$NetBSD: patch-lib_Basic_Targets_OSTargets.h,v 1.4 2019/10/19 13:54:29 adam Exp $

Sync SunOS default defines with a working reality.

--- llvm-18.1.8.src/tools/clang/lib/Basic/Targets/OSTargets.h.orig
+++ llvm-18.1.8.src/tools/clang/lib/Basic/Targets/OSTargets.h
@@ -593,22 +593,15 @@
     DefineStd(Builder, "unix", Opts);
     Builder.defineMacro("__svr4__");
     Builder.defineMacro("__SVR4");
-    // Solaris headers require _XOPEN_SOURCE to be set to 600 for C99 and
-    // newer, but to 500 for everything else.  feature_test.h has a check to
-    // ensure that you are not using C99 with an old version of X/Open or C89
-    // with a new version.
-    if (Opts.C99)
-      Builder.defineMacro("_XOPEN_SOURCE", "600");
-    else
-      Builder.defineMacro("_XOPEN_SOURCE", "500");
+    // Compatibility with GCC to satisfy <sys/feature_tests.h> requirements.
     if (Opts.CPlusPlus) {
-      Builder.defineMacro("__C99FEATURES__");
+      Builder.defineMacro("__STDC_VERSION__", "199901L");
+      Builder.defineMacro("_XOPEN_SOURCE", "600");
       Builder.defineMacro("_FILE_OFFSET_BITS", "64");
-    }
-    // GCC restricts the next two to C++.
     Builder.defineMacro("_LARGEFILE_SOURCE");
     Builder.defineMacro("_LARGEFILE64_SOURCE");
     Builder.defineMacro("__EXTENSIONS__");
+    }
     if (Opts.POSIXThreads)
       Builder.defineMacro("_REENTRANT");
     if (this->HasFloat128)