Port workerd to Windows using clang

.bazelrc

@@ -1,22 +1,4 @@
-build --cxxopt='-std=c++20' --host_cxxopt='-std=c++20' --force_pic --verbose_failures
-build --cxxopt='-fcoroutines-ts' --host_cxxopt='-fcoroutines-ts'
-build --cxxopt='-stdlib=libc++' --host_cxxopt='-stdlib=libc++'
-build --linkopt='-stdlib=libc++' --host_linkopt='-stdlib=libc++'
-
-build --action_env=BAZEL_COMPILER=clang
-build --action_env=CC=clang
-build --action_env=CXX=clang++
-
-build --@capnp-cpp//src/kj:openssl=True --@capnp-cpp//src/kj:zlib=True --@capnp-cpp//src/kj:libdl=True
-
-# Warning options.
-build --cxxopt='-Wall' --host_cxxopt='-Wall'
-build --cxxopt='-Wextra' --host_cxxopt='-Wextra'
-build --cxxopt='-Wno-strict-aliasing' --host_cxxopt='-Wno-strict-aliasing'
-build --cxxopt='-Wno-sign-compare' --host_cxxopt='-Wno-sign-compare'
-build --cxxopt='-Wno-unused-parameter' --host_cxxopt='-Wno-unused-parameter'
-build --cxxopt='-Wno-missing-field-initializers' --host_cxxopt='-Wno-missing-field-initializers'
-build --cxxopt='-Wno-ignored-qualifiers' --host_cxxopt='-Wno-ignored-qualifiers'
+common --enable_platform_specific_config
 
 # Our dependencies (ICU, zlib, etc.) produce a lot of these warnings, so we disable them.
 # TODO(cleanup): Can we disable warnings altogether from our dependencies, without disabling them
@@ -27,7 +9,6 @@ build --cxxopt='-Wno-ambiguous-reversed-operator' --host_cxxopt='-Wno-ambiguous-
 # https://bazel.build/reference/command-line-reference#flag--reuse_sandbox_directories
 build --reuse_sandbox_directories
 
-
 # optimized LTO build. you'll need a fairly recent clang for this to work
 build:thin-lto -c opt
 build:thin-lto --cxxopt='-flto=thin'
@@ -54,3 +35,55 @@ build:fastdbg --@rules_rust//:extra_rustc_flags=-C,panic=unwind,-C,debug-asserti
 # bazel and Rust use different LLVM versions. -C opt-level=s provides a comparatively small size
 # improvement, ~35k or ~75k with LTO.
 build:thin-lto --@rules_rust//:extra_rustc_flags=-C,panic=abort,-C,codegen-units=1
+
+#
+# Linux and macOS
+#
+build:unix --cxxopt='-std=c++20' --host_cxxopt='-std=c++20' --force_pic --verbose_failures
+build:unix --cxxopt='-fcoroutines-ts' --host_cxxopt='-fcoroutines-ts'
+build:unix --cxxopt='-stdlib=libc++' --host_cxxopt='-stdlib=libc++'
+build:unix --linkopt='-stdlib=libc++' --host_linkopt='-stdlib=libc++'
+
+build:unix --action_env=BAZEL_COMPILER=clang
+build:unix --action_env=CC=clang
+build:unix --action_env=CXX=clang++
+
+# Warning options.
+build:unix --cxxopt='-Wall' --host_cxxopt='-Wall'
+build:unix --cxxopt='-Wextra' --host_cxxopt='-Wextra'
+build:unix --cxxopt='-Wno-strict-aliasing' --host_cxxopt='-Wno-strict-aliasing'
+build:unix --cxxopt='-Wno-sign-compare' --host_cxxopt='-Wno-sign-compare'
+build:unix --cxxopt='-Wno-unused-parameter' --host_cxxopt='-Wno-unused-parameter'
+build:unix --cxxopt='-Wno-missing-field-initializers' --host_cxxopt='-Wno-missing-field-initializers'
+build:unix --cxxopt='-Wno-ignored-qualifiers' --host_cxxopt='-Wno-ignored-qualifiers'
+
+build:unix --@capnp-cpp//src/kj:openssl=True --@capnp-cpp//src/kj:zlib=True --@capnp-cpp//src/kj:libdl=True
+
+build:linux --config=unix
+build:macos --config=unix
+
+#
+# Windows
+#
+
+# See https://bazel.build/configure/windows#symlink
+startup --windows_enable_symlinks
+build:windows --enable_runfiles
+# We use LLVM's MSVC-compatible compiler driver to compile our code on Windows,
+# as opposed to using MSVC directly. This enables us to use the "same" compiler
+# frontend on Linux, macOS, and Windows, massively reducing the effort required
+# to compile workerd on Windows. Notably, this provides proper support for
+# `#pragma once` when using symlinked virtual includes, `__atomic_*` functions,
+# a standards-compliant preprocessor, support for GNU statement expressions
+# used by some KJ macros, and understands the `.c++` extension by default.
+build:windows --compiler=clang-cl
+
+build:windows --cxxopt='/std:c++20' --host_cxxopt='/std:c++20' --verbose_failures
+build:windows --cxxopt='/await' --host_cxxopt='/await'
+build:windows --cxxopt='/wo4503' --host_cxxopt='/wo4503'
+build:windows --cxxopt='/DWINDOWS_LEAN_AND_MEAN' --host_cxxopt='/DWINDOWS_LEAN_AND_MEAN'
+# The `/std:c++14` argument is unused during boringssl compilation and we don't
+# want a warning when compiling each file.
+build:windows --cxxopt='-Wno-unused-command-line-argument' --host_cxxopt='-Wno-unused-command-line-argument'
+
+build:windows --@capnp-cpp//src/kj:openssl=True --@capnp-cpp//src/kj:zlib=True

