cmake:msvc分别对不同的target使用不同的运行库选项(/MT或/MD)

今天药忘吃喽~ 2022-05-27 10:40 182阅读 0赞

很久以前写过一篇关于cmake下为msvc设置`/MT`的文章：

> [cmake:msvc编译第三方库时使用/MT静态库连接c/c++ runtime library][cmake_msvc_MT_c_c_ runtime library]

当时是为了解决用msvc编译时使用`/MT`连接static c library的问题。`CMakeLists.txt`中添加如下的代码，即可以将所有默认的C,CXX编译选项中的`/MD`替换成`/MT`.

if(MSVC)     
        # Use the static C library for all build types
        foreach(var 
            CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_RELEASE
            CMAKE_C_FLAGS_MINSIZEREL CMAKE_C_FLAGS_RELWITHDEBINFO
            CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
            CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO
          )
          if(${var} MATCHES "/MD")
            # 正则表达式替换/MD为/MT
            string(REGEX REPLACE "/MD" "/MT" ${var} "${${var}}")
          endif()
        endforeach()    
    endif(MSVC)

如果你希望`CMakeLists.txt`中所有的target都使用c/c++静态库，那么上面的做法就完全满足需要。  
但如果希望针对`CMakeLists.txt`中的不同target使用不同的`/MT`或`/MD`选项，这个办法就不行了。如果希望针对特定的target设置`/MT`选项，该怎么办呢？

这里就用到了[`target_compile_options`][target_compile_options]命令还用到了[`Generator expressions`][Generator expressions],以下为封装成function的实现代码

# Use the static C library for all build types to a target
    # MSVC编译时对指定的target设置'/MT'选项连接static c/c++ library
    function (with_mt_if_msvc target )
    if(MSVC) 
      # Generator expressions
      set(_mt "/MT$<$<CONFIG:Debug>:d")
      get_target_property(_options ${target} COMPILE_OPTIONS)
      if(_options)
        # message(STATUS "${target} COMPILE_OPTIONS=${_options}")
        if(${_options} MATCHES "/MD")
          string(REGEX REPLACE "/MD" "/MT" _options "${_options}")
        else()
          set(_options "${_options} ${_mt}")
        endif()    
      else()
        set(_options "${_mt}")
      endif() 
      get_target_property(_type ${target} TYPE)
      # 判断 ${target}是否为静态库
      if(_type STREQUAL "STATIC_LIBRARY")
        # 静态库将/MT选项加入INTERFACE_COMPILE_OPTIONS
        target_compile_options( ${target} PUBLIC "${_options}")
      else()
        target_compile_options( ${target} PRIVATE "${_options}")
      endif()
      # Cleanup temporary variables.
      unset(_mt)
      unset(_options)
      message(STATUS "target ${target} use static runtime /MT")
    endif(MSVC)
    endfunction()

有了这个`with_mt_if_msvc`函数，你可以针对target设置`/MT`选项，而那些没有指定的target仍使用默认的`/MD`选项

# 参考资料 #

[Is it possible, in the same CMakeLists.txt, to setup projects with /MT and others with /MD?][Is it possible_ in the same CMakeLists.txt_ to setup projects with _MT and others with _MD]  
[target\_compile\_options][target_compile_options]  
[cmake-generator-expressions][Generator expressions]

[cmake_msvc_MT_c_c_ runtime library]: https://blog.csdn.net/10km/article/details/73750410
[target_compile_options]: https://cmake.org/cmake/help/v3.1/command/target_compile_options.html
[Generator expressions]: https://cmake.org/cmake/help/v3.1/manual/cmake-generator-expressions.7.html
[Is it possible_ in the same CMakeLists.txt_ to setup projects with _MT and others with _MD]: http://www.it1352.com/516702.html