diff --git a/constant.h b/constant.h
index f1a13feedb..3f1418df17 100644
--- a/constant.h
+++ b/constant.h
@@ -39,16 +39,12 @@ VALUE rb_mod_private_constant(int argc, const VALUE *argv, VALUE obj);
 VALUE rb_mod_public_constant(int argc, const VALUE *argv, VALUE obj);
 VALUE rb_mod_deprecate_constant(int argc, const VALUE *argv, VALUE obj);
 void rb_free_const_table(struct rb_id_table *tbl);
-VALUE rb_public_const_get(VALUE klass, ID id);
 VALUE rb_public_const_get_at(VALUE klass, ID id);
 VALUE rb_public_const_get_from(VALUE klass, ID id);
-int rb_public_const_defined(VALUE klass, ID id);
-int rb_public_const_defined_at(VALUE klass, ID id);
 int rb_public_const_defined_from(VALUE klass, ID id);
 rb_const_entry_t *rb_const_lookup(VALUE klass, ID id);
 int rb_autoloading_value(VALUE mod, ID id, VALUE *value, rb_const_flag_t *flag);
 VALUE rb_const_source_location(VALUE, ID);
-VALUE rb_const_source_location_from(VALUE, ID);
 VALUE rb_const_source_location_at(VALUE, ID);
 
 #endif /* CONSTANT_H */
diff --git a/error.c b/error.c
index b7aec28940..7a88ccbfd1 100644
--- a/error.c
+++ b/error.c
@@ -127,13 +127,6 @@ rb_syntax_error_append(VALUE exc, VALUE file, int line, int column,
     return exc;
 }
 
-void
-ruby_deprecated_internal_feature(const char *func)
-{
-    rb_print_backtrace();
-    rb_fatal("%s is only for internal use and deprecated; do not use", func);
-}
-
 /*
  * call-seq:
  *    warn(msg)  -> nil
diff --git a/eval_intern.h b/eval_intern.h
index 7c90972103..1ab049d327 100644
--- a/eval_intern.h
+++ b/eval_intern.h
@@ -250,9 +250,6 @@ CREF_OMOD_SHARED_UNSET(rb_cref_t *cref)
     cref->flags &= ~CREF_FL_OMOD_SHARED;
 }
 
-void rb_thread_cleanup(void);
-void rb_thread_wait_other_threads(void);
-
 enum {
     RAISED_EXCEPTION = 1,
     RAISED_STACKOVERFLOW = 2,
diff --git a/hash.c b/hash.c
index a5de9fde07..77c83d9ae3 100644
--- a/hash.c
+++ b/hash.c
@@ -544,7 +544,7 @@ RHASH_TABLE_EMPTY_P(VALUE hash)
     return RHASH_SIZE(hash) == 0;
 }
 
-MJIT_FUNC_EXPORTED int
+int
 rb_hash_ar_table_p(VALUE hash)
 {
     if (FL_TEST_RAW((hash), RHASH_ST_TABLE_FLAG)) {
@@ -563,7 +563,7 @@ rb_hash_ar_table(VALUE hash)
     return RHASH(hash)->as.ar;
 }
 
-MJIT_FUNC_EXPORTED st_table *
+st_table *
 rb_hash_st_table(VALUE hash)
 {
     HASH_ASSERT(!RHASH_AR_TABLE_P(hash));
diff --git a/internal.h b/internal.h
index 1b6cb2605d..ec8725aa59 100644
--- a/internal.h
+++ b/internal.h
@@ -841,12 +841,12 @@ enum ruby_rhash_flags {
 #define RHASH_AR_TABLE_SIZE_RAW(h) \
   ((unsigned int)((RBASIC(h)->flags & RHASH_AR_TABLE_SIZE_MASK) >> RHASH_AR_TABLE_SIZE_SHIFT))
 
-int rb_hash_ar_table_p(VALUE hash);
-struct ar_table_struct *rb_hash_ar_table(VALUE hash);
-st_table *rb_hash_st_table(VALUE hash);
 void rb_hash_st_table_set(VALUE hash, st_table *st);
 
