diff --git a/dir.c b/dir.c
index b1a7a3b8519..9c04e244d1b 100644
--- a/dir.c
+++ b/dir.c
@@ -1704,7 +1704,7 @@ check_dirname(VALUE dir)
 {
     VALUE d = dir;
     char *path, *pend;
-    long len;
+    rb_len_t len;
     rb_encoding *enc;
 
     FilePathValue(d);
@@ -3570,7 +3570,7 @@ static VALUE
 dir_globs(VALUE args, VALUE base, int flags)
 {
     VALUE ary = rb_ary_new();
-    long i;
+    rb_len_t i;
 
     for (i = 0; i < RARRAY_LEN(args); ++i) {
         int status;
diff --git a/file.c b/file.c
index 056a18033ec..24d424c9ec3 100644
--- a/file.c
+++ b/file.c
@@ -288,7 +288,7 @@ rb_str_encode_ospath(VALUE path)
 
 # ifdef HAVE_WORKING_FORK
 static CFMutableStringRef
-mutable_CFString_new(CFStringRef *s, const char *ptr, long len)
+mutable_CFString_new(CFStringRef *s, const char *ptr, rb_len_t len)
 {
     const CFAllocatorRef alloc = kCFAllocatorDefault;
     *s = CFStringCreateWithBytesNoCopy(alloc, (const UInt8 *)ptr, len,
@@ -324,7 +324,7 @@ rb_CFString_class_initialize_before_fork(void)
 
     /* Enough small but non-empty ASCII string to fit in NSTaggedPointerString. */
     const char small_str[] = "/";
-    long len = sizeof(small_str) - 1;
+    rb_len_t len = sizeof(small_str) - 1;
     CFStringRef s;
     /*
      * Touch `CFStringCreateWithBytesNoCopy` *twice* because the implementation
@@ -340,13 +340,13 @@ rb_CFString_class_initialize_before_fork(void)
 # endif /* HAVE_WORKING_FORK */
 
 static VALUE
-rb_str_append_normalized_ospath(VALUE str, const char *ptr, long len)
+rb_str_append_normalized_ospath(VALUE str, const char *ptr, rb_len_t len)
 {
     CFIndex buflen = 0;
     CFRange all;
     CFStringRef s;
     CFMutableStringRef m = mutable_CFString_new(&s, ptr, len);
-    long oldlen = RSTRING_LEN(str);
+    rb_len_t oldlen = RSTRING_LEN(str);
 
     CFStringNormalize(m, kCFStringNormalizationFormC);
     all = CFRangeMake(0, CFStringGetLength(m));
@@ -360,7 +360,7 @@ rb_str_append_normalized_ospath(VALUE str, const char *ptr, long len)
 }
 
 VALUE
-rb_str_normalize_ospath(const char *ptr, long len)
+rb_str_normalize_ospath(const char *ptr, rb_len_t len)
 {
     const char *p = ptr;
     const char *e = ptr + len;
@@ -484,7 +484,7 @@ apply2files(int (*func)(const char *, void *), int argc, VALUE *argv, void *arg)
 {
     VALUE v;
     const size_t size = sizeof(struct apply_filename);
-    const long len = (long)(offsetof(struct apply_arg, fn) + (size * argc));
+    const rb_len_t len = (rb_len_t)(offsetof(struct apply_arg, fn) + (size * argc));
     struct apply_arg *aa = ALLOCV(v, len);
 
     aa->errnum = 0;
@@ -4812,7 +4812,7 @@ ntfs_tail(const char *path, const char *end, bool mb_enc, rb_encoding *enc)
 } while (0)
 
 #define WITH_ROOTDIFF(stmt) do { \
-    long rootdiff = root - buf; \
+    rb_len_t rootdiff = root - buf;  \
     stmt; \
     root = buf + rootdiff; \
 } while (0)
@@ -4821,7 +4821,7 @@ static VALUE
 copy_home_path(VALUE result, const char *dir)
 {
     char *buf;
-    long dirlen;
+    rb_len_t dirlen;
     int encidx;
 
     dirlen = strlen(dir);
@@ -4929,7 +4929,7 @@ rb_default_home_dir(VALUE result)
 }
 
 static VALUE
-ospath_new(const char *ptr, long len, rb_encoding *fsenc)
+ospath_new(const char *ptr, rb_len_t len, rb_encoding *fsenc)
 {
 #if NORMALIZE_UTF8PATH
     VALUE path = rb_str_normalize_ospath(ptr, len);
@@ -4994,7 +4994,7 @@ rb_file_expand_path_internal(VALUE fname, VALUE dname, int abs_mode, int long_na
     if (s < fend && s[0] == '~' && abs_mode == 0) {      /* execute only if NOT absolute_path() */
         BUFINIT(result, buf, p, pend); // TOOD: right size the buffer
 
