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 solution described here, but when I then disconnect from Xcode and re-run the app, it still thinks it's in debug mode. I think what I'm looking for is a Swift version of this function

#include <assert.h> #include <stdbool.h> #include <sys/types.h> #include <unistd.h> #include <sys/sysctl.h>  static bool AmIBeingDebugged(void)     // Returns true if the current process is being debugged (either      // running under the debugger or has a debugger attached post facto). {     int                 junk;     int                 mib[4];     struct kinfo_proc   info;     size_t              size;      // Initialize the flags so that, if sysctl fails for some bizarre      // reason, we get a predictable result.      info.kp_proc.p_flag = 0;      // Initialize mib, which tells sysctl the info we want, in this case     // we're looking for information about a specific process ID.      mib[0] = CTL_KERN;     mib[1] = KERN_PROC;     mib[2] = KERN_PROC_PID;     mib[3] = getpid();      // Call sysctl.     size = sizeof(info);     junk = sysctl(mib, sizeof(mib) / sizeof(*mib), &info, &size, NULL, 0);     assert(junk == 0);      // We're being debugged if the P_TRACED flag is set.     return ( (info.kp_proc.p_flag & P_TRACED) != 0 ); } 

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 do I 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 {     // Buffer for "sysctl(...)" call's result.     var info = kinfo_proc()     // Counts buffer's size in bytes (like C/C++'s `sizeof`).     var size = MemoryLayout.stride(ofValue: info)     // Tells we want info about own process.     var mib : [Int32] = [CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()]     // Call the API (and assert success).     let junk = sysctl(&mib, UInt32(mib.count), &info, &size, nil, 0)     assert(junk == 0, "sysctl failed")     // Finally, checks if debugger's flag is present yet.     return (info.kp_proc.p_flag & P_TRACED) != 0 } 

Update for Swift 5 (Xcode 10.7): strideofValue and the related functions do not exist anymore, they have been replaced by MemoryLayout.stride(ofValue:).

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.

Swift 2 logic:

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 }