I'm trying to cross-compile for a 64-bit ARMv8 / Raspbian (DietPi actually), from Windows, but I'm getting a series of issues with 3rd-party crates.
What I installed
rust toolchain 1.61.0
ARMv8 gcc toolchain (from here)
MS Visual Studio 2019 C++ build tools (from here)
(IntelliJ IDEA UE and the IntelliJ plugin - FYI but not really relevant to the question)
From there it is possible to add the required target - note that it's dependent on the ARM gcc toolchain (for example the 32-bit version is armv7-unknown-linux-gnueabihf):
rustup target add aarch64-unknown-linux-gnu
Then I edited %USERPROFILE%\.cargo\config and added those lines:
[target.aarch64-unknown-linux-gnu]
linker = "aarch64-linux-gnu-gcc.exe"
And finally, I added those to the PATH:
%USERPROFILE%\.cargo\bin
c:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin (for cmake)
c:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\MSBuild\Current\Bin (for msbuild)
[ARMv8 gcc toolchain]\bin
How I cross-compiled
After making sure everything was compiling and running correctly for Windows, I tried to cross-compile:
cargo build -r --target=aarch64-unknown-linux-gnu
The problem I have
While this worked for simple applications, it quickly becomes clear that many crates fail to compile. For example, freetype-sys, which is a dependency of plotters that I'm using:
error: failed to run custom build command for `freetype-sys v0.13.1`
Caused by:
process didn't exit successfully: `D:\projects\rust\humidity\rh\target\release\build\freetype-sys-4feef64f7ae6c484\build-script-build` (exit code: 101)
--- stdout
[...]
running: "cmake" "[...]\\freetype-sys-0.13.1\\freetype2" "-DWITH_BZip2=OFF" "-DWITH_HarfBuzz=OFF" "-DWITH_PNG=OFF" "-DWITH_ZLIB=OFF" "-DCMAKE_INSTALL_PREFIX=D:\\projects\\rust\\hum
idity\\rh\\target\\aarch64-unknown-linux-gnu\\release\\build\\freetype-sys-3464f88f9fbe3bc0\\out" "-DCMAKE_C_FLAGS= -ffunction-sections -fdata-sections -fPIC" "-DCMAKE_CXX_FLAGS= -ffunction-sections -fdata-sections -fPIC" "-DCMAKE_ASM_FLAGS=
-ffunction-sections -fdata-sections -fPIC" "-DCMAKE_BUILD_TYPE=Release"
-- Building for: Visual Studio 15 2017
-- Selecting Windows SDK version 10.0.17763.0 to target Windows 10.0.19043.
-- Configuring incomplete, errors occurred!
See also "D:/projects/rust/humidity/rh/target/aarch64-unknown-linux-gnu/release/build/freetype-sys-3464f88f9fbe3bc0/out/build/CMakeFiles/CMakeOutput.log".
--- stderr
CMake Error at CMakeLists.txt:119 (project):
Failed to run MSBuild command:
MSBuild.exe
to get the value of VCTargetsPath:
Microsoft (R) Build Engine version 16.0.462+g62fb89029d for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.
Build started 11/06/2022 11:53:19.
Project "D:\projects\rust\humidity\rh\target\aarch64-unknown-linux-gnu\release\build\freetype-sys-3464f88f9fbe3bc0\out\build\CMakeFiles\3.13.19031502-MSVC_2\VCTargetsPath.vcxproj" on node 1 (default targets).
c:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\MSBuild\Microsoft\VC\v160\Microsoft.CppBuild.targets(378,5): error MSB8020: The build tools for Visual Studio 2017 (Platform Toolset = 'v141') cannot be found. To build usin
g the v141 build tools, please install Visual Studio 2017 build tools. Alternatively, you may upgrade to the current Visual Studio tools by selecting the Project menu or right-click the solution, and then selecting "Retarget solution". [D:\p
rojects\rust\humidity\rh\target\aarch64-unknown-linux-gnu\release\build\freetype-sys-3464f88f9fbe3bc0\out\build\CMakeFiles\3.13.19031502-MSVC_2\VCTargetsPath.vcxproj]
Done Building Project "D:\projects\rust\humidity\rh\target\aarch64-unknown-linux-gnu\release\build\freetype-sys-3464f88f9fbe3bc0\out\build\CMakeFiles\3.13.19031502-MSVC_2\VCTargetsPath.vcxproj" (default targets) -- FAILED.
