[Webkit-unassigned] [Bug 195605] makeWeakPtr isn't thread-safe

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=195605

--- Comment #3 from Fujii Hironori <Hironori.Fujii at sony.com> ---
(In reply to Chris Dumez from comment #2)
> Is this a problem with actual code right now? Can you provide an example?
> WeakPtr is normally not used across thread since you could check on one line
> that the weak pointer is not null and then dereference it on the next line,
> by which time your object may be dead already.

WTF::WeakReference is a sub-class of ThreadSafeRefCounted. 

> class WeakReference : public ThreadSafeRefCounted<WeakReference<T>> {

And, WTF::WeakPtr doesn't have a method like weak_ptr::lock.

  std::weak_ptr::lock
  https://en.cppreference.com/w/cpp/memory/weak_ptr/lock

These two facts mean WTF::WeakPtr should be used in a single thread, but its WTF::WeakReference can be held in multiple threads by design.

And, it's easy to find code looks like the following under WebCore/platform.

> callOnMainThread([weakPtr = makeWeakPtr(*this)] {

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