Re: SEGV in x_catch_errors_unwind (x86_64-unknown-linux-gnu)

[Chong Yidong]

Richard Stallman <address@hidden> writes:

>     I just checked in some changes to make the x error handler avoid using
>     record_unwind_protect.  I am unable to make Emacs crash now -- can you
>     confirm this?
>
> But if it does not use record_unwind_protect, how does it ensure
> that the x error handler gets turned off if an error happens?
> Have you checked every use of x_catch_errors to make sure that no
> Lisp errors can occur before the matching call to x_uncatch_errors?

I missed two places in xselect.c where code protected in
x_catch_errors can signal Lisp errors (x_reply_selection_request and
x_get_foreign_selection), in corner cases.  Since these two functions
cannot be called from a signal handler, I'll put their
x_uncatch_errors call into a record_unwind_protect.

I have checked several more times, and there is no other such
occurence---most uses of x_catch_errors just wrap one or two Xlib
calls.