[c++20] Implement P0482R6: enable -fchar8_t by default in C++20 mode.

This unfortunately results in a substantial breaking change when
switching to C++20, but it's not yet clear what / how much we should
do about that. We may want to add a compatibility conversion from
u8 string literals to const char*, similar to how C++98 provided a
compatibility conversion from string literals to non-const char*,
but that's not handled by this patch.

The feature can be disabled in C++20 mode with -fno-char8_t.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@346892 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 70 insertions, 64 deletions

diff --git a/test/Lexer/cxx-features.cpp b/test/Lexer/cxx-features.cpp
index 772fa26e96..e4fea0b5bb 100644
--- a/test/Lexer/cxx-features.cpp
+++ b/test/Lexer/cxx-features.cpp
@@ -9,53 +9,64 @@
 // RUN: %clang_cc1 -fno-rtti -fno-threadsafe-statics -verify %s -DNO_EXCEPTIONS -DNO_RTTI -DNO_THREADSAFE_STATICS -fsized-deallocation
 // RUN: %clang_cc1 -fcoroutines-ts -DNO_EXCEPTIONS -DCOROUTINES -verify -fsized-deallocation %s
 // RUN: %clang_cc1 -fchar8_t -DNO_EXCEPTIONS -DCHAR8_T -verify -fsized-deallocation %s
+// RUN: %clang_cc1 -std=c++2a -fno-char8_t -DNO_EXCEPTIONS -DNO_CHAR8_T -verify -fsized-deallocation %s
 
 // expected-no-diagnostics
 
 // FIXME using `defined` in a macro has undefined behavior.
 #if __cplusplus < 201103L
-#define check(macro, cxx98, cxx11, cxx14, cxx17) cxx98 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx98
+#define check(macro, cxx98, cxx11, cxx14, cxx17, cxx20) (cxx98 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx98)
 #elif __cplusplus < 201402L
-#define check(macro, cxx98, cxx11, cxx14, cxx17) cxx11 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx11
-#elif __cplusplus < 201406L
-#define check(macro, cxx98, cxx11, cxx14, cxx17) cxx14 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx14
+#define check(macro, cxx98, cxx11, cxx14, cxx17, cxx20) (cxx11 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx11)
+#elif __cplusplus < 201703L
+#define check(macro, cxx98, cxx11, cxx14, cxx17, cxx20) (cxx14 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx14)
+#elif __cplusplus <= 201703L
+#define check(macro, cxx98, cxx11, cxx14, cxx17, cxx20) (cxx17 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx17)
 #else
-#define check(macro, cxx98, cxx11, cxx14, cxx17) cxx17 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx17
+#define check(macro, cxx98, cxx11, cxx14, cxx17, cxx20) (cxx20 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx20)
+#endif
+
+// --- C++20 features ---
+
+#if defined(CHAR8_T) ? check(char8_t, 201811, 201811, 201811, 201811, 201811) : \
+    defined(NO_CHAR8_T) ? check(char8_t, 0, 0, 0, 0, 0) : \
+    check(char8_t, 0, 0, 0, 0, 201811)
+#error "wrong value for __cpp_char8_t"
 #endif
 
 // --- C++17 features ---
 
-#if check(hex_float, 0, 0, 0, 201603)
+#if check(hex_float, 0, 0, 0, 201603, 201603)
 #error "wrong value for __cpp_hex_float"
 #endif
 
-#if check(inline_variables, 0, 0, 0, 201606)
+#if check(inline_variables, 0, 0, 0, 201606, 201606)
 #error "wrong value for __cpp_inline_variables"
 #endif
 
-#if check(aligned_new, 0, 0, 0, 201606)
+#if check(aligned_new, 0, 0, 0, 201606, 201606)
 #error "wrong value for __cpp_aligned_new"
 #endif
 
-#if check(guaranteed_copy_elision, 0, 0, 0, 201606)
+#if check(guaranteed_copy_elision, 0, 0, 0, 201606, 201606)
 #error "wrong value for __cpp_guaranteed_copy_elision"
 #endif
 