A previous crate required the path to 2019 MSBuild.exe, hence the extra PATH earlier which solved that problem.
This one seems to require MS VS 2017 build tools. This is getting desperate, so I think the problem is coming from something else.
What else I have tried
EDIT1:
I noticed that the Build Tools for Visual Studio 2017 (version 15.9) (here) include a cross-compiler to ARM64. So
I installed this version
launched the (somewhat hidden) vcvarsamd64_arm64.bat script to setup the environment
replaced the aarch64-linux-gnu-gcc.exe executable in %USERPROFILE%\.cargo\config with cl.exe which is the MS compiler/linker.
from the project directory, cargo clean
cargo build -r --target=aarch64-unknown-linux-gnu
It compiles much faster than the gcc toolchain, but it fails compiling the freetype crate:
Compiling freetype v0.7.0
error: could not find native static library `freetype`, perhaps an -L flag is missing?
Same result with the gcc toolchain and MS VC 2017.
Question: What exactly is required to cross-compile to this target? Am I missing something?
do I need to install several versions of VS build tools? I imagine they'll conflict if they're all in the PATH
do I need to install cmake separately, instead of using the one available in VS? (see PATH defined earlier with CMake)
is it simply not possible from Windows?
EDIT2: I'm starting to believe that the freetype create, which hasn't been updated for a few years and is still in version 0.7.0, cannot be cross-compiled for some reason.
UPDATE: I worked around the problem by replacing plotters with something else. It removed the freetype dependency (this module really has an issue) and allowed the cross-compilation to complete successfully.
I'm still interested by a solution to the problem, but it probably involves generating or finding the library for the target and finding a way to feed it to the compiler in the flow, so it may be somewhat convoluted.
I'm trying make a Visual Studio solution with CMake to compile the latest version of aseprite and CMake keeps giving me the:
No CMAKE_C_COMPILER could be found.
No CMAKE_CXX_COMPILER could be found.
I've already downloaded GCC, and I'm using Visual Studio 2015.
I'm following this tutorial:
https://github.com/aseprite/aseprite/blob/master/INSTALL.md
For Ubuntu, please install the below things:
sudo apt-get update && sudo apt-get install build-essential
Those error messages
CMake Error at ... (project):
No CMAKE_C_COMPILER could be found.
-- Configuring incomplete, errors occurred!
See also ".../CMakeFiles/CMakeOutput.log".
See also ".../CMakeFiles/CMakeError.log".
or
CMake Error: your CXX compiler: "CMAKE_CXX_COMPILER-NOTFOUND" was not found.
Please set CMAKE_CXX_COMPILER to a valid compiler path or name.
...
-- Configuring incomplete, errors occurred!
just mean that CMake was unable to find your C/CXX compiler to compile a simple test program (one of the first things CMake tries while detecting your build environment).
The steps to find your problem are dependent on the build environment you want to generate. The following tutorials are a collection of answers here on Stack Overflow and some of my own experiences with CMake on Microsoft Windows 7/8/10 and Ubuntu 14.04.
Preconditions
You have installed the compiler/IDE and it was able to once compile any other program (directly without CMake)
You e.g. may have the IDE, but may not have installed the compiler or supporting framework itself like described in Problems generating solution for VS 2017 with CMake or How do I tell CMake to use Clang on Windows?
You have the latest CMake version
You have access rights on the drive you want CMake to generate your build environment
You have a clean build directory (because CMake does cache things from the last try) e.g. as sub-directory of your source tree
Windows cmd.exe
> rmdir /s /q VS2015
> mkdir VS2015
> cd VS2015
Bash shell
$ rm -rf MSYS
$ mkdir MSYS
$ cd MSYS
and make sure your command shell points to your newly created binary output directory.
General things you can/should try
Is CMake able find and run with any/your default compiler? Run without giving a generator
> cmake ..
-- Building for: Visual Studio 14 2015
...
Perfect if it correctly determined the generator to use - like here Visual Studio 14 2015
What was it that actually failed?
In the previous build output directory look at CMakeFiles\CMakeError.log for any error message that make sense to you or try to open/compile the test project generated at CMakeFiles\[Version]\CompilerIdC|CompilerIdCXX directly from the command line (as found in the error log).
CMake can't find Visual Studio
Try to select the correct generator version:
> cmake --help
> cmake -G "Visual Studio 14 2015" ..
