tox.ini: Add environments for testing with llvm / clang

[mkoeppe]

https://groups.google.com/d/msg/sage-devel/5lzj9n57oRI/09AtJyUBBQAJ

We add

• a tox configuration factor for using llvm
• a script package (without spkg-install) representing system package llvm (https://repology.org/project/llvm/versions)

Examples:

• tox -e local-homebrew-macos-standard-llvm
• tox -e local-homebrew-macos-standard-usrlocal-llvm (use at your own risk - updates the global homebrew installation)
• tox -e docker-fedora-34-standard-llvm

Portability issues (solving them should not be a prerequisite for the present ticket):

• pynac - https://groups.google.com/g/sage-devel/c/N03gtymVUnA/m/9WpvHZZRAAAJ
• linbox - https://groups.google.com/g/sage-devel/c/4ZH2MwIY0js/m/bnax1dsvAAAJ

When it works on at least a few platforms, we will want to create GH Actions workflows that build Sage with llvm on various platforms for each release tag.

CC: @dimpase @jhpalmieri @videlec @kiwifb

Component: porting

Author: Matthias Koeppe

Branch/Commit: 38e3d3e

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/30835

[mkoeppe]

comment:1

Setting new milestone based on a cursory review of ticket status, priority, and last modification date.

[mkoeppe]

comment:3

Is there a need to distinguish several versions of clang / LLVM on the same system for portability testing purposes?

[mkoeppe]

Description changed:

--- 
+++ 
@@ -1,3 +1,9 @@
 https://groups.google.com/d/msg/sage-devel/5lzj9n57oRI/09AtJyUBBQAJ
 
+We add 
+- a `tox` configuration factor for using `llvm`
+- a script package (without spkg-install) representing system package `llvm` (https://repology.org/project/llvm/versions)
+- GH Actions workflows that build Sage with llvm on various platforms
 
+
+

[dimpase]

comment:4

Replying to @mkoeppe:

Is there a need to distinguish several versions of clang / LLVM on the same system for portability testing purposes?

that's probably too much trouble. There is a distinction w.r.t. which standard C++ library clang uses, GNU's (libstdc++) or LLVM's (libc++), which is more important.

[mkoeppe]

Branch: u/mkoeppe/tox_ini__gh_actions__add_environments_for_testing_with_llvm___clang

[mkoeppe]

Commit: 3200b93

[mkoeppe]

comment:6

Here's some preliminary distro package information - just guesswork based on reading https://repology.org/project/llvm/versions

Help with refining it is welcome

---

New commits:

3200b93

build/pkgs/llvm: New

[mkoeppe]

comment:7

What's the Fortran situation with LLVM? Use flang or gfortran?

[sagetrac-git]

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

8b16cf8

tox.ini, build/bin/write-dockerfile.sh: Add configuration factor 'llvm'

[sagetrac-git]

Changed commit from 3200b93 to 8b16cf8

[sagetrac-git]

Changed commit from 8b16cf8 to 38e3d3e

[sagetrac-git]

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

38e3d3e

tox.ini [homebrew-llvm]: Set CC, CXX to full path

[mkoeppe]

Description changed:

--- 
+++ 
@@ -5,5 +5,7 @@
 - a script package (without spkg-install) representing system package `llvm` (https://repology.org/project/llvm/versions)
 - GH Actions workflows that build Sage with llvm on various platforms
 
+Examples:
+- `tox -e local-homebrew-macos-standard-llvm` 
+- `tox -e local-homebrew-macos-standard-usrlocal-llvm` (use at your own risk - updates the global homebrew installation)
 
-

[dimpase]

comment:11

Replying to @mkoeppe:

What's the Fortran situation with LLVM? Use flang or gfortran?

flang is still not quite ready for prime time
(I managed to build Sage using flang/clang, but it was not stable)

gfortran is good.

[mkoeppe]

Author: Matthias Koeppe