• CMake语法—流程控制（if-foreach-while）
  • 1.流程控制
    • 1.1 代码结构
    • 1.2 示例代码
    • 1.3 运行结果
    • 1.4 小结

CMake语法—流程控制（if-foreach-while）

1.流程控制

1.1 代码结构

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

1.2 示例代码

1. 示例代码（CMakeLists.txt文件内容）

   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_PROCESS_CONTROL")
   
   # if example
   set(var_3 "camke")
   
   if (DEFINED var_1)
       message("defined var_1")
   elseif (DEFINED var_2)
       message("defined var_2")
   elseif (DEFINED var_3)
       message("defined var_3")
   else()
       message("defined nothing")
   endif()
   
   # endif
   
   ## foreach example
   
   set(var_list "C++" "JAVA" Python "CMake" 1024)
   
   foreach(item ${var_list})
        message("当前变量是：${item}")
   endforeach()
   
   set(result 0)
   set(end 0)
   
   foreach(element RANGE 0 100)
       math(EXPR result "${result} + ${element}")
       if (result LESS 100)
           continue()   ## continue
       endif()
       if (result GREATER 1000)
           set(end ${element})
           break()    ## break
       endif()
   endforeach()
   
   message("from 0 plus to ${end} is : ${result}")
   
   ## endforeach
   
   ### while example
   
   set(var_max 5)
   
   while(${var_max} GREATER 0)
       message(${var_max})
       math(EXPR var_max "${var_max} - 1")
   endwhile()
   
   ### endwhile
   
   # 打印结束日志
   message(STATUS "########## END_TEST_PROCESS_CONTROL\n")
   
   

2. 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
   pause
   

1.3 运行结果

1. 本地环境

   本地安装VS版本：Visual Studio 2019（2015工具集）

   CMake版本：3.18.2

   F:\learn_cmake
   λ cmake --version
   cmake version 3.18.2
    
   CMake suite maintained and supported by Kitware (kitware.com/cmake).
   

2. 输出结果

   -- 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_PROCESS_CONTROL
   defined var_3
   当前变量是：C++
   当前变量是：JAVA
   当前变量是：Python
   当前变量是：CMake
   当前变量是：1024
   from 0 plus to 45 is : 1035
   5
   4
   3
   2
   1
   -- ########## END_TEST_PROCESS_CONTROL
   
   -- Configuring done
   -- Generating done
   -- Build files have been written to: F:/learn_cmake/build
   请按任意键继续. . .
   

1.4 小结

1. if 概要

   if(<condition>)
       <commands>
   elseif(<condition>) # optional block, can be repeated
       <commands>
   else()              # optional block
       <commands>
   endif()
   

   具体可参考最钟情官方文档：https://cmake.org/cmake/help/latest/command/if.html

2. foreach 概要

   foreach(<loop_var> <items>)
       <commands>
   endforeach()
   

   具体可参考最钟情官方文档：https://cmake.org/cmake/help/latest/command/foreach.html

3. while 概要

   while(<condition>)
       <commands>
   endwhile()
   

   具体看参考最钟情官方文档：https://cmake.org/cmake/help/latest/command/while.html