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Re: Lisp watchpoints

From: Andreas Schwab
Subject: Re: Lisp watchpoints
Date: Sun, 29 Nov 2015 12:28:59 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)

Noam Postavsky <address@hidden> writes:

> On Sat, Nov 28, 2015 at 11:44 PM, Stefan Monnier
> <address@hidden> wrote:
>>> +  while (!NILP (watchers))
>>> +    {
>>> +      Lisp_Object watcher = XCAR (watchers);
>> This will lead to a segmentation fault after something like (put <var>
>> 'watchers [1]).  While very unlikely, it's very easy to avoid this
>> problem: just use CONSP instead of !NILP.
>>> +      else if (FUNCTIONP (watcher))
>>> +        CALLN (Ffuncall, watcher, operation, where, symbol, newval);
>> I don't think you need to test "FUNCTIONP (watcher)".
> Isn't the FUNCTIONP test needed for basically the same reason as using
> CONSP over !NILP? i.e. to avoid segfault in case of (put <var>
> 'watchers '([1])).

Ffuncall does all necessary checks.


Andreas Schwab, address@hidden
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