Force compilation with Clang on windows (newer version of bazel enable --incompatible_enable_cc_toolchain_resolution, and now we are trying to compile with MSVC -- bazelbuild/bazel#7260). In addition: improve the run-format.sh script to automatically find the correct clang-format binary if not provided

Author: ivan444

.bazelrc

@@ -28,13 +28,10 @@ common:macos   --config=unix
 # https://github.com/bazelbuild/bazel/issues/4341#issuecomment-758361769
 common:macos --features=-supports_dynamic_linker --linkopt=-framework --linkopt=CoreFoundation --host_linkopt=-framework --host_linkopt=CoreFoundation
 
-# Force the use clang-cl on Windows instead of MSVC. MSVC has some issues with
-# the codebase, so we focus the effort for now is to have a Windows Verible
-# compiled with clang-cl before fixing the issues unique to MSVC.
-# Since we use designated initializers (C99 ... but >= c++20), compiler really wants the c++20 mode
-common:windows --compiler=clang-cl --cxxopt=/std:c++20 --host_cxxopt=/std:c++20 --client_env=BAZEL_CXXOPTS=/std:c++20
-# Protobuf will be dropping support for MSVC + Bazel in 34.0. See github.com/protocolbuffers/protobuf/issues/20085
-common:windows --define='protobuf_allow_msvc=true'
+# Use clang-cl by default on Windows. MSVC has some issues with the codebase,
+# so we focus the effort for now is to have a Windows Verible compiled with
+# clang-cl before fixing the issues unique to MSVC.
+common:windows --extra_toolchains=@local_config_cc//:cc-toolchain-x64_windows-clang-cl --extra_execution_platforms=//:x64_windows-clang-cl
 
 # For 3rd party code: Disable warnings entirely.
 # They are not actionable and just create noise.

.github/bin/run-format.sh

@@ -31,7 +31,20 @@ done
 
 FORMAT_OUT=${TMPDIR:-/tmp}/clang-format-diff.out
 
-CLANG_FORMAT=${CLANG_FORMAT:-clang-format}
+# Use the provided Clang format binary, or try to fallback to clang-format-17
+# or clang-format.
+if [[ ! -v CLANG_FORMAT ]]; then
+  if command -v "clang-format-17" 2>&1 >/dev/null
+  then
+    CLANG_FORMAT="clang-format-17"
+  elif command -v "clang-format" 2>&1 >/dev/null
+  then
+    CLANG_FORMAT="clang-format"
+  else
+    (echo "-- Missing the clang-format binary! --"; exit 1)
+  fi
+fi
+
 BUILDIFIER=${BUILDIFIER:-buildifier}
 
 # Currently, we're using clang-format 17, as newer versions still have some

BUILD

@@ -55,3 +55,14 @@ genrule(
         "//verible/verilog/tools/lint:verible-verilog-lint",
     ],
 )
+
+# For building with clang-cl on Windows.
+# https://bazel.build/configure/windows#clang
+platform(
+    name = "x64_windows-clang-cl",
+    constraint_values = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:windows",
+        "@bazel_tools//tools/cpp:clang-cl",
+    ],
+)

MODULE.bazel

@@ -23,3 +23,11 @@ bazel_dep(name = "googletest", version = "1.14.0.bcr.1", dev_dependency = True)
 
 # To build compilation DB and run build-cleaning
 bazel_dep(name = "bant", version = "0.2.0", dev_dependency = True)
+
+#":x64_windows-clang-cl" Force clang-cl for the Windows builds.
+register_execution_platforms(
+    ":x64_windows-clang-cl"
+)
+register_toolchains(
+    "@local_config_cc//:cc-toolchain-x64_windows-clang-cl",
+)