menu: fix segfault in ua_event_handler (#1059)

[cspiel1]

A segfault occurs in modules loaded after menu and have an ua_event_handler
that use call object (to collect information about the call). The call object
may not be de-referenced in any ua_event_handler.

[alfredh]

thanks for the patch.

the patch fixes the problem, but there is one thing that I think we should avoid.

call.c calls mem_deref(call), in general it is bad practice and dangerous to destroy a "self" object
inside the object's code. mem_deref should be done on the outside.

a better solution is to add a call_close() function that closes the call object,
but does not destroy it. sample code:

void call_close(struct call *call)
{
	if (!call)
		return;

	list_unlink(&call->le);
	tmr_cancel(&call->tmr_dtmf);

	call->sess = mem_deref(call->sess);

	set_state(call, CALL_STATE_TERMINATED);

	etc ...
}

this function can then be called from ua.c

[cspiel1]

Hi Alfred,

you are right! The call_destructor() does all these things you suggest for call_close(). Maybe the video_error_handler() shows the solution. That's how it was done before the problematic commits mentioned in #1059.

I will push again.

r,c

[alfredh]

is this the final code that you want merged ?

[cspiel1]

Yes, if it's ok for you.

[alfredh]

yes, great. Thanks for fixing the bug!

[cspiel1]

We have much more. ;-) Thanks for review and merging!