python3Packages.cffi: disable tests on FreeBSD

[rhelmot]

Description of changes

This test suite cannot work on FreeBSD under nix. It only works on linux because of hardcoded exceptions in cffi's library loading logic which are not present for FreeBSD, requiring it to fall back to /sbin/ldconfig (does not work obviously).

Disable the tests.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
  • x86_64-freebsd
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[Artturin]

Can it be patched? https://github.com/search?q=repo%3Apython-cffi%2Fcffi+%2Fldconfig%2F&type=code no results for ldconfig

[rhelmot]

Looks like I misremembered - it's cpython that has the fallbackless code, not cffi. https://github.com/python/cpython/blob/c4c7097e64b0c9cb0081de8872b90594865c892b/Lib/ctypes/util.py#L224

[rhelmot]

I was so wrong about the cause of this, it's worse than I thought.

We actually patch out the code that would make this work in cpython (here, here) because it is usually useless and slows down startup. CPython on Linux has an extra case that invokes ld in order to do what could also have been done with gcc, in case the gcc case fails. I think this is why it works on Linux.

Several questions remain:

• Was this final fallback present when the nixpkgs patch was made to cpython?
• If not, should it be patched out too?
• If so, should it be duplicated for FreeBSD?

[rhelmot]

This final fallback was not present when the nixpkgs patch was made to cpython originally. I did some tests and determined that the function being patched out is in fact never called during cpython 3.12 startup, even on importing uuid as mentioned in the code, so I'm going to pivot to try to remove that patch entirely from the cpython derivation.