-        long userlen = 0;
+        rb_len_t userlen = 0;
         if (s + 1 == fend || isdirsep(s[1])) {
             buf = 0;
             b = 0;
@@ -5227,7 +5227,7 @@ str_shrink(VALUE str)
      (void)(NIL_P(dname) ? (dname) : ((dname) = rb_get_path(dname))))
 
 static VALUE
-file_expand_path_1(VALUE fname, long extra_capa)
+file_expand_path_1(VALUE fname, rb_len_t extra_capa)
 {
     VALUE buffer = rb_usascii_str_new(0, RSTRING_LEN(fname) + extra_capa);
     return rb_file_expand_path_internal(fname, Qnil, 0, 0, buffer);
@@ -5395,7 +5395,7 @@ enum rb_realpath_mode {
 };
 
 static int
-realpath_rec(long *prefixlenp, VALUE *resolvedp, const char *unresolved, VALUE fallback,
+realpath_rec(rb_len_t *prefixlenp, VALUE *resolvedp, const char *unresolved, VALUE fallback,
              VALUE loopcheck, enum rb_realpath_mode mode, int last)
 {
     const char *pend = unresolved + strlen(unresolved);
@@ -5405,7 +5405,7 @@ realpath_rec(long *prefixlenp, VALUE *resolvedp, const char *unresolved, VALUE f
     while (unresolved < pend) {
         const char *testname = unresolved;
         const char *unresolved_firstsep = rb_enc_path_next(unresolved, pend, enc);
-        long testnamelen = unresolved_firstsep - unresolved;
+        rb_len_t testnamelen = unresolved_firstsep - unresolved;
         const char *unresolved_nextname = unresolved_firstsep;
         while (unresolved_nextname < pend && isdirsep(*unresolved_nextname))
             unresolved_nextname++;
@@ -5418,7 +5418,7 @@ realpath_rec(long *prefixlenp, VALUE *resolvedp, const char *unresolved, VALUE f
                 const char *resolved_str = RSTRING_PTR(*resolvedp);
                 const char *resolved_names = resolved_str + *prefixlenp;
                 const char *lastsep = strrdirsep(resolved_names, resolved_str + RSTRING_LEN(*resolvedp), mb_enc, enc);
-                long len = lastsep ? lastsep - resolved_names : 0;
+                rb_len_t len = lastsep ? lastsep - resolved_names : 0;
                 rb_str_resize(*resolvedp, *prefixlenp + len);
             }
         }
@@ -5476,7 +5476,7 @@ realpath_rec(long *prefixlenp, VALUE *resolvedp, const char *unresolved, VALUE f
                     VALUE link;
                     VALUE link_orig = Qnil;
                     const char *link_prefix, *link_names;
-                    long link_prefixlen;
+                    rb_len_t link_prefixlen;
                     rb_hash_aset(loopcheck, testpath, ID2SYM(resolving));
                     link = rb_readlink(testpath, enc);
                     link_prefix = RSTRING_PTR(link);
@@ -5528,7 +5528,7 @@ ospath_for_expand(VALUE path)
 static VALUE
 rb_check_realpath_emulate(VALUE basedir, VALUE path, rb_encoding *origenc, enum rb_realpath_mode mode)
 {
-    long prefixlen;
+    rb_len_t prefixlen;
     VALUE resolved;
     VALUE unresolved_path;
     VALUE loopcheck;
@@ -5537,7 +5537,7 @@ rb_check_realpath_emulate(VALUE basedir, VALUE path, rb_encoding *origenc, enum
     rb_encoding *enc;
     char *path_names = NULL, *basedir_names = NULL, *curdir_names = NULL;
     char *ptr, *prefixptr = NULL, *pend;
-    long len;
+    rb_len_t len;
 
