pyrox.dev
1# pkg-config {#sec-pkg-config}
2
3*pkg-config* is a unified interface for declaring and querying built C/C++ libraries.
4
5Nixpkgs provides a couple of facilities for working with this tool.
6
7## Writing packages providing pkg-config modules {#pkg-config-writing-packages}
8
9Packages should set `meta.pkgConfigModules` with the list of package config modules they provide.
10They should also use `testers.testMetaPkgConfig` to check that the final built package matches that list.
11Additionally, the [`validatePkgConfig` setup hook](https://nixos.org/manual/nixpkgs/stable/#validatepkgconfig), will do extra checks on to-be-installed pkg-config modules.
12
13A good example of all these things is zlib:
14
15```
16{ pkg-config, testers, ... }:
17
18stdenv.mkDerivation (finalAttrs: {
19 ...
20
21 nativeBuildInputs = [ pkg-config validatePkgConfig ];
22
23 passthru.tests.pkg-config = testers.testMetaPkgConfig finalAttrs.finalPackage;
24
25 meta = {
26 ...
27 pkgConfigModules = [ "zlib" ];
28 };
29})
30```
31
32## Accessing packages via pkg-config module name {#sec-pkg-config-usage}
33
34### Within Nixpkgs {#sec-pkg-config-usage-internal}
35
36A [setup hook](#setup-hook-pkg-config) is bundled in the `pkg-config` package to bring a derivation's declared build inputs into the environment.
37This will populate environment variables like `PKG_CONFIG_PATH`, `PKG_CONFIG_PATH_FOR_BUILD`, and `PKG_CONFIG_PATH_HOST` based on:
38
39 - how `pkg-config` itself is depended upon
40
41 - how other dependencies are depended upon
42
43For more details see the section on [specifying dependencies in general](#ssec-stdenv-dependencies).
44
45Normal pkg-config commands to look up dependencies by name will then work with those environment variables defined by the hook.
46
47### Externally {#sec-pkg-config-usage-external}
48
49The `defaultPkgConfigPackages` package set is a set of aliases, named after the modules they provide.
50This is meant to be used by language-to-nix integrations.
51Hand-written packages should use the normal Nixpkgs attribute name instead.