[preprocessor] Allow comparing two macro definitions syntactically instead of only lexically.

Syntactically means the function macro parameter names do not need to use the same
identifiers in order for the definitions to be considered identical.

Syntactic equivalence is a microsoft extension for macro redefinitions and we'll also
use this kind of comparison to check for ambiguous macros coming from modules.

rdar://13562254

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178671 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 28 insertions, 12 deletions

diff --git a/lib/Lex/MacroInfo.cpp b/lib/Lex/MacroInfo.cpp
index dc091f625b..5abafe1cb7 100644
--- a/lib/Lex/MacroInfo.cpp
+++ b/lib/Lex/MacroInfo.cpp
@@ -61,11 +61,17 @@ unsigned MacroInfo::getDefinitionLengthSlow(SourceManager &SM) const {
   return DefinitionLength;
 }
 
-// isIdenticalTo - Return true if the specified macro definition is equal to
-// this macro in spelling, arguments, and whitespace.  This is used to emit
-// duplicate definition warnings.  This implements the rules in C99 6.10.3.
-//
-bool MacroInfo::isIdenticalTo(const MacroInfo &Other, Preprocessor &PP) const {
+/// \brief Return true if the specified macro definition is equal to
+/// this macro in spelling, arguments, and whitespace.
+///
+/// \param Syntactically if true, the macro definitions can be identical even
+/// if they use different identifiers for the function macro parameters.
+/// Otherwise the comparison is lexical and this implements the rules in
+/// C99 6.10.3.
+bool MacroInfo::isIdenticalTo(const MacroInfo &Other, Preprocessor &PP,
+                              bool Syntactically) const {
+  bool Lexically = !Syntactically;
+
   // Check # tokens in replacement, number of args, and various flags all match.
   if (ReplacementTokens.size() != Other.ReplacementTokens.size() ||
       getNumArgs() != Other.getNumArgs() ||
@@ -74,10 +80,12 @@ bool MacroInfo::isIdenticalTo(const MacroInfo &Other, Preprocessor &PP) const {
       isGNUVarargs() != Other.isGNUVarargs())
     return false;
 
-  // Check arguments.
-  for (arg_iterator I = arg_begin(), OI = Other.arg_begin(), E = arg_end();
-       I != E; ++I, ++OI)
-    if (*I != *OI) return false;
+  if (Lexically) {
+    // Check arguments.
+    for (arg_iterator I = arg_begin(), OI = Other.arg_begin(), E = arg_end();
+         I != E; ++I, ++OI)
+      if (*I != *OI) return false;
+  }
 
   // Check all the tokens.
   for (unsigned i = 0, e = ReplacementTokens.size(); i != e; ++i) {
@@ -95,7 +103,15 @@ bool MacroInfo::isIdenticalTo(const MacroInfo &Other, Preprocessor &PP) const {
 
     // If this is an identifier, it is easy.
     if (A.getIdentifierInfo() || B.getIdentifierInfo()) {
-      if (A.getIdentifierInfo() != B.getIdentifierInfo())
+      if (A.getIdentifierInfo() == B.getIdentifierInfo())
+        continue;
+      if (Lexically)
+        return false;
+      // With syntactic equivalence the parameter names can be different as long
+      // as they are used in the same place.
+      int AArgNum = getArgumentNum(A.getIdentifierInfo());
+      int BArgNum = Other.getArgumentNum(B.getIdentifierInfo());
+      if (AArgNum == -1 || AArgNum != BArgNum)
         return false;
       continue;
     }
diff --git a/lib/Lex/PPDirectives.cpp b/lib/Lex/PPDirectives.cpp
index 3fc19e41f8..07c1867010 100644
--- a/lib/Lex/PPDirectives.cpp
+++ b/lib/Lex/PPDirectives.cpp
@@ -1949,9 +1949,9 @@ void Preprocessor::HandleDefineDirective(Token &DefineTok) {
       if (OtherMI->isBuiltinMacro())
         Diag(MacroNameTok, diag::ext_pp_redef_builtin_macro);
       // Macros must be identical.  This means all tokens and whitespace
-      // separation must be the same.  C99 6.10.3.2.
+      // separation must be the same.  C99 6.10.3p2.
       else if (!OtherMI->isAllowRedefinitionsWithoutWarning() &&
-               !MI->isIdenticalTo(*OtherMI, *this)) {
+               !MI->isIdenticalTo(*OtherMI, *this, /*Syntactic=*/LangOpts.MicrosoftExt)) {
         Diag(MI->getDefinitionLoc(), diag::ext_pp_macro_redef)
           << MacroNameTok.getIdentifierInfo();
         Diag(OtherMI->getDefinitionLoc(), diag::note_previous_definition);