If that doesn't help, try to set the Visual Studio environment variables first (the path could vary):
> "c:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat"
> cmake ..
or use the Developer Command Prompt for VS2015 short-cut in your Windows Start Menu under All Programs/Visual Studio 2015/Visual Studio Tools (thanks at #Antwane for the hint).
Background: CMake does support all Visual Studio releases and flavors (Express, Community, Professional, Premium, Test, Team, Enterprise, Ultimate, etc.). To determine the location of the compiler it uses a combination of searching the registry (e.g. at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\[Version];InstallDir), system environment variables and - if none of the others did come up with something - plainly try to call the compiler.
CMake can't find GCC (MinGW/MSys)
You start the MSys bash shell with msys.bat and just try to directly call gcc
$ gcc
gcc.exe: fatal error: no input files
compilation terminated.
Here it did find gcc and is complaining that I didn't gave it any parameters to work with.
So the following should work:
$ cmake -G "MSYS Makefiles" ..
-- The CXX compiler identification is GNU 4.8.1
...
$ make
If GCC was not found call export PATH=... to add your compilers path (see How to set PATH environment variable in CMake script?) and try again.
If it's still not working, try to set the CXX compiler path directly by exporting it (path may vary)
$ export CC=/c/MinGW/bin/gcc.exe
$ export CXX=/c/MinGW/bin/g++.exe
$ cmake -G "MinGW Makefiles" ..
-- The CXX compiler identification is GNU 4.8.1
...
$ mingw32-make
For more details see How to specify new GCC path for CMake
Note: When using the "MinGW Makefiles" generator you have to use the mingw32-make program distributed with MinGW
Still not working? That's weird. Please make sure that the compiler is there and it has executable rights (see also preconditions chapter above).
Otherwise the last resort of CMake is to not try any compiler search itself and set CMake's internal variables directly by
$ cmake -DCMAKE_C_COMPILER=/c/MinGW/bin/gcc.exe -DCMAKE_CXX_COMPILER=/c/MinGW/bin/g++.exe ..
For more details see Cmake doesn't honour -D CMAKE_CXX_COMPILER=g++ and Cmake error setting compiler
Alternatively those variables can also be set via cmake-gui.exe on Windows. See Cmake cannot find compiler
Background: Much the same as with Visual Studio. CMake supports all sorts of GCC flavors. It searches the environment variables (CC, CXX, etc.) or simply tries to call the compiler. In addition it will detect any prefixes (when cross-compiling) and tries to add it to all binutils of the GNU compiler toolchain (ar, ranlib, strip, ld, nm, objdump, and objcopy).
This happened to me after I installed Visual Studio 15 2017.
The C++ compiler for Visual Studio 14 2015 was not the problem. It seemed to be a problem with the Windows 10 SDK.
Adding the Windows 10 SDKs to Visual Studio 14 2015 solved the problem for me.
See attached screenshot.
This works for me in Ubuntu 17.10 (Artful Aardvark):
apt-get update
apt-get install build-essential
I also experienced this error when working with CMake:
No CMAKE_C_COMPILER could be found.
No CMAKE_CXX_COMPILER could be found.
The 'warning' box in the MSDN library article Visual C++ in Visual Studio 2015 gave me the help that I needed.
Visual Studio 2015 doesn't come with C++ installed by default. So, creating a new C++ project will prompt you to download the necessary C++ components.
I ran into this issue while building libgit2-0.23.4. For me the problem was that C++ compiler & related packages were not installed with VS2015, therefore "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" file was missing and Cmake wasn't able to find the compiler.
I tried manually creating a C++ project in the Visual Studio 2015 GUI (C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\devenv.exe)
and while creating the project, I got a prompt to download the C++ & related packages.
After downloading required packages, I could see vcvarsall.bat & Cmake was able to find the compiler & executed successfully with following log:
C:\Users\aksmahaj\Documents\MyLab\fritzing\libgit2\build64>cmake ..
-- Building for: Visual Studio 14 2015
-- The C compiler identification is MSVC 19.0.24210.0
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual
Studio 14.0/VC/bin/cl.exe
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual
Studio 14.0/VC/bin/cl.exe -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Could NOT find PkgConfig (missing: PKG_CONFIG_EXECUTABLE)
-- Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
-- zlib was not found; using bundled 3rd-party sources.
-- LIBSSH2 not found. Set CMAKE_PREFIX_PATH if it is installed outside of
the default search path.
