From 2d3bd9fff817f3d2d3fcce3f88590de2657ec085 Mon Sep 17 00:00:00 2001
From: Nunuhara Cabbage <nunuhara@haniwa.technology>
Date: Wed, 4 Dec 2019 20:00:02 -0800
Subject: [PATCH] Handle SP_INC of NULL

'return NULL' generates an SP_INC instruction with -1 as its argument.
---
 vm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/vm.c b/vm.c
index ee0ac35..3526653 100644
--- a/vm.c
+++ b/vm.c
@@ -128,6 +128,8 @@ static void heap_free_slot(int32_t slot)
 
 void heap_ref(int32_t slot)
 {
+	if (slot == -1)
+		return;
 	heap[slot].ref++;
 #ifdef DEBUG_HEAP
 	heap[slot].ref_addr = instr_ptr;