 #ifdef DOSISH_DRIVE_LETTER
     VALUE rootdir = path;
@@ -5636,7 +5636,7 @@ rb_check_realpath_emulate(VALUE basedir, VALUE path, rb_encoding *origenc, enum
     return resolved;
 }
 
-static VALUE rb_file_join(long argc, VALUE *args);
+static VALUE rb_file_join(rb_len_t argc, VALUE *args);
 
 #ifndef HAVE_REALPATH
 static VALUE
@@ -5797,7 +5797,7 @@ rb_file_s_realdirpath(int argc, VALUE *argv, VALUE klass)
 }
 
 static size_t
-rmext(const char *p, long l0, long l1, const char *e, long l2, rb_encoding *enc)
+rmext(const char *p, rb_len_t l0, rb_len_t l1, const char *e, rb_len_t l2, rb_encoding *enc)
 {
     int len1, len2;
     unsigned int c;
@@ -5836,9 +5836,9 @@ static inline const char *
 enc_find_basename(const char *name, rb_len_t *baselen, rb_len_t *alllen, bool mb_enc, rb_encoding *enc)
 {
     const char *p, *q, *e, *end;
-    long f = 0, n = -1;
+    rb_len_t f = 0, n = -1;
 
-    long len = (alllen ? (size_t)*alllen : strlen(name));
+    rb_len_t len = (alllen ? (size_t)*alllen : strlen(name));
 
     if (len <= 0) {
         return name;
@@ -6093,7 +6093,7 @@ rb_file_dirname_n(VALUE fname, int n)
 static inline const char *
 enc_find_extname(const char *name, rb_len_t *len, bool mb_enc, rb_encoding *enc)
 {
-    const char *p, *e, *end = name + (len ? *len : (long)strlen(name));
+    const char *p, *e, *end = name + (len ? *len : (rb_len_t)strlen(name));
 
     p = strrdirsep(name, end, mb_enc, enc);	/* get the last path component */
     if (!p)
@@ -6281,7 +6281,7 @@ file_inspect_join(VALUE ary, VALUE arg, int recur)
 static VALUE
 rb_file_join_ary(VALUE ary)
 {
-    long len, i;
+    rb_len_t len, i;
     VALUE result, tmp;
     const char *name, *tail;
     int checked = TRUE;
@@ -6345,11 +6345,11 @@ rb_file_join_ary(VALUE ary)
 }
 
 static inline VALUE
-rb_file_join_fastpath(long argc, VALUE *args)
+rb_file_join_fastpath(rb_len_t argc, VALUE *args)
 {
-    long size = argc;
+    rb_len_t size = argc;
 
-    long i;
+    rb_len_t i;
     for (i = 0; i < argc; i++) {
         VALUE tmp = args[i];
         if (RB_LIKELY(RB_TYPE_P(tmp, T_STRING) && rb_str_enc_fastpath(tmp))) {
@@ -6369,15 +6369,15 @@ rb_file_join_fastpath(long argc, VALUE *args)
     const char *name = RSTRING_PTR(result);
     for (i = 1; i < argc; i++) {
         VALUE tmp = args[i];
-        long len = RSTRING_LEN(result);
+        rb_len_t len = RSTRING_LEN(result);
 
         const char *tmp_s;
-        long tmp_len;
+        rb_len_t tmp_len;
         RSTRING_GETMEM(tmp, tmp_s, tmp_len);
 
         if (tmp_len > 0 && isdirsep(tmp_s[0])) {
             // right side has a leading separator, remove left side separators.
-            long chomp = len;
+            rb_len_t chomp = len;
             while (chomp > 0 && isdirsep(name[chomp - 1])) {
                 --chomp;
             }
@@ -6402,7 +6402,7 @@ rb_file_join_fastpath(long argc, VALUE *args)
 }
 
 static inline VALUE
-rb_file_join(long argc, VALUE *args)
+rb_file_join(rb_len_t argc, VALUE *args)
 {
     if (RB_UNLIKELY(argc == 0)) {
         return rb_str_new(0, 0);
@@ -8018,7 +8018,7 @@ static bool
 fname_need_expansion_p(VALUE fname)
 {
     const char *s = RSTRING_PTR(fname);
-    const long len = RSTRING_LEN(fname);
+    const rb_len_t len = RSTRING_LEN(fname);
     const char *send = s + len;
 
