BreakingIntoGDB.m

//
//  DebuggingUtilities.h
//  BreakingIntoGDB
//
//  Created by Alexandre Colucci on 23/08/08.
//  Source: http://blog.timac.org/?p=190
//

#import <Foundation/Foundation.h>
#import <ApplicationServices/ApplicationServices.h>

#include <assert.h>
#include <stdbool.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/sysctl.h>
#include <sys/proc.h>

// From Technical Q&A QA1361
// Returns true if the current process
// is being debugged (either running
// under the debugger or has a debugger
// attached post facto).
static bool AmIBeingDebugged(void)
{
    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 );
}

static void BreakIntoGDB()
{
	if(AmIBeingDebugged())
	{
		// GDB is already attached to the application.
		// We simply break using the Debugger function.
		Debugger();
	}
	else
	{
		// GDB is not running. We open a
		// Terminal window and attach the
		// current application.

		ProcessSerialNumber psn = {0,kCurrentProcess};
		pid_t thePID;
		OSStatus err = GetProcessPID(&psn, &thePID);
		if(err == noErr)
		{
			NSString *scriptSource =
 [NSString stringWithFormat:@"tell application \"Terminal\" ndo script \"gdb attach \" & %d nend tell", thePID];

			NSAppleScript *appleScript = [[NSAppleScript alloc] initWithSource:scriptSource];
			if(appleScript != nil)
			{
				NSDictionary *errorDict;

				// Don't check the returned value
				[appleScript executeAndReturnError:&errorDict];
			}

			sleep(2);
		}
	}
}