-- Looking for futimens
-- Looking for futimens - not found
-- Looking for qsort_r
-- Looking for qsort_r - not found
-- Looking for qsort_s
-- Looking for qsort_s - found
-- Looking for clock_gettime in rt
-- Looking for clock_gettime in rt - not found
-- Found PythonInterp: C:/csvn/Python25/python.exe (found version "2.7.1")
-- Configuring done
-- Generating done
-- Build files have been written to:
C:/Users/aksmahaj/Documents/MyLab/fritzing/libgit2/build64
I had the same errors with CMake. In my case, I have used the wrong Visual Studio version in the initial CMake dialog where we have to select the Visual Studio compiler.
Then I changed it to "Visual Studio 11 2012" and things worked. (I have Visual Studio Ultimate 2012 version on my PC). In general, try to input an older version of Visual Studio version in the initial CMake configuration dialog.
For me, this problem went away on Windows when I moved my project to a shallower parent directory, i.e. to:
C:\Users\spenc\Desktop\MyProjectDirectory
instead of
C:\Users\spenc\Desktop\...\MyProjectDirectory.
I think the source of the problem was that MSBuild has a file path length restriction to 260 characters. This causes the basic compiler test CMake performs to build a project called CompilerIdCXX.vcxproj to fail with the error:
C1083: Cannot open source file: 'CMakeCXXCompilerId.cpp'
because the length of the file's path e.g.
C:\Users\spenc\Desktop\...\MyProjectDirectory\build\CMakeFiles\...\CMakeCXXCompilerId.cpp
exceeds the MAX_PATH restriction.
CMake then concludes there is no CXX compiler.
Make sure you have selected the correct version of Visual Studio. This is trickier than it seems because Visual Studio 2015 is actually Visual Studio 14, and similarly Visual Studio 2012 is Visual Studio 11. I had incorrectly selected Visual Studio 15 which is actually Visual Studio 2017, when I had 2015 installed.
After trying out all of the solutions with no luck, I just provided those missing parameter by cmake -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ ...
Make sure you have installed Windows SDK when you were installing Visual Studio. To add windows SDK you can go to Visual Studio Installer and hit "Modify" and then tick the checkbox of Windows SDK and install it.
None of the solutions here solves my problem - only when I install Windows Update for universal C runtime.
Now CMake is working and no more link hangs from Visual Studio.
Update for Universal C Runtime in Windows
You can also make sure you are the sudo user and you have READ/WRITE access on the directory you are working. I had a similar problem on OS X, and I got it fixed just by entering in sudo mode.
Just in case it helps any one like me in future:
I have had this issue for 24 hours now, on 3 different 64-bit machines(Win7 , Windows 8.1 VM and WIn 8.1 laptop) - whilst trying to build WebKit with VS 2017.
The simple issue here is that the VC++ compiler (i.e cl.exe and it's dependent DLLs) is not visible to CMake. Simple. By making the VC++ folders containing those binaries visible to CMake and your working command prompt(if you're running Cmake from a command prompt), voila! (In addition to key points raised by others , above)
Anyway, after all kinds of fixes - as posted on these many forums- I discovered that it was SIMPLY a matter of ensuring that the PATH variable's contents are not cluttered with multiple Visual Studio BIN paths etc; and instead, points to :
a) the location of your compiler (i.e. cl.exe for your preferred version of Visual Studio ), which in my case(targeting 64-bit platform, and developing on a 64-bit host) is:
C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.15.26726\bin\Hostx64\x64
b) and in addition, the folder containing a dependent DLL called (which cl.exe is dependent on):
api-ms-win-crt-runtime-l1-1-0.dll - which on my machine is:
C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\Common7\IDE\Remote Debugger\x64
These two directories being added to a simplified and CUSTOM System Path variable(working under a Admin priviledged commmand prompt), eliminated my "No CMAKE_C_COMPILER could be found" and "No CMAKE_CXX_COMPILER could be found." errors.
Hope it helps someone.
I get exactly the reported error if ccache is enabled, when using CMake's Xcode generator. Disabling ccache fixed the problem for me. Below I present a fix/check that works for MacOS, but should work similarly on other platforms.
Apparently, it is possible to use CMake's Xcode generator (and others) also in combination with ccache, as is described here. But I never tried it out myself.
