本文首发于微信公众号「3Ｄ视觉工坊」——ＣMakeLists.txt文件如何写？

本文以linux平台下CMakeLists.txt文件书写方法总结。

一 开头通用模块

1.1 cmake版本要求

cmake_minimum_required( VERSION 2.8 )

#工程文件名loop_closure,可任取

project( loop_closure )

#工程文件名loop_closure,可任取

project( loop_closure )

1.2 编译模式

IF(NOT CMAKE_BUILD_TYPE)
  SET(CMAKE_BUILD_TYPE Release)
ENDIF()
MESSAGE("Build type: " ${CMAKE_BUILD_TYPE})

当然如果此处在前面加上语句：

set(**CMAKE_BUILD_TYPE**** debug**)

即表示设置为debug模式编译。

1.3 检查C++版本

检查C++的版本

    # Check C++11 or C++0x support
    include(CheckCXXCompilerFlag)
    CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
    CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
    if(COMPILER_SUPPORTS_CXX11)
       set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
       add_definitions(-DCOMPILEDWITHC11)
       message(STATUS "Using flag -std=c++11.")
    elseif(COMPILER_SUPPORTS_CXX0X)
       set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
       add_definitions(-DCOMPILEDWITHC0X)
       message(STATUS "Using flag -std=c++0x.")
    else()
       message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
    endif()

二 项目文件配置模块

接下来，便开始配置各个库模块。

2.1 如果仅包含OpenCV库时

set(OpenCV_DIR "/usr/local/include/opencv3.2.0/share/OpenCV")
find_package(OpenCV REQUIRED)

include_directories( ${OpenCV_INCLUDE_DIRS} )


#生成可执行文件

add_executable(${PROJECT_NAME} src/loop_closure.cpp )

target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS})

备注：这里的OpenCV包含目录为含有OpenCVConfig.cmake的路径。

如下图：

2.2 如果包含第三方库，该库为源码形式（.h和.cpp），非动态链接库

此处以在工程中添加词袋库DBoW2为例，这里的DBoW2是以源码形式包含，也即未编译成.so文件。

2.2.1 包含第三库的头文件

#设置.h文件对应的路径

set( DBoW2_INCLUDE_DIRS ${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/include/)

#包含.h文件路径

 include_directories( ${OpenCV_INCLUDE_DIRS}
             ${DBoW2_INCLUDE_DIRS} ${DBoW2_INCLUDE_DIRS}/DBoW2/)
注：上述为啥要用两条路径${　DBoW2_INCLUDE_DIRS}和${DBoW2_INCLUDE_DIRS}/DBoW2/？

为了防止在include层找不到，继续往下一层路径include/DBoW2/路径下查找，这是为了防止某些文件的包含路径不一致导致头文件查找错误。

2.2.2 包含第三方库的cpp文件

set(DBoW2_SRCS "${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/src")
#生成可执行文件
add_executable(${PROJECT_NAME} src/loop_closure.cpp  src/run_main.cpp
        ${DBoW2_SRCS}/BowVector.cpp ${DBoW2_SRCS}/FBrief.cpp ${DBoW2_SRCS}/FeatureVector.cpp
        ${DBoW2_SRCS}/FORB.cpp ${DBoW2_SRCS}/FSurf64.cpp ${DBoW2_SRCS}/QueryResults.cpp ${DBoW2_SRCS}/ScoringObject.cpp)

其中，src/loop_closure.cpp src/run_main.cpp 为本工程中我自己实现的，而对于其他的cpp文件，则直接添加路径即可。

另一种方式，添加cpp文件路径更为简洁方便。

file(GLOB DBoW2_SRCS ${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/src/*.cpp)
add_executable(${PROJECT_NAME} src/loop_closure.cpp  src/run_main.cpp ${DBoW2_SRCS})

2.3 如果包含第三方库，为库形式（此处以静态库为例(.a后缀)）

在上述工程下，同时还包含有DBoW3库，此库已经按默认路径编译安装到计算机内存中。我们可以按如下方式添加DBoW3库。

1）包含头文件

set( DBoW3_INCLUDE_DIRS "/usr/local/include")

2）添加库

set( DBoW3_LIBS "/usr/local/lib/libDBoW3.a")
target_link_libraries(${PROJECT_NAME　}
${OpenCV_LIBS}
${DBoW3_LIBS}
)

