Implement the GNU __null extension

llvm-svn: 60235

6 files changed, 48 insertions, 1 deletions

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 7a8119c5e3d..3c021c262d6 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -1031,8 +1031,11 @@ bool Expr::isNullPointerConstant(ASTContext &Ctx) const {
                = dyn_cast<CXXDefaultArgExpr>(this)) {
     // See through default argument expressions
     return DefaultArg->getExpr()->isNullPointerConstant(Ctx);
+  } else if (isa<GNUNullExpr>(this)) {
+    // The GNU __null extension is always a null pointer constant.
+    return true;
   }
-  
+
   // This expression must be an integer type.
   if (!getType()->isIntegerType())
     return false;
@@ -1383,6 +1386,10 @@ Stmt::child_iterator TypesCompatibleExpr::child_end() {
 Stmt::child_iterator ChooseExpr::child_begin() { return &SubExprs[0]; }
 Stmt::child_iterator ChooseExpr::child_end() { return &SubExprs[0]+END_EXPR; }
 
+// GNUNullExpr
+Stmt::child_iterator GNUNullExpr::child_begin() { return child_iterator(); }
+Stmt::child_iterator GNUNullExpr::child_end() { return child_iterator(); }
+
 // OverloadExpr
 Stmt::child_iterator OverloadExpr::child_begin() { return &SubExprs[0]; }
 Stmt::child_iterator OverloadExpr::child_end() { return &SubExprs[0]+NumExprs; }
diff --git a/clang/lib/AST/StmtPrinter.cpp b/clang/lib/AST/StmtPrinter.cpp
index fcebdab05c6..b6f07070538 100644
--- a/clang/lib/AST/StmtPrinter.cpp
+++ b/clang/lib/AST/StmtPrinter.cpp
@@ -783,6 +783,10 @@ void StmtPrinter::VisitChooseExpr(ChooseExpr *Node) {
   OS << ")";
 }
 
+void StmtPrinter::VisitGNUNullExpr(GNUNullExpr *) {
+  OS << "__null";
+}
+
 void StmtPrinter::VisitOverloadExpr(OverloadExpr *Node) {
   OS << "__builtin_overload(";
   for (unsigned i = 0, e = Node->getNumSubExprs(); i != e; ++i) {
diff --git a/clang/lib/AST/StmtSerialization.cpp b/clang/lib/AST/StmtSerialization.cpp
index 8bf70396856..3cf1f5497fb 100644
--- a/clang/lib/AST/StmtSerialization.cpp
+++ b/clang/lib/AST/StmtSerialization.cpp
@@ -61,6 +61,9 @@ Stmt* Stmt::Create(Deserializer& D, ASTContext& C) {
     case CharacterLiteralClass:
       return CharacterLiteral::CreateImpl(D, C);
       
+    case ChooseExprClass:
+      return ChooseExpr::CreateImpl(D, C);
+
     case CompoundAssignOperatorClass:
       return CompoundAssignOperator::CreateImpl(D, C);
       
@@ -94,6 +97,9 @@ Stmt* Stmt::Create(Deserializer& D, ASTContext& C) {
     case ForStmtClass:
       return ForStmt::CreateImpl(D, C);
     
+    case GNUNullExprClass:
+      return GNUNullExpr::CreateImpl(D, C);
+
     case GotoStmtClass:
       return GotoStmt::CreateImpl(D, C);
       
@@ -904,6 +910,17 @@ ChooseExpr* ChooseExpr::CreateImpl(llvm::Deserializer& D, ASTContext& C) {
   return CE;
 }
 
+void GNUNullExpr::EmitImpl(llvm::Serializer &S) const {
+  S.Emit(getType());
+  S.Emit(TokenLoc);
+}
+
+GNUNullExpr *GNUNullExpr::CreateImpl(llvm::Deserializer &D, ASTContext &C) {
+  QualType T = QualType::ReadVal(D);
+  SourceLocation TL = SourceLocation::ReadVal(D);
+  return new GNUNullExpr(T, TL);
+}
+
 void OverloadExpr::EmitImpl(llvm::Serializer& S) const {
   S.Emit(getType());
   S.Emit(BuiltinLoc);
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 66b1d180780..df46612b57d 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -378,6 +378,7 @@ Parser::ParseRHSOfBinaryExpression(ExprResult LHS, unsigned MinPrec) {
 /// [GNU]   '__builtin_choose_expr' '(' assign-expr ',' assign-expr ','
 ///                                     assign-expr ')'
 /// [GNU]   '__builtin_types_compatible_p' '(' type-name ',' type-name ')'
+/// [GNU]   '__null'
 /// [OBJC]  '[' objc-message-expr ']'    
 /// [OBJC]  '@selector' '(' objc-selector-arg ')'
 /// [OBJC]  '@protocol' '(' identifier ')'             
@@ -531,6 +532,9 @@ Parser::ExprResult Parser::ParseCastExpression(bool isUnaryExpression) {
   case tok::kw___builtin_overload:
   case tok::kw___builtin_types_compatible_p:
     return ParseBuiltinPrimaryExpression();
+  case tok::kw___null:
+    return Actions.ActOnGNUNullExpr(ConsumeToken());
+    break;
   case tok::plusplus:      // unary-expression: '++' unary-expression
   case tok::minusminus: {  // unary-expression: '--' unary-expression
     SourceLocation SavedLoc = ConsumeToken();
diff --git a/clang/lib/Sema/Sema.h b/clang/lib/Sema/Sema.h
index 57caa6ecf24..044bfbd73be 100644
--- a/clang/lib/Sema/Sema.h
+++ b/clang/lib/Sema/Sema.h
@@ -736,6 +736,9 @@ public:
                                 ExprTy *expr, TypeTy *type,
                                 SourceLocation RPLoc);
 
+  // __null
+  virtual ExprResult ActOnGNUNullExpr(SourceLocation TokenLoc);
+
   //===------------------------- "Block" Extension ------------------------===//
 
   /// ActOnBlockStart - This callback is invoked when a block literal is
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index e21047e10d8..fb964692b35 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -3603,6 +3603,18 @@ Sema::ExprResult Sema::ActOnVAArg(SourceLocation BuiltinLoc,
   return new VAArgExpr(BuiltinLoc, E, T.getNonReferenceType(), RPLoc);
 }
 
+Sema::ExprResult Sema::ActOnGNUNullExpr(SourceLocation TokenLoc) {
+  // The type of __null will be int or long, depending on the size of
+  // pointers on the target.
+  QualType Ty;
+  if (Context.Target.getPointerWidth(0) == Context.Target.getIntWidth())
+    Ty = Context.IntTy;
+  else
+    Ty = Context.LongTy;
+
+  return new GNUNullExpr(Ty, TokenLoc);
+}
+
 bool Sema::DiagnoseAssignmentResult(AssignConvertType ConvTy,
                                     SourceLocation Loc,
                                     QualType DstType, QualType SrcType,