Fix Cython warnings in sage.rings.polynomial.polynomial_modn_dense_ntl

[orlitzky]

[sagelib-9.5.rc2] warning: sage/rings/polynomial/polynomial_modn_dense_ntl.pyx:876:32: local variable 'mod' referenced before assignment
[sagelib-9.5.rc2] warning: sage/rings/polynomial/polynomial_modn_dense_ntl.pyx:880:52: local variable 'mod' referenced before assignment
[sagelib-9.5.rc2] warning: sage/rings/polynomial/polynomial_modn_dense_ntl.pyx:1434:32: local variable 'mod' referenced before assignment
[sagelib-9.5.rc2] warning: sage/rings/polynomial/polynomial_modn_dense_ntl.pyx:1438:52: local variable 'mod' referenced before assignment

CC: @malb

Component: build

Author: Michael Orlitzky

Branch/Commit: b0fcca3

Reviewer: Martin Albrecht

Issue created by migration from https://trac.sagemath.org/ticket/33210

[orlitzky]

New commits:

b0fcca3

Trac #33210: fix uninitialized pointer use in polynomial_modn_dense_ntl.pyx.

[orlitzky]

Author: Michael Orlitzky

[orlitzky]

Commit: b0fcca3

[orlitzky]

Branch: u/mjo/ticket/33210

[orlitzky]

comment:2

I've fixed the warning easy enough, but there's a glaring question to be answered here: if what I think is happening is actually happening (see the commit message), then why doesn't the existing code crash?

[orlitzky]

comment:3

It looks like this code dates back to 2008 (commit 5ccad07).

[malb]

comment:4

Good question, looks we just got lucky here? Your fix looks good to me,

[malb]

Reviewer: Martin Albrecht

[orlitzky]

comment:6

Ok, so long as I'm not overlooking some subtlety. Thanks!

[vbraun]

Changed branch from u/mjo/ticket/33210 to b0fcca3