 #if 0 /* for debug */
+int rb_hash_ar_table_p(VALUE hash);
+struct ar_table_struct *rb_hash_ar_table(VALUE hash);
+st_table *rb_hash_st_table(VALUE hash);
 #define RHASH_AR_TABLE_P(hash)       rb_hash_ar_table_p(hash)
 #define RHASH_AR_TABLE(h)            rb_hash_ar_table(h)
 #define RHASH_ST_TABLE(h)            rb_hash_st_table(h)
@@ -1520,16 +1520,9 @@ VALUE rb_check_backtrace(VALUE);
 NORETURN(void rb_async_bug_errno(const char *,int));
 const char *rb_builtin_type_name(int t);
 const char *rb_builtin_class_name(VALUE x);
-PRINTF_ARGS(void rb_sys_warn(const char *fmt, ...), 1, 2);
-PRINTF_ARGS(void rb_syserr_warn(int err, const char *fmt, ...), 2, 3);
-PRINTF_ARGS(void rb_sys_warning(const char *fmt, ...), 1, 2);
-PRINTF_ARGS(void rb_syserr_warning(int err, const char *fmt, ...), 2, 3);
 #ifdef RUBY_ENCODING_H
 VALUE rb_syntax_error_append(VALUE, VALUE, int, int, rb_encoding*, const char*, va_list);
 PRINTF_ARGS(void rb_enc_warn(rb_encoding *enc, const char *fmt, ...), 2, 3);
-PRINTF_ARGS(void rb_sys_enc_warn(rb_encoding *enc, const char *fmt, ...), 2, 3);
-PRINTF_ARGS(void rb_syserr_enc_warn(int err, rb_encoding *enc, const char *fmt, ...), 3, 4);
-PRINTF_ARGS(void rb_enc_warning(rb_encoding *enc, const char *fmt, ...), 2, 3);
 PRINTF_ARGS(void rb_sys_enc_warning(rb_encoding *enc, const char *fmt, ...), 2, 3);
 PRINTF_ARGS(void rb_syserr_enc_warning(int err, rb_encoding *enc, const char *fmt, ...), 3, 4);
 #endif
@@ -1548,9 +1541,6 @@ VALUE rb_nomethod_err_new(VALUE mesg, VALUE recv, VALUE method, VALUE args, int
 VALUE rb_key_err_new(VALUE mesg, VALUE recv, VALUE name);
 #define rb_key_err_raise(mesg, recv, name) \
     rb_exc_raise(rb_key_err_new(mesg, recv, name))
-NORETURN(void ruby_deprecated_internal_feature(const char *));
-#define DEPRECATED_INTERNAL_FEATURE(func) \
-    (ruby_deprecated_internal_feature(func), UNREACHABLE)
 VALUE rb_warning_warn(VALUE mod, VALUE str);
 PRINTF_ARGS(VALUE rb_warning_string(const char *fmt, ...), 1, 2);
 NORETURN(void rb_vraise(VALUE, const char *, va_list));
@@ -1694,9 +1684,7 @@ int rb_hash_stlike_update(VALUE hash, st_data_t key, st_update_callback_func fun
 void rb_call_inits(void);
 
 /* io.c */
-const char *ruby_get_inplace_mode(void);
 void ruby_set_inplace_mode(const char *);
-ssize_t rb_io_bufread(VALUE io, void *buf, size_t size);
 void rb_stdio_set_default_encoding(void);
 VALUE rb_io_flush_raw(VALUE, int);
 #ifdef RUBY_IO_H
@@ -1707,7 +1695,6 @@ void rb_io_fptr_finalize_internal(void *ptr);
 #define rb_io_fptr_finalize rb_io_fptr_finalize_internal
 
