我正在尝试使用 Cmake 将外部库安装到我的 C++ 项目中。我希望使用该库生成 Xcode 项目。在我的终端中，我从构建目录运行以下命令:

cmake -G Xcode ..

这给了我以下错误:

-- The CXX compiler identification is unknown
-- The C compiler identification is unknown
CMake Error at CMakeLists.txt:6 (project):
No CMAKE_CXX_COMPILER could be found.

CMake Error at CMakeLists.txt:6 (project):
  No CMAKE_C_COMPILER could be found.

我正在使用 g++ 编译器:

 Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
    Apple LLVM version 7.0.0 (clang-700.1.76)
    Target: x86_64-apple-darwin14.5.0
    Thread model: posix

编辑:CMakeLists.txt 文件

file(READ "${CMAKE_CURRENT_SOURCE_DIR}/VERSION" PROJECT_VERSION_FULL)
string(REGEX REPLACE "[\n\r]" "" PROJECT_VERSION_FULL "${PROJECT_VERSION_FULL}")
string(REGEX REPLACE "^([0-9]+)\\.[0-9]+\\.[0-9]+$" "\\1" PROJECT_VERSION_MAJOR "${PROJECT_VERSION_FULL}")
string(REGEX REPLACE "^[0-9]+\\.([0-9]+)\\.[0-9]+$" "\\1" PROJECT_VERSION_MINOR "${PROJECT_VERSION_FULL}")
string(REGEX REPLACE "^[0-9]+\\.[0-9]+\\.([0-9]+)$" "\\1" PROJECT_VERSION_PATCH "${PROJECT_VERSION_FULL}")
set(PROJECT_VERSION "${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}")
math(EXPR LIBRARY_VERSION_MAJOR "${PROJECT_VERSION_MAJOR}")
set(LIBRARY_VERSION_MINOR "${PROJECT_VERSION_MINOR}")
set(LIBRARY_VERSION_PATCH "${PROJECT_VERSION_PATCH}")
set(LIBRARY_VERSION "${LIBRARY_VERSION_MAJOR}.${LIBRARY_VERSION_MINOR}")
set(LIBRARY_VERSION_FULL "${LIBRARY_VERSION}.${LIBRARY_VERSION_PATCH}")


option(CODE_COVERAGE "Set ON to add code coverage compile options" OFF)
option(GENERATE_DOC "Set ON to genrate doxygen API reference in build/doc directory" OFF)

# C++11 compiler Check
if(NOT CMAKE_CXX_COMPILER_VERSION) # work around for cmake versions smaller than 2.8.10
    execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpversion OUTPUT_VARIABLE CMAKE_CXX_COMPILER_VERSION)
endif()
if(CMAKE_CXX_COMPILER MATCHES ".*clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
      set(CMAKE_COMPILER_IS_CLANGXX 1)
endif()
if( (CMAKE_COMPILER_IS_GNUCXX AND ${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 4.7) OR
    (CMAKE_COMPILER_IS_CLANGXX AND ${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 3.2))
  message(FATAL_ERROR "Your C++ compiler does not support C++11. Please install g++ 4.7 (or greater) or clang 3.2 (or greater)")
else()
  message(STATUS "Compiler is recent enough to support C++11.")
endif()

if( CMAKE_COMPILER_IS_GNUCXX )
    append_cxx_compiler_flags("-std=c++11 -Wall -Wextra  -DNDEBUG" "GCC" CMAKE_CXX_FLAGS)
    append_cxx_compiler_flags("-O3 -ffast-math -funroll-loops" "GCC" CMAKE_CXX_OPT_FLAGS)
    if ( CODE_COVERAGE )
        append_cxx_compiler_flags("-g -fprofile-arcs -ftest-coverage -lgcov" "GCC" CMAKE_CXX_FLAGS)
    endif()

