Feature Request: Add windows support

[UebelAndre]

Running builds on windows for bazelbuild/bazel-central-registry#4341 currently fails with

(14:18:37) ERROR: C:/b/xz3jtakb/external/rules_flex++default_toolchain_ext+flex_v2.6.4/BUILD.bazel:22:11: Compiling src/tables.c [for tool] failed: (Exit 2): cl.exe failed: error executing CppCompile command (from target @@rules_flex++default_toolchain_ext+flex_v2.6.4//:flex_lib)
  cd /d C:/b/xz3jtakb/execroot/_main
  SET INCLUDE=C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\include;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Auxiliary\VS\include;C:\Program Files (x86)\Windows Kits\10\include\10.0.22621.0\ucrt;C:\Program Files (x86)\Windows Kits\10\\include\10.0.22621.0\\um;C:\Program Files (x86)\Windows Kits\10\\include\10.0.22621.0\\shared;C:\Program Files (x86)\Windows Kits\10\\include\10.0.22621.0\\winrt;C:\Program Files (x86)\Windows Kits\10\\include\10.0.22621.0\\cppwinrt
    SET PATH=C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\bin\HostX64\x64;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\VC\VCPackages;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\CommonExtensions\Microsoft\TestWindow;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\MSBuild\Current\bin\Roslyn;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\Extensions\Microsoft\CodeCoverage.Console;C:\Program Files (x86)\Windows Kits\10\bin\10.0.22621.0\\x64;C:\Program Files (x86)\Windows Kits\10\bin\\x64;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\\MSBuild\Current\Bin\amd64;C:\Windows\Microsoft.NET\Framework64\v4.0.30319;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\Tools\;;C:\Windows\system32;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\CommonExtensions\Microsoft\CMake\Ninja;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\VC\Linux\bin\ConnectionManagerExe;C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\vcpkg
    SET PWD=/proc/self/cwd
    SET RUNFILES_MANIFEST_ONLY=1
    SET TEMP=C:\temp
    SET TMP=C:\temp
    SET VSLANG=1033
  C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\bin\HostX64\x64\cl.exe @bazel-out/x64_windows-opt-exec-ST-d57f47055a04/bin/external/rules_flex++default_toolchain_ext+flex_v2.6.4/_objs/flex_lib/tables.obj.params
# Configuration: d000bf4d56dd4c5cb23908f7a97865dc05966f2a1246ed2e2c9d6c0eddcbd33d
# Execution platform: @@platforms//host:host
C:\b\xz3jtakb\execroot\_main\external\rules_flex++default_toolchain_ext+flex_v2.6.4\src\flexdef.h(47): fatal error C1083: Cannot open include file: 'libgen.h': No such file or directory

It would be great if the m4, flex, and bison rules all supported windows.

[UebelAndre]

This is blocked by westes/flex#367

[jmillikin]

Patching upstream Flex to support Windows is a large project, and out of scope for rules_flex.

[UebelAndre]

re bazelbuild/bazel-central-registry#4341 (comment)

Flex doesn't work on Windows (westes/flex#367) so you'd need to check in pre-built lexers to support that platform.

@jmillikin Why not add such a patch here?

[UebelAndre]

Patching upstream Flex to support Windows is a large project, and out of scope for rules_flex.

I think it would be better to leave one of these issues open so folks know that the request is active and make it clear it's blocked on upstream issues.

[jmillikin]

Flex doesn't work on Windows (westes/flex#367) so you'd need to check in pre-built lexers to support that platform.

@jmillikin Why not add such a patch here?

I'm not sure what you mean. The lexers are what Flex generates when you run it, so if you want to build Verilator on Windows then you'd need to run Flex on your local machine and check its outputs into the BCR overlay.

Patching upstream Flex to support Windows is a large project, and out of scope for rules_flex.

I think it would be better to leave one of these issues open so folks know that the request is active and make it clear it's blocked on upstream issues.

I'd prefer to leave the rules_flex issue tracker reserved for issues with rules_flex itself.

If Flex supported Windows but rules_flex broke that support then that would be one thing, but there's not much value in keeping open an issue to act just as a redirect.

[UebelAndre]

I'm not sure what you mean. The lexers are what Flex generates when you run it, so if you want to build Verilator on Windows then you'd need to run Flex on your local machine and check its outputs into the BCR overlay.

I thought what you were saying was to use something like https://gnuwin32.sourceforge.net/packages/flex.html and hook flex up to a custom toolchain. Using prebuilt flex binaries feels like a reasonable thing to do in rules_flex given inability to build modern versions from source.