 /* load.c */
-VALUE rb_get_load_path(void);
 VALUE rb_get_expanded_load_path(void);
 int rb_require_internal(VALUE fname, int safe);
 NORETURN(void rb_load_fail(VALUE, const char*));
@@ -1973,7 +1960,6 @@ struct RBasicRaw {
 #ifndef USE_SYMBOL_GC
 #define USE_SYMBOL_GC 1
 #endif
-VALUE rb_parser_get_yydebug(VALUE);
 VALUE rb_parser_set_yydebug(VALUE, VALUE);
 RUBY_SYMBOL_EXPORT_BEGIN
 VALUE rb_parser_set_context(VALUE, const struct rb_iseq_struct *, int);
@@ -1981,23 +1967,12 @@ RUBY_SYMBOL_EXPORT_END
 void *rb_parser_load_file(VALUE parser, VALUE name);
 int rb_is_const_name(VALUE name);
 int rb_is_class_name(VALUE name);
-int rb_is_global_name(VALUE name);
 int rb_is_instance_name(VALUE name);
-int rb_is_attrset_name(VALUE name);
 int rb_is_local_name(VALUE name);
-int rb_is_method_name(VALUE name);
-int rb_is_junk_name(VALUE name);
 PUREFUNC(int rb_is_const_sym(VALUE sym));
-PUREFUNC(int rb_is_class_sym(VALUE sym));
-PUREFUNC(int rb_is_global_sym(VALUE sym));
-PUREFUNC(int rb_is_instance_sym(VALUE sym));
 PUREFUNC(int rb_is_attrset_sym(VALUE sym));
-PUREFUNC(int rb_is_local_sym(VALUE sym));
-PUREFUNC(int rb_is_method_sym(VALUE sym));
-PUREFUNC(int rb_is_junk_sym(VALUE sym));
 ID rb_make_internal_id(void);
 void rb_gc_free_dsymbol(VALUE);
-ID rb_id_attrget(ID id);
 
 /* proc.c */
 VALUE rb_proc_location(VALUE self);
@@ -2130,14 +2105,6 @@ VALUE rb_fstring_cstr(const char *str);
 VALUE rb_fstring_enc_new(const char *ptr, long len, rb_encoding *enc);
 #define rb_fstring_enc_lit(str, enc) rb_fstring_enc_new((str), rb_strlen_lit(str), (enc))
 #define rb_fstring_enc_literal(str, enc) rb_fstring_enc_lit(str, enc)
-VALUE rb_fstring_enc_cstr(const char *ptr, rb_encoding *enc);
-# ifdef HAVE_BUILTIN___BUILTIN_CONSTANT_P
-#  define rb_fstring_enc_cstr(str, enc) RB_GNUC_EXTENSION_BLOCK( \
-    (__builtin_constant_p(str)) ?		\
-	rb_fstring_enc_new((str), (long)strlen(str), (enc)) : \
-	rb_fstring_enc_cstr(str, enc) \
-)
-# endif
 #endif
 int rb_str_buf_cat_escaped_char(VALUE result, unsigned int c, int unicode_p);
 int rb_str_symname_p(VALUE);
@@ -2190,15 +2157,6 @@ rb_str_eql_internal(const VALUE str1, const VALUE str2)
 /* symbol.c */
 #ifdef RUBY_ENCODING_H
 VALUE rb_sym_intern(const char *ptr, long len, rb_encoding *enc);
-VALUE rb_sym_intern_cstr(const char *ptr, rb_encoding *enc);
-#ifdef __GNUC__
-#define rb_sym_intern_cstr(ptr, enc) __extension__ ( \
-{						\
-    (__builtin_constant_p(ptr)) ?		\
-	rb_sym_intern((ptr), (long)strlen(ptr), (enc)) : \
-	rb_sym_intern_cstr((ptr), (enc)); \
-})
-#endif
 #endif
 VALUE rb_sym_intern_ascii(const char *ptr, long len);
 VALUE rb_sym_intern_ascii_cstr(const char *ptr);
@@ -2296,9 +2254,6 @@ void rb_vm_mark(void *ptr);
 void Init_BareVM(void);
 void Init_vm_objects(void);
 PUREFUNC(VALUE rb_vm_top_self(void));
-void rb_thread_recycle_stack_release(VALUE *);
-VALUE *rb_thread_recycle_stack(size_t);
-void rb_vm_change_state(void);
 void rb_vm_inc_const_missing_count(void);
 const void **rb_vm_get_insns_address_table(void);
 VALUE rb_source_location(int *pline);
diff --git a/io.c b/io.c
index bb8036c63b..f4dc499633 100644
--- a/io.c
+++ b/io.c
@@ -2493,16 +2493,6 @@ io_fread(VALUE str, long offset, long size, rb_io_t *fptr)
     return len;
 }
 
