From 77d08772a5b9ece703f85fa0c4b95f4c4b0052bc Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Wed, 21 May 2025 09:52:10 +0900
Subject: [PATCH] error.c (mrb_vformat): prevent SEGV from %s with NULL

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

diff --git a/src/error.c b/src/error.c
index 316223f78..f36c2eb58 100644
--- a/src/error.c
+++ b/src/error.c
@@ -329,6 +329,7 @@ mrb_vformat(mrb_state *mrb, const char *format, va_list ap)
           goto L_cat_obj;
         case 's':
           chars = va_arg(ap, char*);
+          if (chars == NULL) chars = "(null)";
           len = strlen(chars);
           goto L_cat;
         case 't':