[GAP Forum] Segmentation Fault

[Joe Bohanon]

I'm always impressed when someone finds a "bug" in robustly checked
software, even though I can't imagine why someone would legitimately need a
recursive list. :)

This immediately kills gap in Cygwin (no mention of a segfault).  I
duplicated the segfault on my Linux machine.

I know a few functions have "Recursion Depth Traps".  That's probably the
solution here.

Joe

On Tue, Apr 13, 2010 at 11:11 PM, Justin Walker
<justin.walker at comcast.net>wrote:

> Dear Forum,
>
> I was fiddling with lists and tried the following, which resulted in a
> segmentation fault:
>
> gap> l:=ListWithIdenticalEntries(6,[1,2,3]);;
> gap> l[1][1]:=l[3];;
> gap> l;
> [ [ ~[1], 2, 3 ], [ ~[2], 2, 3 ], [ ~[3], 2, 3 ], [ ~[4], 2, 3 ], [ ~[5],
> 2, 3 ],
>  [ ~[6], 2, 3 ] ]
> gap> MakeImmutable(l);
>
> Boom!
>
> I gather that the result of the second assignment is to tie the list into
> knots.  The following call then goes recursive and eventually blows the
> stack (true?).
>
> I thought it worth reporting, in case it's fixable.
>
> Regards,
>
> Justin
>
> --
> Justin C. Walker, Curmudgeon-At-Large
> Institute for the Absorption of Federal Funds
> --------
> If you're not confused,
> You're not paying attention
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>
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