在cmake中检测编译器的架构

这个项目的大部分场景都是嵌入式的，重建后用了很多c 新特性，但原产品系统版本较低，涉及一些移植问题。今天遇到了一个情况:公司arm框架下的产品系统不需要移植c库，但在x系统c库在86架构下的版本太低，需要移植c库。 我想到的计划是通过的cmake检测当前使用的编译器架构，然后通过条件编译指定dynamic-linker以及rpath，但是找不到资料cmake有提供相关的功能可以满足我的需求，最后github找到解决这个问题的方法。

将TargetArch.cmake在工程中cmake需要编译条件的文件夹CMakeLists.txt中include它可以调用TargetArch.cmake 中的target_architecture 函数获取编译器的架构，返回结果是调用target_architecture 时间填写的参数。 TargetArch.cmake ：

# Based on the Qt 5 processor detection code, so should be very accurate # https://qt.gitorious.org/qt/qtbase/blobs/master/src/corelib/global/qprocessordetection.h # Currently handles arm (v5, v6, v7), x86 (32/64), ia64, and ppc (32/64)  # Regarding POWER/PowerPC, just as is noted in the Qt source, # "There are many more known variants/revisions that we do not handle/detect."  set(archdetect_c_code " #if defined(__arm__) || defined(__TARGET_ARCH_ARM)     #if defined(__ARM_ARCH_7__) \\         || defined(__ARM_ARCH_7A__) \\         || defined(__ARM_ARCH_7R__) \\         || defined(__ARM_ARCH_7M__) \\         || (defined(__TARGET_ARCH_ARM) && __TARGET_ARCH_ARM-0 >= 7)         #error cmake_ARCH armv7     #elif defined(__ARM_ARCH_6__) \\         || defined(__ARM_ARCH_6J__) \\         || defined(__ARM_ARCH_6T2__) \\         || defined(__ARM_ARCH_6Z__) \\         || defined(__ARM_ARCH_6K__) \\         || defined(__ARM_ARCH_6ZK__) \\         || defined(__ARM_ARCH_6M__) \\         || (defined(__TARGET_ARCH_ARM) && __TARGET_ARCH_ARM-0 >= 6)         #error cmake_ARCH armv6     #elif defined(__ARM_ARCH_5TEJ__) \\         || (defined(__TARGET_ARCH_ARM) && __TARGET_ARCH_ARM-0 >= 5)         #error cmake_ARCH armv5     #else         #error cmake_ARCH arm     #endif #elif defined(__i386) || defined(__i386__) || defined(_M_IX86)     #error cmake_ARCH i386 #elif defined(__x86_64) || defined(__x86_64__) || defined(__amd64) || defined(_M_X64)     #error cmake_ARCH x86_64 #elif defined(__ia64) || defined(__ia64__) || defined(_M_IA64)     #error cmake_ARCH ia64 #elif defined(__ppc__) || defined(__ppc) || defined(__powerpc__) \\       || defined(_ARCH_COM) || defined(_ARCH_PWR) || defined(_ARCH_PPC)  \\       || defined(_M_MPPC) || defined(_M_PPC)     #if defined(__ppc64__) || defined(__powerpc64__) || defined(__64BIT__)         #error cmake_ARCH ppc64     #else         #error cmake_ARCH ppc     #endif #endif #error cmake_ARCH unknown ")  # Set ppc_support to TRUE before including this file or ppc and ppc64 # will be treated as invalid architectures since they are no longer supported by Apple  function(target_architecture output_var)     if(APPLE AND CMAKE_OSX_ARCHITECTURES)         # On OS X we use CMAKE_OSX_ARCHITECTURES *if* it was set         # First let's normalize the order of the values          # Note that it's not possible to compile PowerPC applications if you are using         # the OS X SDK version 10.6 or later - you'll need 10.4/10.5 for that, so we         # disable it by default         # See this page for more information:         # http://stackoverflow.com/questions/5333490/how-can-we-restore-ppc-ppc64-as-well-as-full-10-4-10-5-sdk-support-to-xcode-4          # Architecture defaults to i386 or ppc on OS X 10.5 and earlier, depending on the CPU type detected at runtime.         # On OS X 10.6  the default is x86_64 if the CPU supports it, i386 otherwise.          foreach(osx_arch ${CMAKE_OSX_ARCHITECTURES})             if("${osx_arch}" STREQUAL "ppc" AND ppc_support)                 set(osx_arch_ppc TRUE)             elseif("${osx_arch}" STREQUAL "i386")                 set(osx_arch_i386 TRUE)             elseif("${osx_arch}" STREQUAL "x86_64")                 set(osx_arch_x86_64 TRUE)             elseif("${osx_arch}" STREQUAL "ppc64" AND ppc_support)                 set(osx_arch_ppc64 TRUE)             else()                 message(FATAL_ERROR "Invalid OS X arch name: ${osx_arch}")             endif()         endforeach()          # Now add all the architectures in our normalized order         if(osx_arch_ppc)             list(APPEND ARCH ppc)         endif()          if(osx_arch_i386)             list(APPEND ARCH i386)         endif()          if(osx_arch_x86_64)             list(APPEND ARCH x86_64)         endif()          if(osx_arch_ppc64)             list(APPEND ARCH ppc64)         endif()     else()         file(WRITE "${CMAKE_BINARY_DIR}/arch.c" "${archdetect_c_code}")          enabl_language(C)

        # Detect the architecture in a rather creative way...
        # This compiles a small C program which is a series of ifdefs that selects a
        # particular #error preprocessor directive whose message string contains the
        # target architecture. The program will always fail to compile (both because
        # file is not a valid C program, and obviously because of the presence of the
        # #error preprocessor directives... but by exploiting the preprocessor in this
        # way, we can detect the correct target architecture even when cross-compiling,
        # since the program itself never needs to be run (only the compiler/preprocessor)
        try_run(
            run_result_unused
            compile_result_unused
            "${CMAKE_BINARY_DIR}"
            "${CMAKE_BINARY_DIR}/arch.c"
            COMPILE_OUTPUT_VARIABLE ARCH
            CMAKE_FLAGS CMAKE_OSX_ARCHITECTURES=${CMAKE_OSX_ARCHITECTURES}
        )

        # Parse the architecture name from the compiler output
        string(REGEX MATCH "cmake_ARCH ([a-zA-Z0-9_]+)" ARCH "${ARCH}")

        # Get rid of the value marker leaving just the architecture name
        string(REPLACE "cmake_ARCH " "" ARCH "${ARCH}")

        # If we are compiling with an unknown architecture this variable should
        # already be set to "unknown" but in the case that it's empty (i.e. due
        # to a typo in the code), then set it to unknown
        if (NOT ARCH)
            set(ARCH unknown)
        endif()
    endif()

    set(${output_var} "${ARCH}" PARENT_SCOPE)
endfunction()

GitHub链接: link.