[Clang] restrict use of attribute names reserved by the C++ standard (#106036)

Fixes #92196

https://eel.is/c++draft/macro.names#2
> A translation unit shall not #define or #undef names lexically
identical to keywords, to the identifiers listed in Table
[4](https://eel.is/c++draft/lex.name#tab:lex.name.special), or to the
[attribute-token](https://eel.is/c++draft/dcl.attr.grammar#nt:attribute-token)s
described in [[dcl.attr]](https://eel.is/c++draft/dcl.attr), except that
the names likely and unlikely may be defined as function-like macros
([[cpp.replace]](https://eel.is/c++draft/cpp.replace))[.](https://eel.is/c++draft/macro.names#2.sentence-1)

Author: a-tarasyuk

clang/docs/ReleaseNotes.rst

@@ -807,6 +807,8 @@ Improvements to Clang's diagnostics
 
 - Clang now emits a ``-Wignored-qualifiers`` diagnostic when a base class includes cv-qualifiers (#GH55474).
 
+- Clang now diagnoses the use of attribute names reserved by the C++ standard (#GH92196).
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/Basic/AttributeCommonInfo.h

@@ -61,13 +61,18 @@ class AttributeCommonInfo {
   };
   enum Kind {
 #define PARSED_ATTR(NAME) AT_##NAME,
-#include "clang/Sema/AttrParsedAttrList.inc"
+#include "clang/Basic/AttrParsedAttrList.inc"
 #undef PARSED_ATTR
     NoSemaHandlerAttribute,
     IgnoredAttribute,
     UnknownAttribute,
   };
   enum class Scope { NONE, CLANG, GNU, MSVC, OMP, HLSL, GSL, RISCV };
+  enum class AttrArgsInfo {
+    None,
+    Optional,
+    Required,
+  };
 
 private:
   const IdentifierInfo *AttrName = nullptr;
@@ -241,6 +246,8 @@ class AttributeCommonInfo {
   static Kind getParsedKind(const IdentifierInfo *Name,
                             const IdentifierInfo *Scope, Syntax SyntaxUsed);
 
+  static AttrArgsInfo getCXX11AttrArgsInfo(const IdentifierInfo *Name);
+
 private:
   /// Get an index into the attribute spelling list
   /// defined in Attr.td. This index is used by an attribute

clang/include/clang/Basic/Attributes.h

@@ -23,6 +23,11 @@ int hasAttribute(AttributeCommonInfo::Syntax Syntax,
                  const IdentifierInfo *Scope, const IdentifierInfo *Attr,
                  const TargetInfo &Target, const LangOptions &LangOpts);
 
+int hasAttribute(AttributeCommonInfo::Syntax Syntax,
+                 const IdentifierInfo *Scope, const IdentifierInfo *Attr,
+                 const TargetInfo &Target, const LangOptions &LangOpts,
+                 bool CheckPlugins);
+
 } // end namespace clang
 
 #endif // LLVM_CLANG_BASIC_ATTRIBUTES_H

clang/include/clang/Basic/CMakeLists.txt

@@ -36,6 +36,11 @@ clang_tablegen(AttrList.inc -gen-clang-attr-list
   SOURCE Attr.td
   TARGET ClangAttrList)
 
+clang_tablegen(AttrParsedAttrList.inc -gen-clang-attr-parsed-attr-list
+  -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
+  SOURCE Attr.td
+  TARGET ClangAttrParsedAttrList)
+
 clang_tablegen(AttrSubMatchRulesList.inc -gen-clang-attr-subject-match-rule-list
   -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
   SOURCE Attr.td
@@ -53,6 +58,12 @@ clang_tablegen(AttrHasAttributeImpl.inc -gen-clang-attr-has-attribute-impl
   TARGET ClangAttrHasAttributeImpl
   )
 
+clang_tablegen(CXX11AttributeInfo.inc -gen-cxx11-attribute-info
+  -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
+  SOURCE Attr.td
+  TARGET CXX11AttributeInfo
+  )
+
 clang_tablegen(Builtins.inc -gen-clang-builtins
   SOURCE Builtins.td
   TARGET ClangBuiltins)

clang/include/clang/Basic/DiagnosticGroups.td

@@ -760,6 +760,7 @@ def AmbiguousMacro : DiagGroup<"ambiguous-macro">;
 def KeywordAsMacro : DiagGroup<"keyword-macro">;
 def ReservedIdAsMacro : DiagGroup<"reserved-macro-identifier">;
 def ReservedIdAsMacroAlias : DiagGroup<"reserved-id-macro", [ReservedIdAsMacro]>;
+def ReservedAttributeIdentifier : DiagGroup<"reserved-attribute-identifier">;
 def RestrictExpansionMacro : DiagGroup<"restrict-expansion">;
 def FinalMacro : DiagGroup<"final-macro">;
 
