Open Radar

 
Summary:
Sometimes, and I don't know what conditions cause this, on meeting a breakpoint in a background thread, Xcode stops in the main thread showing a stop on EXC_BREAKPOINT (usually in __CFRunLoopServiceMachPort, though I think this is a red herring and the main thread just happens to be waiting in a trap there a lot). The thread that should have stopped can be inspected in the debugger, but the app will not continue properly on the 'cont' command.

Steps to Reproduce:
Unfortunately, I don't know. Xcode just sometimes gets this wrong. In the condition that motivated me to report this, I had set up a conditional breakpoint and when the app met this breakpoint, Xcode would stop in the main thread.

Expected Results:
Xcode should stop at my breakpoint, and the debugger commands should all work including 'cont'.

Actual Results:
Xcode stops in a different thread, and the 'cont' command doesn't work because the app has "crashed" due to the breakpoint exception. Even switching thread before typing 'cont' doesn't help.

Regression:
This is a regression since introducing the lldb debugger. If I switch my run scheme to use gdb, the debugger works as expected on the same breakpoint.

Notes:
Provide additional information, such as references to related problems, workarounds and relevant attachments.