SR-3002: DispatchData.enumerateBytes on Linux leaks the block #186
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To avoid leaking the block parameter of enumerateBytes, we need to directly call CDispatch.dispatch_data_apply (not _swift_dispatch_data_apply). However, we need to tell the compiler that the internal closure that translates between the C and Swift layers will not cause the captured block parameter to escape. If SR-2313 were implemented, we could use withoutActuallyEscaping. Since withoutActuallyEscaping is not available, we instead use unsafeBitCast to bypass the compiler's analysis.
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@MadCoder any comments on this one? If the patch looks ok I will go ahead and create a PR to the Swift3 branch as well. |
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sorry for some reason it fell through the cracks. it looks reasonnable to me @mwwa what's your take? do we need the same in the compiler's overlay? |
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I believe it is a Linux-only problem; initial bug report reported it leaked on Linux but not on Darwin. |
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I created the matching Swift3 PR: #189. If we do get a Swift 3.0.2 release it would be nice to get this fix into it. |
das
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Feb 21, 2017
SR-3002: DispatchData.enumerateBytes on Linux leaks the block Signed-off-by: Daniel A. Steffen <dsteffen@apple.com>
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To avoid leaking the block parameter of enumerateBytes,
we need to directly call CDispatch.dispatch_data_apply
(not _swift_dispatch_data_apply). However, we need to tell
the compiler that the internal closure that translates between
the C and Swift layers will not cause the captured block
parameter to escape. If SR-2313 were implemented, we could use
withoutActuallyEscaping. Since withoutActuallyEscaping is not available,
we instead use unsafeBitCast to bypass the compiler's analysis.