51 lines
1.9 KiB
Markdown
51 lines
1.9 KiB
Markdown
# pkg-config {#sec-pkg-config}
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*pkg-config* is a unified interface for declaring and querying built C/C++ libraries.
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Nixpkgs provides a couple of facilities for working with this tool.
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## Writing packages providing pkg-config modules {#pkg-config-writing-packages}
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Packages should set `meta.pkgConfigModules` with the list of package config modules they provide.
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They should also use `testers.testMetaPkgConfig` to check that the final built package matches that list.
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Additionally, the [`validatePkgConfig` setup hook](https://nixos.org/manual/nixpkgs/stable/#validatepkgconfig), will do extra checks on to-be-installed pkg-config modules.
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A good example of all these things is zlib:
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```
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{ pkg-config, testers, ... }:
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stdenv.mkDerivation (finalAttrs: {
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...
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nativeBuildInputs = [ pkg-config validatePkgConfig ];
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passthru.tests.pkg-config = testers.testMetaPkgConfig finalAttrs.finalPackage;
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meta = {
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...
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pkgConfigModules = [ "zlib" ];
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};
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})
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```
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## Accessing packages via pkg-config module name {#sec-pkg-config-usage}
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### Within Nixpkgs {#sec-pkg-config-usage-internal}
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A [setup hook](#setup-hook-pkg-config) is bundled in the `pkg-config` package to bring a derivation's declared build inputs into the environment.
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This will populate environment variables like `PKG_CONFIG_PATH`, `PKG_CONFIG_PATH_FOR_BUILD`, and `PKG_CONFIG_PATH_HOST` based on:
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- how `pkg-config` itself is depended upon
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- how other dependencies are depended upon
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For more details see the section on [specifying dependencies in general](#ssec-stdenv-dependencies).
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Normal pkg-config commands to look up dependencies by name will then work with those environment variables defined by the hook.
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### Externally {#sec-pkg-config-usage-external}
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The `defaultPkgConfigPackages` package set is a set of aliases, named after the modules they provide.
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This is meant to be used by language-to-nix integrations.
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Hand-written packages should use the normal Nixpkgs attribute name instead.
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