     if (nav_component_p(s, send)) {
@@ -8042,7 +8042,7 @@ fname_need_expansion_p(VALUE fname)
 static bool
 expand_feature(VALUE fname, VALUE dname, VALUE buffer, bool need_expansion)
 {
-    long dname_len = RSTRING_LEN(dname);
+    rb_len_t dname_len = RSTRING_LEN(dname);
     const char *dname_ptr = RSTRING_PTR(dname);
 
     RUBY_ASSERT(dname_len > 0);
@@ -8066,7 +8066,7 @@ rb_find_file_ext(VALUE *filep, const char *const *ext)
 {
     const char *f = StringValueCStr(*filep);
     VALUE fname = *filep;
-    long i, j, fnlen;
+    rb_len_t i, j, fnlen;
     int expanded = 0;
 
     if (!ext[0]) return 0;
@@ -8092,7 +8092,7 @@ rb_find_file_ext(VALUE *filep, const char *const *ext)
         return 0;
     }
 
-    long expanded_load_path_maxlen;
+    rb_len_t expanded_load_path_maxlen;
     VALUE load_path = rb_get_expanded_load_path(&expanded_load_path_maxlen);
     if (!load_path) return 0;
 
@@ -8143,14 +8143,14 @@ rb_find_file(VALUE path)
         return path;
     }
 
-    long expanded_load_path_maxlen;
+    rb_len_t expanded_load_path_maxlen;
     VALUE load_path = rb_get_expanded_load_path(&expanded_load_path_maxlen);
 
     if (load_path) {
         bool need_expansion = fname_need_expansion_p(path);
         VALUE tmp = rb_str_tmp_new(expanded_load_path_maxlen + RSTRING_LEN(path) + 2);
         rb_enc_associate_index(tmp, rb_usascii_encindex());
-        for (long i = 0; i < RARRAY_LEN(load_path); i++) {
+        for (rb_len_t i = 0; i < RARRAY_LEN(load_path); i++) {
             VALUE dname = rb_get_path(RARRAY_AREF(load_path, i));
             if (!RSTRING_LEN(dname)) continue;
             expand_feature(path, dname, tmp, need_expansion);
diff --git a/internal/box.h b/internal/box.h
index b5ebc2c3d2c..a03d34bbd7c 100644
--- a/internal/box.h
+++ b/internal/box.h
@@ -25,7 +25,7 @@ struct rb_box_struct {
     VALUE load_path_snapshot;
     VALUE load_path_check_cache;
     VALUE expanded_load_path;
-    long expanded_load_path_maxlen;
+    rb_len_t expanded_load_path_maxlen;
     VALUE loaded_features;
     VALUE loaded_features_snapshot;
     VALUE loaded_features_realpaths;
diff --git a/internal/file.h b/internal/file.h
index 1aa4c670433..859af8d6c3d 100644
--- a/internal/file.h
+++ b/internal/file.h
@@ -33,7 +33,7 @@ RUBY_SYMBOL_EXPORT_BEGIN
 VALUE rb_readlink(VALUE path, rb_encoding *enc);
 #endif
 #ifdef __APPLE__
-VALUE rb_str_normalize_ospath(const char *ptr, long len);
+VALUE rb_str_normalize_ospath(const char *ptr, rb_len_t len);
 #endif
 RUBY_SYMBOL_EXPORT_END
 
diff --git a/internal/load.h b/internal/load.h
index 745a6e46075..7e7d806637d 100644
--- a/internal/load.h
+++ b/internal/load.h
@@ -11,7 +11,7 @@
 #include "ruby/ruby.h"          /* for VALUE */
 
