static std::once_flag ltrContextOnceFlag;
> +	       std::call_once(ltrContextOnceFlag, [&]() {
> +		   ltrContext = &createUncached(0, U_LEFT_TO_RIGHT, false,
FromStyleOrDOM, 0).leakRef();
> +	       });
> +	       return *ltrContext;

I think the superior idiom is something more like this that does not use
leakRef:

    static NeverDestroyed<RefPtr<BidiContext>> ltrContext;
    static std::once_flag ltrContextOnceFlag;
    std::call_once(ltrContextOnceFlag, [&]() {
	 ltrContext = createUncached(0, U_LEFT_TO_RIGHT, false, FromStyleOrDOM,
0);
    });
    return *ltrContext.get();