Re: master 13fe8a2: Fix rare undefined behaviors in replace-match

Re: master 13fe8a2: Fix rare undefined behaviors in replace-match

[Lars Ingebrigtsen]

eggert@cs.ucla.edu (Paul Eggert) writes:

> +	xsignal2 (Qerror,
> +		  build_string ("replace-match subexpression does not exist"),
> +		  subexp);

This is probably a better error to signal here for this error, but it
possibly changes the behaviour.  If somebody previously had
condition-case'd this for args-out-of-range, then they'll get a new
error signalled now (which is why I kept that signal)...

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Re: master 13fe8a2: Fix rare undefined behaviors in replace-match

[Paul Eggert]

Lars Ingebrigtsen wrote:
> This is probably a better error to signal here for this error, but it
> possibly changes the behaviour.  If somebody previously had
> condition-case'd this for args-out-of-range, then they'll get a new
> error signalled now (which is why I kept that signal)...

In this particular case the error is so rare and the signal so inappropriate for 
the error that I thought it better to make the signal more accurate. It's 
possible for (replace-match ... N) to work for N equal to 0, 1, 3, and 4 but to 
signal an error for other N, so signaling an args-out-of-range error when N=2 
would be misleading.

Another possibility would be to signal a domain error when N=2 in that example.

Re: master 13fe8a2: Fix rare undefined behaviors in replace-match

[Stefan Monnier]

>> +	xsignal2 (Qerror,
>> +		  build_string ("replace-match subexpression does not exist"),
>> +		  subexp);
>
> This is probably a better error to signal here for this error, but it
> possibly changes the behaviour.  If somebody previously had
> condition-case'd this for args-out-of-range, then they'll get a new
> error signalled now (which is why I kept that signal)...

One way out is to `define-error` a new error for that, which has
`args-out-of-range` as a parent.


        Stefan