Implement latest C++ feature test macro recommendations.

We don't yet advertise init capture packs, because I found some bugs
while testing it. We reject-valid and then crash on both of these:

template<int ...a> auto x = [...y = a] {};
template<int ...a> auto x = [y = a...] {};

1 files changed, 14 insertions, 4 deletions

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 79360f89fc8..14c9ccd8a66 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -484,6 +484,7 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
                         LangOpts.CPlusPlus2a ? "201907L" :
                         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",
@@ -506,8 +507,9 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
   if (LangOpts.CPlusPlus14) {
     Builder.defineMacro("__cpp_binary_literals", "201304L");
     Builder.defineMacro("__cpp_digit_separators", "201309L");
-    Builder.defineMacro("__cpp_init_captures", "201304L");
-    Builder.defineMacro("__cpp_generic_lambdas", "201304L");
+    Builder.defineMacro("__cpp_init_captures", "201304L"); // (not latest)
+    Builder.defineMacro("__cpp_generic_lambdas",
+                        LangOpts.CPlusPlus2a ? "201707L" : "201304L");
     Builder.defineMacro("__cpp_decltype_auto", "201304L");
     Builder.defineMacro("__cpp_return_type_deduction", "201304L");
     Builder.defineMacro("__cpp_aggregate_nsdmi", "201304L");
@@ -523,7 +525,7 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
     Builder.defineMacro("__cpp_noexcept_function_type", "201510L");
     Builder.defineMacro("__cpp_capture_star_this", "201603L");
     Builder.defineMacro("__cpp_if_constexpr", "201606L");
-    Builder.defineMacro("__cpp_deduction_guides", "201703L");
+    Builder.defineMacro("__cpp_deduction_guides", "201703L"); // (not latest)
     Builder.defineMacro("__cpp_template_auto", "201606L"); // (old name)
     Builder.defineMacro("__cpp_namespace_attributes", "201411L");
     Builder.defineMacro("__cpp_enumerator_attributes", "201411L");
@@ -531,7 +533,8 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
     Builder.defineMacro("__cpp_variadic_using", "201611L");
     Builder.defineMacro("__cpp_aggregate_bases", "201603L");
     Builder.defineMacro("__cpp_structured_bindings", "201606L");
-    Builder.defineMacro("__cpp_nontype_template_args", "201411L");
+    Builder.defineMacro("__cpp_nontype_template_args",
+                        "201411L"); // (not latest)
     Builder.defineMacro("__cpp_fold_expressions", "201603L");
     Builder.defineMacro("__cpp_guaranteed_copy_elision", "201606L");
     Builder.defineMacro("__cpp_nontype_template_parameter_auto", "201606L");
@@ -543,10 +546,17 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
 
   // C++20 features.
   if (LangOpts.CPlusPlus2a) {
+    //Builder.defineMacro("__cpp_aggregate_paren_init", "201902L");
+    //Builder.defineMacro("__cpp_concepts", "201907L");
     Builder.defineMacro("__cpp_conditional_explicit", "201806L");
+    //Builder.defineMacro("__cpp_consteval", "201811L");
     Builder.defineMacro("__cpp_constexpr_dynamic_alloc", "201907L");
     Builder.defineMacro("__cpp_constinit", "201907L");
+    //Builder.defineMacro("__cpp_coroutines", "201902L");
+    Builder.defineMacro("__cpp_designated_initializers", "201707L");
     Builder.defineMacro("__cpp_impl_three_way_comparison", "201907L");
+    //Builder.defineMacro("__cpp_modules", "201907L");
+    //Builder.defineMacro("__cpp_using_enum", "201907L");
   }
   if (LangOpts.Char8)
     Builder.defineMacro("__cpp_char8_t", "201811L");