 /* load.c */
-VALUE rb_get_expanded_load_path(long *maxlen);
+VALUE rb_get_expanded_load_path(rb_len_t *maxlen);
 VALUE rb_load_entrypoint(VALUE fname, VALUE wrap);
 VALUE rb_require_relative_entrypoint(VALUE fname);
 int rb_require_internal(VALUE fname);
diff --git a/load.c b/load.c
index c6b151abd3c..52a265f40ee 100644
--- a/load.c
+++ b/load.c
@@ -55,13 +55,13 @@ enum expand_type {
    string objects in $LOAD_PATH are frozen.
  */
 static void
-rb_construct_expanded_load_path(rb_box_t *box, enum expand_type type, int *has_relative, int *has_non_cache, long *maxlen_out)
+rb_construct_expanded_load_path(rb_box_t *box, enum expand_type type, int *has_relative, int *has_non_cache, rb_len_t *maxlen_out)
 {
     VALUE load_path = box->load_path;
     VALUE expanded_load_path = box->expanded_load_path;
     VALUE snapshot;
     VALUE ary;
-    long i, maxlen = 0;
+    rb_len_t i, maxlen = 0;
 
     ary = rb_ary_hidden_new(RARRAY_LEN(load_path));
     for (i = 0; i < RARRAY_LEN(load_path); ++i) {
@@ -82,7 +82,7 @@ rb_construct_expanded_load_path(rb_box_t *box, enum expand_type type, int *has_r
                 (type == EXPAND_NON_CACHE)) {
                     /* Use cached expanded path. */
                     expanded_path = RARRAY_AREF(expanded_load_path, i);
-                    long len = RSTRING_LEN(expanded_path);
+                    rb_len_t len = RSTRING_LEN(expanded_path);
                     if (len > maxlen) maxlen = len;
                     rb_ary_push(ary, expanded_path);
                     continue;
@@ -98,7 +98,7 @@ rb_construct_expanded_load_path(rb_box_t *box, enum expand_type type, int *has_r
         as_str = rb_get_path_check_convert(as_str);
         expanded_path = rb_check_realpath(Qnil, as_str, NULL);
         if (NIL_P(expanded_path)) expanded_path = as_str;
-        long len = RSTRING_LEN(expanded_path);
+        rb_len_t len = RSTRING_LEN(expanded_path);
         if (len > maxlen) maxlen = len;
         rb_ary_push(ary, rb_fstring(expanded_path));
     }
@@ -117,7 +117,7 @@ get_expanded_load_path(rb_box_t *box)
     const VALUE non_cache = Qtrue;
     const VALUE load_path_snapshot = box->load_path_snapshot;
     const VALUE load_path = box->load_path;
-    long maxlen = 0;
+    rb_len_t maxlen = 0;
 
     if (!rb_ary_shared_with_p(load_path_snapshot, load_path)) {
         /* The load path was modified. Rebuild the expanded load path. */
@@ -163,7 +163,7 @@ get_expanded_load_path(rb_box_t *box)
 }
 
 VALUE
-rb_get_expanded_load_path(long *maxlen)
+rb_get_expanded_load_path(rb_len_t *maxlen)
 {
     rb_box_t *box = (rb_box_t *)rb_loading_box();
     VALUE load_path = get_expanded_load_path((rb_box_t *)box);
@@ -208,8 +208,8 @@ feature_key(const char *str, size_t len)
 static bool
 is_rbext_path(VALUE feature_path)
 {
-    long len = RSTRING_LEN(feature_path);
-    long rbext_len = rb_strlen_lit(".rb");
+    rb_len_t len = RSTRING_LEN(feature_path);
+    rb_len_t rbext_len = rb_strlen_lit(".rb");
     if (len <= rbext_len) return false;
     return IS_RBEXT(RSTRING_PTR(feature_path) + len - rbext_len);
 }
@@ -401,7 +401,7 @@ get_loaded_features_index(const rb_box_t *box)
         reset_loaded_features_snapshot(box);
 
         features = box->loaded_features_snapshot;
-        long j = RARRAY_LEN(features);
+        rb_len_t j = RARRAY_LEN(features);
         for (i = 0; i < j; i++) {
             VALUE as_str = rb_ary_entry(features, i);
             VALUE realpath = rb_hash_aref(previous_realpath_map, as_str);
@@ -429,11 +429,11 @@ get_loaded_features_index(const rb_box_t *box)
    or have any value matching `%r{^\.[^./]*$}`.
 */
 static VALUE
-loaded_feature_path(const char *name, long vlen, const char *feature, long len,
+loaded_feature_path(const char *name, rb_len_t vlen, const char *feature, rb_len_t len,
                     int type, VALUE load_path)
 {
-    long i;
-    long plen;
+    rb_len_t i;
+    rb_len_t plen;
     const char *e;
 
