[PATCH] D153621: [Clang] Correctly handle $, @, and ` when represented as UCN

[Corentin Jabot via Phabricator via cfe-commits]

cor3ntin added inline comments.


================
Comment at: clang/include/clang/Basic/DiagnosticLexKinds.td:200-207
+def warn_c2x_compat_literal_ucn_escape_basic_scs : Warning<
+  "specifying character '%0' with a universal character name is "
+  "incompatible with C standards before C2x">,
+  InGroup<CPre2xCompat>, DefaultIgnore;
+def warn_c2x_compat_literal_ucn_control_character : Warning<
+  "universal character name referring to a control character "
+  "incompatible with C standards before C2x">,
----------------
aaron.ballman wrote:
> Don't we need similar warnings for C++2c?
The change in C++ dates back to C++11, the warning you are looking for are just above (unchanged text)


================
Comment at: clang/lib/Lex/Lexer.cpp:3499-3500
   if (CodePoint < 0xA0) {
-    if (CodePoint == 0x24 || CodePoint == 0x40 || CodePoint == 0x60)
-      return CodePoint;
-
----------------
aaron.ballman wrote:
> Should this be looking for C2x?
See https://github.com/llvm/llvm-project/issues/62133 
This never worked. Making it work in older C mode is something I looked into but it didn't seem worth it.


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Comment at: clang/lib/Lex/LiteralSupport.cpp:630
+                       diag::warn_cxx98_compat_literal_ucn_escape_basic_scs
+                     : diag::warn_c2x_compat_literal_ucn_escape_basic_scs )
             << StringRef(&BasicSCSChar, 1);
----------------
aaron.ballman wrote:
> Won't this give the C warning in C++98  mode? (We should add test coverage for C++98)
I'll be adding test and replace by `Features.CPlusPlus`. But to your question, no, in C++98, `IsError` is true so that branch is not taken


Repository:
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  https://reviews.llvm.org/D153621/new/

https://reviews.llvm.org/D153621