some packages

Could you elaborate on this a bit? It's potentially helpful to have this information to refer back to.

Could you elaborate on this a bit?

Zlib and anything that has headers in the normal system libs/include folders seems to not get their headers picked up without this change.

I think this issue is mostly going to be something people hit when cross compiling since the prefix based system libs/include folder would probably work in most of the usual cases(searching in sys.prefix will not work when cross compiling since it points to the host toolchain prefix rather than the target toolchain sysroot prefix):

When cross compiling we try and make sure pkg-config points to the correct target sysroot however.

@radarhere FYI there's some additional background/discussion around this issue here.

@radarhere Tests should be passing now, I've re-based on main with #6229.

Yes, the tests will pass now, but the failure revealed a problem - on main, libtiff is detected. On this branch, it is not.

On this branch, it is not.

Weird, on ubuntu 20.04 with libtiff-dev installed it seems to get detected fine for me.

FYI there's a repo setting you can change so that you don't have to manually approve most workflows in pull requests:

Ok, I stopped _pkg_config from catching exceptions, and it turned out there was an error occurring - "Unknown option --keep-system-libs".

If I try on my macOS machine,

$ pkg-config --keep-system-libs
Unknown option --keep-system-libs
$ pkg-config --keep-system-cflags
Unknown option --keep-system-cflags

So I guess those options are only available in certain environments. What is surprising though is that you say the flag works for you on your copy of Ubuntu 20.04, but it doesn't in GitHub Actions. Any ideas why that might be?

Perhaps a solution would be to try --keep-system-libs first, and then to try again without it if it doesn't work? jameshilliard#1

What is surprising though is that you say the flag works for you on your copy of Ubuntu 20.04, but it doesn't in GitHub Actions. Any ideas why that might be?

Yeah, not sure why that is happening.

$ pkg-config --version
1.6.3

Is the version in my ubuntu system.

Perhaps a solution would be to try --keep-system-libs first, and then to try again without it if it doesn't work?

That seems to work for me, merged to my branch here.

The version number is was helpful, thanks - I think you are using pkgconf, not pkg-config.

https://pkgs.org/download/pkg-config

There is apparently a "compatibility interface" that means you can run it as pkg-config, hence the confusion.

Ah, yeah, guess that explains why the fallback is needed for some systems.

Rebased on python-pillow:main.

@radarhere This good to merge or anything else I should do?