Re: callback api, isearch, signals issue

[Chet Ramey]

On 1/11/23 6:21 AM, Andrew Burgess wrote:

> I'm afraid that I didn't really understand this explanation.

OK, look at the fix I pushed yesterday.

> I tried setting up the event handler in the demo application (that I
> sent in the first email of this thread), and I don't believe that the
> callback is ever invoked before readline crashes in the example I gave.

It's not; it informs the fix. The issue is that the SIGINT arrives before
rl_getc is called, so the question is how to handle it in a way that's
compatible with signals that arrive during select/pselect/read.

The event handler should be called for those `pending' signals as well, and
is with the fix I pushed. In addition, there should be some default
readline behavior that prevents crashes if the application doesn't do
anything.

> You talk about an expectation mismatch between readline and the
> application using readline, except, in the example I gave, it doesn't
> seem that the application is involved at all, this appears to be
> entirely an internal readline issue; the SIGINT arrives, readline
> cancels the isearch, then readline calls rl_isearch_dispatch.

It is a readline issue -- the question is where and how to fix it. For
instance, should the application get to decide whether or not a SIGINT
cancels the incremental search (or whatever else it happened to be doing),
or should readline make that decision? The fix I pushed leaves it up to the
application if it's installed a signal event handler. The only reasonable
behavior is to longmp out, but to where?

So the remaining question is whether or not this new readline behavior of
calling _rl_abort_internal on SIGINT in callback mode when readline is in
a search or collecting a numeric argument should be unconditional or
performed only when the application hasn't set a signal event handler.

> I'm wondering if _rl_isearch_dispatch should be extended to check if the
> isearch has already been aborted? 

No.

--
``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/