SR-6449: FileManager.removeItem(atPath) leaks

[spevans]

• FileManager.fileSystemRepresentation returns a heap allocated
  pointer that needs to be freed by the caller.

[spevans]

@swift-ci please test

[parkera]

This doesn't seem like the right fix. It would require all clients to insert a deallocate call.

[parkera]

I think we may need to instead introduce a new API here that gives you the representation in a closure, somewhat like withUnsafeBytes. Plus mark this one as unavailable on Linux.

These APIs that rely on an autorelease pool are problematic for us.

[spevans]

@parkera I agree that replacing it with a better API is preferable (as we should with all of the methods that return an autoreleased result). Can we not just return a String and try and avoid any mention of Unsafe?

[spevans]

@parkera Is it worth just fixing this in the 4.1 branch to remove the leak but then coming up with something better for 5 onwards?

[parkera]

I think we're stuck with this until Swift 5, since we shouldn't introduce a source breaking change in a dot release. The Swift 5 solution probably has to be a replacement method.

[parkera]

FileManager could perhaps switch to some other mechanism of getting the C string.

[spevans]

@parkera Sorry, when I said fixing it in 4.1 I meant applying this PR to 4.1-branch to just fix the leak, not change the API.

[parkera]

I thought about this some and I guess this makes sense to do in the short term. Eventually we'll have to just deprecate this API (or remove it, maybe).

[spevans]

@swift-ci please test and merge

[spevans]

@swift-ci please test and merge

[spevans]

@swift-ci please test and merge