expr(1): Fix overflow detection when operand is INTMAX_MIN

PR: 227329 Submitted by: Tobias Stoeckmann <tobias AT stoeckmann.org>
stacktic · Apr 14, 2018 · 60e938b · 60e938b
1 parent ef5bec9
commit 60e938b
Showing 1 changed file with 2 additions and 4 deletions.
diff --git a/bin/expr/expr.y b/bin/expr/expr.y
@@ -422,11 +422,9 @@ op_plus(struct val *a, struct val *b)
 void
 assert_minus(intmax_t a, intmax_t b, intmax_t r)
 {
-	/* special case subtraction of INTMAX_MIN */
-	if (b == INTMAX_MIN && a < 0)
+	if ((a >= 0 && b < 0 && r <= 0) ||
+	    (a < 0 && b > 0 && r >= 0))
 		errx(ERR_EXIT, "overflow");
-	/* check addition of negative subtrahend */
-	assert_plus(a, -b, r);
 }
 
 struct val *