-#if check(noexcept_function_type, 0, 0, 0, 201510)
+#if check(noexcept_function_type, 0, 0, 0, 201510, 201510)
 #error "wrong value for __cpp_noexcept_function_type"
 #endif
 
-#if check(fold_expressions, 0, 0, 0, 201603)
+#if check(fold_expressions, 0, 0, 0, 201603, 201603)
 #error "wrong value for __cpp_fold_expressions"
 #endif
 
-#if check(capture_star_this, 0, 0, 0, 201603)
+#if check(capture_star_this, 0, 0, 0, 201603, 201603)
 #error "wrong value for __cpp_capture_star_this"
 #endif
 
 // constexpr checked below
 
-#if check(if_constexpr, 0, 0, 0, 201606)
+#if check(if_constexpr, 0, 0, 0, 201606, 201606)
 #error "wrong value for __cpp_if_constexpr"
 #endif
 
@@ -63,204 +74,199 @@
 
 // static_assert checked below
 
-#if check(deduction_guides, 0, 0, 0, 201703)
+#if check(deduction_guides, 0, 0, 0, 201703, 201703)
 #error "wrong value for __cpp_deduction_guides"
 #endif
 
-#if check(nontype_template_parameter_auto, 0, 0, 0, 201606)
+#if check(nontype_template_parameter_auto, 0, 0, 0, 201606, 201606)
 #error "wrong value for __cpp_nontype_template_parameter_auto"
 #endif
 
 // This is the old name (from P0096R4) for
 // __cpp_nontype_template_parameter_auto
-#if check(template_auto, 0, 0, 0, 201606)
+#if check(template_auto, 0, 0, 0, 201606, 201606)
 #error "wrong value for __cpp_template_auto"
 #endif
 
-#if check(namespace_attributes, 0, 0, 0, 201411)
+#if check(namespace_attributes, 0, 0, 0, 201411, 201411)
 // FIXME: allowed without warning in C++14 and C++11
 #error "wrong value for __cpp_namespace_attributes"
 #endif
 
-#if check(enumerator_attributes, 0, 0, 0, 201411)
+#if check(enumerator_attributes, 0, 0, 0, 201411, 201411)
 // FIXME: allowed without warning in C++14 and C++11
 #error "wrong value for __cpp_enumerator_attributes"
 #endif
 
 // This is an old name (from P0096R4), now removed from SD-6.
-#if check(nested_namespace_definitions, 0, 0, 0, 201411)
+#if check(nested_namespace_definitions, 0, 0, 0, 201411, 201411)
 #error "wrong value for __cpp_nested_namespace_definitions"
 #endif
 
 // inheriting_constructors checked below
 
-#if check(variadic_using, 0, 0, 0, 201611)
+#if check(variadic_using, 0, 0, 0, 201611, 201611)
 #error "wrong value for __cpp_variadic_using"
 #endif
 
-#if check(aggregate_bases, 0, 0, 0, 201603)
+#if check(aggregate_bases, 0, 0, 0, 201603, 201603)
 #error "wrong value for __cpp_aggregate_bases"
 #endif
 
-#if check(structured_bindings, 0, 0, 0, 201606)
+#if check(structured_bindings, 0, 0, 0, 201606, 201606)
 #error "wrong value for __cpp_structured_bindings"
 #endif
 
-#if check(nontype_template_args, 0, 0, 0, 201411)
+#if check(nontype_template_args, 0, 0, 0, 201411, 201411)
 #error "wrong value for __cpp_nontype_template_args"
 #endif
 
 #if defined(RELAXED_TEMPLATE_TEMPLATE_ARGS) \
-    ? check(template_template_args, 0, 0, 0, 201611) \
-    : check(template_template_args, 0, 0, 0, 0)
+    ? check(template_template_args, 0, 0, 0, 201611, 201611) \
+    : check(template_template_args, 0, 0, 0, 0, 0)
 #error "wrong value for __cpp_template_template_args"
 #endif
 
 // --- C++14 features ---
 
-#if check(binary_literals, 0, 0, 201304, 201304)
+#if check(binary_literals, 0, 0, 201304, 201304, 201304)
 #error "wrong value for __cpp_binary_literals"
 #endif
 
