[SR-8090] UnsafeMutablePointer.withMemoryRebound(to:capacity:_:) crashes

[an0]

Previous ID	SR-8090
Radar	rdar://problem/41202926
Original Reporter	@an0
Type	Bug
Status	Resolved
Resolution	Done

Attachment: Download

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, 4.2Regression, RunTimeCrash
Assignee	@aschwaighofer
Priority	Medium

md5: c5cc09c9166c89fdf7c203ffdac97417

Issue Description:

In swift-DEVELOPMENT-SNAPSHOT-2018-06-22-a-osx, this code:

    var info = task_basic_info()
    var infoSize = mach_msg_type_number_t(MemoryLayout<task_basic_info>.size / MemoryLayout<natural_t>.size)
    withUnsafeMutablePointer(to: &info) { infoPointer in
      infoPointer.withMemoryRebound(to: integer_t.self, capacity: MemoryLayout<task_basic_info>.size / MemoryLayout<integer_t>.size) {
        let result = task_info(mach_task_self_, task_flavor_t(TASK_BASIC_INFO), $0, &infoSize)
        if result != KERN_SUCCESS {
          print("Failed to get task info: \(result)")
        }
      }
    }

causes this crash on devices(mine is iPhone 6s) but not on simulators:

#&#8203;0 0x00000001046f84e4 in thunk for @callee_guaranteed (@unowned UnsafeMutablePointer<Int32>) -> (@error @owned Error) ()
 #&#8203;1 0x00000001046f8800 in partial apply for thunk for @callee_guaranteed (@unowned UnsafeMutablePointer<Int32>) -> (@error @owned Error) ()
 #&#8203;2 0x0000000104c245f4 in UnsafePointer.withMemoryRebound<A, B>(to:capacity:_:) ()
 #&#8203;3 0x0000000104e307f8 in UnsafeMutablePointer.withMemoryRebound<A, B>(to:capacity:_:) ()
 #&#8203;4 0x00000001046f81d0 in closure #&#8203;1 in UIDevice.getTaskInfo() at /Users/an0/Desktop/WithMemoryReboundBug/WithMemoryReboundBug/UIDevice+Memory.swift:18
 #&#8203;5 0x00000001046f8254 in partial apply for closure #&#8203;1 in UIDevice.getTaskInfo() ()
 #&#8203;6 0x00000001046f8554 in thunk for @callee_guaranteed (@unowned UnsafeMutablePointer<task_basic_info>) -> (@error @owned Error) ()
 #&#8203;7 0x00000001046f85e4 in partial apply for thunk for @callee_guaranteed (@unowned UnsafeMutablePointer<task_basic_info>) -> (@error @owned Error) ()
 #&#8203;8 0x0000000104cc825c in withUnsafePointer<A, B>(to:_:) ()
 #&#8203;9 0x0000000104e32438 in withUnsafeMutablePointer<A, B>(to:_:) ()

[belkadan]

aschwaighofer@apple.com (JIRA User), is this the thing you just fixed with withoutActuallyEscaping?

[jckarter]

Would Arnold's fix impact code that doesn't use withoutActuallyEscaping?

[jckarter]

@swift-ci create

[belkadan]

IIUC it was a general problem with thunking of nested closures, but I wasn't following it too closely. You could be right.

[jckarter]

I wasn't able to reproduce the crash with the attached project using the default toolchain in Xcode 10, maybe it's a recent regression.

[jckarter]

Hm, I wasn't able to reproduce with the 4.2 snapshot toolchain from 2018-06-23 either. @an0 did you have any other unusual build settings on the attached project when it crashes for you?

[aschwaighofer]

Reproduces on an arm64 device with a current 4.2 snapshot for me.

[aschwaighofer]

This will be fixed as soon as the toolchains pick up apple/swift-llvm@9283149