Bug 312803 – API::PageConfiguration::Data::LazyInitializedRef wastefully initializes unneeded objects

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Brent Fulgham]

The copy assignment operator for Data::LazyInitializedRef (APIPageConfiguration.h (Line 504:)) triggers an initialization by calling `get()` on the source object:

 void operator=(const LazyInitializedRef& other) { m_value = other.get(); }

This triggers lazy initialization on the source `m_value` for ANY uninitialized member.

During `copyDataFrom`, the Data struct's generated copy assignment calls this for ALL 5 LazyInitializedRef members. For members NOT explicitly set on the source (e.g., visitedLinkStore, defaultWebsitePolicies), this causes us to create throw-away objects as a side-effect of copying.

While this doesn't create any user-facing bug, it does involve allocating/deallocating up to 5 objects for each copy (e.g., during IPC) which uses power and costs us performance.

[Radar WebKit Bug Importer]

<rdar://problem/175189199>

[Brent Fulgham]

Pull request: https://github.com/WebKit/WebKit/pull/63153

[EWS]

Committed 312140@main (f84460ba474e): <https://commits.webkit.org/312140@main>

Reviewed commits have been landed. Closing PR #63153 and removing active labels.