Remove the flag requirement for Bazel+MSVC users.

As discussed in #20085, we were originally intending to drop support for this combination.  With Bazel's recent changes to virtual includes on windows though, we now have ~90 extra characters of runway.  This should be more than enough to continue supporting MSVC into the forseeable future.  Clang-cl support will be kept in place as an alternative on windows

PiperOrigin-RevId: 783798673

Author: mkruskal-google

.github/workflows/test_cpp.yml

@@ -427,7 +427,7 @@ jobs:
           - name: Windows Bazel
             os: windows-2022
             cache_key: windows-2022-msvc-cl
-            bazel: test //src/...  --config=msvc-cl --test_tag_filters=-conformance --build_tag_filters=-conformance --define=protobuf_allow_msvc=true
+            bazel: test //src/...  --config=msvc-cl --test_tag_filters=-conformance --build_tag_filters=-conformance
           - name: Windows Bazel clang-cl
             os: windows-2022
             cache_key: windows-2022-clang-cl

examples/.bazelrc

@@ -3,7 +3,6 @@ common --enable_platform_specific_config
 build:linux --cxxopt=-std=c++17 --host_cxxopt=-std=c++17
 build:macos --cxxopt=-std=c++17 --host_cxxopt=-std=c++17
 
-build:windows --extra_toolchains=@local_config_cc//:cc-toolchain-x64_windows-clang-cl --extra_execution_platforms=//:x64_windows-clang-cl
 common:windows --cxxopt=/std:c++17 --host_cxxopt=/std:c++17 --enable_runfiles
 
 build --experimental_remote_cache_eviction_retries=5

examples/BUILD.bazel

@@ -193,16 +193,3 @@ pkg_files(
     strip_prefix = strip_prefix.from_root(""),
     visibility = ["//visibility:public"],
 )
-
-platform(
-    name = "x64_windows-clang-cl",
-    constraint_values = [
-        "@platforms//cpu:x86_64",
-        "@platforms//os:windows",
-        # This is necessary for Bazel 7 compatibility with a MODULE.bazel file that still works in
-        # Bazel 8.  Using cc_configure_extension from rules_cc produces a @local_config_cc
-        # repository that's not compatible with @bazel_tools//tools/cpp:clang-cl from before
-        # Bazel 8.  See https://github.com/bazelbuild/rules_cc/issues/330.
-        "@rules_cc//cc/private/toolchain:clang-cl",
-    ],
-)

examples/MODULE.bazel

@@ -19,12 +19,7 @@ local_path_override(
 )
 
 bazel_dep(name = "bazel_skylib", version = "1.7.1")
-bazel_dep(name = "platforms", version = "0.0.10")
 bazel_dep(name = "rules_cc", version = "0.0.17")
 bazel_dep(name = "rules_java", version = "8.6.1")
 bazel_dep(name = "rules_pkg", version = "1.0.1")
 bazel_dep(name = "rules_python", version = "1.4.1")
-
-# For clang-cl configuration
-cc_configure = use_extension("@rules_cc//cc:extensions.bzl", "cc_configure_extension")
-use_repo(cc_configure, "local_config_cc")

examples/WORKSPACE

@@ -33,16 +33,6 @@ local_repository(
     path = "..",
 )
 
-# Bazel platform rules, for clang-cl.
-http_archive(
-    name = "platforms",
-    sha256 = "218efe8ee736d26a3572663b374a253c012b716d8af0c07e842e82f238a0a7ee",
-    urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/platforms/releases/download/0.0.10/platforms-0.0.10.tar.gz",
-        "https://github.com/bazelbuild/platforms/releases/download/0.0.10/platforms-0.0.10.tar.gz",
-    ],
-)
-
 load("@com_google_protobuf//:protobuf_deps.bzl", "PROTOBUF_MAVEN_ARTIFACTS", "protobuf_deps")
 
 protobuf_deps()
@@ -59,12 +49,6 @@ load("@rules_python//python:repositories.bzl", "py_repositories")
 
 py_repositories()
 
-load("@rules_cc//cc:repositories.bzl", "rules_cc_dependencies", "rules_cc_toolchains")
-
-rules_cc_dependencies()
-
-rules_cc_toolchains()
-
 load("@rules_jvm_external//:repositories.bzl", "rules_jvm_external_deps")
 
 rules_jvm_external_deps()

src/google/protobuf/stubs/BUILD.bazel

@@ -22,12 +22,6 @@ cc_library(
         "status_macros.h",
     ],
     copts = COPTS,
-    defines = ["GOOGLE_PROTOBUF_USING_BAZEL=1"] + select({
-        "//build_defs:protobuf_allow_msvc": [
-            "GOOGLE_PROTOBUF_MSVC_BAZEL_OVERRIDE=1",
-        ],
-        "//conditions:default": [],
-    }),
     linkopts = LINK_OPTS,
     strip_include_prefix = "/src",
     deps = [

src/google/protobuf/stubs/port.h

@@ -31,13 +31,6 @@
 #include <byteswap.h>  // IWYU pragma: export
 #endif
 
-#if defined(_MSC_VER) && !defined(__clang__) && \
-    defined(GOOGLE_PROTOBUF_USING_BAZEL) &&     \
-    !defined(GOOGLE_PROTOBUF_MSVC_BAZEL_OVERRIDE)
-#error \
-    "Protobuf will be dropping support for MSVC + Bazel in 34.0.  To continue using it until then, use the flag --define=protobuf_allow_msvc=true.  For feedback or discussion, see github.com/protocolbuffers/protobuf/issues/20085."
-#endif
-
 // Legacy: some users reference these (internal-only) macros even though we
 // don't need them any more.
 #if defined(_MSC_VER) && defined(PROTOBUF_USE_DLLS)