150 lines
6.4 KiB
Markdown
150 lines
6.4 KiB
Markdown
# pkgconf [](https://github.com/pkgconf/pkgconf/actions/workflows/test.yml)
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`pkgconf` is a program which helps to configure compiler and linker flags for
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development libraries. It is similar to pkg-config from freedesktop.org.
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`libpkgconf` is a library which provides access to most of `pkgconf`'s functionality,
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to allow other tooling such as compilers and IDEs to discover and use libraries
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configured by pkgconf.
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## using `pkgconf` with autotools
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Implementations of pkg-config, such as pkgconf, are typically used with the
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PKG_CHECK_MODULES autoconf macro. As far as we know, pkgconf is
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compatible with all known variations of this macro. pkgconf detects at
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runtime whether or not it was started as 'pkg-config', and if so, attempts
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to set program options such that its behaviour is similar.
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In terms of the autoconf macro, it is possible to specify the PKG_CONFIG
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environment variable, so that you can test pkgconf without overwriting your
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pkg-config binary. Some other build systems may also respect the PKG_CONFIG
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environment variable.
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To set the environment variable on the bourne shell and clones (i.e. bash), you
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can run:
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$ export PKG_CONFIG=/usr/bin/pkgconf
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## comparison of `pkgconf` and `pkg-config` dependency resolvers
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pkgconf builds an acyclic directed dependency graph. This allows for the user
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to more conservatively link their binaries -- which may be helpful in some
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environments, such as when prelink(1) is being used. As a result of building
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a directed dependency graph designed for the specific problem domain provided
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by the user, more accurate dependencies can be determined.
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Current release versions of pkg-config, on the other hand, build a database of all
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known pkg-config files on the system before attempting to resolve dependencies, which
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is a considerably slower and less efficient design. Efforts have been made recently
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to improve this behaviour.
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As of the 1.1 series, pkgconf also fully implements support for `Provides` rules,
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while pkg-config does not. pkg-config only provides the `--print-provides` functionality
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as a stub. There are other intentional implementation differences in pkgconf's dependency
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resolver versus pkg-config's dependency resolver in terms of completeness and correctness,
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such as, for example, how `Conflicts` rules are processed.
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## linker flags optimization
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As previously mentioned, pkgconf makes optimizations to the linker flags in both the
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case of static and shared linking in order to avoid overlinking binaries and also
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simplifies the `CFLAGS` and `LIBS` output of the pkgconf tool for improved readability.
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This functionality depends on the pkg-config module properly declaring it's dependency
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tree instead of using `Libs` and `Cflags` fields to directly link against other modules
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which have pkg-config metadata files installed.
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Doing so is discouraged by the [freedesktop tutorial][fd-tut] anyway.
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[fd-tut]: http://people.freedesktop.org/~dbn/pkg-config-guide.html
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## compatibility with pkg-config
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I really hate that I have to have this section, I like being a nice person, but we
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unfortunately have to say this because otherwise we get passive-aggressive people who
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try to argue with us about what pkg-config compatibility means.
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We do not provide bug-level compatibility with pkg-config.
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What that means is, if you feel that there is a legitimate regression versus pkg-config,
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do let us know, but also make sure that the .pc files are valid and follow the rules of
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the [pkg-config tutorial][fd-tut], as most likely fixing them to follow the specified
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rules will solve the problem.
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Additionally, **we do not consider pkgconf doing what you tell it to do, in cases for
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which pkg-config fails to do so, to be a bug**.
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If, for example, you use environment variables such as `PKG_CONFIG_SYSTEM_[INCLUDE|LIBRARY]_PATH`
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and then find yourself surprised that `pkgconf` is stripping `-I` and `-L` flags relating
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to those paths, it is not a `pkgconf` problem -- `pkgconf` is doing exactly what you told
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it to do.
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We will reject bugs like this, and if someone insists on fixing such a non-bug, this
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constitutes a violation of our [Code of Conduct](CODE_OF_CONDUCT.md), which may be
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addressed by banning from this repository.
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## debug output
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Please use only the stable interfaces to query pkg-config. Do not screen-scrape the
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output from `--debug`: this is sent to `stderr` for a reason, it is not intended to be
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scraped. The `--debug` output is **not** a stable interface, and should **never** be
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depended on as a source of information. If you need a stable interface to query pkg-config
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which is not covered, please get in touch.
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## compiling `pkgconf` and `libpkgconf` on UNIX
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pkgconf is basically compiled the same way any other autotools-based project is
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compiled:
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$ ./configure
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$ make
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$ sudo make install
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If you are installing pkgconf into a custom prefix, such as `/opt/pkgconf`, you will
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likely want to define the default system includedir and libdir for your toolchain.
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To do this, use the `--with-system-includedir` and `--with-system-libdir` configure
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flags like so:
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$ ./configure \
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--prefix=/opt/pkgconf \
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--with-system-libdir=/lib:/usr/lib \
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--with-system-includedir=/usr/include
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$ make
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$ sudo make install
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## compiling `pkgconf` and `libpkgconf` with Meson (usually for Windows)
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pkgconf is compiled using [Meson](https://mesonbuild.com) on Windows. In theory, you could also use
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Meson to build on UNIX, but this is not recommended at this time as it pkgconf is typically built
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much earlier than Meson.
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$ meson setup build -Dtests=false
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$ meson compile -C build
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$ meson install -C build
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There are a few defines such as SYSTEM_LIBDIR, PKGCONFIGDIR and SYSTEM_INCLUDEDIR.
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However, on Windows, the default PKGCONFIGDIR value is usually overridden at runtime based
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on path relocation.
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## pkg-config symlink
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If you want pkgconf to be used when you invoke `pkg-config`, you should install a
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symlink for this. We do not do this for you, as we believe it is better for vendors
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to make this determination themselves.
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$ ln -sf pkgconf /usr/bin/pkg-config
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## release tarballs
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Release tarballs are available at <https://distfiles.dereferenced.org/pkgconf/>.
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Please only use the tarballs from distfiles.dereferenced.org.
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## contacts
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You can report bugs at <https://github.com/pkgconf/pkgconf/issues>.
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There is a mailing list at <https://lists.sr.ht/~kaniini/pkgconf>.
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You can contact us via IRC at `#pkgconf` at `irc.oftc.net`.
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