Use unique_ptr for cached tokens for default arguments in C++.

Summary:
This changes pointers to cached tokens for default arguments in C++ from raw pointers to unique_ptrs.  There was a fixme in the code where the cached tokens are created  about using a smart pointer.

The change is straightforward, though I did have to track down and fix a memory corruption caused by the change.  memcpy was being used to copy parameter information.  This duplicated the unique_ptr, which led to the cached token buffer being deleted prematurely.

Patch by David Tarditi!

Reviewers: malcolm.parsons

Subscribers: arphaman, malcolm.parsons, cfe-commits

Differential Revision: https://reviews.llvm.org/D26435

llvm-svn: 287241

clang/include/clang/Parse/Parser.h

@@ -1017,8 +1017,8 @@ class Parser : public CodeCompletionHandler {
   /// (C++ [class.mem]p2).
   struct LateParsedDefaultArgument {
     explicit LateParsedDefaultArgument(Decl *P,
-                                       CachedTokens *Toks = nullptr)
-      : Param(P), Toks(Toks) { }
+                                       std::unique_ptr<CachedTokens> Toks = nullptr)
+      : Param(P), Toks(std::move(Toks)) { }
 
     /// Param - The parameter declaration for this parameter.
     Decl *Param;
@@ -1027,7 +1027,7 @@ class Parser : public CodeCompletionHandler {
     /// argument expression, not including the '=' or the terminating
     /// ')' or ','. This will be NULL for parameters that have no
     /// default argument.
-    CachedTokens *Toks;
+    std::unique_ptr<CachedTokens> Toks;
   };
 
   /// LateParsedMethodDeclaration - A method declaration inside a class that

clang/include/clang/Sema/DeclSpec.h

@@ -1188,14 +1188,14 @@ struct DeclaratorChunk {
     /// declaration of a member function), it will be stored here as a
     /// sequence of tokens to be parsed once the class definition is
     /// complete. Non-NULL indicates that there is a default argument.
-    CachedTokens *DefaultArgTokens;
+    std::unique_ptr<CachedTokens> DefaultArgTokens;
 
     ParamInfo() = default;
     ParamInfo(IdentifierInfo *ident, SourceLocation iloc,
               Decl *param,
-              CachedTokens *DefArgTokens = nullptr)
+              std::unique_ptr<CachedTokens> DefArgTokens = nullptr)
       : Ident(ident), IdentLoc(iloc), Param(param),
-        DefaultArgTokens(DefArgTokens) {}
+        DefaultArgTokens(std::move(DefArgTokens)) {}
   };
 
   struct TypeAndRange {
@@ -1310,10 +1310,8 @@ struct DeclaratorChunk {
     ///
     /// This is used in various places for error recovery.
     void freeParams() {
-      for (unsigned I = 0; I < NumParams; ++I) {
-        delete Params[I].DefaultArgTokens;
-        Params[I].DefaultArgTokens = nullptr;
-      }
+      for (unsigned I = 0; I < NumParams; ++I)
+        Params[I].DefaultArgTokens.reset();
       if (DeleteParams) {
         delete[] Params;
         DeleteParams = false;

clang/lib/Parse/ParseCXXInlineMethods.cpp

@@ -319,7 +319,8 @@ void Parser::ParseLexedMethodDeclaration(LateParsedMethodDeclaration &LM) {
     // Introduce the parameter into scope.
     bool HasUnparsed = Param->hasUnparsedDefaultArg();
     Actions.ActOnDelayedCXXMethodParameter(getCurScope(), Param);
-    if (CachedTokens *Toks = LM.DefaultArgs[I].Toks) {
+    std::unique_ptr<CachedTokens> Toks = std::move(LM.DefaultArgs[I].Toks);
+    if (Toks) {
       // Mark the end of the default argument so that we know when to stop when
       // we parse it later on.
       Token LastDefaultArgToken = Toks->back();
@@ -377,9 +378,6 @@ void Parser::ParseLexedMethodDeclaration(LateParsedMethodDeclaration &LM) {
 
       if (Tok.is(tok::eof) && Tok.getEofData() == Param)
         ConsumeAnyToken();
-
-      delete Toks;
-      LM.DefaultArgs[I].Toks = nullptr;
     } else if (HasUnparsed) {
       assert(Param->hasInheritedDefaultArg());
       FunctionDecl *Old = cast<FunctionDecl>(LM.Method)->getPreviousDecl();

clang/lib/Parse/ParseDecl.cpp

@@ -6022,7 +6022,7 @@ void Parser::ParseParameterDeclarationClause(
 
     // DefArgToks is used when the parsing of default arguments needs
     // to be delayed.
-    CachedTokens *DefArgToks = nullptr;
+    std::unique_ptr<CachedTokens> DefArgToks;
 
