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CMake语法—选项（option）

CMake语法—选项（option）
- 1 选项
  - 1.1 定义
  - 1.2 说明
- 2 应用注意事项
  - 2.1 代码结构
  - 2.2 注意事项

CMake语法—选项（option）

1 选项

1.1 定义

option(<variable> "<help_text>" [value])

1.2 说明

variable 选项名
help_text 描述、解释、备注
value 选项初始化值（除ON而外全为OFF）

2 应用注意事项

2.1 代码结构

目录结构

learn_cmake：为根目录
build：为CMake配置输出目录（在此例中即生成sln解决方案的地方）
CMakeLists.txt：CMake脚本

cmake_config.bat：执行CMake配置过程的脚本（双击直接运行）

@echo off
set currentDir=%~dp0
set buildDir=%currentDir%
set cmakeOutputDir=%currentDir%\build
cmake -S %buildDir% -B %cmakeOutputDir% -G"Visual Studio 16 2019" -T v140 -A x64
pause

2.2 注意事项

2.2.1 不初始化或赋为非ON的值，全部视为OFF

示例代码

cmake_minimum_required(VERSION 3.18)

# 设置工程名称
set(PROJECT_NAME KAIZEN)

# 设置工程版本号
set(PROJECT_VERSION "1.0.0.10" CACHE STRING "默认版本号")

# 工程定义
project(${PROJECT_NAME}
    LANGUAGES CXX C
    VERSION ${PROJECT_VERSION}
)

# 打印开始日志
message(STATUS "\n########## BEGIN_TEST_OPTION")

## 示例1：不赋值
option(${PROJECT_NAME}_BUILD_TEST "构建测试模块")

if (DEFINED ${PROJECT_NAME}_BUILD_TEST)
    message(STATUS "defined KAIZEN_BUILD_TEST")
else()
    message(STATUS "not defined KAIZEN_BUILD_TEST")
endif()

if (${PROJECT_NAME}_BUILD_TEST)
    message(STATUS "KAIZEN_BUILD_TEST is ON")
else()
    message(STATUS "KAIZEN_BUILD_TEST is OFF")
endif()
message(STATUS "\n")

## 示例2：赋值为非ON、非OFF值
option(${PROJECT_NAME}_BUILD_EXAMPLE "构建示例模块" AAA)

if (DEFINED ${PROJECT_NAME}_BUILD_EXAMPLE)
    message(STATUS "defined KAIZEN_BUILD_EXAMPLE")
else()
    message(STATUS "not defined KAIZEN_BUILD_EXAMPLE")
endif()

if (${PROJECT_NAME}_BUILD_EXAMPLE)
    message(STATUS "KAIZEN_BUILD_EXAMPLE_1 is ON")
else()
    message(STATUS "KAIZEN_BUILD_EXAMPLE_1 is OFF")
endif()

if (${${PROJECT_NAME}_BUILD_TYPE})
    message(STATUS "KAIZEN_BUILD_EXAMPLE_2 is ON")
else()
    message(STATUS "KAIZEN_BUILD_EXAMPLE_2 is OFF")
endif()
message(STATUS "\n")

## 示例3：赋值为ON
option(${PROJECT_NAME}_BUILD_GUI "构建视图模块" ON)

if (DEFINED ${PROJECT_NAME}_BUILD_GUI)
    message(STATUS "defined KAIZEN_BUILD_GUI")
else()
    message(STATUS "not defined KAIZEN_BUILD_GUI")
endif()

if (${PROJECT_NAME}_BUILD_GUI)
    message(STATUS "KAIZEN_BUILD_GUI is ON")
else()
    message(STATUS "KAIZEN_BUILD_GUI is OFF")
endif()

# 打印结束日志
message(STATUS "########## END_TEST_OPTION\n")

运行结果

-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.17763.
-- The CXX compiler identification is MSVC 19.0.24245.0
-- The C compiler identification is MSVC 19.0.24245.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64/cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
--
########## BEGIN_TEST_OPTION
-- defined KAIZEN_BUILD_TEST
-- KAIZEN_BUILD_TEST is OFF
--

-- defined KAIZEN_BUILD_EXAMPLE
-- KAIZEN_BUILD_EXAMPLE_1 is OFF
-- KAIZEN_BUILD_EXAMPLE_2 is OFF
--

-- defined KAIZEN_BUILD_GUI
-- KAIZEN_BUILD_GUI is ON
-- ########## END_TEST_OPTION

-- Configuring done
-- Generating done
-- Build files have been written to: F:/learn_cmake/build
请按任意键继续. . .

