From 752bd31a3f4fa9d8a8367c4ea933df18cb1648c4 Mon Sep 17 00:00:00 2001
From: Kelvin Sherlock <ksherlock@gmail.com>
Date: Tue, 23 Feb 2016 21:12:07 -0500
Subject: [PATCH] prevent `lda @y` or `lda @x` (which is accepted by the
 parser) from crashing.

---
 expressionSemantics.c | 3 ++-
 operandStuffSD_6502.c | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/expressionSemantics.c b/expressionSemantics.c
index 17db853..94fe23d 100644
--- a/expressionSemantics.c
+++ b/expressionSemantics.c
@@ -1109,7 +1109,8 @@ evaluateExpressionInternally(expressionType *expression, bool isTopLevel, fixupK
 evaluateExpression(expressionType *expression, fixupKindType kindOfFixup)
 {
 	valueType	*result;
-
+	nullEvaluate(expression);
+	
 	expressionFailed = FALSE;
 	referencesToNote[currentOperandNumber] = NULL;
 	result = evaluateExpressionInternally(expression, TRUE, kindOfFixup,
diff --git a/operandStuffSD_6502.c b/operandStuffSD_6502.c
index 7fcd60d..6b36cb5 100644
--- a/operandStuffSD_6502.c
+++ b/operandStuffSD_6502.c
@@ -299,6 +299,7 @@ evaluateOperand(operandType *operand)
 	case Y_INDEXED_OPND:
 		result = evaluateExpression(operand->theOperand.expressionUnion,
 			performingFixups ? NO_FIXUP : OPERAND_FIXUP);
+		nullEvaluate(result);
 		if (operand->kindOfOperand != EXPRESSION_OPND) {
 			if (result->addressMode != EXPRESSION_OPND) {
 				error(BAD_ADDRESS_MODE_ERROR);