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CMake语法入门篇

article 2024/9/27 5:56:59

一、CMake是什么？

1. CMake, make, CMakeLists.txt, CMakeFiles的关系

make：make是一个构建工具，用于根据makefile规则自动化构建项目。它读取一个名为makefile的文件，其中包含用于编译和链接项目的规则和依赖关系。使用make命令，可以基于makefile文件对项目进行编译、链接和执行操作，以及管理代码库中的依赖关系。
CMake：CMake是一个跨平台的构建工具，用于自动生成用于不同编译系统的构建脚本（例如makefile或Visual Studio项目文件）。它提供了一种简化跨平台构建过程的方法，使开发人员能够在各种操作系统和编译器上进行开发和构建。
CMakeLists.txt：CMakeLists.txt是CMake的输入文件，它用于描述如何构建项目。这个文件通常位于项目的根目录中，并指定了要执行的操作、要构建的源文件、依赖项和其他与构建相关的设置。CMake会读取CMakeLists.txt文件，并生成适用于特定构建系统（如makefile）的构建规则。
CMakeFiles：CMake生成的构建系统文件（如makefile）的输出目录通常被称为CMakeFiles目录。这个目录包含了CMake生成的用于构建项目的文件，包括编译命令、链接命令和其他与构建相关的文件。

CMake官方地址：https://cmake.org/cmake/help/latest/index.html

二、快速入门

简单示例

# 设置CMake的最低版本
cmake_minimum_required(VERSION 3.17)

# 强依赖 C++11
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_EXTENSIONS OFF)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

# 项目信息
project(test_logger)
set(PROJECT_SOURCE_DIR "../../")

# 设置编译选项
set(CMAKE_BUILD_TYPE "Debug")
set(CMAKE_CXX_FLAGS_DEBUG "$ENV{CXXFLAGS} -O0 -Wall -g")
set(CMAKE_CXX_FLAGS_RELEASE "$ENV{CXXFLAGS} -O3 -Wall -g")

# 导入文件
include_directories("${PROJECT_SOURCE_DIR}/src/")
include_directories("${PROJECT_SOURCE_DIR}/include/")
aux_source_directory("${PROJECT_SOURCE_DIR}/src/" SRC_LIST)

# 生成可执行文件
add_executable(test_logger test_logger.cpp ${SRC_LIST})

# 添加依赖库
target_link_libraries(test_logger pthread)

三、Cmake语法篇

官方地址：https://cmake.org/cmake/help/latest/manual/cmake-commands.7.html

1. 常用宏变量

PROJECT_SOURCE_DIR			# 工程的根目录
PROJECT_BINARY_DIR			# 运行cmake命令的目录，通常为${PROJECT_SOURCE_DIR}/build
PROJECT_NAME				# 返回通过 project 命令定义的项目名称
CMAKE_CURRENT_SOURCE_DIR	# 当前处理的 CMakeLists.txt 所在的路径
CMAKE_CURRENT_BINARY_DIR	# target 编译目录
CMAKE_CURRENT_LIST_DIR		# CMakeLists.txt 的完整路径
EXECUTABLE_OUTPUT_PATH		# 目标二进制可执行文件的存放位置
LIBRARY_OUTPUT_PATH			# 目标链接库文件的存放位置

2. 脚本命令

2.1 注释

# 这是一个注释

#[[  这里面是多行注释  ]]

2.2 变量

Setting
  set(VARIABLE_NAME value)
  
Reading
  set(SOURCE_FILES main.cpp)
  message("Source files: ${SOURCE_FILES}")  # 输出：Source files: main.cpp
  
Unset
# Unset a variable, cache variable, or environment variable.
unset(<variable> [CACHE | PARENT_SCOPE])

2.3 列表

Reading
  list(LENGTH <list> <out-var>)
  list(GET <list> <element index> [<index> ...] <out-var>)
  list(JOIN <list> <glue> <out-var>)
  list(SUBLIST <list> <begin> <length> <out-var>)

Search
  list(FIND <list> <value> <out-var>)

Modification
  list(APPEND <list> [<element>...])
  list(FILTER <list> {INCLUDE | EXCLUDE} REGEX <regex>)
  list(INSERT <list> <index> [<element>...])
  list(POP_BACK <list> [<out-var>...])
  list(POP_FRONT <list> [<out-var>...])
  list(PREPEND <list> [<element>...])
  list(REMOVE_ITEM <list> <value>...)
  list(REMOVE_AT <list> <index>...)
  list(REMOVE_DUPLICATES <list>)
  list(TRANSFORM <list> <ACTION> [...])

Ordering
  list(REVERSE <list>)
  list(SORT <list> [...])

2.4 条件语句

if(CONDITION)
  # ...
elseif(OTHER_CONDITION)
  # ...
else()
  # ...
endif()

2.5 循环语句

foreach(item IN LISTS some_list)
  # ...
endforeach()

2.6 函数

function(FUNCTION_NAME arg1 arg2)
  # ...
endfunction()

2.7 宏

macro(<name> [<arg1> ...])
  #...
endmacro()

2.8 依赖版本

cmake_minimum_required(VERSION <min>[...<policy_max>] [FATAL_ERROR])

2.9 导入

include(<file|module> [OPTIONAL] [RESULT_VARIABLE <var>] [NO_POLICY_SCOPE])
include_guard([DIRECTORY|GLOBAL])

3. 项目命令

2.1 项目信息

# Set the name of the project.
project(<PROJECT-NAME> [<language-name>...])
project(<PROJECT-NAME>
        [VERSION <major>[.<minor>[.<patch>[.<tweak>]]]]
        [DESCRIPTION <project-description-string>]
        [HOMEPAGE_URL <url-string>]
        [LANGUAGES <language-name>...])
# Sets the name of the project, and stores it in the variable PROJECT_NAME. When called from the top-level CMakeLists.txt also stores the project name in the variable CMAKE_PROJECT_NAME.