 // (Removed from SD-6.)
-#if check(digit_separators, 0, 0, 201309, 201309)
+#if check(digit_separators, 0, 0, 201309, 201309, 201309)
 #error "wrong value for __cpp_digit_separators"
 #endif
 
-#if check(init_captures, 0, 0, 201304, 201304)
+#if check(init_captures, 0, 0, 201304, 201304, 201304)
 #error "wrong value for __cpp_init_captures"
 #endif
 
-#if check(generic_lambdas, 0, 0, 201304, 201304)
+#if check(generic_lambdas, 0, 0, 201304, 201304, 201304)
 #error "wrong value for __cpp_generic_lambdas"
 #endif
 
-#if check(sized_deallocation, 0, 0, 201309, 201309)
+#if check(sized_deallocation, 0, 0, 201309, 201309, 201309)
 #error "wrong value for __cpp_sized_deallocation"
 #endif
 
 // constexpr checked below
 
-#if check(decltype_auto, 0, 0, 201304, 201304)
+#if check(decltype_auto, 0, 0, 201304, 201304, 201304)
 #error "wrong value for __cpp_decltype_auto"
 #endif
 
-#if check(return_type_deduction, 0, 0, 201304, 201304)
+#if check(return_type_deduction, 0, 0, 201304, 201304, 201304)
 #error "wrong value for __cpp_return_type_deduction"
 #endif
 
-#if check(runtime_arrays, 0, 0, 0, 0)
+#if check(runtime_arrays, 0, 0, 0, 0, 0)
 #error "wrong value for __cpp_runtime_arrays"
 #endif
 
-#if check(aggregate_nsdmi, 0, 0, 201304, 201304)
+#if check(aggregate_nsdmi, 0, 0, 201304, 201304, 201304)
 #error "wrong value for __cpp_aggregate_nsdmi"
 #endif
 
-#if check(variable_templates, 0, 0, 201304, 201304)
+#if check(variable_templates, 0, 0, 201304, 201304, 201304)
 #error "wrong value for __cpp_variable_templates"
 #endif
 
 // --- C++11 features ---
 
-#if check(unicode_characters, 0, 200704, 200704, 200704)
+#if check(unicode_characters, 0, 200704, 200704, 200704, 200704)
 #error "wrong value for __cpp_unicode_characters"
 #endif
 
-#if check(raw_strings, 0, 200710, 200710, 200710)
+#if check(raw_strings, 0, 200710, 200710, 200710, 200710)
 #error "wrong value for __cpp_raw_strings"
 #endif
 
-#if check(unicode_literals, 0, 200710, 200710, 200710)
+#if check(unicode_literals, 0, 200710, 200710, 200710, 200710)
 #error "wrong value for __cpp_unicode_literals"
 #endif
 
-#if check(user_defined_literals, 0, 200809, 200809, 200809)
+#if check(user_defined_literals, 0, 200809, 200809, 200809, 200809)
 #error "wrong value for __cpp_user_defined_literals"
 #endif
 
-#if defined(NO_THREADSAFE_STATICS) ? check(threadsafe_static_init, 0, 0, 0, 0) : check(threadsafe_static_init, 200806, 200806, 200806, 200806)
+#if defined(NO_THREADSAFE_STATICS) ? check(threadsafe_static_init, 0, 0, 0, 0, 0) : \
+                                     check(threadsafe_static_init, 200806, 200806, 200806, 200806, 200806)
 #error "wrong value for __cpp_threadsafe_static_init"
 #endif
 
-#if check(lambdas, 0, 200907, 200907, 200907)
+#if check(lambdas, 0, 200907, 200907, 200907, 200907)
 #error "wrong value for __cpp_lambdas"
 #endif
 
-#if check(constexpr, 0, 200704, 201304, 201603)
+#if check(constexpr, 0, 200704, 201304, 201603, 201603)
 #error "wrong value for __cpp_constexpr"
 #endif
 
-#if check(range_based_for, 0, 200907, 200907, 201603)
+#if check(range_based_for, 0, 200907, 200907, 201603, 201603)
 #error "wrong value for __cpp_range_based_for"
 #endif
 
