use of stdckdint.h

C23 is going to have this header.  The industry is already moving
towards accepting it; OSes and compilers started to implement theirs.

Why not detect its presence and if any, prefer over other ways.

See also:

- https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2683.pdf
- https://reviews.freebsd.org/D41734
- https://reviews.llvm.org/D157331
- https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=8441841a1b985d68245954af1ff023db121b0635

configure.ac

@@ -1367,6 +1367,7 @@ AC_CHECK_HEADERS(ucontext.h)
 AC_CHECK_HEADERS(utime.h)
 AC_CHECK_HEADERS(sys/epoll.h)
 AC_CHECK_HEADERS(sys/event.h)
+AC_CHECK_HEADERS(stdckdint.h)
 
 AS_CASE("$target_cpu", [x64|x86_64|i[3-6]86*], [
   AC_CHECK_HEADERS(x86intrin.h)

gc.c

@@ -224,6 +224,9 @@ size_add_overflow(size_t x, size_t y)
     bool p;
 #if 0
 
+#elif defined(ckd_add)
+    p = ckd_add(&z, x, y);
+
 #elif __has_builtin(__builtin_add_overflow)
     p = __builtin_add_overflow(x, y, &z);
 

hrtime.h

@@ -6,6 +6,8 @@
 #  include <sys/time.h>
 #endif
 
+#include "internal/compilers.h"
+
 /*
  * Hi-res monotonic clock.  It is currently nsec resolution, which has over
  * 500 years of range (with an unsigned 64-bit integer).  Developers
@@ -61,7 +63,11 @@ rb_hrtime_mul(rb_hrtime_t a, rb_hrtime_t b)
 {
     rb_hrtime_t c;
 
-#ifdef HAVE_BUILTIN___BUILTIN_MUL_OVERFLOW
+#ifdef ckd_mul
+    if (ckd_mul(&c, a, b))
+        return RB_HRTIME_MAX;
+
+#elif __has_builtin(__builtin_mul_overflow)
     if (__builtin_mul_overflow(a, b, &c))
         return RB_HRTIME_MAX;
 #else
@@ -81,7 +87,11 @@ rb_hrtime_add(rb_hrtime_t a, rb_hrtime_t b)
 {
     rb_hrtime_t c;
 
-#ifdef HAVE_BUILTIN___BUILTIN_ADD_OVERFLOW
+#ifdef ckd_add
+    if (ckd_add(&c, a, b))
+        return RB_HRTIME_MAX;
+
+#elif __has_builtin(__builtin_add_overflow)
     if (__builtin_add_overflow(a, b, &c))
         return RB_HRTIME_MAX;
 #else

include/ruby/internal/memory.h

@@ -56,6 +56,7 @@
 #include "ruby/internal/has/builtin.h"
 #include "ruby/internal/stdalign.h"
 #include "ruby/internal/stdbool.h"
+#include "ruby/internal/stdckdint.h"
 #include "ruby/internal/xmalloc.h"
 #include "ruby/backward/2/limits.h"
 #include "ruby/backward/2/long_long.h"
@@ -567,7 +568,10 @@ rbimpl_size_mul_overflow(size_t x, size_t y)
 {
     struct rbimpl_size_mul_overflow_tag ret = { false,  0, };
 
-#if RBIMPL_HAS_BUILTIN(__builtin_mul_overflow)
+#if defined(ckd_mul)
+    ret.left = ckd_mul(&ret.right, x, y);
+
+#elif RBIMPL_HAS_BUILTIN(__builtin_mul_overflow)
     ret.left = __builtin_mul_overflow(x, y, &ret.right);
 
 #elif defined(DSIZE_T)

include/ruby/internal/stdckdint.h

@@ -0,0 +1,60 @@
+#ifndef RBIMPL_STDCKDINT_H                           /*-*-C++-*-vi:se ft=cpp:*/
+#define RBIMPL_STDCKDINT_H
+/**
+ * @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      C23 shim for <stdckdint.h>
+ */
+#include "ruby/internal/config.h"
+#include "ruby/internal/has/builtin.h"
+#include "ruby/internal/stdbool.h"
+
+#ifdef __has_include
+# if __has_include(<stdckdint.h>)
+#  /* Conforming C23 situation; e.g. recent clang */
+#  define RBIMPL_HAVE_STDCKDINT_H
+# endif
+#endif
+
+#ifdef HAVE_STDCKDINT_H
+# /* Some OSes (most notably FreeBSD) have this file. */
+# define RBIMPL_HAVE_STDCKDINT_H
+#endif
+
+#ifdef RBIMPL_HAVE_STDCKDINT_H
+# /* Take that. */
+# include <stdckdint.h>
+
+#elif RBIMPL_HAS_BUILTIN(__builtin_add_overflow)
+# define ckd_add(x, y, z) ((bool)__builtin_add_overflow((y), (z), (x)))
+# define ckd_sub(x, y, z) ((bool)__builtin_sub_overflow((y), (z), (x)))
+# define ckd_mul(x, y, z) ((bool)__builtin_mul_overflow((y), (z), (x)))
+# define __STDC_VERSION_STDCKDINT_H__ 202311L
+
+#/* elif defined(__cplusplus) */
+#/* :TODO: if we assume C++11 we can use `<type_traits>` to implement them. */
+
+#else
+# /* intentionally leave them undefined */
+# /* to make `#ifdef ckd_add` etc. work as intended. */
+# undef ckd_add
+# undef ckd_sub
+# undef ckd_mul
+# undef __STDC_VERSION_STDCKDINT_H__
+#endif
+
+#endif /* RBIMPL_STDCKDINT_H */