From 9626f9299beab9df0efec0bc3c79787251fa9c3e Mon Sep 17 00:00:00 2001
From: Austin Schuh <austin.linux@gmail.com>
Date: Sat, 5 Jul 2025 16:20:36 -0700
Subject: [PATCH] Register both windows compilers to enable cross compilation

There is a perfectly good cross compiler for the other Windows variant
(arm64 vs x86).  The only problem is that it doesn't get registered by
default, so it isn't easily available.  Register both of them and let
toolchain selection pick the right one automatically.

Signed-off-by: Austin Schuh <austin.linux@gmail.com>
---
 .../toolchain/BUILD.windows_toolchains.tpl    | 34 +++++++++++++++++++
 cc/private/toolchain/cc_configure.bzl         |  9 +++--
 2 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 cc/private/toolchain/BUILD.windows_toolchains.tpl

diff --git a/cc/private/toolchain/BUILD.windows_toolchains.tpl b/cc/private/toolchain/BUILD.windows_toolchains.tpl
new file mode 100644
index 00000000..63f5b6dc
--- /dev/null
+++ b/cc/private/toolchain/BUILD.windows_toolchains.tpl
@@ -0,0 +1,34 @@
+load("@platforms//host:constraints.bzl", "HOST_CONSTRAINTS")
+
+toolchain(
+    name = "cc-toolchain-arm64_windows",
+    exec_compatible_with = HOST_CONSTRAINTS,
+    target_compatible_with = [
+        "@platforms//cpu:arm64",
+        "@platforms//os:windows",
+    ],
+    toolchain = "@local_config_cc//:cc-compiler-arm64_windows",
+    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+)
+
+toolchain(
+    name = "cc-toolchain-x64_windows",
+    exec_compatible_with = HOST_CONSTRAINTS,
+    target_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:windows",
+    ],
+    toolchain = "@local_config_cc//:cc-compiler-x64_windows",
+    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+)
+
+toolchain(
+    name = "cc-toolchain-armeabi-v7a",
+    exec_compatible_with = HOST_CONSTRAINTS,
+    target_compatible_with = [
+        "@platforms//cpu:armv7",
+        "@platforms//os:android",
+    ],
+    toolchain = "@local_config_cc//:cc-compiler-armeabi-v7a",
+    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+)
diff --git a/cc/private/toolchain/cc_configure.bzl b/cc/private/toolchain/cc_configure.bzl
index ce0dac5c..7b1221fa 100644
--- a/cc/private/toolchain/cc_configure.bzl
+++ b/cc/private/toolchain/cc_configure.bzl
@@ -33,12 +33,17 @@ def cc_autoconf_toolchains_impl(repository_ctx):
     should_detect_cpp_toolchain = "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN" not in env or env["BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN"] != "1"
 
     if should_detect_cpp_toolchain:
+        if repository_ctx.os.name.find("windows") != -1:
+            build_path = "@rules_cc//cc/private/toolchain:BUILD.windows_toolchains.tpl"
+        else:
+            build_path = "@rules_cc//cc/private/toolchain:BUILD.toolchains.tpl"
         paths = resolve_labels(repository_ctx, [
-            "@rules_cc//cc/private/toolchain:BUILD.toolchains.tpl",
+            build_path,
         ])
+
         repository_ctx.template(
             "BUILD",
-            paths["@rules_cc//cc/private/toolchain:BUILD.toolchains.tpl"],
+            paths[build_path],
             {"%{name}": get_cpu_value(repository_ctx)},
         )
     else: