#11868: PARI library interface broken by design
-----------------------------------+------------------------------
Reporter: jdemeyer | Owner: was
Type: defect | Status: needs_work
Priority: major | Milestone: sage-5.13
Component: interfaces | Resolution:
Keywords: t0GEN t1GEN gen | Merged in:
Authors: Peter Bruin | Reviewers: Jeroen Demeyer
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
-----------------------------------+------------------------------
Old description:
> The `t0GEN()`, `t1GEN()`,... system in the PARI interface is broken by
> design. Apply [attachment:demonstrate_11868.patch] to see the bug in
> action.
>
> The problem is that the conversion of `b` (Python object) to `t1` (PARI
> GEN) uses the PARI stack and therefore it clobbers the previously
> computed `t0`.
>
> There is no urgent need to fix this, as the bug doesn't seem to occur in
> practice (it was discovered when working on #9334). It only occurs when:
> 1. Calling a PARI function with at least 2 arguments besides `self`.
> 2. Apart from the first non-`self` argument, there should be another
> argument which is a "complicated" Python type (e.g. a number field
> element).
>
> As work-around, it is easy to defeat condition 2 by converting arguments
> to pari before calling the function.
>
> This problem can be solved by using only local variables instead of
> `t0GEN` etc.
>
> Apply: [attachment:trac_11868-t0GEN.patch],
> [attachment:trac_11868-remove_workarounds.patch]
New description:
The `t0GEN()`, `t1GEN()`,... system in the PARI interface is broken by
design. Apply [attachment:demonstrate_11868.patch] to see the bug in
action.
The problem is that the conversion of `b` (Python object) to `t1` (PARI
GEN) uses the PARI stack and therefore it clobbers the previously computed
`t0`.
There is no urgent need to fix this, as the bug doesn't seem to occur in
practice (it was discovered when working on #9334). It only occurs when:
1. Calling a PARI function with at least 2 arguments besides `self`.
2. Apart from the first non-`self` argument, there should be another
argument which is a "complicated" Python type (e.g. a number field
element).
As work-around, it is easy to defeat condition 2 by converting arguments
to pari before calling the function.
This problem can be solved by using only local variables instead of
`t0GEN` etc.
Apply: [attachment:trac_11868-t0GEN.patch],
[attachment:trac_11868-remove_workarounds.patch],
[attachment:trac_11868-get_nf.patch]
--
Comment (by pbruin):
It turns out that `get_nf()` can indeed be done away with entirely.
--
Ticket URL: <http://trac.sagemath.org/ticket/11868#comment:15>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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