From cd3657cf06bb3a32756deea35ea2b6cdfd19eb41 Mon Sep 17 00:00:00 2001
From: Hiroshi SHIBATA <hsbt@ruby-lang.org>
Date: Sun, 27 Sep 2026 05:23:48 +0900
Subject: [PATCH] Remove CharNext from eval_intern.h

ruby_push_include was its last user. A path separator never appears inside a multibyte character, so walk RUBYLIB and -I by bytes everywhere. This also fixes the same skipped separator on Cygwin, where CharNext came from windows.h.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 eval_intern.h | 17 -----------------
 ruby.c        | 11 ++---------
 2 files changed, 2 insertions(+), 26 deletions(-)

diff --git a/eval_intern.h b/eval_intern.h
index 25ea8a9ef1d..ca4e4b50615 100644
--- a/eval_intern.h
+++ b/eval_intern.h
@@ -353,21 +353,4 @@ VALUE rb_ec_backtrace_object(const rb_execution_context_t *ec);
 VALUE rb_ec_backtrace_str_ary(const rb_execution_context_t *ec, long lev, long n);
 VALUE rb_ec_backtrace_location_ary(const rb_execution_context_t *ec, long lev, long n, bool skip_internal);
 
-#ifndef CharNext		/* defined as CharNext[AW] on Windows. */
-# ifdef HAVE_MBLEN
-#  define CharNext(p) rb_char_next(p)
-static inline char *
-rb_char_next(const char *p)
-{
-    if (p) {
-        int len = mblen(p, RUBY_MBCHAR_MAXSIZE);
-        p += len > 0 ? len : 1;
-    }
-    return (char *)p;
-}
-# else
-#  define CharNext(p) ((p) + 1)
-# endif
-#endif
-
 #endif /* RUBY_EVAL_INTERN_H */
diff --git a/ruby.c b/ruby.c
index 58b26320c7b..e1164da05c3 100644
--- a/ruby.c
+++ b/ruby.c
@@ -454,13 +454,6 @@ ruby_push_include(const char *path, VALUE (*filter)(VALUE))
 # define is_path_sep(c) ((c) == sep || (c) == ';')
 #else
 # define is_path_sep(c) ((c) == sep)
-#endif
-#ifdef _WIN32
-    /* RUBYLIB and -I are UTF-8 while CharNext() follows the ANSI code
-     * page, and neither has the separator in a multibyte character. */
-# define next_char(s) ((s) + 1)
-#else
-# define next_char(s) CharNext(s)
 #endif
 
     if (path == 0) return;
@@ -470,10 +463,10 @@ ruby_push_include(const char *path, VALUE (*filter)(VALUE))
         while (is_path_sep(*p))
             p++;
         if (!*p) break;
-        for (s = p; *s && !is_path_sep(*s); s = next_char(s));
+        /* separators never appear inside a multibyte character */
+        for (s = p; *s && !is_path_sep(*s); s++);
         len = s - p;
 #undef is_path_sep
-#undef next_char
 
 #ifdef __CYGWIN__
         if (*s) {