diff --git a/common.mk b/common.mk
index 4cc436dc41..e237a3f51b 100644
--- a/common.mk
+++ b/common.mk
@@ -836,7 +836,10 @@ clean-platform distclean-platform realclean-platform:
 
 RUBYSPEC_CAPIEXT = spec/ruby/optional/capi/ext
 RUBYSPEC_CAPIEXT_SRCDIR = $(srcdir)/$(RUBYSPEC_CAPIEXT)
-RUBYSPEC_CAPIEXT_DEPS = $(RUBYSPEC_CAPIEXT_SRCDIR)/rubyspec.h $(RUBY_H_INCLUDES) $(LIBRUBY) build-ext
+RUBYSPEC_CAPIEXT_DEPS = $(RUBYSPEC_CAPIEXT_SRCDIR)/rubyspec.h $(RUBY_H_INCLUDES) $(LIBRUBY)
+
+rubyspec-capiext: build-ext $(DOT_WAIT)
+# make-dependent rules should be included after this and built after build-ext.
 
 clean-spec: PHONY
 	-$(Q) $(RM) $(RUBYSPEC_CAPIEXT)/*.$(OBJEXT) $(RUBYSPEC_CAPIEXT)/*.$(DLEXT)
@@ -9526,6 +9529,7 @@ marshal.$(OBJEXT): {$(VPATH)}internal/attr/nodiscard.h
 marshal.$(OBJEXT): {$(VPATH)}internal/attr/noexcept.h
 marshal.$(OBJEXT): {$(VPATH)}internal/attr/noinline.h
 marshal.$(OBJEXT): {$(VPATH)}internal/attr/nonnull.h
+marshal.$(OBJEXT): {$(VPATH)}internal/attr/nonstring.h
 marshal.$(OBJEXT): {$(VPATH)}internal/attr/noreturn.h
 marshal.$(OBJEXT): {$(VPATH)}internal/attr/packed_struct.h
 marshal.$(OBJEXT): {$(VPATH)}internal/attr/pure.h
@@ -10135,6 +10139,7 @@ miniinit.$(OBJEXT): {$(VPATH)}internal/attr/nodiscard.h
 miniinit.$(OBJEXT): {$(VPATH)}internal/attr/noexcept.h
 miniinit.$(OBJEXT): {$(VPATH)}internal/attr/noinline.h
 miniinit.$(OBJEXT): {$(VPATH)}internal/attr/nonnull.h
+miniinit.$(OBJEXT): {$(VPATH)}internal/attr/nonstring.h
 miniinit.$(OBJEXT): {$(VPATH)}internal/attr/noreturn.h
 miniinit.$(OBJEXT): {$(VPATH)}internal/attr/packed_struct.h
 miniinit.$(OBJEXT): {$(VPATH)}internal/attr/pure.h
@@ -16472,6 +16477,7 @@ signal.$(OBJEXT): {$(VPATH)}internal/attr/nodiscard.h
 signal.$(OBJEXT): {$(VPATH)}internal/attr/noexcept.h
 signal.$(OBJEXT): {$(VPATH)}internal/attr/noinline.h
 signal.$(OBJEXT): {$(VPATH)}internal/attr/nonnull.h
+signal.$(OBJEXT): {$(VPATH)}internal/attr/nonstring.h
 signal.$(OBJEXT): {$(VPATH)}internal/attr/noreturn.h
 signal.$(OBJEXT): {$(VPATH)}internal/attr/packed_struct.h
 signal.$(OBJEXT): {$(VPATH)}internal/attr/pure.h
@@ -17231,6 +17237,7 @@ string.$(OBJEXT): {$(VPATH)}internal/attr/nodiscard.h
 string.$(OBJEXT): {$(VPATH)}internal/attr/noexcept.h
 string.$(OBJEXT): {$(VPATH)}internal/attr/noinline.h
 string.$(OBJEXT): {$(VPATH)}internal/attr/nonnull.h
+string.$(OBJEXT): {$(VPATH)}internal/attr/nonstring.h
 string.$(OBJEXT): {$(VPATH)}internal/attr/noreturn.h
 string.$(OBJEXT): {$(VPATH)}internal/attr/packed_struct.h
 string.$(OBJEXT): {$(VPATH)}internal/attr/pure.h
@@ -17689,6 +17696,7 @@ symbol.$(OBJEXT): {$(VPATH)}internal/attr/nodiscard.h
 symbol.$(OBJEXT): {$(VPATH)}internal/attr/noexcept.h
 symbol.$(OBJEXT): {$(VPATH)}internal/attr/noinline.h
 symbol.$(OBJEXT): {$(VPATH)}internal/attr/nonnull.h
+symbol.$(OBJEXT): {$(VPATH)}internal/attr/nonstring.h
 symbol.$(OBJEXT): {$(VPATH)}internal/attr/noreturn.h
 symbol.$(OBJEXT): {$(VPATH)}internal/attr/packed_struct.h
 symbol.$(OBJEXT): {$(VPATH)}internal/attr/pure.h
diff --git a/defs/gmake.mk b/defs/gmake.mk
index a14fb8f650..c3201e2502 100644
--- a/defs/gmake.mk
+++ b/defs/gmake.mk
@@ -500,7 +500,8 @@ update-deps:
 