@@ -935,7 +936,8 @@ def SignedEnumBitfield : DiagGroup<"signed-enum-bitfield">;
 
 def ReservedModuleIdentifier : DiagGroup<"reserved-module-identifier">;
 def ReservedIdentifier : DiagGroup<"reserved-identifier",
-    [ReservedIdAsMacro, ReservedModuleIdentifier, UserDefinedLiterals]>;
+    [ReservedIdAsMacro, ReservedModuleIdentifier,
+     UserDefinedLiterals, ReservedAttributeIdentifier]>;
 
 // Unreachable code warning groups.
 //

clang/include/clang/Basic/DiagnosticLexKinds.td

@@ -407,6 +407,9 @@ def warn_pp_macro_hides_keyword : Extension<
 def warn_pp_macro_is_reserved_id : Warning<
   "macro name is a reserved identifier">, DefaultIgnore,
   InGroup<ReservedIdAsMacro>;
+def warn_pp_macro_is_reserved_attribute_id : Warning<
+  "%0 is a reserved attribute identifier">, DefaultIgnore,
+  InGroup<ReservedAttributeIdentifier>;
 def warn_pp_objc_macro_redef_ignored : Warning<
   "ignoring redefinition of Objective-C qualifier macro">,
   InGroup<DiagGroup<"objc-macro-redefinition">>;

clang/include/clang/Lex/Preprocessor.h

@@ -2271,6 +2271,11 @@ class Preprocessor {
     }
   }
 
+  /// Determine whether the next preprocessor token to be
+  /// lexed is a '('.  If so, consume the token and return true, if not, this
+  /// method should have no observable side-effect on the lexed tokens.
+  bool isNextPPTokenLParen();
+
 private:
   /// Identifiers used for SEH handling in Borland. These are only
   /// allowed in particular circumstances
@@ -2648,11 +2653,6 @@ class Preprocessor {
 
   void removeCachedMacroExpandedTokensOfLastLexer();
 
-  /// Determine whether the next preprocessor token to be
-  /// lexed is a '('.  If so, consume the token and return true, if not, this
-  /// method should have no observable side-effect on the lexed tokens.
-  bool isNextPPTokenLParen();
-
   /// After reading "MACRO(", this method is invoked to read all of the formal
   /// arguments specified for the macro invocation.  Returns null on error.
   MacroArgs *ReadMacroCallArgumentList(Token &MacroName, MacroInfo *MI,

clang/include/clang/Sema/CMakeLists.txt

@@ -3,11 +3,6 @@ clang_tablegen(AttrTemplateInstantiate.inc -gen-clang-attr-template-instantiate
   SOURCE ../Basic/Attr.td
   TARGET ClangAttrTemplateInstantiate)
 
-clang_tablegen(AttrParsedAttrList.inc -gen-clang-attr-parsed-attr-list
-  -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
-  SOURCE ../Basic/Attr.td
-  TARGET ClangAttrParsedAttrList)
-
 clang_tablegen(AttrParsedAttrKinds.inc -gen-clang-attr-parsed-attr-kinds
   -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
   SOURCE ../Basic/Attr.td

clang/lib/Basic/Attributes.cpp

@@ -33,7 +33,8 @@ static int hasAttributeImpl(AttributeCommonInfo::Syntax Syntax, StringRef Name,
 
 int clang::hasAttribute(AttributeCommonInfo::Syntax Syntax,
                         const IdentifierInfo *Scope, const IdentifierInfo *Attr,
-                        const TargetInfo &Target, const LangOptions &LangOpts) {
+                        const TargetInfo &Target, const LangOptions &LangOpts,
+                        bool CheckPlugins) {
   StringRef Name = Attr->getName();
   // Normalize the attribute name, __foo__ becomes foo.
   if (Name.size() >= 4 && Name.starts_with("__") && Name.ends_with("__"))
@@ -61,14 +62,23 @@ int clang::hasAttribute(AttributeCommonInfo::Syntax Syntax,
   if (res)
     return res;
 
-  // Check if any plugin provides this attribute.
-  for (auto &Ptr : getAttributePluginInstances())
-    if (Ptr->hasSpelling(Syntax, Name))
-      return 1;
+  if (CheckPlugins) {
+    // Check if any plugin provides this attribute.
+    for (auto &Ptr : getAttributePluginInstances())
+      if (Ptr->hasSpelling(Syntax, Name))
+        return 1;
+  }
 
   return 0;
 }
 
+int clang::hasAttribute(AttributeCommonInfo::Syntax Syntax,
+                        const IdentifierInfo *Scope, const IdentifierInfo *Attr,
+                        const TargetInfo &Target, const LangOptions &LangOpts) {
+  return hasAttribute(Syntax, Scope, Attr, Target, LangOpts,
+                      /*CheckPlugins=*/true);
+}
+
 const char *attr::getSubjectMatchRuleSpelling(attr::SubjectMatchRule Rule) {
   switch (Rule) {
 #define ATTR_MATCH_RULE(NAME, SPELLING, IsAbstract)                            \
@@ -151,6 +161,17 @@ AttributeCommonInfo::getParsedKind(const IdentifierInfo *Name,
   return ::getAttrKind(normalizeName(Name, ScopeName, SyntaxUsed), SyntaxUsed);
 }
 