     if (vlen < len+1) return 0;
@@ -463,7 +463,7 @@ loaded_feature_path(const char *name, long vlen, const char *feature, long len,
     for (i = 0; i < RARRAY_LEN(load_path); ++i) {
         VALUE p = RARRAY_AREF(load_path, i);
         const char *s = StringValuePtr(p);
-        long n = RSTRING_LEN(p);
+        rb_len_t n = RSTRING_LEN(p);
 
         if (n != plen) continue;
         if (n && strncmp(name, s, n)) continue;
@@ -474,7 +474,7 @@ loaded_feature_path(const char *name, long vlen, const char *feature, long len,
 
 struct loaded_feature_searching {
     const char *name;
-    long len;
+    rb_len_t len;
     int type;
     VALUE load_path;
     const char *result;
@@ -503,7 +503,7 @@ rb_feature_p(const rb_box_t *box, const char *feature, const char *ext, int rb,
 {
     VALUE features, this_feature_index = Qnil, v, p, load_path = 0;
     const char *f, *e;
-    long i, len, elen, n;
+    rb_len_t i, len, elen, n;
     st_table *loading_tbl, *features_index;
     st_data_t data;
     st_data_t key;
@@ -1118,7 +1118,7 @@ rb_f_require_relative(VALUE obj, VALUE fname)
 static char *
 find_ext(VALUE str, char **ptr, const char **end)
 {
-    long len = RSTRING_LEN(str);
+    rb_len_t len = RSTRING_LEN(str);
     *ptr = RSTRING_PTR(str);
     *end = *ptr + len;
     return memrchr(*ptr, '.', len);
diff --git a/pathname.c b/pathname.c
index d221b9ed141..5e2eebc1d00 100644
--- a/pathname.c
+++ b/pathname.c
@@ -247,7 +247,7 @@ path_absolute_p(VALUE self)
 {
     VALUE path = get_strpath(self);
     const char *ptr = RSTRING_PTR(path);
-    long len = RSTRING_LEN(path);
+    rb_len_t len = RSTRING_LEN(path);
     if (len < 1) return Qfalse;
     if (drive_letter) {
         if (len >= 2 && ISALPHA(ptr[0]) && (ptr[1] == ':')) return Qtrue;
@@ -387,7 +387,7 @@ add_trailing_separator(VALUE self, VALUE path)
 static VALUE
 del_trailing_separator(VALUE self, VALUE path)
 {
-    long len = RSTRING_LEN(check_strpath(path));
+    rb_len_t len = RSTRING_LEN(check_strpath(path));
     if (len <= 0) return path;
     rb_encoding *enc = rb_enc_get(path);
     const char *name = RSTRING_PTR(path);
diff --git a/ruby.c b/ruby.c
index 3d4931ab5e0..31b6ba6c6b2 100644
--- a/ruby.c
+++ b/ruby.c
@@ -829,7 +829,7 @@ static int
 process_sflag(int sflag)
 {
     if (sflag > 0) {
-        long n;
+        rb_len_t n;
         const VALUE *args;
         VALUE argv = rb_argv;
 
@@ -2384,7 +2384,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     int i = (int)proc_options(argc, argv, opt, 0);
     unsigned int dump = opt->dump & dump_exit_bits;
     const rb_box_t *box = rb_root_box();
-    const long loaded_before_enc = RARRAY_LEN(box->loaded_features);
+    const rb_len_t loaded_before_enc = RARRAY_LEN(box->loaded_features);
 
     if (opt->dump & (DUMP_BIT(usage)|DUMP_BIT(help))) {
         const char *const progname =
@@ -2536,7 +2536,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
 #endif
     rb_obj_freeze(opt->script_name);
     if (IF_UTF8_PATH(uenc != lenc, 1)) {
-        long i;
+        rb_len_t i;
         VALUE load_path = box->load_path;
         const ID id_initial_load_path_mark = INITIAL_LOAD_PATH_MARK;
         int modifiable = FALSE;
@@ -2566,7 +2566,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     {
         VALUE loaded_features = box->loaded_features;
         bool modified = false;
-        for (long i = loaded_before_enc; i < RARRAY_LEN(loaded_features); ++i) {
+        for (rb_len_t i = loaded_before_enc; i < RARRAY_LEN(loaded_features); ++i) {
             VALUE path = RARRAY_AREF(loaded_features, i);
             if (!(path = copy_str(path, IF_UTF8_PATH(uenc, lenc), true))) continue;
             if (!modified) {
@@ -2728,7 +2728,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
 
