Suppress elided variadic macro argument extension diagnostic for macr…

…os using

the related comma pasting extension.

In certain cases, we used to get two diagnostics for what is essentially one
extension.  This change suppresses the first diagnostic in certain cases
where we know we're going to print the second diagnostic.  The
diagnostic is redundant, and it can't be suppressed in the definition
of the macro because it points at the use of the macro, so we want to
avoid printing it if possible.

The implementation works by detecting constructs which look like comma
pasting at the time of the definition of the macro; this information
is then used when the macro is used.  (We can't actually detect
whether we're using the comma pasting extension until the macro is
actually used, but we can detecting constructs which will be comma
pasting if the varargs argument is elided.)

<rdar://problem/12292192>



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167907 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Lex/MacroInfo.h

@@ -76,6 +76,9 @@ class MacroInfo {
   /// it has not yet been redefined or undefined.
   bool IsBuiltinMacro : 1;
 
+  /// \brief Whether this macro contains the sequence ", ## __VA_ARGS__"
+  bool HasCommaPasting : 1;
+
   /// \brief True if this macro was loaded from an AST file.
   bool IsFromAST : 1;
 
@@ -253,6 +256,9 @@ class MacroInfo {
   /// __LINE__, which requires processing before expansion.
   bool isBuiltinMacro() const { return IsBuiltinMacro; }
 
+  bool hasCommaPasting() const { return HasCommaPasting; }
+  void setHasCommaPasting() { HasCommaPasting = true; }
+
   /// isFromAST - Return true if this macro was loaded from an AST file.
   bool isFromAST() const { return IsFromAST; }
 

lib/Lex/MacroInfo.cpp

@@ -25,6 +25,7 @@ MacroInfo::MacroInfo(SourceLocation DefLoc)
     IsC99Varargs(false),
     IsGNUVarargs(false),
     IsBuiltinMacro(false),
+    HasCommaPasting(false),
     IsFromAST(false),
     ChangedAfterLoad(false),
     IsDisabled(false),
@@ -50,6 +51,7 @@ MacroInfo::MacroInfo(const MacroInfo &MI, llvm::BumpPtrAllocator &PPAllocator)
     IsC99Varargs(MI.IsC99Varargs),
     IsGNUVarargs(MI.IsGNUVarargs),
     IsBuiltinMacro(MI.IsBuiltinMacro),
+    HasCommaPasting(MI.HasCommaPasting),
     IsFromAST(MI.IsFromAST),
     ChangedAfterLoad(MI.ChangedAfterLoad),
     IsDisabled(MI.IsDisabled),

lib/Lex/PPDirectives.cpp

@@ -1809,14 +1809,43 @@ void Preprocessor::HandleDefineDirective(Token &DefineTok) {
     while (Tok.isNot(tok::eod)) {
       LastTok = Tok;
 
-      if (Tok.isNot(tok::hash)) {
+      if (Tok.isNot(tok::hash) && Tok.isNot(tok::hashhash)) {
         MI->AddTokenToBody(Tok);
 
         // Get the next token of the macro.
         LexUnexpandedToken(Tok);
         continue;
       }
 
+      if (Tok.is(tok::hashhash)) {
+
+        // If we see token pasting, check if it looks like the gcc comma
+        // pasting extension.  We'll use this information to suppress
+        // diagnostics later on.
+
+        // Get the next token of the macro.
+        LexUnexpandedToken(Tok);
+
+        if (Tok.is(tok::eod)) {
+          MI->AddTokenToBody(LastTok);
+          break;
+        }
+
+        unsigned NumTokens = MI->getNumTokens();
+        if (NumTokens && Tok.getIdentifierInfo() == Ident__VA_ARGS__ &&
+            MI->getReplacementToken(NumTokens-1).is(tok::comma))
+          MI->setHasCommaPasting();
+
+        // Things look ok, add the '##' and param name tokens to the macro.
+        MI->AddTokenToBody(LastTok);
+        MI->AddTokenToBody(Tok);
+        LastTok = Tok;
+
+        // Get the next token of the macro.
+        LexUnexpandedToken(Tok);
+        continue;
+      }
+
       // Get the next token of the macro.
       LexUnexpandedToken(Tok);
 

lib/Lex/PPMacroExpansion.cpp

@@ -619,9 +619,14 @@ MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(Token &MacroName,
       // Varargs where the named vararg parameter is missing: OK as extension.
       //   #define A(x, ...)
       //   A("blah")
-      Diag(Tok, diag::ext_missing_varargs_arg);
-      Diag(MI->getDefinitionLoc(), diag::note_macro_here)
-        << MacroName.getIdentifierInfo();
+      //
+      // If the macro contains the comma pasting extension, the diagnostic
+      // is suppressed; we know we'll get another diagnostic later.
+      if (!MI->hasCommaPasting()) {
+        Diag(Tok, diag::ext_missing_varargs_arg);
+        Diag(MI->getDefinitionLoc(), diag::note_macro_here)
+          << MacroName.getIdentifierInfo();
+      }
 
       // Remember this occurred, allowing us to elide the comma when used for
       // cases like:

lib/Serialization/ASTReader.cpp

@@ -1141,6 +1141,7 @@ void ASTReader::ReadMacroRecord(ModuleFile &F, uint64_t Offset,
         // Decode function-like macro info.
         bool isC99VarArgs = Record[NextIndex++];
         bool isGNUVarArgs = Record[NextIndex++];
+        bool hasCommaPasting = Record[NextIndex++];
         MacroArgs.clear();
         unsigned NumArgs = Record[NextIndex++];
         for (unsigned i = 0; i != NumArgs; ++i)
@@ -1150,6 +1151,7 @@ void ASTReader::ReadMacroRecord(ModuleFile &F, uint64_t Offset,
         MI->setIsFunctionLike();
         if (isC99VarArgs) MI->setIsC99Varargs();
         if (isGNUVarArgs) MI->setIsGNUVarargs();
+        if (hasCommaPasting) MI->setHasCommaPasting();
         MI->setArgumentList(MacroArgs.data(), MacroArgs.size(),
                             PP.getPreprocessorAllocator());
       }

lib/Serialization/ASTWriter.cpp

@@ -1855,6 +1855,7 @@ void ASTWriter::WritePreprocessor(const Preprocessor &PP, bool IsModule) {
 
         Record.push_back(MI->isC99Varargs());
         Record.push_back(MI->isGNUVarargs());
+        Record.push_back(MI->hasCommaPasting());
         Record.push_back(MI->getNumArgs());
         for (MacroInfo::arg_iterator I = MI->arg_begin(), E = MI->arg_end();
              I != E; ++I)

test/Preprocessor/macro_fn.c

@@ -44,3 +44,9 @@ one_dot()   /* empty first argument, elided ...: expected-warning {{must specify
 #define E() (i == 0)
 #if E
 #endif
+
+
+/* <rdar://problem/12292192> */
+#define NSAssert(condition, desc, ...) /* expected-warning {{variadic macros are a C99 feature}} */ \
+    SomeComplicatedStuff((desc), ##__VA_ARGS__) /* expected-warning {{token pasting of ',' and __VA_ARGS__ is a GNU extension}} */
+NSAssert(somecond, somedesc)