Re: pending signal after rl_callback_read_char

[Chet Ramey]

On 9/21/22 10:53 AM, Simon Marchi wrote:

> > > So, I'm not entirely sure how things work when you are sitting at the
> > > GDB prompt and press ^C.  Does readline get involved at all in that
> > > case?
> >
> > If readline is in the middle of a call to rl_callback_read_char, then yes.
> > If not, then no.
>
> Ok...  I thought GDB would need to tell readline to flush the current
> line somehow.  When the user has typed some text and not pressed enter
> yet, the current line is saved in readline, right?

If you want to make sure the right thing happens to abort the current line,
gdb can call rl_cleanup_after_signal if it gets SIGINT while readline's
signal handlers aren't installed. Otherwise it gets cleaned up on the next
call to rl_callback_handler_install. I assume gdb does something like this now.

> > > What are readline signals useful for?
> >
> > Readline changes the terminal settings and other user state, and allocates
> > per-call memory and other resources, and has to catch signals so it can
> > clean that up.
> >
> > > I see we can also disable
> > > readline's signal handling (set rl_catch_signals to 0), I'm wondering if
> > > that would work for us.
> >
> > Sure, if you want to do all that work for yourself.
>
> Difficult to say without knowing what "that work" consists of exactly
> (haven't had time to dig in that).

You can look at what _rl_handle_signal does and the functions it calls.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/