From be68b3a49030f592a10eacc180d21c38c5d5d5db Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Fri, 7 Jan 2022 09:47:09 -0500
Subject: [PATCH] Change termlen when changing encoding during concatenation

After changing the encoding, we should update the terminator length.
---
 string.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/string.c b/string.c
index d1b2e5aee0..777f9fadc4 100644
--- a/string.c
+++ b/string.c
@@ -3189,6 +3189,7 @@ rb_enc_cr_str_buf_cat(VALUE str, const char *ptr, long len,
             if (RSTRING_LEN(str) == 0) {
                 rb_str_buf_cat(str, ptr, len);
                 ENCODING_CODERANGE_SET(str, ptr_encindex, ptr_cr);
+                rb_str_change_terminator_length(str, rb_enc_mbminlen(str_enc), rb_enc_mbminlen(ptr_enc));
                 return str;
             }
             goto incompatible;