Detect if Swift app is being run from Xcode - ios

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).
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
}

Answer 2

For those looking for a simpler solution - this works perfectly:
func isDebuggerAttached() -> Bool {
return getppid() != 1
}