通过上述方式，即可调用。

三 一个简单的CMakeLists.txt文件demo

该demo中相较于上述总结添加的库，还额外包含了DLib库。

cmake_minimum_required( VERSION 2.8 )
project( loop_closure )

#set(CMAKE_BUILD_TYPE  Debug)
IF(NOT CMAKE_BUILD_TYPE)
  SET(CMAKE_BUILD_TYPE Release)
ENDIF()

MESSAGE("Build type: " ${CMAKE_BUILD_TYPE})

# Check C++11 or C++0x support
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
if(COMPILER_SUPPORTS_CXX11)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
   add_definitions(-DCOMPILEDWITHC11)
   message(STATUS "Using flag -std=c++11.")
elseif(COMPILER_SUPPORTS_CXX0X)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
   add_definitions(-DCOMPILEDWITHC0X)
   message(STATUS "Using flag -std=c++0x.")
else()
   message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
endif()

#opencv
#set(OpenCV_DIR "/usr/local/include/opencv3.2.0/share/OpenCV")
set(OpenCV_DIR "/opt/ros/kinetic/share/OpenCV-3.3.1-dev")

find_package(OpenCV REQUIRED)

set( DBoW3_INCLUDE_DIRS "/usr/local/include")

set( DBoW2_INCLUDE_DIRS ${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/include/)
message(${DBoW2_INCLUDE_DIRS})

#important
#file(GLOB DBoW2_SRCS ${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/src/*.cpp)
#message(${DBoW2_SRCS})

set(DBoW2_SRCS "${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/src")
message(${DBoW2_SRCS})


find_package(DLib QUIET
        PATHS ${DEPENDENCY_INSTALL_DIR})
if(${DLib_FOUND})
   message("DLib library found, using it from the system")
   include_directories(${DLib_INCLUDE_DIRS})
   add_custom_target(Dependencies)
else(${DLib_FOUND})
   message("DLib library not found in the system, it will be downloaded on build")
   option(DOWNLOAD_DLib_dependency "Download DLib dependency" ON)
   if(${DOWNLOAD_DLib_dependency})
      ExternalProject_Add(DLib
              PREFIX ${DEPENDENCY_DIR}
              GIT_REPOSITORY http://github.com/dorian3d/DLib
              GIT_TAG master
              INSTALL_DIR ${DEPENDENCY_INSTALL_DIR}
              CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>)
      add_custom_target(Dependencies ${CMAKE_COMMAND} ${CMAKE_SOURCE_DIR} DEPENDS DLib)
   else()
      message(SEND_ERROR "Please, activate DOWNLOAD_DLib_dependency option or download manually")
   endif(${DOWNLOAD_DLib_dependency})
endif(${DLib_FOUND})


include_directories( ${OpenCV_INCLUDE_DIRS}
        ${DBoW3_INCLUDE_DIRS} ${DBoW2_INCLUDE_DIRS} ${DBoW2_INCLUDE_DIRS}/DBoW2/)

message("DBoW3_INCLUDE_DIRS ${DBoW3_INCLUDE_DIRS}")
message("DBoW2_INCLUDE_DIRS ${DBoW2_INCLUDE_DIRS}")

message("opencv ${OpenCV_VERSION}")

# dbow3
# dbow3 is a simple lib so I assume you installed it in default directory
set( DBoW3_LIBS "/usr/local/lib/libDBoW3.a")

add_executable(${PROJECT_NAME} src/loop_closure.cpp  src/run_main.cpp
        ${DBoW2_SRCS}/BowVector.cpp ${DBoW2_SRCS}/FBrief.cpp ${DBoW2_SRCS}/FeatureVector.cpp
        ${DBoW2_SRCS}/FORB.cpp ${DBoW2_SRCS}/FSurf64.cpp ${DBoW2_SRCS}/QueryResults.cpp ${DBoW2_SRCS}/ScoringObject.cpp
        )
message(${DBoW2_SRCS}/BowVector.cpp)

target_link_libraries(${PROJECT_NAME}
${OpenCV_LIBS}

${DLib_LIBS}
${DBoW3_LIBS}
)

四 跋

以上仅仅为CMakeLists.txt的一个简单用法梳理，如有不到之处，还请批评指正。对于大型工程的管理，还有很多学问可以挖掘，此处限于篇幅便不再展示，欢迎加入我们的学习圈「3D视觉技术」进一步探讨、交流、学习。

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