# 1) To check if ccache is enabled:
echo $CC
echo $CXX
# This prints something like the following:
# ccache clang -Qunused-arguments -fcolor-diagnostics.
# CC or CXX are typically set in the `.bashrc` or `.zshrc` file.
# 2) To disable ccache, use the following:
CC=clang
CXX=clang++
# 3) Then regenerate the cmake project
cmake -G Xcode <path/to/CMakeLists.txt>
I know this question is about visual studio 2015. I faced this issue with visual studio 2017. When searched on google I landed to this page. After looking at first 2,3 answers I realized this is the problem with vc++ installation. Installing the workload "Desktop development with c++" resolved the issue.
I updated Visual Studio 2015 update 2 to Visual Studio 2015 update 3, and it solved my problem.
I had the same issue with cmake-gui (No CMAKE_CXX_COMPILER could be found.), while running CMake from the command line worked fine. After manually adding the entries
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin
C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\15.0\Bin
to the PATH environment variable it worked for me.
For me it worked to use the Developer Command Prompt that comes with Visual Studio and then just cd to your/jcef/dir and run cmake -G "Visual Studio 14 Win64" ..
I had the same problem.
I was trying to install dlib on my machine and it gave me this error.
The tutorial mentioned in the question leads to downloading visual studio 2017. I solved this by uninstalling VS 2017 and installing VS 2015
One can install VS 2015 via this stackoverflow thread :
How to download Visual Studio Community Edition 2015 (not 2017)
Look in the Cmakelists.txt if you find ARM you need to install C++ for ARM
It's these packages:
C++ Universal Windows Platform for ARM64 "Not Required"
Visual C++ Compilers and libraries for ARM "Not Required"
Visual C++ Compilers and libraries for ARM64 "Very Likely Required"
Required for finding Threads on ARM
enable_language(C)
enable_language(CXX)
Then the problems
No CMAKE_C_COMPILER could be found.
No CMAKE_CXX_COMPILER could be found.
Might disappear unless you specify c compiler like clang, and maybe installing clang will work in other favour.
You can with optional remove in cmakelists.txt both with # before enable_language if you are not compiling for ARM.
On M1 Mac, add the following config to fix it for me
-DCMAKE_C_COMPILER="${OTHER_CXX_FLAG}" -DCMAKE_C_COMPILER="/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -DCMAKE_CXX_COMPILER="/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++"
The config result is:
cmake ../build -DCMAKE_C_COMPILER="${OTHER_CXX_FLAG}" -DCMAKE_C_COMPILER="/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -DCMAKE_CXX_COMPILER="/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++" -DCMAKE_SYSTEM_NAME=Darwin -DCMAKE_TARGET_SYSTEM=mac -GXcode
I'm compiling Berkley's Caffe to a static library, MT, MSVC 12 (VS2013) and linking it to a dll.
It works fine.
Now I'm trying to compile it with Intel C++ 2015 compiler - the static lib build fine, but the dependent dll fails with the following linker error:
fatal error LNK1104: cannot open file
'libboost_thread-iw-mt-s-1_58.lib'
There isn't such library in my Boost build indeed, but I don't know where this dependency came from. Except for the compiler I didn't change any other setting, and I can't find that Boost lib in either Caffe of my dll's Linker->Input->Additional dependencies.
How can I fix this?
Thanks!
Found the solution here: https://software.intel.com/en-us/articles/intel-c-compiler-for-windows-fatal-link-error-lnk1104-when-using-intel-c-compiler-with-boost-libraries
Copied:
When building an application that uses the Boost libraries with the
Intel® C++ Compiler, you may get linker errors like the ones shown
below due to incorrect libraries being linked to the application:
fatal error LNK1104: cannot open file
'libboost_thread-iw-mt-1_33_1.lib' fatal error LNK1104: cannot open
file 'libboost_thread-iw-1_33_1.lib' ... The root cause is missing
Boost libraries for the Intel® C++ Compiler.
The preferred solution is to recompile all required Boost libraries
with the Intel® C++ Compiler (libraries with the infix "iw" are
created because of this). However, this is not mandatory. The
libraries provided for the different Microsoft Visual Studio* versions
are safe to use as well. Perform the following steps to use them
instead:
Open the Boost configuration file "auto_link.hpp". Search for 1
elif defined(__ICL) 2 3 4
// Intel C++, no version number: 5 6
# define BOOST_LIB_TOOLSET "iw" Change "iw" depending on which Microsoft Visual Studio version you're using:
"vc71": Microsoft Visual Studio .NET 2003 "vc80": Microsoft Visual
Studio 2005 "vc90": Microsoft Visual Studio 2008 "vc100": Microsoft
Visual Studio 2010 "vc110": Microsoft Visual Studio 2012 "vc120":
Microsoft Visual Studio 2013 "vc140": Microsoft Visual Studio 2015
Rebuild your application to resolve the linker errors.
