From 0b08bbb9d93c2e9ae1ad79fe156084dcebb855b7 Mon Sep 17 00:00:00 2001
From: "Adam Perry @ OpenAI" <anp@openai.com>
Date: Thu, 11 Jun 2026 11:21:47 -0700
Subject: [PATCH] [codex] Provide ARM64 MinGW powl compatibility support
 (#27323)

## Why

Windows ARM64 uses 64-bit `long double`, but the LLVM MinGW Bazel
configuration omits the upstream `powl` compatibility source and does
not link the `mingwex` archive that owns it. Cross-linking the release
binary therefore fails with an unresolved `powl` symbol.

## What changed

Patch the LLVM module to compile `math/arm-common/powl.c` into the ARM64
MinGW extension sources and add `-lmingwex` to the Windows toolchain
defaults.

## Validation

- `just bazel-lock-check`

Stack: 3 of 6. Depends on #27322.
---
 MODULE.bazel                          |  1 +
 patches/BUILD.bazel                   |  1 +
 patches/llvm_windows_arm64_powl.patch | 24 ++++++++++++++++++++++++
 3 files changed, 26 insertions(+)
 create mode 100644 patches/llvm_windows_arm64_powl.patch

diff --git a/MODULE.bazel b/MODULE.bazel
index 63c8df726..559516bd1 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -11,6 +11,7 @@ single_version_override(
     patch_strip = 1,
     patches = [
         "//patches:llvm_rusty_v8_custom_libcxx.patch",
+        "//patches:llvm_windows_arm64_powl.patch",
         "//patches:llvm_windows_symlink_extract.patch",
     ],
 )
diff --git a/patches/BUILD.bazel b/patches/BUILD.bazel
index 347b0f7ae..a431c3f3a 100644
--- a/patches/BUILD.bazel
+++ b/patches/BUILD.bazel
@@ -5,6 +5,7 @@ exports_files([
     "aws-lc-sys_windows_msvc_memcmp_probe.patch",
     "bzip2_windows_stack_args.patch",
     "llvm_rusty_v8_custom_libcxx.patch",
+    "llvm_windows_arm64_powl.patch",
     "llvm_windows_symlink_extract.patch",
     "rules_rust_windows_bootstrap_process_wrapper_linker.patch",
     "rules_rust_windows_build_script_runner_paths.patch",
diff --git a/patches/llvm_windows_arm64_powl.patch b/patches/llvm_windows_arm64_powl.patch
new file mode 100644
index 000000000..5e12bd7d3
--- /dev/null
+++ b/patches/llvm_windows_arm64_powl.patch
@@ -0,0 +1,24 @@
+# What: provide and link MinGW's ARM64 long-double `powl` compatibility shim.
+# Why: Windows ARM64 uses 64-bit long doubles, but LLVM's Bazel source list
+# omits the upstream `powl -> pow` implementation and its default link flags
+# omit the MinGW extension archive that owns the shim.
+
+diff --git a/runtimes/mingw/crt_sources.bzl b/runtimes/mingw/crt_sources.bzl
+--- a/runtimes/mingw/crt_sources.bzl
++++ b/runtimes/mingw/crt_sources.bzl
+@@ -420,4 +420,5 @@
+ MINGWEX_ARM64_SRCS = [
++    "math/arm-common/powl.c",
+     "math/sincos.c",
+     "math/sincosf.c",
+     "math/arm-common/sincosl.c",
+diff --git a/toolchain/args/windows/BUILD.bazel b/toolchain/args/windows/BUILD.bazel
+--- a/toolchain/args/windows/BUILD.bazel
++++ b/toolchain/args/windows/BUILD.bazel
+@@ -49,5 +49,6 @@ cc_args(
++        "-lmingwex",
+         # For now, we force on ucrt.
+         # TODO(cerisier): make this either a constraint or a build setting
+         "-lucrt",
+     ],
+     data = [