     // If no parameter was specified, verify that *something* was specified,
     // otherwise we have a missing type and identifier.
@@ -6058,13 +6058,11 @@ void Parser::ParseParameterDeclarationClause(
           // If we're inside a class definition, cache the tokens
           // corresponding to the default argument. We'll actually parse
           // them when we see the end of the class definition.
-          // FIXME: Can we use a smart pointer for Toks?
-          DefArgToks = new CachedTokens;
+          DefArgToks.reset(new CachedTokens);
 
           SourceLocation ArgStartLoc = NextToken().getLocation();
           if (!ConsumeAndStoreInitializer(*DefArgToks, CIK_DefaultArgument)) {
-            delete DefArgToks;
-            DefArgToks = nullptr;
+            DefArgToks.reset();
             Actions.ActOnParamDefaultArgumentError(Param, EqualLoc);
           } else {
             Actions.ActOnParamUnparsedDefaultArgument(Param, EqualLoc,
@@ -6100,7 +6098,7 @@ void Parser::ParseParameterDeclarationClause(
 
       ParamInfo.push_back(DeclaratorChunk::ParamInfo(ParmII,
                                           ParmDeclarator.getIdentifierLoc(), 
-                                          Param, DefArgToks));
+                                          Param, std::move(DefArgToks)));
     }
 
     if (TryConsumeToken(tok::ellipsis, EllipsisLoc)) {

clang/lib/Parse/ParseDeclCXX.cpp

@@ -2039,7 +2039,7 @@ void Parser::HandleMemberFunctionDeclDelays(Declarator& DeclaratorInfo,
     LateMethod->DefaultArgs.reserve(FTI.NumParams);
     for (unsigned ParamIdx = 0; ParamIdx < FTI.NumParams; ++ParamIdx)
       LateMethod->DefaultArgs.push_back(LateParsedDefaultArgument(
-        FTI.Params[ParamIdx].Param, FTI.Params[ParamIdx].DefaultArgTokens));
+        FTI.Params[ParamIdx].Param, std::move(FTI.Params[ParamIdx].DefaultArgTokens)));
   }
 }
 

clang/lib/Sema/DeclSpec.cpp

@@ -223,13 +223,19 @@ DeclaratorChunk DeclaratorChunk::getFunction(bool hasProto,
     if (!TheDeclarator.InlineStorageUsed &&
         NumParams <= llvm::array_lengthof(TheDeclarator.InlineParams)) {
       I.Fun.Params = TheDeclarator.InlineParams;
+      // Zero the memory block so that unique pointers are initialized
+      // properly.
+      memset(I.Fun.Params, 0, sizeof(Params[0]) * NumParams);
       I.Fun.DeleteParams = false;
       TheDeclarator.InlineStorageUsed = true;
     } else {
-      I.Fun.Params = new DeclaratorChunk::ParamInfo[NumParams];
+      // Call the version of new that zeroes memory so that unique pointers
+      // are initialized properly.
+      I.Fun.Params = new DeclaratorChunk::ParamInfo[NumParams]();
       I.Fun.DeleteParams = true;
     }
-    memcpy(I.Fun.Params, Params, sizeof(Params[0]) * NumParams);
+    for (unsigned i = 0; i < NumParams; i++)
+      I.Fun.Params[i] = std::move(Params[i]);    
   }
 
   // Check what exception specification information we should actually store.

clang/lib/Sema/SemaDeclCXX.cpp

@@ -395,7 +395,7 @@ void Sema::CheckExtraCXXDefaultArguments(Declarator &D) {
            ++argIdx) {
         ParmVarDecl *Param = cast<ParmVarDecl>(chunk.Fun.Params[argIdx].Param);
         if (Param->hasUnparsedDefaultArg()) {
-          CachedTokens *Toks = chunk.Fun.Params[argIdx].DefaultArgTokens;
+          std::unique_ptr<CachedTokens> Toks = std::move(chunk.Fun.Params[argIdx].DefaultArgTokens);
           SourceRange SR;
           if (Toks->size() > 1)
             SR = SourceRange((*Toks)[1].getLocation(),
@@ -404,8 +404,6 @@ void Sema::CheckExtraCXXDefaultArguments(Declarator &D) {
             SR = UnparsedDefaultArgLocs[Param];
           Diag(Param->getLocation(), diag::err_param_default_argument_nonfunc)
             << SR;
-          delete Toks;
-          chunk.Fun.Params[argIdx].DefaultArgTokens = nullptr;
         } else if (Param->getDefaultArg()) {
           Diag(Param->getLocation(), diag::err_param_default_argument_nonfunc)
             << Param->getDefaultArg()->getSourceRange();