[C23] Implement N2490, Remove trigraphs??!

This follows the same implementation logic as with C++ and is
compatible with the GCC behavior in C.

Trigraphs are enabled by default in -std=c* conformance modes before
C23, but are disabled in GNU and Microsoft modes as well as in C23 or
later.

1 files changed, 5 insertions, 3 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index ed9cd12..7edea77 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3480,7 +3480,8 @@ void CompilerInvocationBase::GenerateLangArgs(const LangOptions &Opts,
                 Twine(Major) + "." + Twine(Minor) + "." + Twine(Subminor));
   }
 
-  if ((!Opts.GNUMode && !Opts.MSVCCompat && !Opts.CPlusPlus17) || T.isOSzOS()) {
+  if ((!Opts.GNUMode && !Opts.MSVCCompat && !Opts.CPlusPlus17 && !Opts.C23) ||
+      T.isOSzOS()) {
     if (!Opts.Trigraphs)
       GenerateArg(Consumer, OPT_fno_trigraphs);
   } else {
@@ -3876,10 +3877,11 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   // Mimicking gcc's behavior, trigraphs are only enabled if -trigraphs
   // is specified, or -std is set to a conforming mode.
-  // Trigraphs are disabled by default in c++1z onwards.
+  // Trigraphs are disabled by default in C++17 and C23 onwards.
   // For z/OS, trigraphs are enabled by default (without regard to the above).
   Opts.Trigraphs =
-      (!Opts.GNUMode && !Opts.MSVCCompat && !Opts.CPlusPlus17) || T.isOSzOS();
+      (!Opts.GNUMode && !Opts.MSVCCompat && !Opts.CPlusPlus17 && !Opts.C23) ||
+      T.isOSzOS();
   Opts.Trigraphs =
       Args.hasFlag(OPT_ftrigraphs, OPT_fno_trigraphs, Opts.Trigraphs);