Karim Belabas on Sat, 26 Aug 2023 15:54:19 +0200


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Re: bug in simplify_shallow 

* Karim Belabas [2023-08-26 15:47]:
> You'll see it with valgrind.

Meaning: you'll see that we are reading freed memory. Which may or
may not trigger the reported 'bug in simplify_shallow'
(it doesn't trigger for me either). But it's undoubtedly a bug.

Cheers,

    K.B.

> From the GP code, I can guess what's happening: the lexical variable L
> will be destroyed (gunclone) when we leave the user function scope. But
> that user function still returns the return value of listput() which is
> the element stored in the list. The latter is a 'clone' (as all list
> entries), so supposedly safe. The lexical variable destructor breaks
> that asumption.
> 
> I don't think the reference count machinery currently in place can
> deal with this. Adding a gcopy somewhere should be enough (but slow down
> all 'listput' operations...). Don't have time to delve in the C code
> right now to confirm this; I'll have a look later if Bill doesn't beat
> me to it :-)
> 
> Cheers,
> 
>     K.B.
> 
> 
> * Charles Greathouse [2023-08-26 15:36]:
> > I don’t see it on version 2.16.1, df828f1c94.
> > 
> > On Sat, Aug 26, 2023 at 9:04 AM Ruud H.G. van Tol <rvtol@isolution.nl>
> > wrote:
> > 
> > >
> > > ? version()
> > > % [2, 15, 4]
> > >
> > > ? my(L=List()); listput(L,1);
> > >    ***   bug in simplify_shallow, type unknown, please report.
> > >
> > > -- Ruud
> > >
> > >
> > >
> 
>     K.B.
> -- 
> Pr. Karim Belabas, U. Bordeaux, Vice-président en charge du Numérique
> Institut de Mathématiques de Bordeaux UMR 5251 - (+33) 05 40 00 29 77
> http://www.math.u-bordeaux.fr/~kbelabas/

    K.B.
-- 
Pr. Karim Belabas, U. Bordeaux, Vice-président en charge du Numérique
Institut de Mathématiques de Bordeaux UMR 5251 - (+33) 05 40 00 29 77
http://www.math.u-bordeaux.fr/~kbelabas/