.bazelversion

@@ -1 +1 @@
-6.0.0
+6.1.1

.github/workflows/test.yml

@@ -12,31 +12,34 @@ jobs:
   test:
     strategy:
       matrix:
-        os: [ubuntu-22.04, macos-latest]
+        os: [ubuntu-22.04, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2
-      - uses: bazelbuild/setup-bazelisk@v2
       - name: Cache
         id: cache
         uses: actions/cache@v2
         with:
           path: ~/bazel-disk-cache
           key: ${{ runner.os }}-${{ runner.arch }}-bazel-disk-cache
-      - run: mkdir -p ~/bazel-disk-cache
-      - name: Install dependencies
+      - name: Setup Linux
         if: ${{ runner.os == 'Linux' }}
         run: |
             export DEBIAN_FRONTEND=noninteractive
             sudo apt-get install -y build-essential git clang libc++-dev
+      - name: Setup Windows
+        if: ${{ runner.os == 'Windows' }}
+        run: |
+            [System.IO.File]::WriteAllLines((Join-Path -Path $env:USERPROFILE -ChildPath '.bazelrc'), 'startup --output_user_root=C:/tmp')
       - name: Bazel build
         run: |
-            bazel build --disk_cache=~/bazel-disk-cache --remote_cache=https://bazel:${{ secrets.BAZEL_CACHE_KEY }}@bazel-remote-cache.devprod.cloudflare.dev --verbose_failures //...
+            bazelisk build --disk_cache=~/bazel-disk-cache --remote_cache=https://bazel:${{ secrets.BAZEL_CACHE_KEY }}@bazel-remote-cache.devprod.cloudflare.dev --verbose_failures //...
       - name: Bazel tests
         run: |
-            bazel test --disk_cache=~/bazel-disk-cache --remote_cache=https://bazel:${{ secrets.BAZEL_CACHE_KEY }}@bazel-remote-cache.devprod.cloudflare.dev --verbose_failures --show_timestamps --keep_going --test_output=errors //...
+            bazelisk test --disk_cache=~/bazel-disk-cache --remote_cache=https://bazel:${{ secrets.BAZEL_CACHE_KEY }}@bazel-remote-cache.devprod.cloudflare.dev --verbose_failures --show_timestamps --keep_going --test_output=errors //...
       - name: Report disk usage
         if: success() || failure()
+        shell: bash
         run: |
             BAZEL_OUTPUT_BASE=$(bazel info --ui_event_filters=-WARNING output_base)
             BAZEL_REPOSITORY_CACHE=$(bazel info --ui_event_filters=-WARNING repository_cache)

README.md

@@ -59,12 +59,14 @@ With that said, if you discover a bug that allows malicious code to break out of
 
 ### Supported Platforms
 
-In theory, `workerd` should work on any POSIX system that is supported by V8.
+In theory, `workerd` should work on any POSIX system that is supported by V8 and Windows.
 
-In practice, `workerd` is tested on Linux and macOS under x86-64 and arm64 architectures.
-On other platforms, you may have to do tinkering to make things work.
+In practice, `workerd` is tested on:
+
+- Linux and macOS (x86-64 and arm64 architectures)
+- Windows (x86-64 architecture)
 
-Windows users should run `workerd` under WSL (1 or 2).
+On other platforms, you may have to do tinkering to make things work.
 
