failed to send the qLaunchSuccess packet

Question

I am using XCode 4.3.2 and trying to open an already existing project based on the Facebook SDK sample Project for XCODE and run it on a target IPhone with IOS 4.2. Although it runs on the simulator it crashes on the IPhone printing this error on the console:

failed to send the qLaunchSuccess packet

I really do not know what could be the problem

Answer 1

I get this every time my app crashes, and I restart it by doing a Run. If I hit the Stop button before doing a run then I don't get this.

After some time, if I keep hitting Run instead of Stop first, the iPhone will only show the above error message and the only solution is to restart the iPhone. Quitting and restarting Xcode does not help.

This may be an Xcode bug.

Answer 2

I had this error when I was trying to install over a bad version of the app that had been crashing on launch. Restarting Xcode and the device did not make the error go away, but deleting the app fixed the problem.

Answer 3

In Xcode 4.3.3, this is caused by re-running the app (command+R) or stopping it (command+.) while halted on a breakpoint. To fix the error once you've gotten it, it usually works to stop the app, (command+.), unplug the device, plug it back in, and run the app again.

To avoid the issue in the future, remember to continue (command+control+y or hit the play button near the debugger output) before stopping. If you have many breakpoints or are in a loop, you can deactivate one breakpoint by going to that line and hitting command + \ or you can deactivate all breakpoints by hitting command + y.

If you eventually get the error ending in "This generally means that another instance of this process was already running or is hung in the debugger," you need to reboot the device.

I submitted a bug report to Apple. I suggest you all do the same so that this gets the attention it deserves.

Edit: the "qLaunchSuccess packet" bug doesn't happen in Xcode 4.4 or 4.5 as it did in 4.3. However, 4.4 and 4.5 experience "Timed out waiting for app to launch" instead--possibly the same issue with a new message. See this question for some possible solutions. Nothing works for met yet. The behavior seems different than 4.3.3 because the error doesn't come up every time I stop while halted on a breakpoint. I will experiment and see if my workaround for 4.3 also fixes the 4.4/4.5 issue.

Answer 4

You might have some broken privileges or a hung debugger process (one that didn't quite exit fast enough). Restart Xcode or restart your phone, either way, it's not as bad as it's more annoying cousin, Processes That Can't Be Registered To The BootStrap Server

If all else fails, restore it from a backup.

Answer 5

This happened to me when I accidentally tried to do a device debug using a distribution profile. As soon as I noticed and switched it to a dev profile, the issue went away.

Answer 6

A slightly quicker way to resolve this issue without restarting the device is to change the language.

Settings - > General - > International (4th from bottom) - > Language (top)

Alternatively If you have a bugged News stand app (in a folder) just tap it to restart springboard.