[clang] [Driver] Switch clang++ to default Solaris 11.4 compilation environment (PR #201063)

[Rainer Orth via cfe-commits]

https://github.com/rorth created https://github.com/llvm/llvm-project/pull/201063

`clang++` has long followed `g++`'s lead predefining `_XOPEN_SOURCE=600` on Solaris.  As detailed in [Switch g++ to default Solaris 11.4 compilation environment](https://gcc.gnu.org/pipermail/gcc-patches/2026-May/716990.html), this is no longer necessary in Solaris 11.4.

Tested on `amd64-pc-solaris2.11` and `sparcv9-sun-solaris2.11`.

>From 7db4ec6e2714fdc126152fcbe51ef043a7064cf8 Mon Sep 17 00:00:00 2001
From: Rainer Orth <ro at gcc.gnu.org>
Date: Tue, 2 Jun 2026 10:47:50 +0200
Subject: [PATCH] [Driver] Switch clang++ to default Solaris 11.4 compilation
 environment

`clang++` has long followed `g++`'s lead predefining `_XOPEN_SOURCE=600` on
Solaris.  As detailed in [Switch g++ to default Solaris 11.4 compilation
environment](https://gcc.gnu.org/pipermail/gcc-patches/2026-May/716990.html),
this is no longer necessary in Solaris 11.4.

Tested on `amd64-pc-solaris2.11` and `sparcv9-sun-solaris2.11`.
---
 clang/lib/Basic/Targets/OSTargets.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
index 0fc387c90b280..943373c20af32 100644
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -670,7 +670,6 @@ class LLVM_LIBRARY_VISIBILITY SolarisTargetInfo : public OSTargetInfo<Target> {
     DefineStd(Builder, "unix", Opts);
     Builder.defineMacro("__svr4__");
     Builder.defineMacro("__SVR4");
-    Builder.defineMacro("_XOPEN_SOURCE", "600");
     if (Opts.CPlusPlus) {
       Builder.defineMacro("__C99FEATURES__");
       Builder.defineMacro("_FILE_OFFSET_BITS", "64");