From cbdc4f2c5c290173b17fd7b4cf23244f1acc39e1 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 13 Aug 2021 10:02:01 +0900
Subject: codegen.c: `mrb_prev_pc` can return `NULL` at the top of `iseq`.

---
 mrbgems/mruby-compiler/core/codegen.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'mrbgems/mruby-compiler/core/codegen.c')

diff --git a/mrbgems/mruby-compiler/core/codegen.c b/mrbgems/mruby-compiler/core/codegen.c
index 4b55ca6ff..1bac4e061 100644
--- a/mrbgems/mruby-compiler/core/codegen.c
+++ b/mrbgems/mruby-compiler/core/codegen.c
@@ -323,12 +323,13 @@ struct mrb_insn_data
 mrb_decode_insn(const mrb_code *pc)
 {
   struct mrb_insn_data data = { 0 };
-  data.addr = pc;
+  if (pc == 0) return data;
   mrb_code insn = READ_B();
   uint16_t a = 0;
   uint16_t b = 0;
   uint16_t c = 0;
 
+  data.addr = pc;
   switch (insn) {
 #define FETCH_Z() /* empty */
 #define OPCODE(i,x) case OP_ ## i: FETCH_ ## x (); break;
-- 
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