make the unused expression warning less noisy by not warning about comma exprs whose

LHS and RHS both have side effects.

llvm-svn: 44486

1 files changed, 9 insertions, 2 deletions

diff --git a/clang/AST/Expr.cpp b/clang/AST/Expr.cpp
index 15fbb24a0d4..5871a5c8682 100644
--- a/clang/AST/Expr.cpp
+++ b/clang/AST/Expr.cpp
@@ -243,8 +243,15 @@ bool Expr::hasLocalSideEffect() const {
       return UO->getSubExpr()->hasLocalSideEffect();
     }
   }
-  case BinaryOperatorClass:
-    return cast<BinaryOperator>(this)->isAssignmentOp();
+  case BinaryOperatorClass: {
+    const BinaryOperator *BinOp = cast<BinaryOperator>(this);
+    // Consider comma to have side effects if the LHS and RHS both do.
+    if (BinOp->getOpcode() == BinaryOperator::Comma)
+      return BinOp->getLHS()->hasLocalSideEffect() &&
+             BinOp->getRHS()->hasLocalSideEffect();
+      
+    return BinOp->isAssignmentOp();
+  }
   case CompoundAssignOperatorClass:
     return true;