-ssize_t
-rb_io_bufread(VALUE io, void *buf, size_t size)
-{
-    rb_io_t *fptr;
-
-    GetOpenFile(io, fptr);
-    rb_io_check_readable(fptr);
-    return (ssize_t)io_bufread(buf, (long)size, fptr);
-}
-
 static long
 remain_size(rb_io_t *fptr)
 {
@@ -12870,12 +12860,6 @@ opt_i_set(VALUE val, ID id, VALUE *var)
     argf_inplace_mode_set(*var, val);
 }
 
-const char *
-ruby_get_inplace_mode(void)
-{
-    return RSTRING_PTR(ARGF.inplace);
-}
-
 void
 ruby_set_inplace_mode(const char *suffix)
 {
diff --git a/iseq.c b/iseq.c
index 6c2d2256ff..c2f241284e 100644
--- a/iseq.c
+++ b/iseq.c
@@ -1012,12 +1012,6 @@ rb_iseq_compile_with_option(VALUE src, VALUE file, VALUE realpath, VALUE line, V
     return iseq;
 }
 
-rb_iseq_t *
-rb_iseq_compile(VALUE src, VALUE file, VALUE line)
-{
-    return rb_iseq_compile_with_option(src, file, Qnil, line, Qnil);
-}
-
 VALUE
 rb_iseq_path(const rb_iseq_t *iseq)
 {
@@ -3308,14 +3302,6 @@ rb_iseq_trace_set_all(rb_event_flag_t turnon_events)
     rb_objspace_each_objects(trace_set_i, &turnon_events);
 }
 
-/* This is exported since Ruby 2.5 but not internally used for now. If you're going to use this, please
-   update `ruby_vm_event_enabled_global_flags` and set `mjit_call_p = FALSE` as well to cancel MJIT code. */
-void
-rb_iseq_trace_on_all(void)
-{
-    rb_iseq_trace_set_all(RUBY_EVENT_TRACEPOINT_ALL);
-}
-
 VALUE
 rb_iseqw_local_variables(VALUE iseqval)
 {
diff --git a/iseq.h b/iseq.h
index 1fcf7cb210..9e19d090f1 100644
--- a/iseq.h
+++ b/iseq.h
@@ -182,11 +182,9 @@ void rb_iseq_mark_insn_storage(struct iseq_compile_data_storage *arena);
 /* iseq.c */
 VALUE rb_iseq_load(VALUE data, VALUE parent, VALUE opt);
 VALUE rb_iseq_parameters(const rb_iseq_t *iseq, int is_proc);
-struct st_table *ruby_insn_make_insn_table(void);
 unsigned int rb_iseq_line_no(const rb_iseq_t *iseq, size_t pos);
 void rb_iseq_trace_set(const rb_iseq_t *iseq, rb_event_flag_t turnon_events);
 void rb_iseq_trace_set_all(rb_event_flag_t turnon_events);
-void rb_iseq_trace_on_all(void);
 void rb_iseq_insns_info_encode_positions(const rb_iseq_t *iseq);
 
 VALUE rb_iseqw_new(const rb_iseq_t *iseq);
diff --git a/load.c b/load.c
index 3060c81cbc..b95d22848a 100644
--- a/load.c
+++ b/load.c
@@ -28,13 +28,6 @@ static const char *const loadable_ext[] = {
     0
 };
 
-VALUE
-rb_get_load_path(void)
-{
-    VALUE load_path = GET_VM()->load_path;
-    return load_path;
-}
-
 enum expand_type {
     EXPAND_ALL,
     EXPAND_RELATIVE,
diff --git a/method.h b/method.h
index 1cfa9e1f3d..806790ffb8 100644
--- a/method.h
+++ b/method.h
@@ -215,11 +215,8 @@ int rb_method_entry_eq(const rb_method_entry_t *m1, const rb_method_entry_t *m2)
 st_index_t rb_hash_method_entry(st_index_t hash, const rb_method_entry_t *me);
 
