iPhone: Failed to launch simulated application: Unknown error

Question

This is a new iPhone project, only 1 target (different from this question)

On build we get:

Failed to launch simulated application: Unknown error.

The google again gives us nothing, lots of people have encountered this and there are lots of crazy ideas to try "oh clean the build", "clear the cache", "twiddle this flag" and none of them work and work consistently. We can reproduce this on two different machines with SDK 2.2.1 and 3.0 beta. Not the install on the machines since other iphone projects work just fine so we believe it has something to do with the config of this particular project but after combing through the config twice we can't spot the problem.

Vanna, I'd like to buy a clue for $200 please.

• Tried: XCode menu->Clear cache
• Tried: clean all targets
• Tried: rm -rf ~/Library/Application\ Support/iPhone\ Simulator

Answer 1

This happened to me once and I think I saw in a blog to simply quit and restart Xcode. Miraculously, it worked for me. I doubt this is the end all solutions to all problems like these though, but if you haven't yet closed Xcode, it's worth a try.

Answer 2

I sometimes see this problem and it is fixed by rebooting the maching. I suspect the internal state of the simulator gets screwed. Doesn't sound like your problem though.

I agree with MiRAGe; if this persists, start a new project and import your source.

Answer 3

If other projects work fine; start a new one and copy the files. Combing through configs just won't do it (since XCode has, well, thousands of config possibilities).

You can send me a check with the $200.

P.S: When you actually do start a new project, do it step by step. Run it after each change. Maybe you will find your problem. It might be a ton of work, but it might also help the other thousands of lost souls who have an 'Unkown Error'.