[Webkit-unassigned] [Bug 196392] New: [JSC] JSWrapperMap should not use Objective-C Weak map (NSMapTable with NSPointerFunctionsWeakMemory) for m_cachedObjCWrappers

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=196392

            Bug ID: 196392
           Summary: [JSC] JSWrapperMap should not use Objective-C Weak map
                    (NSMapTable with NSPointerFunctionsWeakMemory) for
                    m_cachedObjCWrappers
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ysuzuki at apple.com

We do not use Objective-C weak semantics here. Objective-C JSValue has a dealloc function, and JSValue is tightly coupled to JSContext (it has _context field).
So JSValue is only stored in one wrapper map held by JSContext (JSWrapperMap). So, we can manage lifetime just unregistering itself from JSWrapperMap in [JSValue dealloc].
Why we would like to avoid Objective-C weak semantics is that it allocates much memory. In very simple hello_world case, we create 4 JSValue wrappers, and it consumes 10KB for weak semantics.

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