[SentryFramesTracker removeListener:] crash

[SebastianKumor-Oura]

Platform

iOS

Environment

TestFlight

Installed

Swift Package Manager

Version

8.57.0 and 8.56.0

Xcode Version

26.0.1

Did it work on previous versions?

Not sure, only enabled frozen frames tracking recently

Steps to Reproduce

It happens randomly. I cannot easily reproduce this. And I think its related to enableUIViewControllerTracing setting being set to true

Expected Result

It should not cause crash

Actual Result

For some users app crashes sometimes.

Are you willing to submit a PR?

No response

[linear]

COCOA-869

[philipphofmann]

Thanks for reporting this, @SebastianKumor-Oura. I found a potential root cause

We use a lock for removing all objects of the listeners here

sentry-cocoa/Sources/Swift/Core/Integrations/FramesTracking/SentryFramesTracker.swift

Lines 117 to 119 in 45e9fb1

	lock.synchronized {
	listeners.removeAllObjects()
	}

Here we don't use locks but instead add and remove listeners on the main thread

sentry-cocoa/Sources/Swift/Core/Integrations/FramesTracking/SentryFramesTracker.swift

Lines 162 to 172 in 45e9fb1

	@objc public func addListener(_ listener: SentryFramesTrackerListener) {
	dispatchQueueWrapper.dispatchAsyncOnMainQueueIfNotMainThread {
	self.listeners.add(listener)
	}
	}
	@objc public func removeListener(_ listener: SentryFramesTrackerListener) {
	dispatchQueueWrapper.dispatchAsyncOnMainQueueIfNotMainThread {
	self.listeners.remove(listener)
	}
	}

[SebastianKumor-Oura]

@philipphofmann thanks for a quick response. Do you have any plans to address this issue ?

[philipphofmann]

@SebastianKumor-Oura, sorry no we don't have an ETA, but we're are going to fix the root cause at some point.

[GianmarcoSalerno]

I am still seeing this in 9.x btw....

[philipphofmann]

Thanks for the info @GianmarcoSalerno.

[philprime]

@denrase any update on this issue? Anything we can help with?

[denrase]

@philprime Last I tried I could not reproduce this issue.

[philprime]

@denrase Thanks for the update, then I would propose we change addListener(_:) and removeListener(_:) to also use the lock.synchronized approach for consistency as proposed by @philipphofmann