WIP: gobject-introspection: Support cross

[Ericson2314]

Motivation for this change

The idea is to build the python tools separate from the C bits, and the python tools are run natively (including C extension module, in particular), but the C bits are either the installed library, or tools that must be run with an emulator (during cross compilation) and in both cases are non-native.

I need to still need to wrap the two together for downstream consumption, and I am also debating exactly how I'd like to do that.

CC @jtojnar @samueldr

Upstream issue: https://gitlab.gnome.org/GNOME/gobject-introspection/-/issues/337
Upstream PR: https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/224

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[jtojnar]

Where do docs fit into this #87904?

[Ericson2314]

@jtojnar Those look perfectly compatible for me :), We could build them with the python stuff or the C stuff. If you merge your PR I'll be happy to rebase mine on top.

[matthewbauer]

Do all dependents of gobject-introspection need exe_wrapper?

When cross compiling nixos, I ended up having to disable gobject-introspection, vala, and gtk-docs. It ends up working pretty well, since you're already building everything from scratch, and I've never encountered a point where I need any of the 3 (matthewbauer@f33e8c3). Annoyingly there are a few things that you have to patch to disable introspection correctly.

[Ericson2314]

The exe wrapper is sadly mandatory for anything generating typelibs (compiled gir files), but anything purely consuming them at runtime doesn't need the exe wrapper: it just links girepository like any other C library.

I would like to split up the package (different wrappers around specific outputs from the two underlying builds) to reflect this.

[matthewbauer]

The exe wrapper is sadly mandatory for anything generating typelibs (compiled gir files), but anything purely consuming them at runtime doesn't need the exe wrapper: it just links girepository like any other C library.

Well I would be kind of surprised if you needed the emulator at runtime - it would be the cross compiled architecture :)

Meson could just provide exe_wrapper everywhere for consistency. qemu-user at least has few dependencies.

[Mic92]

Can you explain the when to use what? It's not clear from the commit message.

[Ericson2314]

Well I think I'll need to make a wrapper package so this isn't actually used directly. But the idea is (whether directly or via some wrapper) than the py tools are need when generating new gir files and type libs when building some C library, and aren't needed by the programs in python etc that just consume typelibs.

[matthewbauer]

I don’t think we should make that distinction if it’s not made by gobject introspection. IIUC things that consume gir also produce gir without much distinction.

[Ericson2314]

That's fine, but we will need the wrapper anyways to combine the build platform py tools with host platform everything else.

[Ericson2314]

I'm happy to say https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/227 was finally merged 11 months later. Hopefully https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/224, which thus became much smaller and simpler, has a chance of being merged now. Then we can finish this off.

[Atemu]

What's the status on this?

One of the patches was merged a few months ago.

[Artturin]

rebased in https://github.com/Artturin/nixpkgs/tree/gobject-introspectcross
left the source at the normal gi src

during build it fails with

gobject-introspection> substitute(): ERROR: file '/nix/store/zq92yh2l39qnjmjdn6zmiyav9ai6yb7i-gobject-introspection-hook'does not exist

What's the status on this?

One of the patches was merged a few months ago.

need this for tests https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/224

[Ericson2314]

@Artturin @SuperSandro2000 the remaining is https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/224 is small enough that we could try to just do it downstream, and then use that to try to get the maintainer's attention.

I am pulled in many directions right now and don' feel I have the time/energy to push this, but if someone else wants to give it a shot I would be very happy to mentor them. (This also can help me be less of a chokepoint with this sort of upstream-adventure-for-better-bootstrapping stuff in general.)

[stale]

I marked this as stale due to inactivity. → More info

[SuperSandro2000]

Do we actually need the patch at all? Could we just build everything both times and throw away what we don't need? That would be a bit wasteful for processing power but maintaining the patch is also much work in the long run.