else()
    if(MSVC)
        append_cxx_compiler_flags("/EHsc" "MSVC" CMAKE_CXX_FLAGS)
        append_cxx_compiler_flags("/Od" "MSVC" CMAKE_CXX_FLAGS_DEBUG)
        append_cxx_compiler_flags("/Ox" "MSVC" CMAKE_CXX_FLAGS_RELEASE)
        set(vars CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
        foreach(var ${vars})
            string(REPLACE "/MD" "-MT" ${var} "${${var}}")
        endforeach(var)

        add_definitions("/DMSVC_COMPILER")
    else()
        append_cxx_compiler_flags("-std=c++11 -DNDEBUG" "CLANG" CMAKE_CXX_FLAGS)
        append_cxx_compiler_flags("-stdlib=libc++" "CLANG" CMAKE_CXX_FLAGS)
        append_cxx_compiler_flags("-O3 -ffast-math -funroll-loops" "CLANG" CMAKE_CXX_OPT_FLAGS)
    endif()
endif()

还有 CMakeEdit.log:

Compiling the CXX compiler identification source file "CMakeCXXCompilerId.cpp" failed.
Compiler:  
Build flags: 
Id flags: 

The output was:
1
xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance


Compiling the C compiler identification source file "CMakeCCompilerId.c" failed.
Compiler:  
Build flags: 
Id flags: 

The output was:
1
xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance

编辑:

当 xcode-select 开发者目录指向/Library/Developer/CommandLineTools 时，当需要完整的常规 XCode(在 XCode 之后安装 CLT 时发生)时，会发生此问题。

我发现解决办法是这样的:

sudo xcode-select -s /Applications/Xcode.app/Contents/Developer

完成此操作后，当我运行 cmake -G Xcode .. 时出现其他错误:

-- The CXX compiler identification is AppleClang 7.0.0.7000176
-- The C compiler identification is AppleClang 7.0.0.7000176
CMake Error at /usr/local/Cellar/cmake/3.4.0/share/cmake/Modules/Platform/Darwin.cmake:76 (message):
  CMAKE_OSX_DEPLOYMENT_TARGET is '10.10' but CMAKE_OSX_SYSROOT:

   ""

  is not set to a MacOSX SDK with a recognized version.  Either set
  CMAKE_OSX_SYSROOT to a valid SDK or set CMAKE_OSX_DEPLOYMENT_TARGET to
  empty.
Call Stack (most recent call first):
  /usr/local/Cellar/cmake/3.4.0/share/cmake/Modules/CMakeSystemSpecificInformation.cmake:36 (include)
  CMakeLists.txt:6 (project)

编辑 2 好像是操作系统指定的SDK不对。

CMAKE_OSX_DEPLOYMENT_TARGET is '10.10' but the matching SDK does not exist
  at:

   "/Applications/DEV/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk"

  Instead using SDK:

   "/Applications/DEV/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk".
Call Stack (most recent call first):
  /usr/local/Cellar/cmake/3.4.0/share/cmake/Modules/CMakeSystemSpecificInitialize.cmake:18 (include)
  CMakeLists.txt:6 (project)


-- The CXX compiler identification is AppleClang 7.0.0.7000176
-- The C compiler identification is AppleClang 7.0.0.7000176
CMake Error at /usr/local/Cellar/cmake/3.4.0/share/cmake/Modules/Platform/Darwin.cmake:76 (message):
  CMAKE_OSX_DEPLOYMENT_TARGET is '10.10' but CMAKE_OSX_SYSROOT:

   ""

  is not set to a MacOSX SDK with a recognized version.  Either set
  CMAKE_OSX_SYSROOT to a valid SDK or set CMAKE_OSX_DEPLOYMENT_TARGET to
  empty.
Call Stack (most recent call first):
  /usr/local/Cellar/cmake/3.4.0/share/cmake/Modules/CMakeSystemSpecificInformation.cmake:36 (include)
  CMakeLists.txt:6 (project)

最佳答案

我遇到了同样的问题，但我解决了:

sudo xcode-select --reset

在执行上述操作之前，xcode-select -p 报告路径为 /Library/Developer/CommandLineTools。

重置后路径为/Applications/Xcode.app/Contents/Developer。

关于c++ - CXX 编译器标识未知 : xcode，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33998853/