Detect if Swift app is being run from Xcode

Question

I would like to programmatically determine if the iOS app is being run directly from XCode (either in the simulator or on a tethered device). I\'ve tried the -D DEBUG soluti

Answer 1

Clarification: Your C code (and the Swift version below) checks if the program is run under debugger control, not if it's being run from Xcode. One can debug a program outside of Xcode (by calling lldb or gdb directly) and one can run a program from Xcode without debugging it (if the “Debug Executable” checkbox in the scheme setting is off).

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You could simply keep the C function and call it from Swift. The recipes given in How to call Objective-C code from Swift apply to pure C code as well.

But it is actually not too complicated to translate that code to Swift:

func amIBeingDebugged() -> Bool {

    var info = kinfo_proc()
    var mib : [Int32] = [CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()]
    var size = strideofValue(info)
    let junk = sysctl(&mib, UInt32(mib.count), &info, &size, nil, 0)
    assert(junk == 0, "sysctl failed")
    return (info.kp_proc.p_flag & P_TRACED) != 0
}

Remarks:

• kinfo_proc() creates a fully initialized structure with all fields set to zero, therefore setting info.kp_proc.p_flag = 0 is not necessary.
• The C int type is Int32 is Swift.
• sizeof(info) from the C code has to be strideOfValue(info) in Swift to include the structure padding. With sizeofValue(info) the above code always returned false in the Simulator for 64-bit devices. This was the most difficult part to figure out.

Update for Swift 3 (Xcode 8):

strideofValue and the related functions do not exist anymore, they have been replaced by MemoryLayout:

func amIBeingDebugged() -> Bool {

    var info = kinfo_proc()
    var mib : [Int32] = [CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()]
    var size = MemoryLayout<kinfo_proc>.stride
    let junk = sysctl(&mib, UInt32(mib.count), &info, &size, nil, 0)
    assert(junk == 0, "sysctl failed")
    return (info.kp_proc.p_flag & P_TRACED) != 0
}