Zephyr build fail with LLVM on Windows

[yanzhouy]

Describe the bug
I am trying to build zephyr project in Windows with llvm compiler, but it failed.

To Reproduce
Steps to reproduce the behavior:
I installed llvm version 11.0.0 for windows and set the patch to the location.
In zephyr/samples/hello_world directory, delete all the /build content,

1. set ZEPHYR_TOOLCHAIN_VARIANT=llvm
2. set LLVM_TOOLCHAIN_PATH=C:\tools\windows\toolchains\llvm_11_0_0\
3. west build -b qemu_x86 .
4. See error: Re-running CMake. It seems to go to infinite loop and cannot build the application.

Expected behavior
Build can be done for hello-world as cross-compile with gcc i486.

Logs and console output

-- The C compiler identification is Clang 11.0.0
-- The CXX compiler identification is Clang 11.0.0
-- The ASM compiler identification is Clang

-- Configuring done
-- Generating done
-- Build files have been written to: /zephyr/zephyr-intel/samples/hello_world/build
[0/1] Re-running CMake...
Including boilerplate (Zephyr base (cached)):
...
[0/1] Re-running CMake...
...
[0/1] Re-running CMake...

Environment (please complete the following information):

• OS: Windows
• Toolchain: llvm

Additional context
Tried LLVM and Intel oneApi ICX compiler in Linux, both of them work.
Also tried with 'set ZEPHYR_TOOLCHAIN_VARIANT=cross-compile' and 'set CROSS_COMPILE=path to \ish_gcc_8_3\bin\i486-elf-' on Windows, samples/hello_world can be built successfully by 'west build -b qemu_x86 . '
How to build Zephyr project with clang or icx compiler on Windows?

[nashif]

Windows support is planned and is not done yet.

[yanzhouy]

Windows support is planned and is not done yet.

@nashif Hi Nashif, many thanks for your reply. When will zephyr could support llvm on windows platform? Do we have an ETA? Or maybe is there any workaround which I can do for using llvm compiler for zephyr on windows?

[nashif]

@tejlmand any idea what is going on here and why we go into a loop?

[yanzhouy]

**Also tried with latest LLVM toolchain, error reported below:

CMake Error at ../../cmake/extensions.cmake:1735 (message):
Assertion failed: The toolchain is unable to build a dummy C file. See
CMakeError.log.
Call Stack (most recent call first):
../../CMakeLists.txt:42 (assert)

**In CMakeError.log, it shows that:

Checking whether the ASM compiler is GNU using "--version" did not match "(GNU assembler)|(GCC)|(Free Software Foundation)":
clang version 11.0.0
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:/Users/yanzhouy/source/ish/ish_pic_base/ish/firmware/tools/windows/toolchains/llvm_11_0_0/bin

[yanzhouy]

hi @tejlmand Attached more log for the build error, could you please give some help for llvm build on Windows？ Many thanks.

[nashif]

i finally got to it and I am able to reproduce the recursive issue.

[yanzhouy]

Hi @nashif
Mostly, when I tried with 'set ZEPHYR_TOOLCHAIN_VARIANT=llvm' and 'set LLVM_TOOLCHAIN_PATH=C:\tools\windows\toolchains\llvm_11', Then I built with 'west build -b qemu_x86 .' for samples/hello_world.

It got the below CMake error reported:
CMake Error at ../../cmake/extensions.cmake:1735 (message): Assertion failed: The toolchain is unable to build a dummy C file. See CMakeError.log.

In ../../cmake/extensions.cmake:1735, it has the code as:

And in CMakeError.log, it shows:
Checking whether the ASM compiler is GNU using "--version" did not match "(GNU assembler)|(GCC)|(Free Software Foundation)":
clang version 11.0.0
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:/Users/yanzhouy/source/ish/pic_base/ish/firmware/tools/windows/toolchains/llvm_11/bin