How to tell LLDB debugger not to handle SIGBUS?

Question

I'm embedding MonoTouch in an Xcode project, and want to stop LLDB debugger from handling SIGBUS signals, since they are used by the mono runtime. How can I do that?

Solution

You can control how lldb intercepts/passes signals with the "process handle" command. For your case, you'd want to do

(lldb) pro hand -p true -s false SIGBUS
NAME        PASS   STOP   NOTIFY
==========  =====  =====  ======
SIGBUS      true   false  true 

now the signals will be passed to your process without lldb getting in the way. The "NOTIFY" field indicates whether lldb should print that the signal was received - the default is that it will be printed in the debugger console but that doesn't seem to be happening right now. But the signal is correctly passed along, which is the important bit.

Comments

[Martin R]

According to stackoverflow.com/questions/10431579/…, "process handle SIGBUS -n true -p true -s false" should do the trick.

[ed22]

Is there any way to set this in XCode?

[uliwitness]

Add a breakpoint e.g. on main() and then in its breakpoint action add an LLDB command with this line in it, then check the "continue after breakpoint" checkbox.

[user239546]

To do this automatically in Xcode, add the command to ~/.lldbinit-Xcode. If you want this to apply even when using lldb from the command line, add the same to ~/.lldbinit

[Jacob Wallström]

It doesn't work to add it to ~/.lldbinit because it gives the error error: No current target; cannot handle signals until you have a valid target and process.

[Artyom Gevorgyan]

I have a similar problem when debugging swiftc executable with lldb. On hitting some breakpoints, even though I have applied the suggested change to how lldb handles SIGCHLD (not SIGBUS), it keeps dying. What can I do? Maybe I should file a bug?

[Artyom Gevorgyan]

Process X stopped and restarted: thread 1 received signal: SIGCHLD This is what I keep getting instead of a stop at breakpoint.

[Ben Voigt]

@ArtyomGevorgyan: Your program died. The debugger received SIGCHLD. Setting the debugger to break when your program receives SIGCHLD doesn't help because your program didn't receive SIGCHLD.