Swift3: SR-3002: DispatchData.enumerateBytes on Linux leaks the block #189
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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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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.