 ### Building `workerd`
 
@@ -76,6 +78,15 @@ To build `workerd`, you need:
   * libc++ 11+ (e.g. packages `libc++-dev` and `libc++abi-dev` on Debian Bullseye)
 * On macOS:
   * full XCode 13+ installation
+* On Windows:
+  * Visual Studio Community 2022, including "Desktop development with C++" features
+  * [LLVM 15](https://github.com/llvm/llvm-project/releases/)
+  * [MSYS2](https://www.msys2.org/) installed to `C:\tools\msys64` with the `BAZEL_SH` environment variable set to `C:\tools\msys64\usr\bin\bash.exe`
+  * [Python 3](https://www.python.org/downloads/) with a `python3` executable on the `PATH`
+  * GNU `patch` executable on the `PATH` (e.g. `pacman -S patch` in MSYS2 terminal, then copy `patch.exe` and `msys-2.0.dll` from `C:\tools\msys64\usr\bin` to a directory on the `PATH`)
+  * Add `startup --output_user_root=C:/tmp` to the `.bazelrc` file in your user directory
+  * Enable 8.3 filename support with `fsutil 8dot3name set 0` in an administrator command prompt
+  * Enable [developer mode](https://docs.microsoft.com/en-us/windows/uwp/get-started/enable-your-device-for-development) for symlink support
 
 You may then build using:
 

WORKSPACE

@@ -35,10 +35,10 @@ rules_foreign_cc_dependencies()
 
 http_archive(
     name = "capnp-cpp",
-    sha256 = "62e337ef35061c774678be5d0b0abc8b69f78a0481b253bffe4992e74f649757",
-    strip_prefix = "capnproto-capnproto-6a3dd15/c++",
+    sha256 = "9dd4850a9cd8d2ff9a3cff2aedd0b1af956c3645d11c443adcdd9c8d312bb623",
+    strip_prefix = "capnproto-capnproto-4544af1/c++",
     type = "tgz",
-    urls = ["https://github.com/capnproto/capnproto/tarball/6a3dd152d0d1245b1c44af8e76c78169cedadf03"],
+    urls = ["https://github.com/capnproto/capnproto/tarball/4544af13a83d6ed4127e6f91d48f8a1b57b44c91"],
 )
 
 http_archive(
@@ -152,6 +152,16 @@ http_file(
     ],
 )
 
+http_file(
+    name = "cargo_bazel_win_x64",
+    executable = True,
+    sha256 = "a57c496e8ff9d1b2dcd4f6a3a43c41ed0c54e9f3d48183ed411097c3590176d3",
+    urls = [
+        "https://github.com/bazelbuild/rules_rust/releases/download/0.10.0/cargo-bazel-x86_64-pc-windows-msvc.exe",
+    ],
+    downloaded_file_path = "downloaded.exe" # .exe extension required for Windows to recognise as executable
+)
+
 http_archive(
     name = "rules_rust",
     sha256 = "0cc7e6b39e492710b819e00d48f2210ae626b717a3ab96e048c43ab57e61d204",
@@ -263,6 +273,7 @@ git_repository(
         "//:patches/v8/0004-Add-ArrayBuffer-MaybeNew.patch",
         "//:patches/v8/0005-Allow-compiling-on-macOS-catalina-and-ventura.patch",
         "//:patches/v8/0006-Fix-v8-code_generator-imports.patch",
+        "//:patches/v8/0007-Allow-Windows-builds-under-Bazel.patch",
     ],
 )
 
@@ -272,7 +283,8 @@ new_git_repository(
     commit = "c6b68522318204f795a8f04caebf6c0beb679cc4",
     shallow_since = "1676561136 +0000",
     build_file = "@v8//:bazel/BUILD.icu",
-    patch_cmds = [ "find source -name BUILD.bazel | xargs rm" ]
+    patch_cmds = [ "find source -name BUILD.bazel | xargs rm" ],
+    patch_cmds_win = [ "Get-ChildItem -Path source -File -Include BUILD.bazel -Recurse | Remove-Item" ],
 )
 
 new_git_repository(

build/kj_test.bzl

@@ -9,6 +9,8 @@ def kj_test(
         srcs = [src],
         deps = [
             "@capnp-cpp//src/kj:kj-test",
-            "@workerd//src/workerd/util:symbolizer",
-        ] + deps,
+        ] + select({
+            "@platforms//os:windows": [],
+            "//conditions:default": ["@workerd//src/workerd/util:symbolizer"],
+        }) + deps,
     )

