问题描述
您有一个启用了CMake的库项目。您需要在另一个库或可执行文件中使用它。如何使用CMake找到并链接到图书馆？您可能有以下偏好设置：
- 写尽可能少的样板代码
- 将链接库的内部细节从使用目标中解耦
理想情况下，库的使用应如下所示：
c> a href =http://www.cmake.org/cmake/help/v3.3> CMake文档。最重要的相关命令是：
- li>
和两个详细文章：
You have a CMake-enabled library project. You need to use it in another library or executable. How to use CMake to find and link to the library? You may have the following preferences:
- write the least possible amount of boiler-plate code
- decouple the internal details of the linked library from the consuming target
Ideally, the usage of the library should look like this:
add_executable(myexe ...) target_link_libraries(myexe mylib)
Let me demonstrate a possible solution on a concrete example:
The myapp project
We have an executable target myapp. We're linking it with mylib, which is built in its own build tree. In the CMakeLists.txt of myapp we find and specify mylib as a dependency of myexe:
find_package(mylib REQUIRED) ... add_executable(myexe ...) target_link_libraries(myexe mylib)
Let's see how to set up mylib and the build of myexe to make this work.
The mylib project
The directory layout of mylib:
mylib - CMakeLists.txt - mylib.c + include - mylib.h # single public header
In the CMakeLists.txt of mylib we need to create the target and specify its source files:
add_library(mylib mylib.c include/mylib.h)
The public header mylib.h will be included as #include "mylib.h" both by mylib and the clients of mylib:
- mylib itself and other targets built in mylib's CMake project (for example tests) need to find include/mylib.h from the mylib source tree
- clients of mylib built in their own projects (like myexe) need to find include/mylib.h at its installed location
CMake allows us to specify both include paths for mylib:
target_include_directories(mylib PUBLIC
$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
$<INSTALL_INTERFACE:include>)
We're using the PUBLIC option here since this header is needed on the public interface of mylib. Use PRIVATE for include paths internal to mylib.
The INSTALL_INTERFACE specifies a path relative to the install root, that is, CMAKE_INSTALL_PREFIX. To actually install the public header:
install(FILES include/mylib.h DESTINATION include)
We also need to install the library itself and the so-called config-module and related files. The config-module is the file which will be used by consuming projects, like myapp to find mylib and get all the parameters needed to link with it. It is similar to the pkg-config's .pc files.
We need two, related install commands. The first one:
install(TARGETS mylib
EXPORT mylib-targets
ARCHIVE DESTINATION lib
LIBRARY DESTINATION lib
RUNTIME DESTINATION bin)
The list of destinations needed to cover all the standard install locations of static libraries, dll's and so's. If you're sure your library will be built exclusively as a static lib, a single DESTINATION lib would make it.
The interesting part is the EXPORT option. It assigns the list of targets (currently, it's only mylib) to the identifier mylib-targets. This identifier will be used in the next command to generate and install some special files which make find_package(mylib) work in the consuming projects:
install(EXPORT mylib-targets
FILE mylib-config.cmake
DESTINATION lib/cmake/mylib)
This command generates multiple files:
- one file for each build configuration (Debug, Release, etc..) which describes the library file and configuration-dependent parameters
- a file which describes the configuration-agnostic parameters and also includes all the config-dependent files. Since this file can also be used as a config-module on its own we simply rename it as mylib-config.cmake
The files will be installed into ${CMAKE_INSTALL_PREFIX}/lib/cmake/mylib which is one of the many standard locations the find_package(mylib) command will search for mylib-config.cmake.
Building mylib
We need to specify an install location in the variable CMAKE_INSTALL_PREFIX:
mkdir build cd build cmake -DCMAKE_INSTALL_PREFIX=$PWD/../out ../mylib
and build and install the library:
cmake --build . --target install
Building myexe
myexe needs to know where to look for mylib. The variable CMAKE_PREFIX_PATH can be a list of paths. We need to specify the previous install location:
mkdir build cd build cmake -DCMAKE_PREFIX_PATH=$PWD/../out ../mylib cmake --build .
A note on building multiple configurations
Usually we need to build multiple configurations (Debug, Release). A critical issue is to specify configuration-dependent filenames or install locations. For example, you can set the default value of the DEBUG_POSTFIX property for the library project:
set(CMAKE_DEBUG_POSTFIX d)
The debug version of the mylib library file will be named libmylibd.lib (or mylibd.lib on Windows). The generated EXPORT files will contain the modified filenames.
If you're using makefile-style CMake generators you can control the build configuration by setting the CMAKE_BUILD_TYPE variable:
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$PWD/../out ../mylib cmake --build . --target install
You may need seperate build directories for each configuration or you can re-use the same build dir. In that case, to play it safe it's best to explicitly clean before build:
cmake --build . --target install --clean-first
If you're using a multiconfig IDE generator, like Xcode or Visual Studio, you need to specify the configuration in build time:
cmake -DCMAKE_INSTALL_PREFIX=$PWD/../out ../mylib cmake --build . --target install --config Release
References
You can clone and build this repository which contains the mylib and myexe projects (tested on Windows and Linux).
Check out the CMake documentation. The most important related commands are:
- add_library
- target_link_libraries
- find_package
- install
- target_include_directories
- target_compile_definitions
and two detailed articles:
这篇关于如何使用CMake查找和链接到库使用install-export和find_package？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！