Add a new warning when a NULL constant is used in arithmetic operations. The warning will fire on cases such as:

int x = 1 + NULL;



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133196 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 76612cd6d8..2c988d15e3 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -8925,6 +8925,60 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
     rhs = move(resolvedRHS);
   }
 
+  bool LeftNull = Expr::NPCK_GNUNull ==
+      lhs.get()->isNullPointerConstant(Context,
+                                       Expr::NPC_ValueDependentIsNotNull);
+  bool RightNull = Expr::NPCK_GNUNull ==
+      rhs.get()->isNullPointerConstant(Context,
+                                       Expr::NPC_ValueDependentIsNotNull);
+
+  // Detect when a NULL constant is used improperly in an expression.  These
+  // are mainly cases where the null pointer is used as an integer instead
+  // of a pointer.
+  if (LeftNull || RightNull) {
+    if (Opc == BO_Mul || Opc == BO_Div || Opc == BO_Rem || Opc == BO_Add ||
+        Opc == BO_Sub || Opc == BO_Shl || Opc == BO_Shr || Opc == BO_And ||
+        Opc == BO_Xor || Opc == BO_Or || Opc == BO_MulAssign ||
+        Opc == BO_DivAssign || Opc == BO_AddAssign || Opc == BO_SubAssign ||
+        Opc == BO_RemAssign || Opc == BO_ShlAssign || Opc == BO_ShrAssign ||
+        Opc == BO_AndAssign || Opc == BO_OrAssign || Opc == BO_XorAssign) {
+      // These are the operations that would not make sense with a null pointer
+      // no matter what the other expression is.
+      if (LeftNull && RightNull) {
+        Diag(OpLoc, diag::warn_null_in_arithmetic_operation)
+             << lhs.get()->getSourceRange() << rhs.get()->getSourceRange();
+      } else if (LeftNull) {
+        Diag(OpLoc, diag::warn_null_in_arithmetic_operation)
+             << lhs.get()->getSourceRange();
+      } else if (RightNull) {
+        Diag(OpLoc, diag::warn_null_in_arithmetic_operation)
+             << rhs.get()->getSourceRange();
+      }
+    } else if (Opc == BO_LE || Opc == BO_LT || Opc == BO_GE || Opc == BO_GT ||
+               Opc == BO_EQ || Opc == BO_NE) {
+      // These are the operations that would not make sense with a null pointer
+      // if the other expression the other expression is not a pointer.
+      QualType LeftType = lhs.get()->getType();
+      QualType RightType = rhs.get()->getType();
+      bool LeftPointer = LeftType->isPointerType() ||
+                         LeftType->isBlockPointerType() ||
+                         LeftType->isMemberPointerType() ||
+                         LeftType->isObjCObjectPointerType();
+      bool RightPointer = RightType->isPointerType() ||
+                          RightType->isBlockPointerType() ||
+                          RightType->isMemberPointerType() ||
+                          RightType->isObjCObjectPointerType();
+      if ((LeftNull != RightNull) && !LeftPointer && !RightPointer) {
+        if (LeftNull)
+          Diag(OpLoc, diag::warn_null_in_arithmetic_operation)
+               << lhs.get()->getSourceRange();
+        if (RightNull)
+          Diag(OpLoc, diag::warn_null_in_arithmetic_operation)
+               << rhs.get()->getSourceRange();
+      }
+    }
+  }
+
   switch (Opc) {
   case BO_Assign:
     ResultTy = CheckAssignmentOperands(lhs.get(), rhs, OpLoc, QualType());