FindPackageHandleStandardArgs

This module provides commands intended for use in Find Modules implementing find_package(<PackageName>) calls.

Load this module in a CMake find module with:

FindFoo.cmake
include(FindPackageHandleStandardArgs)

命令

該模組提供了以下命令：

find_package_handle_standard_args

Handles the REQUIRED, QUIET and version-related arguments of find_package().

There are two signatures:

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

find_package_handle_standard_args(
  <PackageName>
  [REQUIRED_VARS <required-vars>...]
  [VERSION_VAR <version-var>]
  [HANDLE_VERSION_RANGE]
  [HANDLE_COMPONENTS]
  [CONFIG_MODE]
  [NAME_MISMATCHED]
  [REASON_FAILURE_MESSAGE <reason-failure-message>]
  [FAIL_MESSAGE <custom-failure-message>]
  [FOUND_VAR <result-var>] # Deprecated
)

This command sets the <PackageName>_FOUND variable to TRUE if all the variables listed in <required-vars>... contain valid results (e.g., valid filepaths) 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 arguments are:

<PackageName>

The name of the package. For example, as written in the Find<PackageName>.cmake find module filename.

(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.

REQUIRED_VARS <required-vars>...

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.

在 3.18 版的變更: If HANDLE_COMPONENTS is specified, this option can be omitted.

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_VERSION_RANGE

在 3.19 版被加入.

Enable handling of a version range, if one is specified. Without this option, a developer warning will be displayed if a version range is specified.

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.

NAME_MISMATCHED

在 3.17 版被加入.

Indicate that the <PackageName> does not match the value of CMAKE_FIND_PACKAGE_NAME variable. This is usually a mistake and raises a warning, but it may be intentional for usage of the command for components of a larger package.

REASON_FAILURE_MESSAGE <reason-failure-message>

在 3.16 版被加入.

Specify a custom message of the reason for the failure which will be appended to the default generated message.

FAIL_MESSAGE <custom-failure-message>

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

FOUND_VAR <result-var>

在 3.3 版之後被棄用: This option should no longer be used.

Specifies either <PackageName>_FOUND or <PACKAGENAME>_FOUND as the result variable. This exists only for backward compatibility with older versions of CMake and is now ignored. Result variables of both names are now always set for compatibility also with or without this option.

備註

If <PackageName> does not match CMAKE_FIND_PACKAGE_NAME for the calling module, a warning that there is a mismatch is given. The FPHSA_NAME_MISMATCHED variable may be set to bypass the warning if using the old signature and the NAME_MISMATCHED argument using the new signature. To avoid forcing the caller to require newer versions of CMake for usage, the variable's value will be used if defined when the NAME_MISMATCHED argument is not passed for the new signature (but using both is an error).

find_package_check_version

在 3.19 版被加入.

Checks if a given version is valid against the version-related arguments of find_package():

find_package_check_version(
  <version>
  <result-var>
  [HANDLE_VERSION_RANGE]
  [RESULT_MESSAGE_VARIABLE <message-var>]
)

The arguments are:

<version>

The version string to check.

<result-var>

Name of the result variable that will hold a boolean value giving the result of the check.

HANDLE_VERSION_RANGE

Enable handling of a version range, if one is specified. Without this option, a developer warning will be displayed if a version range is specified.

RESULT_MESSAGE_VARIABLE <message-var>

Specify a variable to get back a message describing the result of the check.

範例

Examples: Full Signature

Example for using a full signature of find_package_handle_standard_args():

FindLibArchive.cmake
include(FindPackageHandleStandardArgs)
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 of find_package_handle_standard_args():

FindAutomoc4.cmake
find_package(Automoc4 QUIET NO_MODULE HINTS /opt/automoc4)

include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(Automoc4 CONFIG_MODE)

In this case, a FindAutomoc4.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.

Example: Simple Signature

Example for using a simple signature of find_package_handle_standard_args():

FindLibXml2.cmake
include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(
  LibXml2
  DEFAULT_MSG
  LIBXML2_LIBRARY LIBXML2_INCLUDE_DIR
)

In this example, the LibXml2 package is considered to be found if both LIBXML2_LIBRARY and LIBXML2_INCLUDE_DIR variables 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 variable specified in <required-vars>.... On repeated CMake runs, the same message will not be printed again.

Example: Checking Version

Example for the find_package_check_version() usage:

FindFoo.cmake
include(FindPackageHandleStandardArgs)
find_package_check_version(
  1.2.3
  result
  HANDLE_VERSION_RANGE
  RESULT_MESSAGE_VARIABLE reason
)
if(result)
  message(STATUS "${reason}")
else()
  # Logic when version check is not successful.
  message(WARNING "${reason}")
endif()

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