 VALUE rb_method_entry_location(const rb_method_entry_t *me);
-VALUE rb_mod_method_location(VALUE mod, ID id);
-VALUE rb_obj_method_location(VALUE obj, ID id);
 
 void rb_free_method_entry(const rb_method_entry_t *me);
-void rb_sweep_method_entry(void *vm);
 
 const rb_method_entry_t *rb_method_entry_clone(const rb_method_entry_t *me);
 const rb_callable_method_entry_t *rb_method_entry_complement_defined_class(const rb_method_entry_t *src_me, ID called_id, VALUE defined_class);
diff --git a/mjit.h b/mjit.h
index 6c6e80024e..e89a2b9a6f 100644
--- a/mjit.h
+++ b/mjit.h
@@ -79,8 +79,6 @@ RUBY_SYMBOL_EXPORT_END
 
 extern bool mjit_compile(FILE *f, const rb_iseq_t *iseq, const char *funcname);
 extern void mjit_init(struct mjit_options *opts);
-extern void mjit_postponed_job_register_start_hook(void);
-extern void mjit_postponed_job_register_finish_hook(void);
 extern void mjit_gc_start_hook(void);
 extern void mjit_gc_exit_hook(void);
 extern void mjit_free_iseq(const rb_iseq_t *iseq);
@@ -164,8 +162,6 @@ void mjit_child_after_fork(void);
 #else // USE_MJIT
 static inline struct mjit_cont *mjit_cont_new(rb_execution_context_t *ec){return NULL;}
 static inline void mjit_cont_free(struct mjit_cont *cont){}
-static inline void mjit_postponed_job_register_start_hook(void){}
-static inline void mjit_postponed_job_register_finish_hook(void){}
 static inline void mjit_gc_start_hook(void){}
 static inline void mjit_gc_exit_hook(void){}
 static inline void mjit_free_iseq(const rb_iseq_t *iseq){}
diff --git a/node.h b/node.h
index 79fa29d56b..84f7464e6e 100644
--- a/node.h
+++ b/node.h
@@ -414,22 +414,15 @@ void rb_ast_delete_node(rb_ast_t*, NODE *n);
 VALUE rb_parser_new(void);
 VALUE rb_parser_end_seen_p(VALUE);
 VALUE rb_parser_encoding(VALUE);
-VALUE rb_parser_get_yydebug(VALUE);
 VALUE rb_parser_set_yydebug(VALUE, VALUE);
 VALUE rb_parser_dump_tree(const NODE *node, int comment);
 void rb_parser_set_options(VALUE, int, int, int, int);
 
-rb_ast_t *rb_parser_compile_cstr(VALUE, const char*, const char*, int, int);
 rb_ast_t *rb_parser_compile_string(VALUE, const char*, VALUE, int);
-rb_ast_t *rb_parser_compile_file(VALUE, const char*, VALUE, int);
 rb_ast_t *rb_parser_compile_string_path(VALUE vparser, VALUE fname, VALUE src, int line);
 rb_ast_t *rb_parser_compile_file_path(VALUE vparser, VALUE fname, VALUE input, int line);
 rb_ast_t *rb_parser_compile_generic(VALUE vparser, VALUE (*lex_gets)(VALUE, int), VALUE fname, VALUE input, int line);
 
-rb_ast_t *rb_compile_cstr(const char*, const char*, int, int);
-rb_ast_t *rb_compile_string(const char*, VALUE, int);
-rb_ast_t *rb_compile_file(const char*, VALUE, int);
-
 void rb_node_init(NODE *n, enum node_type type, VALUE a0, VALUE a1, VALUE a2);
 const char *ruby_node_name(int node);
 
diff --git a/parse.y b/parse.y
index 099d55eeba..9eb7bedf34 100644
--- a/parse.y
+++ b/parse.y
@@ -6044,13 +6044,6 @@ parser_compile_string(VALUE vparser, VALUE fname, VALUE s, int line)
     return yycompile(vparser, p, fname, line);
 }
 