2.2 宏定义

# 全局添加宏定义：Add -D define flags to the compilation of source files.
add_definitions(-DFOO -DBAR ...)

# 当前make文件添加宏定义：Add preprocessor definitions to the compilation of source files.
add_compile_definitions(<definition> ...)

# 移除宏定义：Remove -D define flags added by add_definitions().
remove_definitions(-DFOO -DBAR ...)

2.3 添加编译选项

# Add options to the compilation of source files.
add_compile_options(<option> ...)
示例：
add_compile_options(-Wall -Wextra -Wpedantic)

2.4 添加子目录

# Add a subdirectory to the build.
add_subdirectory(source_dir [binary_dir] [EXCLUDE_FROM_ALL] [SYSTEM])

2.5 添加头文件目录

# Add include directories to the build.
include_directories([AFTER|BEFORE] [SYSTEM] dir1 [dir2 ...])

2.6 遍历源文件，并保存到列表

# Find all source files in a directory.
aux_source_directory(<dir> <variable>)
# Collects the names of all the source files in the specified directory and stores the list in the <variable> provided

2.7 生成库

# Add a library to the project using the specified source files.
add_library(<name> [STATIC | SHARED | MODULE]
            [EXCLUDE_FROM_ALL]
            [<source>...])

2.8 生成可执行文件

# Add an executable to the project using the specified source files.
add_executable(<name> [WIN32] [MACOSX_BUNDLE]
               [EXCLUDE_FROM_ALL]
               [source1] [source2 ...])

2.9 添加链接库

# Specify libraries or flags to use when linking a given target and/or its dependents.
target_link_libraries(<target> ... <item>... ...)

2.10 添加链接库的目录

# Add link directories to a target.
target_link_directories(<target> [BEFORE]
  <INTERFACE|PUBLIC|PRIVATE> [items1...]
  [<INTERFACE|PUBLIC|PRIVATE> [items2...] ...])
# Specifies the paths in which the linker should search for libraries when linking a given target.

2.11 安装规则

# Specify rules to run at install time.
install(TARGETS <target>... [...])
install(IMPORTED_RUNTIME_ARTIFACTS <target>... [...])
install({FILES | PROGRAMS} <file>... [...])
install(DIRECTORY <dir>... [...])
install(SCRIPT <file> [...])
install(CODE <code> [...])
install(EXPORT <export-name> [...])
install(RUNTIME_DEPENDENCY_SET <set-name> [...])
# This command generates installation rules for a project. Install rules specified by calls to the install() command within a source directory are executed in order during installation.

2.12 字符串处理

Search and Replace
  string(FIND <string> <substring> <out-var> [...])
  string(REPLACE <match-string> <replace-string> <out-var> <input>...)
  string(REGEX MATCH <match-regex> <out-var> <input>...)
  string(REGEX MATCHALL <match-regex> <out-var> <input>...)
  string(REGEX REPLACE <match-regex> <replace-expr> <out-var> <input>...)

Manipulation
  string(APPEND <string-var> [<input>...])
  string(PREPEND <string-var> [<input>...])
  string(CONCAT <out-var> [<input>...])
  string(JOIN <glue> <out-var> [<input>...])
  string(TOLOWER <string> <out-var>)
  string(TOUPPER <string> <out-var>)
  string(LENGTH <string> <out-var>)
  string(SUBSTRING <string> <begin> <length> <out-var>)
  string(STRIP <string> <out-var>)
  string(GENEX_STRIP <string> <out-var>)
  string(REPEAT <string> <count> <out-var>)

Comparison
  string(COMPARE <op> <string1> <string2> <out-var>)

Hashing
  string(<HASH> <out-var> <input>)

Generation
  string(ASCII <number>... <out-var>)
  string(HEX <string> <out-var>)
  string(CONFIGURE <string> <out-var> [...])
  string(MAKE_C_IDENTIFIER <string> <out-var>)
  string(RANDOM [<option>...] <out-var>)
  string(TIMESTAMP <out-var> [<format string>] [UTC])
  string(UUID <out-var> ...)

JSON
  string(JSON <out-var> [ERROR_VARIABLE <error-var>]
         {GET | TYPE | LENGTH | REMOVE}
         <json-string> <member|index> [<member|index> ...])
  string(JSON <out-var> [ERROR_VARIABLE <error-var>]
         MEMBER <json-string>
         [<member|index> ...] <index>)
  string(JSON <out-var> [ERROR_VARIABLE <error-var>]
         SET <json-string>
         <member|index> [<member|index> ...] <value>)
  string(JSON <out-var> [ERROR_VARIABLE <error-var>]
         EQUAL <json-string1> <json-string2>)