2.2.2 在定义语句执行后才有效；在定义之前均视为未定义（除过在CMake命令中通过-D预定义）

示例代码

cmake_minimum_required(VERSION 3.18)

# 设置工程名称
set(PROJECT_NAME KAIZEN)

# 设置工程版本号
set(PROJECT_VERSION "1.0.0.10" CACHE STRING "默认版本号")

# 工程定义
project(${PROJECT_NAME}
    LANGUAGES CXX C
    VERSION ${PROJECT_VERSION}
)

# 打印开始日志
message(STATUS "\n########## BEGIN_TEST_OPTION")

## 定义之前是看不到的
if (DEFINED ${PROJECT_NAME}_BUILD_TEST)
    message(STATUS "defined KAIZEN_BUILD_TEST")
else()
    message(STATUS "not defined KAIZEN_BUILD_TEST")
endif()

## 定义语句
option(${PROJECT_NAME}_BUILD_TEST "构建测试模块" ON)

## 定义后才可以看到
if (DEFINED ${PROJECT_NAME}_BUILD_TEST)
    message(STATUS "defined KAIZEN_BUILD_TEST")
else()
    message(STATUS "not defined KAIZEN_BUILD_TEST")
endif()

## 定义后再应用
if (${PROJECT_NAME}_BUILD_TEST)
    message(STATUS "KAIZEN_BUILD_TEST is ON")
else()
    message(STATUS "KAIZEN_BUILD_TEST is OFF")
endif()

# 打印结束日志
message(STATUS "########## END_TEST_OPTION\n")

运行结果

-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.17763.
-- The CXX compiler identification is MSVC 19.0.24245.0
-- The C compiler identification is MSVC 19.0.24245.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64/cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
--
########## BEGIN_TEST_OPTION
-- not defined KAIZEN_BUILD_TEST
-- defined KAIZEN_BUILD_TEST
-- KAIZEN_BUILD_TEST is ON
-- ########## END_TEST_OPTION

-- Configuring done
-- Generating done
-- Build files have been written to: F:/learn_cmake/build
请按任意键继续. . .

2.2.3 已定义option选项会存储在CMakeCache.txt中。等价于缓存变量作用。

运行2.2.1中的示例代码，然后可以查看build目录下的CMakeCache.txt文件。如下图：

2.2.4 如果出现同名的变量（普通或缓存变量），则option会被忽略

示例代码

cmake_minimum_required(VERSION 3.18)

# 设置工程名称
set(PROJECT_NAME KAIZEN)

# 设置工程版本号
set(PROJECT_VERSION "1.0.0.10" CACHE STRING "默认版本号")

# 工程定义
project(${PROJECT_NAME}
    LANGUAGES CXX C
    VERSION ${PROJECT_VERSION}
)

# 打印开始日志
message(STATUS "\n########## BEGIN_TEST_OPTION")

## 1.1先定义普通变量
set(${PROJECT_NAME}_BUILD_TEST "构建测试模块")

if (DEFINED ${PROJECT_NAME}_BUILD_TEST)
    message(STATUS "defined KAIZEN_BUILD_TEST")
else()
    message(STATUS "not defined KAIZEN_BUILD_TEST")
endif()

message(STATUS "KAIZEN_BUILD_TEST_1: ${${PROJECT_NAME}_BUILD_TEST}\n")

## 1.2再定义同名option选项
option(${PROJECT_NAME}_BUILD_TEST "构建测试模块" ON)

message(STATUS "KAIZEN_BUILD_TEST_2: ${${PROJECT_NAME}_BUILD_TEST}\n")

### 2.1先定义option选项
option(${PROJECT_NAME}_BUILD_EXAMPLE "构建示例模块" OFF)

if (DEFINED ${PROJECT_NAME}_BUILD_EXAMPLE)
    message(STATUS "defined KAIZEN_BUILD_EXAMPLE")
else()
    message(STATUS "not defined KAIZEN_BUILD_EXAMPLE")
endif()

message(STATUS "KAIZEN_BUILD_EXAMPLE_1: ${KAIZEN_BUILD_EXAMPLE}")

### 2.2再定义普通同名变量
set(${PROJECT_NAME}_BUILD_EXAMPLE "构建示例模块")

message(STATUS "KAIZEN_BUILD_EXAMPLE_2: ${KAIZEN_BUILD_EXAMPLE}")

# 打印结束日志
message(STATUS "########## END_TEST_OPTION\n")

运行结果

-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.17763.
-- The CXX compiler identification is MSVC 19.0.24245.0
-- The C compiler identification is MSVC 19.0.24245.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64/cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
--
########## BEGIN_TEST_OPTION
-- defined KAIZEN_BUILD_TEST
-- KAIZEN_BUILD_TEST_1: 构建测试模块

-- KAIZEN_BUILD_TEST_2: 构建测试模块

-- defined KAIZEN_BUILD_EXAMPLE
-- KAIZEN_BUILD_EXAMPLE_1: OFF
-- KAIZEN_BUILD_EXAMPLE_2: 构建示例模块
-- ########## END_TEST_OPTION

-- Configuring done
-- Generating done
-- Build files have been written to: F:/learn_cmake/build
请按任意键继续. . .

