Fix trivial -Wundef warnings

* See [Feature #17752]

Co-authored-by: xtkoba (Tee KOBAYASHI) <xtkoba+ruby@gmail.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/ruby.c b/ruby.c
index 21c2daa977..9ca7c2a2eb 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1826,7 +1826,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     opt->script_name = rb_str_new_cstr(opt->script);
     opt->script = RSTRING_PTR(opt->script_name);
 
-#if _WIN32
+#ifdef _WIN32
     translit_char_bin(RSTRING_PTR(opt->script_name), '\\', '/');
 #elif defined DOSISH
     translit_char(RSTRING_PTR(opt->script_name), '\\', '/');