如何在 CMake 中导出包？答案

【问题标题】：How to Export a Package in CMake?如何在 CMake 中导出包？
【发布时间】：2020-10-18 11:43:38
【问题描述】：

我无法在 CMake 中正确导出一个包，以便可以使用 find_package 命令导入它，而且无论我做什么，它仍然无法正常工作。我重新创建了最简单的场景，展示了我的导出过程，因此应该更容易诊断。

我设置了两个项目，我将它们放在同一个文件夹中：foo 和 bar，其中foo 是一个库，bar 是一个依赖于foo 的可执行文件。

├───bar
│       bar.c
│       CMakeLists.txt
│
└───foo
        CMakeLists.txt
        foo.c
        foo.h

请注意，这是两个独立的项目，而不是一个总体项目的子项目。

foo/CMakeLists.txt的内容：

cmake_minimum_required (VERSION 3.8)

project (Foo)

set (LIB_NAME foo)

add_library (${LIB_NAME} STATIC foo.c foo.h)

install (TARGETS ${LIB_NAME} EXPORT ${LIB_NAME}Targets
        ARCHIVE DESTINATION lib
        LIBRARY DESTINATION lib
        RUNTIME DESTINATION bin
        INCLUDES DESTINATION include
)

install (FILES foo.h
        DESTINATION include
)

install (EXPORT ${LIB_NAME}Targets
        NAMESPACE foo::
        DESTINATION lib/cmake
)

bar/CMakeLists.txt的内容：

cmake_minimum_required (VERSION 3.8)

project (Bar)

set (EXE_NAME bar)

find_package (foo REQUIRED)

add_executable (${EXE_NAME} bar.c)
target_link_libraries (${EXE_NAME} PRIVATE foo::foo)

我用来构建这两个项目的命令序列：

md foo_build
md bar_build
cd foo_build
cmake ..\foo -DCMAKE_INSTALL_PREFIX=..\install\foo
cmake --build . --target INSTALL
cd ..\bar_build
cmake ..\bar -DCMAKE_PREFIX_PATH=..\install\foo

当所有这些都完成后，产生的错误是：

CMake Error at CMakeLists.txt:7 (find_package):
  By not providing "Findfoo.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "foo", but
  CMake did not find one.

  Could not find a package configuration file provided by "foo" with any of
  the following names:

    fooConfig.cmake
    foo-config.cmake

  Add the installation prefix of "foo" to CMAKE_PREFIX_PATH or set "foo_DIR"
  to a directory containing one of the above files.  If "foo" provides a
  separate development package or SDK, be sure it has been installed.

当我尝试使用 Config 后缀而不是 Target 后缀导出包导出时，输出似乎没有任何区别：

CMake Error at CMakeLists.txt:7 (find_package):
  By not providing "Findfoo.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "foo", but
  CMake did not find one.

  Could not find a package configuration file provided by "foo" with any of
  the following names:

    fooConfig.cmake
    foo-config.cmake

  Add the installation prefix of "foo" to CMAKE_PREFIX_PATH or set "foo_DIR"
  to a directory containing one of the above files.  If "foo" provides a
  separate development package or SDK, be sure it has been installed.

我不知道我做错了什么，CMake Documentation 似乎根本没有帮助我。

如果有帮助，我的 CMake 版本是 3.17.3。

提前谢谢你。

编辑：

我遵循了@Tsyvarev 给出的建议，不幸的是，它似乎并没有解决问题。我阅读了documentation that he sent，并遵循了与我当前方法不同的所有部分。

该方法的两个主要区别是创建单独的 -Targets、-Config 和 -ConfigVersion cmake 文件，并进行了以下更改。

整个程序的新结构：

├───bar
│       bar.c
│       CMakeLists.txt
│
└───foo
    │   CMakeLists.txt
    │   foo.c
    │   foo.h
    │
    └───cmake
            fooConfig.cmake

我添加到 foo 的 CMakeLists.txt 文件中的行：

include (CMakePackageConfigHelpers)
write_basic_package_version_file (
        ${CMAKE_CURRENT_BINARY_DIR}/${LIB_NAME}ConfigVersion.cmake
        VERSION ${${PROJECT_NAME}_VERSION}
        COMPATIBILITY AnyNewerVersion
)

install (
        FILES
            cmake/${LIB_NAME}Config.cmake
            ${CMAKE_CURRENT_BINARY_DIR}/${LIB_NAME}ConfigVersion.cmake
        DESTINATION lib/cmake
)

fooConfig.cmake的内容：

include ("${CMAKE_CURRENT_LIST_DIR}/fooTargets.cmake")

仅供参考，安装foo的输出结果如预期：

├───include
│       foo.h
│
└───lib
    │   foo.lib
    │
    └───cmake
            fooConfig.cmake
            fooConfigVersion.cmake
            fooTargets-debug.cmake
            fooTargets.cmake

而在bar项目上运行cmake时，出现同样的错误：

  By not providing "Findfoo.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "foo", but
  CMake did not find one.

  Could not find a package configuration file provided by "foo" with any of
  the following names:

    fooConfig.cmake
    foo-config.cmake

  Add the installation prefix of "foo" to CMAKE_PREFIX_PATH or set "foo_DIR"
  to a directory containing one of the above files.  If "foo" provides a
  separate development package or SDK, be sure it has been installed.

顺便说一句，CMAKE_PREFIX_PATH 正在设置中，尽管错误消息会有所不同，我似乎无法弄清楚我还需要做些什么来安抚它。

任何帮助将不胜感激。

【问题讨论】：

CMake 有打包的文档，甚至还有一个例子：cmake.org/cmake/help/v3.19/manual/…。你读过那个文件吗？有什么不清楚的地方？
@Tsyvarev 我以前没有看过这个文档，我一直在看文档，但似乎从来没有来过这个页面。谢谢;如果有任何问题，我会看一下并更新帖子。

标签： c windows cmake dependency-management

【解决方案1】：

经过一些非常令人沮丧的研究，我终于在way that find_package works 中找到了这个问题的答案。事实证明，我给它的目录结构不够好，但是一旦我将“lib/cmake”更改为“lib/cmake/${LIB_NAME}”，并将CMAKE_PREFIX_PATH 更改为..\install 而不是@ 987654327@，一切似乎都很顺利，我终于让这个简单的程序运行起来了。

【讨论】：