 # order-only-prerequisites doesn't work for $(RUBYSPEC_CAPIEXT)
 # because the same named directory exists in the source tree.
-$(RUBYSPEC_CAPIEXT)/%.$(DLEXT): $(srcdir)/$(RUBYSPEC_CAPIEXT)/%.c $(RUBYSPEC_CAPIEXT_DEPS)
+$(RUBYSPEC_CAPIEXT)/%.$(DLEXT): $(srcdir)/$(RUBYSPEC_CAPIEXT)/%.c $(RUBYSPEC_CAPIEXT_DEPS) \
+	| build-ext
 	$(ECHO) building $@
 	$(Q) $(MAKEDIRS) $(@D)
 	$(Q) $(DLDSHARED) -L. $(XDLDFLAGS) $(XLDFLAGS) $(LDFLAGS) $(INCFLAGS) $(CPPFLAGS) $(OUTFLAG)$@ $< $(LIBRUBYARG)
diff --git a/enc/depend b/enc/depend
index 12ddbc223a..cf2ca2d9da 100644
--- a/enc/depend
+++ b/enc/depend
@@ -6972,6 +6972,7 @@ enc/trans/iso2022.$(OBJEXT): internal/attr/nodiscard.h
 enc/trans/iso2022.$(OBJEXT): internal/attr/noexcept.h
 enc/trans/iso2022.$(OBJEXT): internal/attr/noinline.h
 enc/trans/iso2022.$(OBJEXT): internal/attr/nonnull.h
+enc/trans/iso2022.$(OBJEXT): internal/attr/nonstring.h
 enc/trans/iso2022.$(OBJEXT): internal/attr/noreturn.h
 enc/trans/iso2022.$(OBJEXT): internal/attr/packed_struct.h
 enc/trans/iso2022.$(OBJEXT): internal/attr/pure.h
diff --git a/enc/trans/iso2022.trans b/enc/trans/iso2022.trans
index a441f1596d..ea7d2c8aec 100644
--- a/enc/trans/iso2022.trans
+++ b/enc/trans/iso2022.trans
@@ -1,4 +1,5 @@
 #include "transcode_data.h"
+#include "ruby/internal/attr/nonstring.h"
 
 <%
   map = {
@@ -443,7 +444,7 @@ rb_cp50221_encoder = {
     iso2022jp_encoder_reset_sequence_size, finish_iso2022jp_encoder
 };
 
