codex/patches/llvm_windows_gnullvm_abi.patch

# What: mark hermetic LLVM's Windows targets as gnullvm-only.
# Why: the toolchain uses *-w64-windows-gnu triples and MinGW runtimes; it does
# not contain the licensed MSVC linker libraries or Windows SDK.

diff --git a/constraints/windows_abi/BUILD.bazel b/constraints/windows_abi/BUILD.bazel
new file mode 100644
index 0000000..42aa1aa
--- /dev/null
+++ b/constraints/windows_abi/BUILD.bazel
@@ -0,0 +1,15 @@
+package(default_visibility = ["//visibility:public"])
+
+constraint_setting(
+    name = "windows_abi",
+)
+
+constraint_value(
+    name = "gnullvm",
+    constraint_setting = ":windows_abi",
+)
+
+constraint_value(
+    name = "msvc",
+    constraint_setting = ":windows_abi",
+)
diff --git a/toolchain/bootstrap/declare_toolchains.bzl b/toolchain/bootstrap/declare_toolchains.bzl
index 906ba7e..608ec56 100644
--- a/toolchain/bootstrap/declare_toolchains.bzl
+++ b/toolchain/bootstrap/declare_toolchains.bzl
@@ -260,7 +260,9 @@ def declare_toolchains(
                 target_compatible_with = [
                     "@platforms//cpu:{}".format(target_cpu),
                     "@platforms//os:{}".format(target_os),
-                ],
+                ] + ([
+                    "@llvm//constraints/windows_abi:gnullvm",
+                ] if target_os == "windows" else []),
                 target_settings = [
                     "@llvm//toolchain:bootstrapped_toolchain",
                 ],
diff --git a/toolchain/declare_toolchains.bzl b/toolchain/declare_toolchains.bzl
index 9870bdd..5d06829 100644
--- a/toolchain/declare_toolchains.bzl
+++ b/toolchain/declare_toolchains.bzl
@@ -34,7 +34,9 @@ def declare_toolchains(*, execs = SUPPORTED_EXECS, targets = SUPPORTED_TARGETS):
                 target_compatible_with = [
                     "@platforms//cpu:{}".format(target_cpu),
                     "@platforms//os:{}".format(target_os),
-                ],
+                ] + ([
+                    "@llvm//constraints/windows_abi:gnullvm",
+                ] if target_os == "windows" else []),
                 target_settings = [
                     "@llvm//toolchain:prebuilt_toolchain",
                 ],