CMake find_package 配置模式详解-优快云博客

学习find_package的 config 模式及package configure文件相关知识

find_package 的 config 模式

当CMakeLists.txt中使用find_package命令时，首先启用的是 module 模式：

按照 CMAKE_MODULE_PATH 路径和cmake的安装路径去搜索finder文件 Find<package>.cmake

如果finder未找到，则开始 config 模式：

将在下列路径下查找配置文件 <name>Config.cmake 或 <lower-case-name>-config.cmake

<prefix>/	(W)
<prefix>/(cmake\|CMake)/	(W)
<prefix>/<name>*/	(W)
<prefix>/<name>*/(cmake\|CMake)/	(W)
<prefix>/(share\|lib)/cmake/<name>*/	(U)
<prefix>/(share\|lib)/<name>*/	(U)
<prefix>/(share\|lib)/<name>*/(cmake\|CMake)/	(U)

find_package 参数及规则见manual

<name>Config.cmake

该文件至少需提供头文件路径和库文件信息。比如 ApiExtractorConfig.cmake 在Windows下一个例子：

# - try to find APIEXTRACTOR
#  APIEXTRACTOR_INCLUDE_DIR   - Directories to include to use APIEXTRACTOR
#  APIEXTRACTOR_LIBRARIES     - Files to link against to use APIEXTRACTOR

SET(APIEXTRACTOR_INCLUDE_DIR "D:/shiboken/dist/include/apiextractor")
if(MSVC)
    SET(APIEXTRACTOR_LIBRARY "D:/shiboken/dist/lib/apiextractor.lib")
elseif(WIN32)
    SET(APIEXTRACTOR_LIBRARY "D:/shiboken/dist/bin/apiextractor.dll")
else()
    SET(APIEXTRACTOR_LIBRARY "D:/shiboken/dist/lib/apiextractor.dll")
endif()

该文件是通过 configure_file 机制生成的，我们看看 ApiExtractorConfig.cmake.in 文件：

SET(APIEXTRACTOR_INCLUDE_DIR "@CMAKE_INSTALL_PREFIX@/include/apiextractor@apiextractor_SUFFIX@")
if(MSVC)
    SET(APIEXTRACTOR_LIBRARY "@LIB_INSTALL_DIR@/@CMAKE_SHARED_LIBRARY_PREFIX@apiextractor@apiextractor_SUFFIX@@LIBRARY_OUTPUT_SUFFIX@.lib")
elseif(WIN32)
    SET(APIEXTRACTOR_LIBRARY "@CMAKE_INSTALL_PREFIX@/bin/@CMAKE_SHARED_LIBRARY_PREFIX@apiextractor@apiextractor_SUFFIX@@LIBRARY_OUTPUT_SUFFIX@@CMAKE_SHARED_LIBRARY_SUFFIX@")
else()
    SET(APIEXTRACTOR_LIBRARY "@LIB_INSTALL_DIR@/@CMAKE_SHARED_LIBRARY_PREFIX@apiextractor@apiextractor_SUFFIX@@LIBRARY_OUTPUT_SUFFIX@@CMAKE_SHARED_LIBRARY_SUFFIX@")
endif()

对应的命令(变量的定义略过)

configure_file("${CMAKE_CURRENT_SOURCE_DIR}/ApiExtractorConfig.cmake.in" "${CMAKE_CURRENT_BINARY_DIR}/ApiExtractorConfig.cmake" @ONLY)

<name>ConfigVersion.cmake

该文件用来比对版本是否匹配，看看ApiExtractorConfigVersion.cmake.in 的内容：

set(PACKAGE_VERSION @apiextractor_VERSION@)

if("${PACKAGE_VERSION}" VERSION_LESS "${PACKAGE_FIND_VERSION}" )
   set(PACKAGE_VERSION_COMPATIBLE FALSE)
else("${PACKAGE_VERSION}" VERSION_LESS "${PACKAGE_FIND_VERSION}" )
   set(PACKAGE_VERSION_COMPATIBLE TRUE)
   if( "${PACKAGE_FIND_VERSION}" STREQUAL "${PACKAGE_VERSION}")
      set(PACKAGE_VERSION_EXACT TRUE)
   endif( "${PACKAGE_FIND_VERSION}" STREQUAL "${PACKAGE_VERSION}")
endif("${PACKAGE_VERSION}" VERSION_LESS "${PACKAGE_FIND_VERSION}" )

一般提供设置下面的变量

PACKAGE_VERSION	完整的版本字符串
PACKAGE_VERSION_EXACT	如果完全匹配为真
PACKAGE_VERSION_COMPATIBLE	如果兼容为真
PACKAGE_VERSION_UNSUITABLE	如果不可用为真

find_package进而根据这些设置

<package>_VERSION	full provided version string
<package>_VERSION_MAJOR	major version if provided, else 0
<package>_VERSION_MINOR	minor version if provided, else 0
<package>_VERSION_PATCH	patch version if provided, else 0
<package>_VERSION_TWEAK	tweak version if provided, else 0