FindPackageHandleStandardArgs

This module provides a function intended to be used in Find Modules implementing find_package(<PackageName>) calls. It handles the REQUIRED, QUIET and version-related arguments of find_package. It also sets the <PackageName>_FOUND variable. The package is considered found if all variables listed contain valid results, e.g. valid filepaths.

find_package_handle_standard_args

There are two signatures:

find_package_handle_standard_args(<PackageName>
  (DEFAULT_MSG|<custom-failure-message>)
  <required-var>...
  )

find_package_handle_standard_args(<PackageName>
  [FOUND_VAR <result-var>]
  [REQUIRED_VARS <required-var>...]
  [VERSION_VAR <version-var>]
  [HANDLE_COMPONENTS]
  [CONFIG_MODE]
  [FAIL_MESSAGE <custom-failure-message>]
  )

The <PackageName>_FOUND variable will be set to TRUE if all the variables <required-var>... are valid and any optional constraints are satisfied, and FALSE otherwise. A success or failure message may be displayed based on the results and on whether the REQUIRED and/or QUIET option was given to the find_package() call.

The options are:

(DEFAULT_MSG|<custom-failure-message>)

In the simple signature this specifies the failure message. Use DEFAULT_MSG to ask for a default message to be computed (recommended). Not valid in the full signature.

FOUND_VAR <result-var>

Obsolete. Specifies either <PackageName>_FOUND or <PACKAGENAME>_FOUND as the result variable. This exists only for compatibility with older versions of CMake and is now ignored. Result variables of both names are always set for compatibility.

REQUIRED_VARS <required-var>...

Specify the variables which are required for this package. These may be named in the generated failure message asking the user to set the missing variable values. Therefore these should typically be cache entries such as FOO_LIBRARY and not output variables like FOO_LIBRARIES.

VERSION_VAR <version-var>

Specify the name of a variable that holds the version of the package that has been found. This version will be checked against the (potentially) specified required version given to the find_package() call, including its EXACT option. The default messages include information about the required version and the version which has been actually found, both if the version is ok or not.

HANDLE_COMPONENTS

Enable handling of package components. In this case, the command will report which components have been found and which are missing, and the <PackageName>_FOUND variable will be set to FALSE if any of the required components (i.e. not the ones listed after the OPTIONAL_COMPONENTS option of find_package()) are missing.

CONFIG_MODE

Specify that the calling find module is a wrapper around a call to find_package(<PackageName> NO_MODULE). This implies a VERSION_VAR value of <PackageName>_VERSION. The command will automatically check whether the package configuration file was found.

FAIL_MESSAGE <custom-failure-message>

Specify a custom failure message instead of using the default generated message. Not recommended.

Example for the simple signature:

find_package_handle_standard_args(LibXml2 DEFAULT_MSG
  LIBXML2_LIBRARY LIBXML2_INCLUDE_DIR)

The LibXml2 package is considered to be found if both LIBXML2_LIBRARY and LIBXML2_INCLUDE_DIR are valid. Then also LibXml2_FOUND is set to TRUE. If it is not found and REQUIRED was used, it fails with a message(FATAL_ERROR), independent whether QUIET was used or not. If it is found, success will be reported, including the content of the first <required-var>. On repeated CMake runs, the same message will not be printed again.

Example for the full signature:

find_package_handle_standard_args(LibArchive
  REQUIRED_VARS LibArchive_LIBRARY LibArchive_INCLUDE_DIR
  VERSION_VAR LibArchive_VERSION)

In this case, the LibArchive package is considered to be found if both LibArchive_LIBRARY and LibArchive_INCLUDE_DIR are valid. Also the version of LibArchive will be checked by using the version contained in LibArchive_VERSION. Since no FAIL_MESSAGE is given, the default messages will be printed.

Another example for the full signature:

find_package(Automoc4 QUIET NO_MODULE HINTS /opt/automoc4)
find_package_handle_standard_args(Automoc4  CONFIG_MODE)

In this case, a FindAutmoc4.cmake module wraps a call to find_package(Automoc4 NO_MODULE) and adds an additional search directory for automoc4. Then the call to find_package_handle_standard_args produces a proper success/failure message.