QEPCAD: improve installation locations

[mkoeppe]

QEPCAD assumes unusual locations for several files, including

• $SAGE_LOCAL/default.qepcadrc (which would better live in $SAGE_ETC (= $SAGE_LOCAL/etc)
• $SAGE_LOCAL/bin/qepcad.help (which would better live in $SAGE_LOCAL/share/qepcad)

(We already use Fedora's patches (​https://src.fedoraproject.org/rpms/qepcad-B/blob/master/f/qepcad-B.spec), which make some changes to qepcad's environment.)

It would be good to improve this.

[jhpalmieri]

Also, very low on the priority list since this is an experimental package, but the spkg-install.in script could be rewritten to use the sdh tools.

[mkoeppe]

I think we can just remove default.qepcadrc entirely and just set SINGULARPATH as an env var

[mkoeppe]

As noted in #29024, we should get rid of qepcad's use of the environment variable SINGULARPATH - as preparation for singular spkg-configure.

[mjo]

SINGULARPATH is only mentioned in qepcad-B-env.patch whose value I doubt. The default for $qe is Fedora-specific, and $SINGULARPATH should not be needed at all because the compiled Singular executable knows it.

What's more, we seem to be setting SINGULAR in QEPCAD's rc file...

cat > "$SAGE_LOCAL/default.qepcadrc" <<EOF
# THIS FILE IS AUTOMATICALLY GENERATED by build/pkgs/qepcad/spkg-install.in -- DO NOT EDIT

#####################################################
# QEPCAD rc file.
# This file allows for some customization of QEPCAD.
# Right now, the ability to give a path to Singular,
# so that it gets used for some computer algebra
# computations is the only feature.
#####################################################
SINGULAR $SAGE_LOCAL/bin
EOF

but the only place that's used is to execute "Singular" (in source/db/SINGULAR.c):

   string SingularCall = SingularBase + "/Singular";
   ...
    execlp(SingularCall.c_str(),
           SingularCall.c_str(),
           "-q",
           "--no-warn",
           "--min-time=0.001",
           "--ticks-per-sec=1000",
           NULL);

Since execlp() searches PATH, the whole mess can simply be replaced by execlp("Singular",...). If we want to create a nice backwards-compatible patch, we could use SingularBase + "/Singular" when SINGULAR is defined, and "Singular" otherwise. Then deleting SINGULAR from our qepcad rc file would make it do the right thing, but the patch could be used by others without breaking configs that rely on SINGULAR being set.

[mjo]

This seems to work. I dropped the nonsensical qepcad-B-env.patch, and added a new patch that chaged the SINGULAR variable in default.qepcadrc into a boolean. Now "yes" makes it launch Singular from the $PATH, and anything else disables it.

---

New commits:

​8243319	Trac #31275: drop qepcad-B-env.patch.
​7c43cf6	Trac #31275: use boolean SINGULAR variable.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​5d7022f	Trac #31275: move qepcad.help and default.qepcadrc to better locations.
​991ff3e	Trac #31275: use $CXXFLAGS instead of hard-coding "-g -O3".

[dimpase]

test errors like

 File "/mnt/opt/Sage/sage-dev/local/lib/python3.8/site-packages/sage/interfaces/qepcad.py", line 687, in _update_command_info
        with open(os.path.join(SAGE_LOCAL, 'bin', 'qepcad.help')) as help:
    FileNotFoundError: [Errno 2] No such file or directory: '/mnt/opt/Sage/sage-dev/local/bin/qepcad.help'

whereas the location used now is $SAGE_LOCAL/share/qepcad/qepcad.help.

So one needs to change sage/interfaces/qepcad.py to fix this.

[dimpase]

few other tests need a fix. I'll provide a branch.

[dimpase]

New commits:

​036b431

fix locations of qepcad.help and qepcadrc

[mjo]

Thanks for the fix! I guess I forgot to re-test after I realized that I hadn't actually solved the problem in $description and moved the help/rc files.