-static const char *tbl0208 =
+RBIMPL_ATTR_NONSTRING() static const char *tbl0208 =
     "\x21\x23\x21\x56\x21\x57\x21\x22\x21\x26\x25\x72\x25\x21\x25\x23" \
     "\x25\x25\x25\x27\x25\x29\x25\x63\x25\x65\x25\x67\x25\x43\x21\x3C" \
     "\x25\x22\x25\x24\x25\x26\x25\x28\x25\x2A\x25\x2B\x25\x2D\x25\x2F" \
diff --git a/include/ruby/internal/attr/nonstring.h b/include/ruby/internal/attr/nonstring.h
new file mode 100644
index 0000000000..de26e926d4
--- /dev/null
+++ b/include/ruby/internal/attr/nonstring.h
@@ -0,0 +1,32 @@
+#ifndef RBIMPL_ATTR_NONSTRING_H                        /*-*-C++-*-vi:se ft=cpp:*/
+#define RBIMPL_ATTR_NONSTRING_H
+/**
+ * @file
+ * @author     Ruby developers <ruby-core@ruby-lang.org>
+ * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
+ *             Permission  is hereby  granted,  to  either redistribute  and/or
+ *             modify this file, provided that  the conditions mentioned in the
+ *             file COPYING are met.  Consult the file for details.
+ * @warning    Symbols   prefixed  with   either  `RBIMPL`   or  `rbimpl`   are
+ *             implementation details.   Don't take  them as canon.  They could
+ *             rapidly appear then vanish.  The name (path) of this header file
+ *             is also an  implementation detail.  Do not expect  it to persist
+ *             at the place it is now.  Developers are free to move it anywhere
+ *             anytime at will.
+ * @note       To  ruby-core:  remember  that   this  header  can  be  possibly
+ *             recursively included  from extension  libraries written  in C++.
+ *             Do not  expect for  instance `__VA_ARGS__` is  always available.
+ *             We assume C99  for ruby itself but we don't  assume languages of
+ *             extension libraries.  They could be written in C++98.
+ * @brief      Defines #RBIMPL_ATTR_NONSTRING.
+ */
+#include "ruby/internal/has/attribute.h"
+
+/** Wraps (or simulates) `__attribute__((nonstring))` */
+#if RBIMPL_HAS_ATTRIBUTE(nonstring)
+# define RBIMPL_ATTR_NONSTRING() __attribute__((nonstring))
+#else
+# define RBIMPL_ATTR_NONSTRING() /* void */
+#endif
+
+#endif /* RBIMPL_ATTR_NONSTRING_H */
diff --git a/iseq.c b/iseq.c
index 3bdb1c0af5..d28d68206b 100644
--- a/iseq.c
+++ b/iseq.c
@@ -3484,7 +3484,7 @@ rb_vm_encoded_insn_data_table_init(void)
     const void * const *table = rb_vm_get_insns_address_table();
 #define INSN_CODE(insn) ((VALUE)table[insn])
 #else
-#define INSN_CODE(insn) (insn)
+#define INSN_CODE(insn) ((VALUE)(insn))
 #endif
     st_data_t insn;
     encoded_insn_data = st_init_numtable_with_size(VM_INSTRUCTION_SIZE / 2);
diff --git a/marshal.c b/marshal.c
index b5164bcaec..3ef3ef3636 100644
--- a/marshal.c
+++ b/marshal.c
@@ -40,6 +40,7 @@
 #include "ruby/util.h"
 #include "builtin.h"
 #include "shape.h"
+#include "ruby/internal/attr/nonstring.h"
 
 #define BITSPERSHORT (2*CHAR_BIT)
 #define SHORTMASK ((1<<BITSPERSHORT)-1)
@@ -1541,7 +1542,7 @@ name_equal(const char *name, size_t nlen, const char *p, long l)
 static int
 sym2encidx(VALUE sym, VALUE val)
 {
-    static const char name_encoding[8] = "encoding";
+    RBIMPL_ATTR_NONSTRING() static const char name_encoding[8] = "encoding";
     const char *p;
     long l;
     if (rb_enc_get_index(sym) != ENCINDEX_US_ASCII) return -1;
diff --git a/regenc.h b/regenc.h
index 352a8d7980..4b4d21a715 100644
--- a/regenc.h
+++ b/regenc.h
@@ -118,6 +118,11 @@ typedef struct {
 
 typedef struct {
   short int len;
+#if defined(__has_attribute)
+# if __has_attribute(nonstring)
+  __attribute__((nonstring))
+# endif
+#endif
   const UChar name[6];
   int       ctype;
 } PosixBracketEntryType;
diff --git a/signal.c b/signal.c
index bef3b2e537..589ee05cbd 100644
--- a/signal.c
+++ b/signal.c
@@ -45,6 +45,7 @@
 #include "ruby_atomic.h"
 #include "vm_core.h"
 #include "ractor_core.h"
+#include "ruby/internal/attr/nonstring.h"
 
