Crate pkg_config Copy item path

A build dependency for Cargo libraries to find system artifacts through the pkg-config utility.

This library will shell out to pkg-config as part of build scripts and probe the system to determine how to link to a specified library. The Config structure serves as a method of configuring how pkg-config is invoked in a builder style.

After running pkg-config all appropriate Cargo metadata will be printed on stdout if the search was successful.

§Environment variables

A number of environment variables are available to globally configure how this crate will invoke pkg-config:

• FOO_NO_PKG_CONFIG - if set, this will disable running pkg-config when probing for the library named foo.

§Linking

There are also a number of environment variables which can configure how a library is linked to (dynamically vs statically). These variables control whether the --static flag is passed. Note that this behavior can be overridden by configuring explicitly on Config. The variables are checked in the following order:

• FOO_STATIC - pass --static for the library foo
• FOO_DYNAMIC - do not pass --static for the library foo
• PKG_CONFIG_ALL_STATIC - pass --static for all libraries
• PKG_CONFIG_ALL_DYNAMIC - do not pass --static for all libraries

§Cross-compilation

In cross-compilation context, it is useful to manage separately PKG_CONFIG_PATH and a few other variables for the host and the target platform.

The supported variables are: PKG_CONFIG_PATH, PKG_CONFIG_LIBDIR, and PKG_CONFIG_SYSROOT_DIR.

Each of these variables can also be supplied with certain prefixes and suffixes, in the following prioritized order:

1. <var>_<target> - for example, PKG_CONFIG_PATH_x86_64-unknown-linux-gnu
2. <var>_<target_with_underscores> - for example, PKG_CONFIG_PATH_x86_64_unknown_linux_gnu
3. <build-kind>_<var> - for example, HOST_PKG_CONFIG_PATH or TARGET_PKG_CONFIG_PATH
4. <var> - a plain PKG_CONFIG_PATH

This crate will allow pkg-config to be used in cross-compilation if PKG_CONFIG_SYSROOT_DIR or PKG_CONFIG is set. You can set PKG_CONFIG_ALLOW_CROSS=1 to bypass the compatibility check, but please note that enabling use of pkg-config in cross-compilation without appropriate sysroot and search paths set is likely to break builds.

§Example

Find the system library named foo, with minimum version 1.2.3:

fn main() {
    pkg_config::Config::new().atleast_version("1.2.3").probe("foo").unwrap();
}

Find the system library named foo, with no version requirement (not recommended):

fn main() {
    pkg_config::probe_library("foo").unwrap();
}

Configure how library foo is linked to.

fn main() {
    pkg_config::Config::new().atleast_version("1.2.3").statik(true).probe("foo").unwrap();
}