I want to write parallel program in C++ using OpenMP, so I am getting started with OpenMP.
On the other words I am a beginner and I need good OpenMP guide telling how to install it.
Does someone know how to install OpenMP on Windows, then compile and run the program?
OpenMP is not something that you install. It comes with your compiler. You just need a decent compiler that supports OpenMP and you need to know how to enable OpenMP support since it is usually disabled by default.
The standard compiler for Windows comes from Microsoft and it is the Microsoft Visual C/C++ compiler from Visual Studio. Unfortunately its OpenMP support is a bit outdated - even the latest and greatest Visual Studio only supports OpenMP 2.0 (an outdated standard version from 2002). See here for more information on how to use OpenMP in Visual Studio. There are other compilers available as well - both Intel C/C++ Compiler (commercial license required) and GCC (freely available) support newer OpenMP versions and other compilers are available too.
You can start learning OpenMP by visiting the OpenMP web site here. Also there is a great tutorial on OpenMP from Lawrence Livermore National Laboratory available here.
2020 Update: Microsoft now ships Clang for Windows with Visual Studio. Although it is a bit convoluted, one can (ab)use the Clang-cl toolset to produce working 32-bit OpenMP programs. A number of steps are necessary:
If not already installed, add Clang and Clang-cl using the Visual Studio 2019 Installer.
Set the project's platform toolset (project Properties -> General -> Platform Toolset) to "LLVM (clang-cl)".
Enable Clang OpenMP support by adding -Xclang -fopenmp to the compiler options in project Properties -> C/C++ -> All Options -> Additional Options.Important: make sure that OpenMP support is disabled before switching the platform toolset (this is the default for new C++ projects). It seems that VS remembers the setting and still passes /openmp even though the language configuration for Clang has no option for OpenMP. If clang-cl.exe throws error MSB8055 (unsupported /openmp option) during build, set the platform toolset back to "Visual Studio 2019 (vXXX)" and disable the OpenMP support in Properties -> C/C++ -> Language -> Open MP Support, then switch the platform toolset again to "LLVM (Clang-cl)".
Add libomp.lib to the additional libraries in project Properties -> Linker -> Input -> Additional Dependencies.
Add the path to libomp.lib to the linker search path by adding a new entry with value $(LLVMInstallDir)\lib in project Properties -> Linker -> General -> Additional Library Directories.
Add a post-build action that copies LLVM's libomp.dll to the project output directory (without this step, running the executable will fail unless libomp.dll is in the DLL search path). In project Properties -> Build Events -> Post-Build Event -> Command Line:
xcopy /y "$(LLVMInstallDir)\bin\libomp.dll" "$(SolutionDir)$(Configuration)"
Build and run the project.
Note: this is very much likely still unsupported by Microsoft and it only works for x86 projects since the LLVM libraries shipped with VS are 32-bit only.
So here is what I did to finally get OpenMP working on my Windows 10 PC:
Get MinGW - Download and grab what you need to get the basic gcc compiler and the g++ pakage (its really easy to do). You can always run g++ -v to make sure it is up and running
Run mingw-get upgrade --recursive "gcc<4.7.*" "gcc-g++<4.7.*" This is the "Fun" part. Because at this time there was no libgomp library supported in their 4.9.* version my gcc wasn't able to recognize <omp.h> the last support version was 4.7.2 so with this I finally was able to run my openMP
To compile run g++ -fopenmp myOpenMPFile.cpp -o myOpenMP and it will all work from there
gcc -fopenmp myOpenMPFile.cpp -o myOpenMP will also work for C code
I would like to share what I did to get OpenMP working on my Windows 10 PC (things have got even simpler in 2019)
I installed MinGW distribution from here with GCC 8.2.0 compiler. The maintainer of the distribution has already added winpthreads and OpenMP support to GCC.
I compiled my code with -fopenmp flag as follows: g++ -fopenmp main.cpp -o exec
Note: the MinGW distribution provides support for many useful libraries (such as Boost 1.69.0) and other utilities. I found it to be very useful.