[clang] Bump __cpp_constexpr in accordance with P2493R0

[MarcusBoay]

Summary

[clang] Bump __cpp_constexpr in accordance with P2493R0

https://github.com/llvm/llvm-project/issues/54052

[cor3ntin]

Thanks for the patch. However, wg21.link/P0848 need to be fully implemented before we can update __cpp_concepts. Could you only modify __cpp_constexpr ? Thanks

[MarcusBoay]

Revert __cpp_concepts since it is not fully implemented yet.

[MarcusBoay]

In D120456#3343348, @cor3ntin wrote:

Thanks for the patch. However, wg21.link/P0848 need to be fully implemented before we can update __cpp_concepts. Could you only modify __cpp_constexpr ? Thanks

Thanks for the info! I reverted the change to __cpp_concepts.

clang/lib/Frontend/InitPreprocessor.cpp

static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
 
   // C++11 features.
   if (LangOpts.CPlusPlus11) {
     Builder.defineMacro("__cpp_unicode_characters", "200704L");
     Builder.defineMacro("__cpp_raw_strings", "200710L");
     Builder.defineMacro("__cpp_unicode_literals", "200710L");
     Builder.defineMacro("__cpp_user_defined_literals", "200809L");
     Builder.defineMacro("__cpp_lambdas", "200907L");
-    Builder.defineMacro("__cpp_constexpr",
-                        LangOpts.CPlusPlus20 ? "201907L" :
-                        LangOpts.CPlusPlus17 ? "201603L" :
-                        LangOpts.CPlusPlus14 ? "201304L" : "200704");
+    Builder.defineMacro("__cpp_constexpr", LangOpts.CPlusPlus20
+                                               ? "202110L"
+                                               : LangOpts.CPlusPlus17
+                                                     ? "201603L"
+                                                     : LangOpts.CPlusPlus14
+                                                           ? "201304L"
+                                                           : "200704");
     Builder.defineMacro("__cpp_constexpr_in_decltype", "201711L");
     Builder.defineMacro("__cpp_range_based_for",
                         LangOpts.CPlusPlus17 ? "201603L" : "200907");
     Builder.defineMacro("__cpp_static_assert",
                         LangOpts.CPlusPlus17 ? "201411L" : "200410");
     Builder.defineMacro("__cpp_decltype", "200707L");
     Builder.defineMacro("__cpp_attributes", "200809L");
     Builder.defineMacro("__cpp_rvalue_references", "200610L");

clang/test/Lexer/cxx-features.cpp

#if defined(NO_THREADSAFE_STATICS) ? check(threadsafe_static_init, 0, 0, 0, 0, 0, 0) : \
                                      check(threadsafe_static_init, 200806, 200806, 200806, 200806, 200806, 200806)
 #error "wrong value for __cpp_threadsafe_static_init"
 #endif
 
 #if check(lambdas, 0, 200907, 200907, 200907, 200907, 200907)
 #error "wrong value for __cpp_lambdas"
 #endif
 
-#if check(constexpr, 0, 200704, 201304, 201603, 201907, 201907)
+#if check(constexpr, 0, 200704, 201304, 201603, 202110L, 202110L)
 #error "wrong value for __cpp_constexpr"
 #endif
 
 #if check(range_based_for, 0, 200907, 200907, 201603, 201603, 201603)
 #error "wrong value for __cpp_range_based_for"
 #endif
 
 #if check(static_assert, 0, 200410, 200410, 201411, 201411, 201411)