From 155aaa5967e262728b8f2952817078f54e3dec08 Mon Sep 17 00:00:00 2001
From: Patric Stout <truebrain@openttd.org>
Date: Sun, 16 Feb 2025 15:31:36 +0100
Subject: [PATCH] Fix fd2949d: use std::prev() to walk back from a possible
 string::end()

---
 src/string_func.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/string_func.h b/src/string_func.h
index 00f1d3fcfd..25cc86489e 100644
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -166,9 +166,11 @@ inline const char *Utf8PrevChar(const char *s)
 
 inline std::string::iterator Utf8PrevChar(std::string::iterator &s)
 {
-	auto *cur = &*s;
-	auto *prev = Utf8PrevChar(cur);
-	return s - (cur - prev);
+	auto cur = s;
+	do {
+		cur = std::prev(cur);
+	} while (IsUtf8Part(*cur));
+	return cur;
 }
 
 size_t Utf8StringLength(const char *s);