-#if check(static_assert, 0, 200410, 200410, 201411)
+#if check(static_assert, 0, 200410, 200410, 201411, 201411)
 #error "wrong value for __cpp_static_assert"
 #endif
 
-#if check(decltype, 0, 200707, 200707, 200707)
+#if check(decltype, 0, 200707, 200707, 200707, 200707)
 #error "wrong value for __cpp_decltype"
 #endif
 
-#if check(attributes, 0, 200809, 200809, 200809)
+#if check(attributes, 0, 200809, 200809, 200809, 200809)
 #error "wrong value for __cpp_attributes"
 #endif
 
-#if check(rvalue_references, 0, 200610, 200610, 200610)
+#if check(rvalue_references, 0, 200610, 200610, 200610, 200610)
 #error "wrong value for __cpp_rvalue_references"
 #endif
 
-#if check(variadic_templates, 0, 200704, 200704, 200704)
+#if check(variadic_templates, 0, 200704, 200704, 200704, 200704)
 #error "wrong value for __cpp_variadic_templates"
 #endif
 
-#if check(initializer_lists, 0, 200806, 200806, 200806)
+#if check(initializer_lists, 0, 200806, 200806, 200806, 200806)
 #error "wrong value for __cpp_initializer_lists"
 #endif
 
-#if check(delegating_constructors, 0, 200604, 200604, 200604)
+#if check(delegating_constructors, 0, 200604, 200604, 200604, 200604)
 #error "wrong value for __cpp_delegating_constructors"
 #endif
 
-#if check(nsdmi, 0, 200809, 200809, 200809)
+#if check(nsdmi, 0, 200809, 200809, 200809, 200809)
 #error "wrong value for __cpp_nsdmi"
 #endif
 
-#if check(inheriting_constructors, 0, 201511, 201511, 201511)
+#if check(inheriting_constructors, 0, 201511, 201511, 201511, 201511)
 #error "wrong value for __cpp_inheriting_constructors"
 #endif
 
-#if check(ref_qualifiers, 0, 200710, 200710, 200710)
+#if check(ref_qualifiers, 0, 200710, 200710, 200710, 200710)
 #error "wrong value for __cpp_ref_qualifiers"
 #endif
 
-#if check(alias_templates, 0, 200704, 200704, 200704)
+#if check(alias_templates, 0, 200704, 200704, 200704, 200704)
 #error "wrong value for __cpp_alias_templates"
 #endif
 
 // --- C++98 features ---
 
-#if defined(NO_RTTI) ? check(rtti, 0, 0, 0, 0) : check(rtti, 199711, 199711, 199711, 199711)
+#if defined(NO_RTTI) ? check(rtti, 0, 0, 0, 0, 0) : check(rtti, 199711, 199711, 199711, 199711, 199711)
 #error "wrong value for __cpp_rtti"
 #endif
 
-#if defined(NO_EXCEPTIONS) ? check(exceptions, 0, 0, 0, 0) : check(exceptions, 199711, 199711, 199711, 199711)
+#if defined(NO_EXCEPTIONS) ? check(exceptions, 0, 0, 0, 0, 0) : check(exceptions, 199711, 199711, 199711, 199711, 199711)
 #error "wrong value for __cpp_exceptions"
 #endif
 
 // --- TS features --
 
-#if check(experimental_concepts, 0, 0, CONCEPTS_TS, CONCEPTS_TS)
+#if check(experimental_concepts, 0, 0, CONCEPTS_TS, CONCEPTS_TS, CONCEPTS_TS)
 #error "wrong value for __cpp_experimental_concepts"
 #endif
 
-#if defined(COROUTINES) ? check(coroutines, 201703L, 201703L, 201703L, 201703L) : check(coroutines, 0, 0, 0, 0)
+#if defined(COROUTINES) ? check(coroutines, 201703L, 201703L, 201703L, 201703L, 201703L) : check(coroutines, 0, 0, 0, 0, 0)
 #error "wrong value for __cpp_coroutines"
 #endif
-
-// --- not-yet-standard features --
-
-#if defined(CHAR8_T) ? check(char8_t, 201803, 201803, 201803, 201803) : check(char8_t, 0, 0, 0, 0)
-#error "wrong value for __cpp_char8_t"
-#endif