Remove gcc spkg, keep gfortran

[dimpase]

Discussions:

https://groups.google.com/g/sage-devel/c/cSsAsPuVnxg/m/yVSGUFi7BQAJ (June 2021)
https://groups.google.com/g/sage-devel/c/NfUKjAaTcUg/m/JwqDd7mVAwAJ (September 2021)
In this ticket:

Just downgrade the gcc spkg to experimental, to match our recommendations in the installation guide in #34528.
CC: @mkoeppe @vbraun @orlitzky @jhpalmieri

Component: packages: standard

Author: Dima Pasechnik

Branch/Commit: u/dimpase/packages/gcc_experimental @ 58ca5d2

Issue created by migration from https://trac.sagemath.org/ticket/32532

(NB: reverted to the original state; copuous edits by @mkoeppe, done in 2024 are still in history)

[dimpase]

comment:1

Dima's original ticket description:

This is a followup to #32060. Building gcc from source is very hard, and unnecessary for any platform Sage supports now.

Same applies to gfortran, with macOS being an exception - there is no (g)fortran coming from the system.

So we need such an easy to install replacement, e.g. one provided by Conda, Homebrew, MacPorts, etc.

Should the need arise for something more isolated, (hopefully not), there are experimental standalone distributions of gfortran for macOS, by the gfortran maintainer of the Homebrew package. This offers a way to entirety remove gcc and gfortran spkgs from Sage.

​https://github.com/fxcoudert/gfortran-for-macOS - specifically,
https://github.com/fxcoudert/gfortran-for-macOS/releases/tag/11.2-bigsur-intel
provides a signed and notarized installed of gcc 11.1 to /usr/local (I tested it, it works)

Other Fortran possibilities are various closed source offers, e.g. from Intel and NAG,
as well as open-source flang, etc.

[dimpase]

Description changed:

--- 
+++ 
@@ -4,7 +4,7 @@
 
 So we need such an easy to install replacement (as opposed to ones provided by Conda, Homebrew, MacPorts, etc. which come as a part of a complete distro).
 
-There are standalone distributions of gfortran for macOS, by the gfortran maintainer of the Homebrew package. To me this offers a way to entirety remove gcc and gfortran spkgs from Sage.
+There are standalone distributions of gfortran for macOS, by the gfortran maintainer of the Homebrew package. This offers a way to entirety remove gcc and gfortran spkgs from Sage.
 
 ​https://github.com/fxcoudert/gfortran-for-macOS
 

[mkoeppe]

comment:3

There are no build problems with gfortran - #32060 comment:36

[dimpase]

comment:5

yet, building gfortran is useless waste of resources - it takes a lot of time, etc.

[mkoeppe]

comment:6

Removing it puts a fresh obstacle in the way of pip-installability -- no, thanks.

[jhpalmieri]

comment:7

Since removing gfortran is controversial, please drop the idea or discuss on sage-devel. It should not be settled here.

[dimpase]

comment:8

Replying to @mkoeppe:

Removing it puts a fresh obstacle in the way of pip-installability -- no, thanks.

how come removing gcc spkg does not create such an obstacle, whereas it does for gfortran?

Besides, if you need to build gcc in order to build gfortran, the latter cannot be counted as unproblematic.

[dimpase]

comment:9

still needs adding some Fortran to CI for the minimal macOS configuration.

---

Last 10 new commits:

48cdeb4	configure.ac, sage_spkg_configure.m4: Set default --with-system-gcc=force, --with-system-python3=force
8e92b98	tox.ini: Override new configure --with-system-python3=force default from #32060
19efe21	configure.ac: Revert the change to the default for --with-system-python3
c5e1dec	add gfortran to _prereq/distros
2482aa1	error out if C/C++ is not good enough
6366b2a	error out if no good Fortran found.
f103f2a	remove *gcc_spkg workflows
f58e236	correct the order of messages
657c1e0	adjust tox.ini for no gcc spkg
5461d81	correct order of messages

[dimpase]

Branch: u/dimpase/packages/removegcc