Unity 4.3 crashes on Mac when debugging on Monodevelop 4.0.1

Unity Editor 4.3 consistently crashes when debugging on Monodevelop-Unity 4.0.1 on OSX 10.8.5 (Mac)

Make sure the options at File/Build Settings / “Development Build” and “Script Debugging” are ticked.
If we ‘attach to process’ in Monodevelop, and then press the play button on the Unity Editor, Unity will freeze. Monodevelop still works but adding breakpoints, stepping through code, playing and pausing, all stop working. Detaching process doesn’t bring Unity back, the only way is to Force Quit.

Sometimes if we press the play button in the Unity Editor first, and attach to process after, then debugging starts to work as expected.

I know at least one other person having the same issue on a Mac since updating to Unity 4.3. It seems to work fine on Windows.

Is anybody else having the same issue? Can anyone recommend a hotfix / workaround?

Update: here’s the reply about the bug report I’ve submitted:

“We have identified this it as a duplicate of an existing known bug and we will be closing the issue. The information you have supplied will help us further in the resolution.”

I hope they give this the proper priority, this is a BIG issue if it’s affecting every Mac user. I’m surprised they even decided to release it like this, they should have shipped Unity 4.3 with the previous version of Monodevelop, at least that (kind of) worked.

I know this is not a final answer, but a work around. I was researching this same problem and came across this post where someone was trying to port MD 4.0 to be used with Unity:


You can read about half way down where they talk about it not working well with Unity 4.x. They mention that if you Play your scene BEFORE you attach MD for debugging and then detach BEFORE you stop playing then it doesn’t hang Unity. I found this to work.

It is a major pain in the butt, but at least you can debug.

I hope they fix the root problem soon.

,I am using Xamarin, it seems to be a little bit more stable, but crashes as well too often.

I’ve been using the following procedure that seems to work.


On the Unity3d IDE

  1. Go to Assets->Sync MonoDevelop Project.
  2. Start the game. The game must be started before doing anything on MonoDevelop! This is the key step that works.

On MonoDevelop.

  1. Attach MonoDevelop to the Unity Editor. Press the play button situated in the top left of the MonoDevelop IDE.

On MonoDevelop

  1. Detach MonoDevelop (press the square button situated top left). Do this before stopping the game, etc. on the IDE