Memory leak in Combine when using Concatenate with MergeMany

Using Swift
1

Here's a straightforward way to create a leak in Combine:

self.cancellable = Publishers.Concatenate(
  prefix: Empty<Int, Never>(completeImmediately: true),
  suffix: Publishers.MergeMany(Empty(completeImmediately: true))
)
  .sink { _ in }

Just concatenate a publisher with a suffix that is a MergeMany. Interestingly if you swap the prefix and suffix the leak disappears, but then of course the publisher has substantially changed.

I filed a feedback about this (FB7746024), but posting here too to make sure there isn't something simple I'm missing.

3 Likes
2

Thanks for posting this @mbrandonw! Just curious if you've heard anything from Apple about this?

3

Is it still leaking? I don't see anything on Instrument.

4

I was testing on iOS 13.5, and the leak was there. Going to check later versions.

5

Looks like the issue is gone starting from Xcode 12 (iOS 14). That means all iOS 13 version are affected (was able to reproduce this in Xcode 11.7).