FindPkgConfig——a pkg-config module for CMake

Usage:

pkg_check_modules( [REQUIRED] [QUIET]  []*)
  checks for all the given modules

pkg_search_module( [REQUIRED] [QUIET]  []*)
  checks for given modules and uses the first working one

When the ‘REQUIRED’ argument was set, macros will fail with an error when module(s) could not be found

When the ‘QUIET’ argument is set, no status messages will be printed.

It sets the following variables:

PKG_CONFIG_FOUND          ... if pkg-config executable was found
PKG_CONFIG_EXECUTABLE     ... pathname of the pkg-config program
PKG_CONFIG_VERSION_STRING ... the version of the pkg-config program found
                              (since CMake 2.8.8)

For the following variables two sets of values exist; first one is the common one and has the given PREFIX. The second set contains flags which are given out when pkgconfig was called with the ‘–static’ option.

_FOUND          ... set to 1 if module(s) exist
_LIBRARIES      ... only the libraries (w/o the '-l')
_LIBRARY_DIRS   ... the paths of the libraries (w/o the '-L')
_LDFLAGS        ... all required linker flags
_LDFLAGS_OTHER  ... all other linker flags
_INCLUDE_DIRS   ... the '-I' preprocessor flags (w/o the '-I')
_CFLAGS         ... all required cflags
_CFLAGS_OTHER   ... the other compiler flags

 =         for common case
 = _STATIC for static linking

There are some special variables whose prefix depends on the count of given modules. When there is only one module, stays unchanged. When there are multiple modules, the prefix will be changed to _:

_VERSION    ... version of the module
_PREFIX     ... prefix-directory of the module
_INCLUDEDIR ... include-dir of the module
_LIBDIR     ... lib-dir of the module

 =   when |MODULES| == 1, else
 = _

A parameter can have the following formats:

{MODNAME}            ... matches any version
{MODNAME}>={VERSION} ... at least version  is required
{MODNAME}={VERSION}  ... exactly version  is required
{MODNAME}<={VERSION} ... modules must not be newer than 

Examples

pkg_check_modules (GLIB2   glib-2.0)

pkg_check_modules (GLIB2   glib-2.0>=2.10)
  requires at least version 2.10 of glib2 and defines e.g.
    GLIB2_VERSION=2.10.3

pkg_check_modules (FOO     glib-2.0>=2.10 gtk+-2.0)
  requires both glib2 and gtk2, and defines e.g.
    FOO_glib-2.0_VERSION=2.10.3
    FOO_gtk+-2.0_VERSION=2.8.20

pkg_check_modules (XRENDER REQUIRED xrender)
  defines e.g.:
    XRENDER_LIBRARIES=Xrender;X11
    XRENDER_STATIC_LIBRARIES=Xrender;X11;pthread;Xau;Xdmcp

pkg_search_module (BAR     libxml-2.0 libxml2 libxml>=2)

https://cmake.org/cmake/help/v3.0/module/FindPkgConfig.html