-rb_ast_t*
-rb_compile_string(const char *f, VALUE s, int line)
-{
-    must_be_ascii_compatible(s);
-    return parser_compile_string(rb_parser_new(), rb_filesystem_str_new_cstr(f), s, line);
-}
-
 rb_ast_t*
 rb_parser_compile_string(VALUE vparser, const char *f, VALUE s, int line)
 {
@@ -6064,20 +6057,6 @@ rb_parser_compile_string_path(VALUE vparser, VALUE f, VALUE s, int line)
     return parser_compile_string(vparser, f, s, line);
 }
 
-rb_ast_t*
-rb_compile_cstr(const char *f, const char *s, int len, int line)
-{
-    VALUE str = rb_str_new(s, len);
-    return parser_compile_string(rb_parser_new(), rb_filesystem_str_new_cstr(f), str, line);
-}
-
-rb_ast_t*
-rb_parser_compile_cstr(VALUE vparser, const char *f, const char *s, int len, int line)
-{
-    VALUE str = rb_str_new(s, len);
-    return parser_compile_string(vparser, rb_filesystem_str_new_cstr(f), str, line);
-}
-
 VALUE rb_io_gets_internal(VALUE io);
 
 static VALUE
@@ -6086,20 +6065,6 @@ lex_io_gets(struct parser_params *p, VALUE io)
     return rb_io_gets_internal(io);
 }
 
-rb_ast_t*
-rb_compile_file(const char *f, VALUE file, int start)
-{
-    VALUE vparser = rb_parser_new();
-
-    return rb_parser_compile_file(vparser, f, file, start);
-}
-
-rb_ast_t*
-rb_parser_compile_file(VALUE vparser, const char *f, VALUE file, int start)
-{
-    return rb_parser_compile_file_path(vparser, rb_filesystem_str_new_cstr(f), file, start);
-}
-
 rb_ast_t*
 rb_parser_compile_file_path(VALUE vparser, VALUE fname, VALUE file, int start)
 {
@@ -12472,6 +12437,7 @@ rb_parser_encoding(VALUE vparser)
     return rb_enc_from_encoding(p->enc);
 }
 
+#ifdef RIPPER
 /*
  *  call-seq:
  *    ripper.yydebug   -> true or false
@@ -12486,6 +12452,7 @@ rb_parser_get_yydebug(VALUE self)
     TypedData_Get_Struct(self, struct parser_params, &parser_data_type, p);
     return p->debug ? Qtrue : Qfalse;
 }
+#endif
 
 /*
  *  call-seq:
diff --git a/proc.c b/proc.c
index 560b641557..762f704345 100644
--- a/proc.c
+++ b/proc.c
@@ -2736,19 +2736,6 @@ rb_method_entry_location(const rb_method_entry_t *me)
     return method_def_location(me->def);
 }
 
-VALUE
-rb_mod_method_location(VALUE mod, ID id)
-{
-    const rb_method_entry_t *me = original_method_entry(mod, id);
-    return rb_method_entry_location(me);
-}
-
-MJIT_FUNC_EXPORTED VALUE
-rb_obj_method_location(VALUE obj, ID id)
-{
-    return rb_mod_method_location(CLASS_OF(obj), id);
-}
-
 /*
  * call-seq:
  *    meth.source_location  -> [String, Integer]
diff --git a/string.c b/string.c
index 065339026b..554aabad4b 100644
--- a/string.c
+++ b/string.c
@@ -60,7 +60,6 @@
 #undef rb_str_cat2
 #undef rb_str_cat_cstr
 #undef rb_fstring_cstr
-#undef rb_fstring_enc_cstr
 
 static VALUE rb_str_clear(VALUE str);
 
@@ -414,12 +413,6 @@ rb_fstring_cstr(const char *ptr)
     return rb_fstring_new(ptr, strlen(ptr));
 }
 