 #ifdef NEED_RUBY_ATOMIC_OPS
 rb_atomic_t
@@ -968,7 +969,7 @@ check_reserved_signal_(const char *name, size_t name_len, int signo)
     if (prev) {
         ssize_t RB_UNUSED_VAR(err);
         static const int stderr_fd = 2;
-#define NOZ(name, str) name[sizeof(str)-1] = str
+#define NOZ(name, str) RBIMPL_ATTR_NONSTRING() name[sizeof(str)-1] = str
         static const char NOZ(msg1, " received in ");
         static const char NOZ(msg2, " handler\n");
 
diff --git a/siphash.c b/siphash.c
index 61b8604fc9..62de622778 100644
--- a/siphash.c
+++ b/siphash.c
@@ -140,6 +140,9 @@ xor64_to(uint64_t *v, const uint64_t s)
 #endif
 
 static const union {
+#if defined(__has_attribute) && __has_attribute(nonstring)
+    __attribute__((nonstring))
+#endif
     char bin[32];
     uint64_t u64[4];
 } sip_init_state_bin = {"uespemos""modnarod""arenegyl""setybdet"};
diff --git a/string.c b/string.c
index 1fdb04a52f..41cdfe0c65 100644
--- a/string.c
+++ b/string.c
@@ -44,6 +44,7 @@
 #include "ruby/util.h"
 #include "ruby_assert.h"
 #include "vm_sync.h"
+#include "ruby/internal/attr/nonstring.h"
 
 #if defined HAVE_CRYPT_R
 # if defined HAVE_CRYPT_H
@@ -11123,7 +11124,7 @@ enc_str_scrub(rb_encoding *enc, VALUE str, VALUE repl, int cr)
     encidx = rb_enc_to_index(enc);
 
 #define DEFAULT_REPLACE_CHAR(str) do { \
-        static const char replace[sizeof(str)-1] = str; \
+        RBIMPL_ATTR_NONSTRING() static const char replace[sizeof(str)-1] = str; \
         rep = replace; replen = (int)sizeof(replace); \
     } while (0)
 
diff --git a/symbol.c b/symbol.c
index bdbfbae831..325afccfe0 100644
--- a/symbol.c
+++ b/symbol.c
@@ -22,6 +22,7 @@
 #include "symbol.h"
 #include "vm_sync.h"
 #include "builtin.h"
+#include "ruby/internal/attr/nonstring.h"
 
 #if defined(USE_SYMBOL_GC) && !(USE_SYMBOL_GC+0)
 # undef USE_SYMBOL_GC
diff --git a/template/id.c.tmpl b/template/id.c.tmpl
index 5b9e879730..5aa8e47ce7 100644
--- a/template/id.c.tmpl
+++ b/template/id.c.tmpl
@@ -22,7 +22,8 @@ ops = ids[:token_op].uniq {|id, op, token| token && op}
 
 static const struct {
     unsigned short token;
-    const char name[3], term;
+    RBIMPL_ATTR_NONSTRING() const char name[3];
+    const char term;
 } op_tbl[] = {
 % ops.each do |_id, op, token|
 %   next unless token
diff --git a/template/prelude.c.tmpl b/template/prelude.c.tmpl
index 74f6c08da7..1f0910de18 100644
--- a/template/prelude.c.tmpl
+++ b/template/prelude.c.tmpl
@@ -93,6 +93,7 @@ Prelude.new(output, ARGV, vpath).instance_eval do
 #include "internal/ruby_parser.h"
 #include "internal/warnings.h"
 #include "iseq.h"
+#include "ruby/internal/attr/nonstring.h"
 #include "ruby/ruby.h"
 #include "vm_core.h"
 
@@ -112,12 +113,12 @@ static const struct {
 %       size += line.size
 %       next
 %     end
-    char L<%=beg%><%=%>[<%=size%><%=%>]; /* <%=beg+1%>..<%=n%> */
+    RBIMPL_ATTR_NONSTRING() char L<%=beg%><%=%>[<%=size%><%=%>]; /* <%=beg+1%>..<%=n%> */
 %     size = line.size
 %     beg = n
 %   }
 %   if size > 0
-    char L<%=beg%><%=%>[<%=size%><%=%>]; /* <%=beg+1%>..<%=lines.size+1%> */
+    RBIMPL_ATTR_NONSTRING() char L<%=beg%><%=%>[<%=size%><%=%>]; /* <%=beg+1%>..<%=lines.size+1%> */
 %   end
 } prelude_code<%=i%><%=%> = {
 %   size = 0
diff --git a/version.h b/version.h
index 18f042fd19..eb6de0bc2c 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 8
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 166
+#define RUBY_PATCHLEVEL 167
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"