[llvm] Update the libc BUILD.bazel file with selects for Windows builds. (PR #131172)

[Brian Ledger via llvm-commits]

https://github.com/bashi-bazouk created https://github.com/llvm/llvm-project/pull/131172

The Windows toolchain needs to build libc targets in order to support libc++. Currently, some targets fail to resolve, due to non-exhaustive select statements, not accounting for Windows builds.

This change adds clauses to select statements so that Windows builds can proceed.

Additionally, `__support_osutil_exit`, is configured to pass nothing to `srcs` for non-Linux builds. `__support_osutil_exit `is unconditionally included in the transitive dependencies of `extern_libc_shared`. 

>From 9e8fc53f437d66a50352e3f731cb9074b62c77fa Mon Sep 17 00:00:00 2001
From: Brian Ledger <brianpl at google.com>
Date: Thu, 13 Mar 2025 12:22:29 -0400
Subject: [PATCH 1/2] Update the libc BUILD file with selects for Windows
 builds.

The Windows toolchain needs to build libc targets in order to support libc++. Currently, some targets fail to resolve, due to non-exhaustive select statements, not accounting for Windows builds.

This change adds clauses to select statements so that Windows builds can proceed.

Additionally, `__support_osutil_exit`, is configured to pass nothing to `srcs` for non-Linux builds. `__support_osutil_exit `is unconditionally included in the transitive dependencies of `extern_libc_shared`.
---
 utils/bazel/llvm-project-overlay/libc/BUILD.bazel | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 757db65ca8a77..457aa7281d4e2 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -1,5 +1,5 @@
 # This file is licensed under the Apache License v2.0 with LLVM Exceptions.
-# See https://llvm.org/LICENSE.txt for license information.
+got# See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 # LLVM libc project.
@@ -1319,6 +1319,7 @@ libc_support_library(
             "src/__support/OSUtil/linux/aarch64/syscall.h",
             "src/__support/OSUtil/linux/x86_64/syscall.h",
         ],
+	"@platforms//os:windows": [],
     }),
     deps = [
         ":__support_common",
@@ -1360,6 +1361,7 @@ libc_support_library(
     textual_hdrs = select({
         "@platforms//os:macos": ["src/__support/OSUtil/darwin/io.h"],
         "@platforms//os:linux": ["src/__support/OSUtil/linux/io.h"],
+	"@platforms//os:windows": ["src/__support/OSUtil/windows/io.h"],
     }),
     deps = [
         ":__support_common",
@@ -1371,7 +1373,10 @@ libc_support_library(
 
 libc_support_library(
     name = "__support_osutil_exit",
-    srcs = ["src/__support/OSUtil/linux/exit.cpp"],
+    srcs = select({
+        "@platforms//os:linux": ["src/__support/OSUtil/linux/exit.cpp"],
+	"//condition:default": [],
+    }),
     hdrs = ["src/__support/OSUtil/exit.h"],
     target_compatible_with = select({
         "@platforms//os:linux": [],

>From 109398cb6f2543933d9c7244668f348c4908d95e Mon Sep 17 00:00:00 2001
From: Brian Ledger <brianpl at google.com>
Date: Thu, 13 Mar 2025 13:20:50 -0400
Subject: [PATCH 2/2] fix a typo

---
 utils/bazel/llvm-project-overlay/libc/BUILD.bazel | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 457aa7281d4e2..25a9736b3671e 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -1,5 +1,5 @@
 # This file is licensed under the Apache License v2.0 with LLVM Exceptions.
-got# See https://llvm.org/LICENSE.txt for license information.
+# See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 # LLVM libc project.