-VALUE
-rb_fstring_enc_cstr(const char *ptr, rb_encoding *enc)
-{
-    return rb_fstring_enc_new(ptr, strlen(ptr), enc);
-}
-
 static int
 fstring_set_class_i(st_data_t key, st_data_t val, st_data_t arg)
 {
diff --git a/symbol.c b/symbol.c
index 046c8e1105..14517df01e 100644
--- a/symbol.c
+++ b/symbol.c
@@ -92,8 +92,6 @@ WARN_UNUSED_RESULT(static VALUE dsymbol_check(const VALUE sym));
 WARN_UNUSED_RESULT(static ID lookup_str_id(VALUE str));
 WARN_UNUSED_RESULT(static VALUE lookup_str_sym(const VALUE str));
 WARN_UNUSED_RESULT(static VALUE lookup_id_str(ID id));
-WARN_UNUSED_RESULT(static ID attrsetname_to_attr(VALUE name));
-WARN_UNUSED_RESULT(static ID attrsetname_to_attr_id(VALUE name));
 WARN_UNUSED_RESULT(static ID intern_str(VALUE str, int mutable));
 
 ID
@@ -154,12 +152,6 @@ rb_id_attrset(ID id)
     return id;
 }
 
-ID
-rb_id_attrget(ID id)
-{
-    return attrsetname_to_attr(rb_id2str(id));
-}
-
 static int
 is_special_global_name(const char *m, const char *e, rb_encoding *enc)
 {
@@ -906,42 +898,12 @@ rb_is_const_sym(VALUE sym)
     return is_const_sym(sym);
 }
 
-int
-rb_is_class_sym(VALUE sym)
-{
-    return is_class_sym(sym);
-}
-
-int
-rb_is_global_sym(VALUE sym)
-{
-    return is_global_sym(sym);
-}
-
-int
-rb_is_instance_sym(VALUE sym)
-{
-    return is_instance_sym(sym);
-}
-
 int
 rb_is_attrset_sym(VALUE sym)
 {
     return is_attrset_sym(sym);
 }
 
-int
-rb_is_local_sym(VALUE sym)
-{
-    return is_local_sym(sym);
-}
-
-int
-rb_is_junk_sym(VALUE sym)
-{
-    return is_junk_sym(sym);
-}
-
 /**
  * Returns ID for the given name if it is interned already, or 0.
  *
@@ -1049,13 +1011,11 @@ rb_check_symbol_cstr(const char *ptr, long len, rb_encoding *enc)
     return Qnil;
 }
 
-#undef rb_sym_intern_cstr
 #undef rb_sym_intern_ascii_cstr
 #ifdef __clang__
 NOINLINE(VALUE rb_sym_intern(const char *ptr, long len, rb_encoding *enc));
 #else
 FUNC_MINIMIZED(VALUE rb_sym_intern(const char *ptr, long len, rb_encoding *enc));
-FUNC_MINIMIZED(VALUE rb_sym_intern_cstr(const char *ptr, rb_encoding *enc));
 FUNC_MINIMIZED(VALUE rb_sym_intern_ascii(const char *ptr, long len));
 FUNC_MINIMIZED(VALUE rb_sym_intern_ascii_cstr(const char *ptr));
 #endif
@@ -1068,12 +1028,6 @@ rb_sym_intern(const char *ptr, long len, rb_encoding *enc)
     return rb_str_intern(name);
 }
 
-VALUE
-rb_sym_intern_cstr(const char *ptr, rb_encoding *enc)
-{
-    return rb_sym_intern(ptr, strlen(ptr), enc);
-}
-
 VALUE
 rb_sym_intern_ascii(const char *ptr, long len)
 {
@@ -1092,34 +1046,6 @@ rb_to_symbol_type(VALUE obj)
     return rb_convert_type_with_id(obj, T_SYMBOL, "Symbol", idTo_sym);
 }
 
-static ID
-attrsetname_to_attr_id(VALUE name)
-{
-    ID id;
-    struct RString fake_str;
-    /* make local name by chopping '=' */
-    const VALUE localname = rb_setup_fake_str(&fake_str,
-					      RSTRING_PTR(name), RSTRING_LEN(name) - 1,
-					      rb_enc_get(name));
-    OBJ_FREEZE(localname);
-
-    if ((id = lookup_str_id(localname)) != 0) {
-	return id;
-    }
-    RB_GC_GUARD(name);
-    return (ID)0;
-}
-
-static ID
-attrsetname_to_attr(VALUE name)
-{
-    if (rb_is_attrset_name(name)) {
-	return attrsetname_to_attr_id(name);
-    }
-
-    return (ID)0;
-}
-
 int
 rb_is_const_name(VALUE name)
 {
@@ -1132,44 +1058,16 @@ rb_is_class_name(VALUE name)
     return rb_str_symname_type(name, 0) == ID_CLASS;
 }
 
