John Lindal’s Blog

X over SSH

Recently, Code Crusader started crashing when I tried to run it remotely on my Linux desktop from my OS X laptop, even though it worked just fine on the Linux desktop. Debugging revealed that I was getting BadAtom errors from an XChangeProperty() call. More testing revealed the terrifying fact that other programs, like xprop, also crashed with BadAtom errors! Finally, some googling revealed that the latest version of SSH requires the -Y option instead of the -X option for X connection forwarding. Blargh!

The good part of all this is that I now know a lot more about how to debug X programs. Use XSetErrorHandler() to store errors in a queue, and then use XSetAfterFunction() to install a function that first calls XSync(..., False), and then checks the queue and dumps core.