Since #34411, pkgconf/pkg-config is no longer strictly required.
It is currently required for ZeroMQ on several major distributions and operating systems, including Debian, Ubuntu, the BSD derivatives, and Gentoo.
Regarding QRencode, our FindQRencode.cmake module treats pkgconf/pkg-config as optional and can successfully locate the package without it.
This PR amends #34411 and updates the build notes accordingly.
Addresses #34411#pullrequestreview-4553185425.
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It is now only needed for ZeroMQ on certain (though mainstream) platforms.
This could be less vague, it's needed for mainstream distros that we primarily use, like Debian and Ubuntu, as well as at least all the BSDs, and others, like Gentoo and macOS.
Regarding QRencode, our FindQRencode.cmake module treats pkgconf/pkg-config as optional and can successfully locate the package without it.
If it works without pkg-config, then we should remove the usage of pkgconfig entirely, rather than say it will work without it, and leave the dependency in the code?
It is now only needed for ZeroMQ on certain (though mainstream) platforms.
This could be less vague, it's needed for mainstream distros that we primarily use, like Debian and Ubuntu, as well as at least all the BSDs, and others, like Gentoo.
The PR description has been updated.
Regarding QRencode, our FindQRencode.cmake module treats pkgconf/pkg-config as optional and can successfully locate the package without it.
If it works without pkg-config, then we should remove the usage of pkgconfig entirely, rather than say it will work without it, and leave the dependency in the code?
The current approach is suggested in the official CMake docs:
First, we try to use
pkg-configto find the library. Note that we cannot rely on this, as it may not be available, but it provides a good starting point.
The same approach is used by CMake in Find Modules they ship. For example, in FindCURL.
@purpleKarrot
What are your thoughts on this?
The current approach is suggested in the official CMake docs:
I don't read this as a suggestion, but rather as an example. Relying on pkg-config may be useful when the the library author provides necessary compile flags etc in a .pc file but no .cmake or .cps package. With QRencode, we are really just interested in the include directory and library locations. That is simple enough to do without pkg-config`.
While cleaning up this module, you may also get rid of SelectLibraryConfigurations. We don't want that QRencode_LIBRARY or QRencode_LIBRARIES is used anywhere; there is no need to set a variable with that name.
ACK fb8a1038867b6e8a938d2c0b66cd961e2fd538d4
ACK fb8a1038867b6e8a938d2c0b66cd961e2fd538d4