Re: Use of rl_echo_signal_char in _rl_handle_signal

[Chet Ramey]

On 6/7/23 8:52 AM, Andrew Burgess wrote:

> I did some experimentation at my end and updated my sample program to
> make use of rl_persistent_signal_handlers.  I agree with your first
> suggestion, having the rl_echo_signal_char call conditional on
> rl_persistent_signal_handlers (when in CALLBACK mode) seems to allow for
> both options.

OK, this is a good start. It's missing several cases, so let's see if we
can tighten it up.


>      In callback mode when rl_persistent_signal_handlers is on then the
>      readline signal handler is always in place for the duration of the
>      readline prompt being in use.  In this case it does make sense to
>      always call rl_echo_signal_char.  By the time the application's signal
>      handler is invoked we are on the way out of readline, and it is no
>      longer the applications job to call rl_echo_signal_char.
>      
>      In non-callback mode, this patch changes nothing, rl_echo_signal_char
>      is always called.

These paragraphs are not correct. It's common practice to install a
readline library that was compiled with READLINE_CALLBACKS defined as the
standard readline library. I'm pretty sure Red Hat does it, for example.
The idea is that callbacks won't be active unless the application calls
rl_callback_handler_install().

This patch makes the call to rl_echo_signal_char() dependent on the setting
of rl_persistent_signal_handlers, which an application *not* using callback
mode will never set.

That test needs to be augmented with a condition that won't be true unless
callback mode is actually active. You should be able to test
RL_STATE_CALLBACK using RL_ISSTATE(), but you might also want to test
whether rl_linefunc is non-null. Let me know what works for you.

Chet
--
``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/