编写CMakeLists.txt

 

#在当前目录新建一个build目录，然后cd build；cmake ..

#这样的好处是，可以将cmake生成的内容，和源码文件分离

 

#设置编译结果发布路径

set( CMAKE_INSTALL_PREFIX ./_install)

#配置一个头文件，可以让一些cmake设置传到源码里，比如可以传版本号，传宏定义等等

configure_file ( "${PROJECT_SOURCE_DIR}/TutorialConfig.h.in"
"${PROJECT_BINARY_DIR}/TutorialConfig.h" )

#将可执行文件与其源码关联起来

add_executable(Tutorial tutorial.c)

#如果是很多源码，可以写一个变量，先把源码文件收集起来,比如下面这样，

set(SRC_FILES avl.c rb.c splay.c)
add_executable(Tutorial ${SRC_FILES})

#增加库文件

add_library(MathFunctions mysqrt.cxx)

#增加动态库，SRC_TREE_FILES是实现定义好的源码文件列表

add_library(tree SHARED ${SRC_TREE_FILES})

#增加静态库

add_library(tree_static STATIC ${SRC_TREE_FILES})

#将库文件和可执行文件链接起来

target_link_libraries (Tutorial MathFunctions)

#如何连接系统库，但是必须在add_executable之前加才有效

LINK_LIBRARIES(-lpthread -lm)

#验证系统是否提供某些函数

# does this system provide the log and exp functions?

include (CheckFunctionExists)
check_function_exists (log HAVE_LOG)
check_function_exists (exp HAVE_EXP)

#也还需要在配置文件TutorialConfig.h中增加，这样源码中就能用这个宏定义来确定函数是否支持

#cmakedefine HAVE_LOG
#cmakedefine HAVE_EXP

#可以增加头文件搜索路径

include_directories ("${PROJECT_BINARY_DIR}")

#或者为某一个目标添加

target_include_directories(os_demo PRIVATE ${CMAKE_SOURCE_DIR} ${CMAKE_SOURCE_DIR}/inc )

#如何添加编译选项； 设置编译选项可以通过add_compile_options命令，也可以通过set命令修改CMAKE_CXX_FLAGS或CMAKE_C_FLAGS

SET(CMAKE_C_FLAGS "-O3 -ffast-math -Wall -std=gnu99 -fPIC")

#疑问？

${CMAKE_CURRENT_BINARY_DIR}，${PROJECT_SOURCE_DIR}，${PROJECT_BINARY_DIR}在哪定义的

#通过打印显示；CMAKE_CURRENT_BINARY_DIR，PROJECT_BINARY_DIR是当前目录，PROJECT_SOURCE_DIR是CMakeLists.txt所在目录。

-- This is the engine CMAKE_CURRENT_BINARY_DIR: /home/xxxx/engine/build.tx1
-- This is the engine PROJECT_SOURCE_DIR: /home/xxxx/engine
-- This is the engine PROJECT_BINARY_DIR: /home/xxxx/build.tx1

#如何方便的进行交叉编译？一般要用到CMAKE_TOOLCHAIN_FILE

cmake .. -DCMAKE_TOOLCHAIN_FILE=../tx1.toolchain.cmake

#下面是一个简单的toolchain.cmake例子

# this is required
SET(CMAKE_SYSTEM_NAME Linux)
 
# specify the cross compiler
SET(CMAKE_C_COMPILER   /opt/nvidia/gcc-linaro-5.3.1-2016.05-x86_64_aarch64-linux-gnu//bin/aarch64-linux-gnu-gcc)
SET(CMAKE_CXX_COMPILER /opt/nvidia/gcc-linaro-5.3.1-2016.05-x86_64_aarch64-linux-gnu//bin/aarch64-linux-gnu-g++)
 
# where is the target environment
SET(CMAKE_FIND_ROOT_PATH /opt/nvidia/gcc-linaro-5.3.1-2016.05-x86_64_aarch64-linux-gnu/aarch64-linux-gnu/include/c++/5.3.1)
 
# search for programs in the build host directories (not necessary)
SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
# for libraries and headers in the target directories
SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)