-int
-rb_is_global_name(VALUE name)
-{
-    return rb_str_symname_type(name, 0) == ID_GLOBAL;
-}
-
 int
 rb_is_instance_name(VALUE name)
 {
     return rb_str_symname_type(name, 0) == ID_INSTANCE;
 }
 
-int
-rb_is_attrset_name(VALUE name)
-{
-    return rb_str_symname_type(name, IDSET_ATTRSET_FOR_INTERN) == ID_ATTRSET;
-}
-
 int
 rb_is_local_name(VALUE name)
 {
     return rb_str_symname_type(name, 0) == ID_LOCAL;
 }
 
-int
-rb_is_method_name(VALUE name)
-{
-    switch (rb_str_symname_type(name, 0)) {
-      case ID_LOCAL: case ID_ATTRSET: case ID_JUNK:
-	return TRUE;
-    }
-    return FALSE;
-}
-
-int
-rb_is_junk_name(VALUE name)
-{
-    return rb_str_symname_type(name, IDSET_ATTRSET_FOR_SYNTAX) == -1;
-}
-
 #include "id_table.c"
diff --git a/variable.c b/variable.c
index b0f87923d4..afa633151d 100644
--- a/variable.c
+++ b/variable.c
@@ -2418,12 +2418,6 @@ rb_public_const_get_from(VALUE klass, ID id)
     return rb_const_get_0(klass, id, TRUE, TRUE, TRUE);
 }
 
-VALUE
-rb_public_const_get(VALUE klass, ID id)
-{
-    return rb_const_get_0(klass, id, FALSE, TRUE, TRUE);
-}
-
 MJIT_FUNC_EXPORTED VALUE
 rb_public_const_get_at(VALUE klass, ID id)
 {
@@ -2476,12 +2470,6 @@ rb_const_location(VALUE klass, ID id, int exclude, int recurse, int visibility)
     return rb_const_location_from(rb_cObject, id, FALSE, recurse, visibility);
 }
 
-VALUE
-rb_const_source_location_from(VALUE klass, ID id)
-{
-    return rb_const_location(klass, id, TRUE, TRUE, FALSE);
-}
-
 VALUE
 rb_const_source_location(VALUE klass, ID id)
 {
@@ -2725,18 +2713,6 @@ rb_public_const_defined_from(VALUE klass, ID id)
     return rb_const_defined_0(klass, id, TRUE, TRUE, TRUE);
 }
 
-int
-rb_public_const_defined(VALUE klass, ID id)
-{
-    return rb_const_defined_0(klass, id, FALSE, TRUE, TRUE);
-}
-
-int
-rb_public_const_defined_at(VALUE klass, ID id)
-{
-    return rb_const_defined_0(klass, id, TRUE, FALSE, TRUE);
-}
-
 static void
 check_before_mod_set(VALUE klass, ID id, VALUE val, const char *dest)
 {
diff --git a/vm_core.h b/vm_core.h
index 9c5b723d6a..ea2e7a20cd 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -1029,7 +1029,6 @@ rb_iseq_t *rb_iseq_new_with_callback(const struct rb_iseq_new_with_callback_call
     const rb_iseq_t *parent, enum iseq_type, const rb_compile_option_t*);
 
 /* src -> iseq */
-rb_iseq_t *rb_iseq_compile(VALUE src, VALUE file, VALUE line);
 rb_iseq_t *rb_iseq_compile_with_option(VALUE src, VALUE file, VALUE realpath, VALUE line, VALUE opt);
 
 VALUE rb_iseq_disasm(const rb_iseq_t *iseq);
@@ -1132,8 +1131,6 @@ typedef struct rb_call_info *CALL_INFO;
 typedef struct rb_call_cache *CALL_CACHE;
 typedef struct rb_call_data *CALL_DATA;
 
-void rb_vm_change_state(void);
-
 typedef VALUE CDHASH;
 
 #ifndef FUNC_FASTCALL