CMake：什么用途是find_package（）如果你需要指定CMAKE_MODULE_PATH无论如何？ [英] CMake: Of what use is find_package() if you need to specify CMAKE_MODULE_PATH anyway?

问题描述

我正在尝试使用CMake工作的跨平台构建系统。现在软件有一些依赖。

安装了一些示例文件：

   - 安装：/ usr / local / share / SomeLib / SomeDir / somefile 
  - 安装：/ usr / local / share / SomeLib / SomeDir / someotherfile 
  - 安装：/ usr / local / lib / SomeLib / somesharedlibrary 
  - 安装：/usr/local/lib/SomeLib/cmake/FindSomeLib.cmake 
  - 安装：/ usr / local / lib / SomeLib / cmake / HelperFile.cmake 
  

现在CMake有一个 find_package c $ c>，它会打开一个 Find * .cmake 文件并在系统上的库之后搜索，并定义一些变量，例如 SomeLib_FOUND 等。

我的CMakeLists.txt包含如下内容：

  set（CMAKE_MODULE_PATH/ usr / local / lib / SomeLib / cmake /; $ {CMAKE_MODULE_PATH}）
 find_package（SomeLib REQUIRED）
  

第一个命令定义了CMake在 Find * .cmake 之后搜索的位置，并添加了 SomeLib 其中可以找到 FindSomeLib.cmake ，因此 find_package（）工作$ b

但这很奇怪，因为 find_package（）存在的原因之一是以避开非跨平台硬编码路径。

这通常是如何做的？应该将 SomeLib 的 cmake / 目录复制到我的项目中，并设置 CMAKE_MODULE_PATH 相对？

解决方案

命令 find_package ：模块模式和配置模式。您实际需要配置模式时，尝试
使用模块模式。

模块模式

查找位于的< package> .cmake 在之内。像这样：

  CMakeLists.txt 
 cmake / FindFoo.cmake 
 cmake / FindBoo.cmake 
  

CMakeLists.txt 内容：

 列表（APPEND CMAKE_MODULE_PATH$ {CMAKE_CURRENT_LIST_DIR} / cmake）
 find_package（Foo REQUIRED）＃FOO_INCLUDE_DIR，FOO_LIBRARIES 
 find_package（Boo REQUIRED）＃BOO_INCLUDE_DIR，BOO_LIBRARIES 
 
 include_directories（$ {FOO_INCLUDE_DIR}）
 include_directories（$ {BOO_INCLUDE_DIR}）
 add_executable（Bar Bar.hpp Bar .cpp）
 target_link_libraries（Bar $ {FOO_LIBRARIES} $ {BOO_LIBRARIES}）
  

CMAKE_MODULE_PATH 具有高优先级，并且当您需要重写标准查找< package> .cmake 文件时， p>

配置模式（安装）

< package> Config.cmake $ <$ c> c $ <$ c> $ <$ c> $ c>）。

foo

 > cat CMakeLists.txt 
 cmake_minimum_required（VERSION 2.8）
 project（Foo）
 
 add_library（foo Foo.hpp Foo.cpp）
 install（FILES Foo.hpp DESTINATION include）
 install（TARGETS foo DESTINATION lib）
 install（FILES FooConfig.cmake DESTINATION lib / cmake / Foo）
  

配置文件的简化版本：

 > cat FooConfig.cmake 
 add_library（foo STATIC IMPORTED）
 find_library（FOO_LIBRARY_PATH foo HINTS$ {CMAKE_CURRENT_LIST_DIR} /../../）
 set_target_properties（foo PROPERTIES IMPORTED_LOCATION$ {FOO_LIBRARY_PATH }）
  

默认情况下，项目安装在 CMAKE_INSTALL_PREFIX 目录：

 > cmake -H。 -B_builds 
> cmake --build _builds --target install 
  - 安装配置：
  - 安装：/usr/local/include/Foo.hpp 
  - 安装：/ usr / local /lib/libfoo.a 
  - 安装：/usr/local/lib/cmake/Foo/FooConfig.cmake 
  

配置模式（使用）

使用 find_package（... CONFIG） FooConfig.cmake 与导入目标 foo ：

 > cat CMakeLists.txt 
 cmake_minimum_required（VERSION 2.8）
 project（Boo）
 
＃import library target`foo` 
 find_package（Foo CONFIG REQUIRED）
 
 add_executable（boo Boo.cpp Boo.hpp）
 target_link_libraries（boo foo）
> cmake -H。 -B_builds -DCMAKE_VERBOSE_MAKEFILE = ON 
> cmake --build _builds 
链接CXX可执行文件Boo 
 / usr / bin / c ++ ... -o Boo /usr/local/lib/libfoo.a 
  

请注意，导入的目标是高度可配置的。请参阅我的回答。

更新

• 示例
• 
  

I'm trying to get a cross-plattform build system working using CMake. Now the software has a few dependencies. I compiled them myself and installed them on my system.

