Fix a few cython "referenced before assignment" warnings

[orlitzky]

Our build displays several warnings like

warning: sage/libs/ntl/ntl_ZZ.pyx:274:23: local variable 'ans' referenced before assignment

for variables that are passed by reference to a C function that overwrites them (meaning that there is no real bug). Here we fix a few easy ones by initializing the variable.

Component: build

Author: Michael Orlitzky

Branch/Commit: 93f2e90

Reviewer: Markus Wageringel, Marc Mezzarobba

Issue created by migration from https://trac.sagemath.org/ticket/33176

[orlitzky]

Author: Michael Orlitzky

[orlitzky]

Commit: d33a9e7

[orlitzky]

Branch: u/mjo/ticket/33176

[orlitzky]

New commits:

48c2b15	Trac #33176: fix Cython warnings in sage.libs.ntl.
38444da	Trac #33176: update API usage in sage.libs.gap.element.
12bfe01	Trac #33176: fix a Cython warning in sage.libs.singular.groebner_strategy.
d33a9e7	Trac #33176: fix Cython warning in sage.matrix.matrix_modn_dense_template.

[mwageringel]

comment:3

        cdef long mini, minval = 0

Did you intend to set mini to 0 as well, here? There is still a warning about it

[sagelib-9.6.beta2] warning: sage/libs/ntl/ntl_ZZ_pX.pyx:1175:44: local variable 'mini' referenced before assignment

Otherwise, the changes look good to me.

[mwageringel]

comment:4

Related discussion in #33201.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

92acd43	Trac #33176: fix Cython warnings in sage.libs.ntl.
5594ba8	Trac #33176: update API usage in sage.libs.gap.element.
01176df	Trac #33176: fix a Cython warning in sage.libs.singular.groebner_strategy.
93f2e90	Trac #33176: fix Cython warning in sage.matrix.matrix_modn_dense_template.

[sagetrac-git]

Changed commit from d33a9e7 to 93f2e90

[orlitzky]

comment:6

Replying to @mwageringel:

        cdef long mini, minval = 0

Did you intend to set mini to 0 as well, here? There is still a warning about it

I think so. The first time it's used (if it's used) is when it's passed by reference to,

Z_pX_min_val_coeff(minval, mini, self.x, pZZ.x)

According to ntlwrap_impl.h, that function overwrites both minval and mini. I've updated that one commit and rebased it onto 9.6-beta2.

[mezzarobba]

Reviewer: Markus Wageringel, Marc Mezzarobba

[vbraun]

Changed branch from u/mjo/ticket/33176 to 93f2e90