From 484ea00d2e1c2f2409cf1b58575cdb2c298c6a45 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Sat, 26 Oct 2024 22:13:18 +0900
Subject: [PATCH] [ruby/stringio] An empty string should be converted to empty
 in any encoding

https://github.com/ruby/stringio/commit/ef03f9368d
---
 ext/stringio/stringio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 6f68e46cf1..4a9cd6f1d9 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -961,6 +961,7 @@ strio_ungetc(VALUE self, VALUE c)
     }
     else {
 	StringValue(c);
+	if (RSTRING_LEN(c) == 0) return Qnil;
 	enc = rb_enc_get(ptr->string);
 	enc2 = rb_enc_get(c);
 	if (enc != enc2 && enc != rb_ascii8bit_encoding()) {