build/rust_cxx_bridge.bzl

@@ -1,20 +1,32 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
 
-def rust_cxx_include(name, deps = [], visibility = [], include_prefix = None):
+def rust_cxx_include(name, deps = [], visibility = [], include_prefix = None, target_compatible_with = None):
     native.genrule(
         name = "%s/generated" % name,
         outs = ["cxx.h"],
         cmd = "$(location @cxxbridge_vendor//:cxxbridge-cmd__cxxbridge) --header > \"$@\"",
-        tools = ["@cxxbridge_vendor//:cxxbridge-cmd__cxxbridge"],
+        tools = select({
+            # "@cxxbridge_vendor//:cxxbridge-cmd__cxxbridge" cannot be found on Windows
+            "@platforms//os:windows": [],
+            "//conditions:default": ["@cxxbridge_vendor//:cxxbridge-cmd__cxxbridge"],
+        }),
+        target_compatible_with = select({
+            "@platforms//os:windows": ["@platforms//:incompatible"],
+            "//conditions:default": [],
+        }),
     )
     cc_library(
         name = name,
         hdrs = ["cxx.h"],
         include_prefix = include_prefix,
         visibility = visibility,
+        target_compatible_with = select({
+            "@platforms//os:windows": ["@platforms//:incompatible"],
+            "//conditions:default": [],
+        }),
     )
 
-def rust_cxx_bridge(name, src, deps = [], visibility = [], strip_include_prefix = None, include_prefix = None):
+def rust_cxx_bridge(name, src, deps = [], visibility = [], strip_include_prefix = None, include_prefix = None, target_compatible_with = None):
     native.genrule(
         name = "%s/generated" % name,
         srcs = [src],
@@ -23,7 +35,15 @@ def rust_cxx_bridge(name, src, deps = [], visibility = [], strip_include_prefix
             src + ".cc",
         ],
         cmd = "$(location @cxxbridge_vendor//:cxxbridge-cmd__cxxbridge) $(location %s) -o $(location %s.h) -o $(location %s.cc)" % (src, src, src),
-        tools = ["@cxxbridge_vendor//:cxxbridge-cmd__cxxbridge"],
+        tools = select({
+            # "@cxxbridge_vendor//:cxxbridge-cmd__cxxbridge" cannot be found on Windows
+            "@platforms//os:windows": [],
+            "//conditions:default": ["@cxxbridge_vendor//:cxxbridge-cmd__cxxbridge"],
+        }),
+        target_compatible_with = select({
+            "@platforms//os:windows": ["@platforms//:incompatible"],
+            "//conditions:default": [],
+        }),
     )
 
     cc_library(
@@ -39,4 +59,8 @@ def rust_cxx_bridge(name, src, deps = [], visibility = [], strip_include_prefix
         strip_include_prefix = strip_include_prefix,
         include_prefix = include_prefix,
         visibility = visibility,
+        target_compatible_with = select({
+            "@platforms//os:windows": ["@platforms//:incompatible"],
+            "//conditions:default": [],
+        }),
     )

build/wd_test.bzl

@@ -36,18 +36,31 @@ def wd_test(
     )
 
 def _wd_test_impl(ctx):
+    is_windows = ctx.target_platform_has_constraint(ctx.attr._platforms_os_windows[platform_common.ConstraintValueInfo])
+
     # Bazel insists that the rule must actually create the executable that it intends to run; it
     # can't just specify some other executable with some args. OK, fine, we'll use a script that
     # just execs its args.
-    ctx.actions.write(
-        output = ctx.outputs.executable,
-        content = "#! /bin/sh\nexec \"$@\"\n",
-        is_executable = True,
-    )
+    if is_windows:
+        # Batch script executables must end with ".bat"
+        executable = ctx.actions.declare_file("%s_wd_test.bat" % ctx.label.name)
+        ctx.actions.write(
+            output = executable,
+            # PowerShell correctly handles forward slashes in executable paths generated by Bazel (e.g. "bazel-bin/src/workerd/server/workerd.exe")
+            content = "powershell -Command \"%*\"\r\n",
+            is_executable = True,
+        )
+    else:
+        executable = ctx.outputs.executable
+        ctx.actions.write(
+            output = executable,
+            content = "#! /bin/sh\nexec \"$@\"\n",
+            is_executable = True,
+        )
 
     return [
         DefaultInfo(
-            executable = ctx.outputs.executable,
+            executable = executable,
             runfiles = ctx.runfiles(files = ctx.files.data)
         ),
     ]
@@ -64,5 +77,6 @@ _wd_test = rule(
         ),
         "flags": attr.string_list(),
         "data": attr.label_list(allow_files = True),
-    },
+        "_platforms_os_windows": attr.label(default = "@platforms//os:windows"),
+    }
 )

patches/capnp-ts@0.7.0.patch

@@ -3,7 +3,7 @@
 @@ -107,8 +107,6 @@ export class Struct extends Pointer {
    static readonly setText = setText;
    static readonly testWhich = testWhich;
- 
+
 -  readonly _capnp!: _Struct;
 -
    /**