Some example files which got installed:

-- Installing: /usr/local/share/SomeLib/SomeDir/somefile
-- Installing: /usr/local/share/SomeLib/SomeDir/someotherfile
-- Installing: /usr/local/lib/SomeLib/somesharedlibrary
-- Installing: /usr/local/lib/SomeLib/cmake/FindSomeLib.cmake
-- Installing: /usr/local/lib/SomeLib/cmake/HelperFile.cmake

Now CMake has a find_package() which opens a Find*.cmake file and searches after the library on the system and defines some variables like SomeLib_FOUND etc.

My CMakeLists.txt contains something like this:

set(CMAKE_MODULE_PATH "/usr/local/lib/SomeLib/cmake/;${CMAKE_MODULE_PATH}")
find_package(SomeLib REQUIRED)

The first command defines where CMake searches after the Find*.cmake and I added the directory of SomeLib where the FindSomeLib.cmake can be found, so find_package() works as expected.

But this is kind of weird because one of the reasons why find_package() exists is to get away from non-cross-plattform hard coded paths.

How is this usually done? Should I copy the cmake/ directory of SomeLib into my project and set the CMAKE_MODULE_PATH relatively?

解决方案

Command find_package has two modes: Module mode and Config mode. You are trying to use Module mode when you actually need Config mode.

Module mode

Find<package>.cmake file located within your project. Something like this:

CMakeLists.txt
cmake/FindFoo.cmake
cmake/FindBoo.cmake

CMakeLists.txt content:

list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake")
find_package(Foo REQUIRED) # FOO_INCLUDE_DIR, FOO_LIBRARIES
find_package(Boo REQUIRED) # BOO_INCLUDE_DIR, BOO_LIBRARIES

include_directories("${FOO_INCLUDE_DIR}")
include_directories("${BOO_INCLUDE_DIR}")
add_executable(Bar Bar.hpp Bar.cpp)
target_link_libraries(Bar ${FOO_LIBRARIES} ${BOO_LIBRARIES})

Note that CMAKE_MODULE_PATH has high priority and may be usefull when you need to rewrite standard Find<package>.cmake file.

Config mode (install)

<package>Config.cmake file located outside and produced by install command of other project (Foo for example).

foo library:

> cat CMakeLists.txt 
cmake_minimum_required(VERSION 2.8)
project(Foo)

add_library(foo Foo.hpp Foo.cpp)
install(FILES Foo.hpp DESTINATION include)
install(TARGETS foo DESTINATION lib)
install(FILES FooConfig.cmake DESTINATION lib/cmake/Foo)

Simplified version of config file:

> cat FooConfig.cmake 
add_library(foo STATIC IMPORTED)
find_library(FOO_LIBRARY_PATH foo HINTS "${CMAKE_CURRENT_LIST_DIR}/../../")
set_target_properties(foo PROPERTIES IMPORTED_LOCATION "${FOO_LIBRARY_PATH}")

By default project installed in CMAKE_INSTALL_PREFIX directory:

> cmake -H. -B_builds
> cmake --build _builds --target install
-- Install configuration: ""
-- Installing: /usr/local/include/Foo.hpp
-- Installing: /usr/local/lib/libfoo.a
-- Installing: /usr/local/lib/cmake/Foo/FooConfig.cmake

Config mode (use)

Use find_package(... CONFIG) to include FooConfig.cmake with imported target foo:

> cat CMakeLists.txt 
cmake_minimum_required(VERSION 2.8)
project(Boo)

# import library target `foo`
find_package(Foo CONFIG REQUIRED)

add_executable(boo Boo.cpp Boo.hpp)
target_link_libraries(boo foo)
> cmake -H. -B_builds -DCMAKE_VERBOSE_MAKEFILE=ON
> cmake --build _builds
Linking CXX executable Boo
/usr/bin/c++ ... -o Boo /usr/local/lib/libfoo.a

Note that imported target is highly configurable. See my answer.

Update

• Example

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