在windows中配置CMake以从命令行使用clang来获得现代OpenMP支持

Question

我有一个使用 OpenMP 进行并行化的小型测试项目。我的目标是编译它，以便它为库生成 .dll 和 .lib（因为我的真实项目链接到使用这些类型分发的外部库），支持 OpenMP 4.5 或更高版本，并从命令行执行此操作，以便可以在 docker 上完成进行测试和检查（docker 部分超出了这个问题的范围， 它只是为了参考为什么我需要它从命令行工作）。我可以使用我不满意的不同编译器编译这个项目：

< Li > MSVC:< code > mkdir build-msvc ，然后< code>cmake..(来自新创建的文件夹)，最后< code>cmake - build。-配置版本。这可以很好地编译，但是只支持OpenMP 2.0，因此对我的实际项目来说不是一个好的选择。 < li >英特尔Parallel Studio:< code > mkdir build-Intel ，然后< code>cmake..-T "英特尔C编译器19.0"(从新创建的文件夹中)，最后是< code>cmake - build。-配置版本。这支持OpenMP 5.0，但它的许可证对我来说相当昂贵。 < Li > MinGW x64 g:< code > mkdir build-g ，然后< code>cmake..-G "MinGW Makefiles"(来自新创建的文件夹)，最后是< code>cmake - build。。它支持OpenMP 4.5，但该编译器与< code >不兼容。lib(据我所知)我已经提到的对我来说是必要的。

我试过用铿锵声，但没有成功:

< li >来自MSVC的CLANG:< code > mkdir build-CLANG-msvc ，然后< code > cmake-G Ninja-DCMAKE _ CXX _ COMPILER = CLANG-cl..(从新创建的文件夹中)，但它失败并显示以下错误:

-- The CXX compiler identification is Clang 8.0.1 with MSVC-like command-line
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/clang-cl.exe
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/clang-cl.exe -- broken
CMake Error at C:/Program Files/CMake/share/cmake-3.15/Modules/CMakeTestCXXCompiler.cmake:53 (message):
  The C++ compiler

    "C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/clang-cl.exe"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: C:/Users/[USER NAME]/source/repos/test_openmp/build-clang-msvc/CMakeFiles/CMakeTmp

    Run Build Command(s):C:/PROGRA~2/MICROS~1/2019/COMMUN~1/Common7/IDE/COMMON~1/MICROS~1/CMake/Ninja/ninja.exe cmTC_bd131 && [1/2] Building CXX object CMakeFiles\cmTC_bd131.dir\testCXXCompiler.cxx.obj
    [2/2] Linking CXX executable cmTC_bd131.exe
    FAILED: cmTC_bd131.exe
    cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --intdir=CMakeFiles\cmTC_bd131.dir --rc=rc --mt=CMAKE_MT-NOTFOUND --manifests  -- C:\PROGRA~1\MINGW-~1\X86_64~1.0-P\mingw64\bin\ld.exe /nologo CMakeFiles\cmTC_bd131.dir\testCXXCompiler.cxx.obj  /out:cmTC_bd131.exe /implib:cmTC_bd131.lib /pdb:cmTC_bd131.pdb /version:0.0  /machine:X86  /debug /INCREMENTAL /subsystem:console  kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cd ."
    RC Pass 1: command "rc /fo CMakeFiles\cmTC_bd131.dir/manifest.res CMakeFiles\cmTC_bd131.dir/manifest.rc" failed (exit code 0) with the following output:
    The system cannot find the file specified
    ninja: build stopped: subcommand failed.





  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:2 (project)


-- Configuring incomplete, errors occurred!
See also "C:/Users/[USER NAME]/source/repos/test_openmp/build-clang-msvc/CMakeFiles/CMakeOutput.log".
See also "C:/Users/[USER NAME]/source/repos/test_openmp/build-clang-msvc/CMakeFiles/CMakeError.log".

• 除了 MSVC 之外的 Clang 和 Ninja：mkdir build-clang-ninja，然后 cmake -G Ninja -DCMAKE_CXX_COMPILER=clang-cl ..（从新创建的文件夹并更改 PATH 环境变量以便首先找到非 msvc），但它失败并显示以下错误：

-- The CXX compiler identification is Clang 9.0.0 with MSVC-like command-line
-- Check for working CXX compiler: C:/Program Files/LLVM/bin/clang-cl.exe
-- Check for working CXX compiler: C:/Program Files/LLVM/bin/clang-cl.exe -- broken
CMake Error at C:/Program Files/CMake/share/cmake-3.15/Modules/CMakeTestCXXCompiler.cmake:53 (message):
  The C++ compiler

    "C:/Program Files/LLVM/bin/clang-cl.exe"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: C:/Users/[USER NAME]/source/repos/test_openmp/buid-clang-ninja/CMakeFiles/CMakeTmp

    Run Build Command(s):C:/Ninja/ninja.exe cmTC_50b73 && [1/2] Building CXX object CMakeFiles\cmTC_50b73.dir\testCXXCompiler.cxx.obj
    [2/2] Linking CXX executable cmTC_50b73.exe
    FAILED: cmTC_50b73.exe
    cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --intdir=CMakeFiles\cmTC_50b73.dir --rc=rc --mt=CMAKE_MT-NOTFOUND --manifests  -- CMAKE_LINKER-NOTFOUND /nologo CMakeFiles\cmTC_50b73.dir\testCXXCompiler.cxx.obj  /out:cmTC_50b73.exe /implib:cmTC_50b73.lib /pdb:cmTC_50b73.pdb /version:0.0  /machine:x64  /debug /INCREMENTAL /subsystem:console  kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cd ."
    RC Pass 1: command "rc /fo CMakeFiles\cmTC_50b73.dir/manifest.res CMakeFiles\cmTC_50b73.dir/manifest.rc" failed (exit code 0) with the following output:
    The system cannot find the file specified
    ninja: build stopped: subcommand failed.





