Re: [Chicken-hackers] [PATCH] alist-update: don't segfault on non-list

[Jim Ursetto]

I don't believe that will work; the list check must be done
inside the loop.  Otherwise this will crash:

(alist-update 'foo 'bar '((a . b) . 3))

This should also be true for alist-update! as well
(i.e. replace (and (pair? lst) ...) with ##sys#check)
or the one I showed below won't error out:

(alist-update! 'foo 'bar '((a . b) 3 (c . d)) (cut equal? <> <>))
 
On Mar 16, 2013, at 3:16 PM, Christian Kellermann wrote:

> * Jim Ursetto <address@hidden> [130314 08:13]:
>> Nice catch.  Actually, it might be better rewritten with (##sys#check-list 
>> lst 'alist-update), although that is not that important.
>> 
>> Related, alist-update! behaves weird but doesn't crash on non-alists:
>> 
>> (alist-update! 'foo 'bar 3)
>> ;=> ((foo . bar) . 3)
>> 
>> And it's inconsistent when you give it a comparator:
>> 
>> ;; this uses assoc
>> (alist-update! 'foo 'bar '((a . b) 3 (c . d)) equal?)
>> Error: (assoc) bad argument type: 3
>> 
>> ;; this uses an assoc-like loop which does not check for lists 
>> (alist-update! 'foo 'bar '((a . b) 3 (c . d)) (cut equal? <> <>))
>> ;=> ((foo . bar) (a . b) 3 (c . d))
>> 
> 
> I propose the following patch, which checks the argument for both
> procedures with the usual ##sys#check...
> 
> Kind regards,
> 
> Christian
> 
> -- 
> In the world, there is nothing more submissive and weak than
> water. Yet for attacking that which is hard and strong, nothing can
> surpass it. --- Lao Tzu
> <0001-alist-update-don-t-segfault-on-non-list.patch>