From 86b1c8ff87071c25234397a57bb5e0be898f4db4 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 3 May 2024 07:50:40 +0900
Subject: [PATCH] string.c (utf8_strlen): add assertion `utf8_len <= byte_len`

---
 src/string.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/string.c b/src/string.c
index cd1a01cbc..ae0cf20ac 100644
--- a/src/string.c
+++ b/src/string.c
@@ -447,6 +447,7 @@ utf8_strlen(mrb_value str)
   }
   else {
     mrb_int utf8_len = mrb_utf8_strlen(RSTR_PTR(s), byte_len);
+    mrb_assert(utf8_len <= byte_len);
     if (byte_len == utf8_len) RSTR_SET_SINGLE_BYTE_FLAG(s);
     return utf8_len;
   }