  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:2 (project)


-- Configuring incomplete, errors occurred!
See also "C:/Users/[USER NAME]/source/repos/test_openmp/buid-clang-ninja/CMakeFiles/CMakeOutput.log".
See also "C:/Users/[USER NAME]/source/repos/test_openmp/buid-clang-ninja/CMakeFiles/CMakeError.log".

关于如何进行叮当声的任何想法？我认为这是我想要实现的目标的最佳选择（编译我的测试程序，支持 OpenMP 4.5 或更高版本并生成 .lib 和 .dll）。

我查看过的相关帖子/网页，但对解决这个问题没有帮助:

• 在Windows上使用Cake、Clang和Ninja构建c项目
• 在Windows上使用Cake、Ninja和Clang构建
• Windows上使用Clang编译的方法，特别是设置链接器：-DCMAKE_LINKER="C：/Program Files/LLVM/bin/lld-link.exe"
• 使用忍者生成器为Windows（clang-cl）构建
• Clang-cl用户手册

Answer 1

我能够为Clang MSVC案例复制此错误。因为我们正尝试从Visual Studio外部（即命令行）使用Visual Studio定制的编译器，所以在使用编译器之前，有必要在我们的命令行中初始化VS构建环境。VCVarsXX.bat文件完成了这一点；它们是VS命令提示符工具的一部分。因此，通过选择您的架构（x86、x64等）并运行脚本，这应该允许Cake使用clang-cl构建简单的测试程序并继续。这是VS 2019的位置：

>"C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvarsall.bat" x86

>cmake -G Ninja -DCMAKE_CXX_COMPILER=clang-cl ..
-- The CXX compiler identification is Clang 8.0.1
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/clang-cl.exe
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/clang-cl.exe -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
...

扩展一下OpenMP的问题，我个人发现使用< code > find _ package(OpenMP REQUIRED)是没有用的。正如您提到的，我也收到了这个CMake错误:

Could NOT find OpenMP_CXX (missing: OpenMP_CXX_FLAGS OpenMP_CXX_LIB_NAMES)

在这个网站上有一些建议（例如这里和这里），声称手动填充所有变量可以让FindOpenMP.cmake成功找到库。我用你的示例 CMake 文件尝试了这个，取得了一些成功：

cmake_minimum_required (VERSION 2.8)
project(test_openmp LANGUAGES CXX)

set(OpenMP_CXX "${CMAKE_CXX_COMPILER}")
set(OpenMP_CXX_FLAGS "-Xclang -fopenmp")
set(OpenMP_CXX_LIB_NAMES "libomp" "libiomp5")
set(OpenMP_libomp_LIBRARY libomp)
set(OpenMP_libiomp5_LIBRARY libiomp5)

#OPENMP
find_package(OpenMP REQUIRED)
if(OPENMP_FOUND)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")
    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${OpenMP_EXE_LINKER_FLAGS}")
endif()

# Library
add_library(example_lib SHARED example_lib.h example_lib.cpp)
target_link_libraries(example_lib PUBLIC ${OpenMP_CXX_LIBRARIES})
target_compile_definitions(example_lib PRIVATE EXEMPLE_LIB_EXPORT)

# Executable
add_executable(test_openmp test_openmp.cpp)
target_link_libraries(test_openmp example_lib)

这成功地“找到”了第二次配置尝试时的库（第一次总是产生与之前相同的找不到OpenMP_CXX错误）：

>cmake -G Ninja -DCMAKE_CXX_COMPILER=clang-cl ..
-- Found OpenMP_CXX: -Xclang -fopenmp (found version "3.1")
-- Found OpenMP: TRUE (found version "3.1")
-- Configuring done
-- Generating done

但是，这无法生成可执行文件，因为CMake OpenMP变量（尤其是OpenMP_CX_LIBRARIES）实际上都没有指向库位置。CMake的＜code＞FindOpenMP的缺点。cmake＜/code＞已经在这里的cmake问题网站上提出，并且LLVM/Clang端似乎也存在相关限制。

不管怎样，我能让这个例子工作的最干净的方法是完全抛弃< code>find_package()。以下代码允许我成功地生成构建系统，并编译和运行可执行文件:

cmake_minimum_required (VERSION 2.8)
project(test_openmp LANGUAGES CXX)

set(OpenMP_LIBRARY_DIR "C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/lib")
set(OpenMP_CXX_FLAGS "-Xclang -fopenmp")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")

# Tell CMake where to find the OpenMP libraries.
link_directories(${OpenMP_LIBRARY_DIR})

# Library
add_library(example_lib SHARED example_lib.h example_lib.cpp)
# Link in the OpenMP libraries.
target_link_libraries(example_lib PUBLIC libomp libiomp5md)
target_compile_definitions(example_lib PRIVATE EXEMPLE_LIB_EXPORT)

# Executable
add_executable(test_openmp test_openmp.cpp)
target_link_libraries(test_openmp example_lib)