Teach clang to tolerate the 'p = nullptr + n' idiom used by glibc

Differential Revision: https://reviews.llvm.org/D37042

llvm-svn: 313666

1 files changed, 39 insertions, 0 deletions

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 7c62ccf052c..f04a78f609a 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -1829,6 +1829,45 @@ OverloadedOperatorKind BinaryOperator::getOverloadedOperator(Opcode Opc) {
   return OverOps[Opc];
 }
 
+bool BinaryOperator::isNullPointerArithmeticExtension(ASTContext &Ctx,
+                                                      Opcode Opc,
+                                                      Expr *LHS, Expr *RHS) {
+  if (Opc != BO_Add)
+    return false;
+
+  // Check that we have one pointer and one integer operand.
+  Expr *PExp;
+  Expr *IExp;
+  if (LHS->getType()->isPointerType()) {
+    if (!RHS->getType()->isIntegerType())
+      return false;
+    PExp = LHS;
+    IExp = RHS;
+  } else if (RHS->getType()->isPointerType()) {
+    if (!LHS->getType()->isIntegerType())
+      return false;
+    PExp = RHS;
+    IExp = LHS;
+  } else {
+    return false;
+  }
+
+  // Check that the pointer is a nullptr.
+  if (!PExp->IgnoreParenCasts()
+          ->isNullPointerConstant(Ctx, Expr::NPC_ValueDependentIsNotNull))
+    return false;
+
+  // Check that the pointee type is char-sized.
+  const PointerType *PTy = PExp->getType()->getAs<PointerType>();
+  if (!PTy || !PTy->getPointeeType()->isCharType())
+    return false;
+
+  // Check that the integer type is pointer-sized.
+  if (Ctx.getTypeSize(IExp->getType()) != Ctx.getTypeSize(PExp->getType()))
+    return false;
+
+  return true;
+}
 InitListExpr::InitListExpr(const ASTContext &C, SourceLocation lbraceloc,
                            ArrayRef<Expr*> initExprs, SourceLocation rbraceloc)
   : Expr(InitListExprClass, QualType(), VK_RValue, OK_Ordinary, false, false,