+AttributeCommonInfo::AttrArgsInfo
+AttributeCommonInfo::getCXX11AttrArgsInfo(const IdentifierInfo *Name) {
+  StringRef AttrName =
+      normalizeAttrName(Name, /*NormalizedScopeName*/ "", Syntax::AS_CXX11);
+#define CXX11_ATTR_ARGS_INFO
+  return llvm::StringSwitch<AttributeCommonInfo::AttrArgsInfo>(AttrName)
+#include "clang/Basic/CXX11AttributeInfo.inc"
+      .Default(AttributeCommonInfo::AttrArgsInfo::None);
+#undef CXX11_ATTR_ARGS_INFO
+}
+
 std::string AttributeCommonInfo::getNormalizedFullName() const {
   return static_cast<std::string>(
       normalizeName(getAttrName(), getScopeName(), getSyntax()));

clang/lib/Lex/PPDirectives.cpp

@@ -11,6 +11,8 @@
 ///
 //===----------------------------------------------------------------------===//
 
+#include "clang/Basic/AttributeCommonInfo.h"
+#include "clang/Basic/Attributes.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/DirectoryEntry.h"
 #include "clang/Basic/FileManager.h"
@@ -97,7 +99,8 @@ SourceRange Preprocessor::DiscardUntilEndOfDirective(Token &Tmp) {
 enum MacroDiag {
   MD_NoWarn,        //> Not a reserved identifier
   MD_KeywordDef,    //> Macro hides keyword, enabled by default
-  MD_ReservedMacro  //> #define of #undef reserved id, disabled by default
+  MD_ReservedMacro, //> #define of #undef reserved id, disabled by default
+  MD_ReservedAttributeIdentifier
 };
 
 /// Enumerates possible %select values for the pp_err_elif_after_else and
@@ -173,6 +176,22 @@ static bool isLanguageDefinedBuiltin(const SourceManager &SourceMgr,
   return false;
 }
 
+static bool isReservedCXXAttributeName(Preprocessor &PP, IdentifierInfo *II) {
+  const LangOptions &Lang = PP.getLangOpts();
+  if (Lang.CPlusPlus &&
+      hasAttribute(AttributeCommonInfo::AS_CXX11, /* Scope*/ nullptr, II,
+                   PP.getTargetInfo(), Lang, /*CheckPlugins*/ false) > 0) {
+    AttributeCommonInfo::AttrArgsInfo AttrArgsInfo =
+        AttributeCommonInfo::getCXX11AttrArgsInfo(II);
+    if (AttrArgsInfo == AttributeCommonInfo::AttrArgsInfo::Required)
+      return PP.isNextPPTokenLParen();
+
+    return !PP.isNextPPTokenLParen() ||
+           AttrArgsInfo == AttributeCommonInfo::AttrArgsInfo::Optional;
+  }
+  return false;
+}
+
 static MacroDiag shouldWarnOnMacroDef(Preprocessor &PP, IdentifierInfo *II) {
   const LangOptions &Lang = PP.getLangOpts();
   StringRef Text = II->getName();
@@ -182,6 +201,8 @@ static MacroDiag shouldWarnOnMacroDef(Preprocessor &PP, IdentifierInfo *II) {
     return MD_KeywordDef;
   if (Lang.CPlusPlus11 && (Text == "override" || Text == "final"))
     return MD_KeywordDef;
+  if (isReservedCXXAttributeName(PP, II))
+    return MD_ReservedAttributeIdentifier;
   return MD_NoWarn;
 }
 
@@ -190,6 +211,8 @@ static MacroDiag shouldWarnOnMacroUndef(Preprocessor &PP, IdentifierInfo *II) {
   // Do not warn on keyword undef.  It is generally harmless and widely used.
   if (isReservedInAllContexts(II->isReserved(Lang)))
     return MD_ReservedMacro;
+  if (isReservedCXXAttributeName(PP, II))
+    return MD_ReservedAttributeIdentifier;
   return MD_NoWarn;
 }
 
@@ -365,6 +388,9 @@ bool Preprocessor::CheckMacroName(Token &MacroNameTok, MacroUse isDefineUndef,
     }
     if (D == MD_ReservedMacro)
       Diag(MacroNameTok, diag::warn_pp_macro_is_reserved_id);
+    if (D == MD_ReservedAttributeIdentifier)
+      Diag(MacroNameTok, diag::warn_pp_macro_is_reserved_attribute_id)
+          << II->getName();
   }
 
   // Okay, we got a good identifier.