2.2.5 CMake命令中通过-D预设同名变量，则option也会被忽略（其本质与2.2.4相同）

示例代码

cmake_minimum_required(VERSION 3.18)

# 设置工程名称
set(PROJECT_NAME KAIZEN)

# 设置工程版本号
set(PROJECT_VERSION "1.0.0.10" CACHE STRING "默认版本号")

# 工程定义
project(${ PROJECT_NAME }
    LANGUAGES CXX C
    VERSION ${ PROJECT_VERSION }
)

# 打印开始日志
message(STATUS "\n########## BEGIN_TEST_OPTION")

if (DEFINED ${ PROJECT_NAME }_BUILD_EXAMPLE)
    message(STATUS "defined KAIZEN_BUILD_EXAMPLE")
else()
    message(STATUS "not defined KAIZEN_BUILD_EXAMPLE")
endif()

## 定义option选项
option(${ PROJECT_NAME }_BUILD_EXAMPLE "构建示例模块" OFF)

message(STATUS "KAIZEN_BUILD_EXAMPLE: ${KAIZEN_BUILD_EXAMPLE}")

# 打印结束日志
message(STATUS "########## END_TEST_OPTION\n")

cmake_config.bat

@echo off
set currentDir=%~dp0
set buildDir=%currentDir%
set cmakeOutputDir=%currentDir%\build
cmake -S %buildDir% -B %cmakeOutputDir% -G"Visual Studio 16 2019" -T v140 -A x64 -DKAIZEN_BUILD_EXAMPLE=ON
pause

运行结果

--Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.17763.
--The CXX compiler identification is MSVC 19.0.24245.0
--The C compiler identification is MSVC 19.0.24245.0
--Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler : C: / Program Files(x86) / Microsoft Visual Studio 14.0 / VC / bin / amd64 / cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler : C: / Program Files(x86) / Microsoft Visual Studio 14.0 / VC / bin / amd64 / cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
--
########## BEGIN_TEST_OPTION
-- defined KAIZEN_BUILD_EXAMPLE
-- KAIZEN_BUILD_EXAMPLE: ON
-- ########## END_TEST_OPTION

-- Configuring done
-- Generating done
-- Build files have been written to : F: / learn_cmake / build
请按任意键继续. . .

2.2.6 修改option选项值（建议通过缓存变量方式修改）

示例代码

cmake_minimum_required(VERSION 3.18)

# 设置工程名称
set(PROJECT_NAME KAIZEN)

# 设置工程版本号
set(PROJECT_VERSION "1.0.0.10" CACHE STRING "默认版本号")

# 工程定义
project(${ PROJECT_NAME }
    LANGUAGES CXX C
    VERSION ${ PROJECT_VERSION }
)

# 打印开始日志
message(STATUS "\n########## BEGIN_TEST_OPTION")

if (DEFINED ${ PROJECT_NAME }_BUILD_EXAMPLE)
    message(STATUS "defined KAIZEN_BUILD_EXAMPLE")
else()
    message(STATUS "not defined KAIZEN_BUILD_EXAMPLE")
endif()

## 定义option选项
option(${ PROJECT_NAME }_BUILD_EXAMPLE "构建示例模块" OFF)

message(STATUS "KAIZEN_BUILD_EXAMPLE_1: ${KAIZEN_BUILD_EXAMPLE}")

## 方式一：修改option选项值（无效方式，请忽略）
option(${ PROJECT_NAME }_BUILD_EXAMPLE "构建示例模块" ON)

message(STATUS "KAIZEN_BUILD_EXAMPLE_2: ${KAIZEN_BUILD_EXAMPLE}")

## 方式二：通过cache变量方式修改（正确方式，力推荐）
set(${ PROJECT_NAME }_BUILD_EXAMPLE ON CACHE BOOL "构建示例模块" FORCE)

message(STATUS "KAIZEN_BUILD_EXAMPLE_3: ${KAIZEN_BUILD_EXAMPLE}")

# 打印结束日志
message(STATUS "########## END_TEST_OPTION\n")

运行结果

--Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.17763.
--The CXX compiler identification is MSVC 19.0.24245.0
--The C compiler identification is MSVC 19.0.24245.0
--Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler : C: / Program Files(x86) / Microsoft Visual Studio 14.0 / VC / bin / amd64 / cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler : C: / Program Files(x86) / Microsoft Visual Studio 14.0 / VC / bin / amd64 / cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
--
########## BEGIN_TEST_OPTION
-- not defined KAIZEN_BUILD_EXAMPLE
-- KAIZEN_BUILD_EXAMPLE_1: OFF
-- KAIZEN_BUILD_EXAMPLE_2 : OFF
-- KAIZEN_BUILD_EXAMPLE_3 : ON
-- ########## END_TEST_OPTION

-- Configuring done
-- Generating done
-- Build files have been written to : F: / learn_cmake / build
请按任意键继续. . .

当然，也可以通过定义同名普通变量方式进行修改。

但是，通过普通变量方式修改后，CMakeCache.txt中的值仍然为旧值。感兴趣可自行验证。

option选项本质与缓存变量相同，即会存储在CMakeCache.txt中。因此修改其值也推荐使用缓存变量的方式，这样会直接修改CMakeCache.txt中的存储值，更彻底、更本质、更安全。

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原文地址：https://www.cnblogs.com/Braveliu/p/15665143.html