[Clang] Improve type traits recognition in __has_builtin

[cor3ntin]

__has_builtin was relying on reversible identifiers and string matching to recognize builtin-type traits, leading to some newer type traits not being recognized.

Fixes #111477

[llvmbot]

@llvm/pr-subscribers-clang

Author: cor3ntin (cor3ntin)

Changes

__has_builtin was relying on reversible identifiers and string matching to recognize builtin-type traits, leading to some newer type traits not being recognized.

Fixes #111477

---

Full diff: https://github.com/llvm/llvm-project/pull/111516.diff

4 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+4-2)
• (modified) clang/include/clang/Basic/TokenKinds.def (+4-1)
• (modified) clang/lib/Lex/PPMacroExpansion.cpp (+33-19)
• (modified) clang/test/Preprocessor/feature_tests.cpp (+4-1)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 44d5f348ed2d54..d17d45c9331614 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -404,6 +404,8 @@ Bug Fixes to Compiler Builtins
 
 - ``__noop`` can now be used in a constant expression. (#GH102064)
 
+- Fix ``__has_builtin`` incorrectly returning ``false`` for some C++ type traits. (#GH111477)
+
 Bug Fixes to Attribute Support
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -635,8 +637,8 @@ New features
   if class of allocation and deallocation function mismatches.
   `Documentation <https://clang.llvm.org/docs/analyzer/checkers.html#unix-mismatcheddeallocator-c-c>`__.
 
-- Function effects, e.g. the ``nonblocking`` and ``nonallocating`` "performance constraint" 
-  attributes, are now verified. For example, for functions declared with the ``nonblocking`` 
+- Function effects, e.g. the ``nonblocking`` and ``nonallocating`` "performance constraint"
+  attributes, are now verified. For example, for functions declared with the ``nonblocking``
   attribute, the compiler can generate warnings about the use of any language features, or calls to
   other functions, which may block.
 
diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
index c5c3838407cf48..fdfb35de9cf287 100644
--- a/clang/include/clang/Basic/TokenKinds.def
+++ b/clang/include/clang/Basic/TokenKinds.def
@@ -64,6 +64,10 @@
 #ifndef EXPRESSION_TRAIT
 #define EXPRESSION_TRAIT(I,E,K) KEYWORD(I,K)
 #endif
+#ifndef TRANSFORM_TYPE_TRAIT_DEF
+#define TRANSFORM_TYPE_TRAIT_DEF(K, Trait) KEYWORD(__##Trait, KEYCXX)
+#endif
+
 #ifndef ALIAS
 #define ALIAS(X,Y,Z)
 #endif
@@ -534,7 +538,6 @@ TYPE_TRAIT_1(__has_unique_object_representations,
 TYPE_TRAIT_2(__is_layout_compatible, IsLayoutCompatible, KEYCXX)
 TYPE_TRAIT_2(__is_pointer_interconvertible_base_of, IsPointerInterconvertibleBaseOf, KEYCXX)
 
-#define TRANSFORM_TYPE_TRAIT_DEF(_, Trait) KEYWORD(__##Trait, KEYCXX)
 #include "clang/Basic/TransformTypeTraits.def"
 
 // Clang-only C++ Type Traits
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 2b62f573857ee8..63402de894594d 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1614,6 +1614,34 @@ asm("_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_"
     "RSt8ios_basecPK2tmPKcSB_");
 #endif
 
+static bool IsBuiltinTrait(Token &Tok) {
+
+#define TYPE_TRAIT_1(Spelling, Name, Key)                                      \
+  case tok::kw_##Spelling:                                                     \
+    return true;
+#define TYPE_TRAIT_2(Spelling, Name, Key)                                      \
+  case tok::kw_##Spelling:                                                     \
+    return true;
+#define TYPE_TRAIT_N(Spelling, Name, Key)                                      \
+  case tok::kw_##Spelling:                                                     \
+    return true;
+#define ARRAY_TYPE_TRAIT(Spelling, Name, Key)                                  \
+  case tok::kw_##Spelling:                                                     \
+    return true;
+#define EXPRESSION_TRAIT(Spelling, Name, Key)                                  \
+  case tok::kw_##Spelling:                                                     \
+    return true;
+#define TRANSFORM_TYPE_TRAIT_DEF(K, Spelling)                                  \
+  case tok::kw___##Spelling:                                                   \
+    return true;
+
+  switch (Tok.getKind()) {
+  default:
+    return false;
+#include "clang/Basic/TokenKinds.def"
+  }
+}
+
 /// ExpandBuiltinMacro - If an identifier token is read that is to be expanded
 /// as a builtin macro, handle it and return the next token as 'Tok'.
 void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
@@ -1812,25 +1840,11 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
                 getTargetInfo().getTargetOpts().FeatureMap);
           }
           return true;
-        } else if (II->getTokenID() != tok::identifier ||
-                   II->hasRevertedTokenIDToIdentifier()) {
-          // Treat all keywords that introduce a custom syntax of the form
-          //
-          //   '__some_keyword' '(' [...] ')'
-          //
-          // as being "builtin functions", even if the syntax isn't a valid
-          // function call (for example, because the builtin takes a type
-          // argument).
-          if (II->getName().starts_with("__builtin_") ||
-              II->getName().starts_with("__is_") ||
-              II->getName().starts_with("__has_"))
-            return true;
-          return llvm::StringSwitch<bool>(II->getName())
-              .Case("__array_rank", true)
-              .Case("__array_extent", true)
-#define TRANSFORM_TYPE_TRAIT_DEF(_, Trait) .Case("__" #Trait, true)
-#include "clang/Basic/TransformTypeTraits.def"
-              .Default(false);
+        } else if (IsBuiltinTrait(Tok)) {
+          return true;
+        } else if (II->getTokenID() != tok::identifier &&
+                   II->getName().starts_with("__builtin_")) {
+          return true;
         } else {
           return llvm::StringSwitch<bool>(II->getName())
               // Report builtin templates as being builtins.
diff --git a/clang/test/Preprocessor/feature_tests.cpp b/clang/test/Preprocessor/feature_tests.cpp
index 00421d74e6282a..a73d7dbe716d13 100644
--- a/clang/test/Preprocessor/feature_tests.cpp
+++ b/clang/test/Preprocessor/feature_tests.cpp
@@ -31,7 +31,10 @@
     !__has_builtin(__underlying_type) || \
     !__has_builtin(__is_trivial) || \
     !__has_builtin(__is_same_as) || \
-    !__has_builtin(__has_unique_object_representations)
+    !__has_builtin(__has_unique_object_representations) || \
+    !__has_builtin(__is_trivially_equality_comparable) || \
+    !__has_builtin(__reference_constructs_from_temporary) || \
+    !__has_builtin(__reference_binds_to_temporary)
 #error Clang should have these
 #endif
 

[erichkeane]

This seems reasonable to me. Its a shame that TRANSFORM_TYPE_TRAIT_DEF can't be done in terms of TYPE_TRAIT, but otherwiseI think this is a good direction.

[erichkeane]

unrelated :(

[timsong-cpp]

Can a fix be backported to 19?

[timsong-cpp]

__reference_converts_from_temporary too?