Expose SDL2 as sdl2 in pkgconfig to maintian consistency with other distros

[devins2518]

Describe the bug

I was attempting to use this zig wrapper for SDL, and compilation failed because ld couldn't find sdl2. At first, I thought this was because of #24744, however, after changing the build script to use SDL2 instead of sdl2, it worked. I assume the library used sdl2 because it is how every other distro exposes the library, and I don't see a reason why Nix needs to change this.

Steps To Reproduce

Steps to reproduce the behavior:

1. Use this shell.nix

{ pkgs ? import <nixpkgs> { } }:
pkgs.mkShell {
  nativeBuildInputs = with pkgs; [ SDL2 pkgconf ];
  }

2. Clone and build https://github.com/MasterQ32/SDL.zig

Expected behavior

The line exe.linkSystemLibrary("sdl2"); is able to find SDL2.

Notify maintainers

@cpages

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.10.70, NixOS, 21.11 (Porcupine)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.4pre20210922_bcd73eb`
 - channels(root): `"nixos-21.11pre293730.1ca6b0a0cc3"`
 - nixpkgs: `/nix/store/51b74bw26ldmlj9yi3h7v3scsjl8fdg8-z7qikyiq6zfhxc7k7721z3zcrlpxy9s6-source`

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:

[sagehane]

I assume the library used sdl2 because it is how every other distro exposes the library, and I don't see a reason why Nix needs to change this.

Looking at https://archlinux.org/packages/extra/x86_64/sdl2/ and the "Package Contents" section, it seems like Arch Linux also uses SDL2 in uppercase. Installing pkgconf made it so the library name is case insensitive, however. (Meaning I could do something like SdL2)

And judging from the Windows MinGW development library on https://libsdl.org/download-2.0.php, it seems like the upstream uses SDL2 in uppercase too.

$ ls -lA SDL2-2.0.16/x86_64-w64-mingw32/lib
total 15064
drwxr-xr-x 3 plumeus plumeus       18 Oct 14 01:48 cmake
-rw-r--r-- 1 plumeus plumeus 14293518 Aug 11 00:54 libSDL2.a
-rwxr-xr-x 1 plumeus plumeus   483488 Aug 11 00:54 libSDL2.dll.a
-rwxr-xr-x 1 plumeus plumeus     1058 Aug 11 00:54 libSDL2.la
-rw-r--r-- 1 plumeus plumeus   616058 Aug 11 00:54 libSDL2_test.a
-rwxr-xr-x 1 plumeus plumeus      925 Aug 11 00:54 libSDL2_test.la
-rw-r--r-- 1 plumeus plumeus     9422 Aug 11 00:54 libSDL2main.a
-rwxr-xr-x 1 plumeus plumeus      922 Aug 11 00:54 libSDL2main.la
drwxr-xr-x 2 plumeus plumeus       21 Oct 14 01:48 pkgconfig

I haven't checked how other distros deal with this, but I think having it in uppercase should be perfectly reasonable.

[sagehane]

{ pkgs ? import <nixpkgs> { } }:

pkgs.mkShell {
  buildInputs = with pkgs; [
    SDL2
    pkg-config
  ];
}

Using this shell.nix file for one of my SDL projects allowed the program to compile fine with exe.linkSystemLibrary("sdl2");.

However, pkgconf didn't work. So I presume the problem is that pkgconf doesn't have feature parity with pkg-config on Nix for some reason?

Edit: For clarity, I'm using the master branch of Zig, and not 0.8.1. I don't think it should make a difference, but just thought it was worth mentioning.

[devins2518]

Yes, you're right! Changing pkgconf to pkg-config does fix this issue

[sagehane]

I find it strange that pkgconf doesn't work on NixOS when it works fine on Arch Linux. So, I don't know if this issue should be closed yet. Although maybe investigating that should be left up to a different issue?