 #ifndef DOSISH
 static void
-warn_cr_in_shebang(const char *str, long len)
+warn_cr_in_shebang(const char *str, rb_len_t len)
 {
     if (len > 1 && str[len-1] == '\n' && str[len-2] == '\r') {
         rb_warn("shebang line ending with \\r may cause problems");
@@ -2769,7 +2769,7 @@ load_file_internal(VALUE argp_v)
         VALUE c = 1;		/* something not nil */
         VALUE line;
         char *p, *str;
-        long len;
+        rb_len_t len;
         int no_src_enc = !opt->src.enc.name;
         int no_ext_enc = !opt->ext.enc.name;
         int no_int_enc = !opt->intern.enc.name;
@@ -2907,7 +2907,7 @@ open_load_file(VALUE fname_v, int *xflag)
 {
     const char *fname = (fname_v = rb_str_encode_ospath(fname_v),
                          StringValueCStr(fname_v));
-    long flen = RSTRING_LEN(fname_v);
+    rb_len_t flen = RSTRING_LEN(fname_v);
     VALUE f;
     int e;
 
diff --git a/win32/file.c b/win32/file.c
index b5bf663aee3..f961c09ecb8 100644
--- a/win32/file.c
+++ b/win32/file.c
@@ -312,10 +312,10 @@ rb_file_expand_path_internal(VALUE fname, VALUE dname, int abs_mode, int long_na
 
     /* convert char * to wchar_t */
     if (!NIL_P(path)) {
-        const long path_len = RSTRING_LEN(path);
+        const rb_len_t path_len = RSTRING_LEN(path);
 #if SIZEOF_INT < SIZEOF_LONG
-        if ((long)(int)path_len != path_len) {
-            rb_raise(rb_eRangeError, "path (%ld bytes) is too long",
+        if ((rb_len_t)(int)path_len != path_len) {
+            rb_raise(rb_eRangeError, "path (%"PRIdLEN" bytes) is too long",
                      path_len);
         }
 #endif
@@ -390,11 +390,11 @@ rb_file_expand_path_internal(VALUE fname, VALUE dname, int abs_mode, int long_na
 
         /* convert char * to wchar_t */
         if (!NIL_P(dir)) {
-            const long dir_len = RSTRING_LEN(dir);
+            const rb_len_t dir_len = RSTRING_LEN(dir);
 #if SIZEOF_INT < SIZEOF_LONG
-            if ((long)(int)dir_len != dir_len) {
+            if ((rb_len_t)(int)dir_len != dir_len) {
                 free(wpath);
-                rb_raise(rb_eRangeError, "base directory (%ld bytes) is too long",
+                rb_raise(rb_eRangeError, "base directory (%"PRIdLEN" bytes) is too long",
                          dir_len);
             }
 #endif
@@ -622,12 +622,12 @@ rb_freopen(VALUE fname, const char *mode, FILE *file)
     WCHAR *wname, wmode[4];
     VALUE wtmp;
     char *name;
-    long len;
+    rb_len_t len;
     int e = 0, n = MultiByteToWideChar(CP_ACP, 0, mode, -1, NULL, 0);
     if (n > numberof(wmode)) return EINVAL;
     MultiByteToWideChar(CP_ACP, 0, mode, -1, wmode, numberof(wmode));
     RSTRING_GETMEM(fname, name, len);
-    n = rb_long2int(len);
+    n = rb_len2int(len);
     len = MultiByteToWideChar(CP_UTF8, 0, name, n, NULL, 0);
     wname = ALLOCV_N(WCHAR, wtmp, len + 1);
     len = MultiByteToWideChar(CP_UTF8, 0, name, n, wname, len);