Merge pull request #2991 from shyouhei/ruby.h

Split ruby.h

8 files changed, 506 insertions, 0 deletions

diff --git a/include/ruby/3/has/attribute.h b/include/ruby/3/has/attribute.h
new file mode 100644
index 0000000000..229e092b30
--- /dev/null
+++ b/include/ruby/3/has/attribute.h
@@ -0,0 +1,154 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_ATTRIBUTE.
+ */
+#include "ruby/3/config.h"
+#include "ruby/3/compiler_since.h"
+#include "ruby/3/token_paste.h"
+
+/** Wraps (or simulates) `__has_attribute`. */
+#if defined(RUBY3_HAS_ATTRIBUTE)
+# /* Take that. */
+
+#elif defined(__has_attribute)
+# define RUBY3_HAS_ATTRIBUTE(_) __has_attribute(_)
+
+#elif RUBY3_COMPILER_IS(GCC)
+# /* GCC  <= 4  lack __has_attribute  predefined macro,  while have  attributes
+#  * themselves.  We can simulate the macro like the following: */
+# define RUBY3_HAS_ATTRIBUTE(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_ATTRIBUTE_, _)
+# define RUBY3_HAS_ATTRIBUTE_aligned                    RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_alloc_size                 RUBY3_COMPILER_SINCE(GCC, 4, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_artificial                 RUBY3_COMPILER_SINCE(GCC, 4, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_always_inline              RUBY3_COMPILER_SINCE(GCC, 3, 1, 0)
+# define RUBY3_HAS_ATTRIBUTE_cdecl                      RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_cold                       RUBY3_COMPILER_SINCE(GCC, 4, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_const                      RUBY3_COMPILER_SINCE(GCC, 2, 6, 0)
+# define RUBY3_HAS_ATTRIBUTE_deprecated                 RUBY3_COMPILER_SINCE(GCC, 3, 1, 0)
+# define RUBY3_HAS_ATTRIBUTE_dllexport                  RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_dllimport                  RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_error                      RUBY3_COMPILER_SINCE(GCC, 4, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_format                     RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_hot                        RUBY3_COMPILER_SINCE(GCC, 4, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_leaf                       RUBY3_COMPILER_SINCE(GCC, 4, 6, 0)
+# define RUBY3_HAS_ATTRIBUTE_malloc                     RUBY3_COMPILER_SINCE(GCC, 3, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_no_address_safety_analysis RUBY3_COMPILER_SINCE(GCC, 4, 8, 0)
+# define RUBY3_HAS_ATTRIBUTE_no_sanitize_address        RUBY3_COMPILER_SINCE(GCC, 4, 8, 0)
+# define RUBY3_HAS_ATTRIBUTE_no_sanitize_undefined      RUBY3_COMPILER_SINCE(GCC, 4, 9, 0)
+# define RUBY3_HAS_ATTRIBUTE_noinline                   RUBY3_COMPILER_SINCE(GCC, 3, 1, 0)
+# define RUBY3_HAS_ATTRIBUTE_nonnull                    RUBY3_COMPILER_SINCE(GCC, 3, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_noreturn                   RUBY3_COMPILER_SINCE(GCC, 2, 5, 0)
+# define RUBY3_HAS_ATTRIBUTE_nothrow                    RUBY3_COMPILER_SINCE(GCC, 3, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_pure                       RUBY3_COMPILER_SINCE(GCC, 2,96, 0)
+# define RUBY3_HAS_ATTRIBUTE_returns_nonnull            RUBY3_COMPILER_SINCE(GCC, 4, 9, 0)
+# define RUBY3_HAS_ATTRIBUTE_returns_twice              RUBY3_COMPILER_SINCE(GCC, 4, 1, 0)
+# define RUBY3_HAS_ATTRIBUTE_stdcall                    RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_unused                     RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_ATTRIBUTE_visibility                 RUBY3_COMPILER_SINCE(GCC, 3, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_warn_unused_result         RUBY3_COMPILER_SINCE(GCC, 3, 4, 0)
+# define RUBY3_HAS_ATTRIBUTE_warning                    RUBY3_COMPILER_SINCE(GCC, 4, 3, 0)
+# define RUBY3_HAS_ATTRIBUTE_weak                       RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# /* Note that "0, 0, 0" might be inaccurate. */
+
+#elif RUBY3_COMPILER_IS(SunPro)
+# /* Oracle Solaris Studio 12.4 (cc version 5.11) introduced __has_attribute.
+#  * Before that, following attributes were available. */
+# /* See https://docs.oracle.com/cd/F24633_01/index.html */
+# define RUBY3_HAS_ATTRIBUTE(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_ATTRIBUTE_, _)
+# define RUBY3_HAS_ATTRIBUTE_alias                      RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_aligned                    RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_always_inline              RUBY3_COMPILER_SINCE(SunPro, 5, 10, 0)
+# define RUBY3_HAS_ATTRIBUTE_const                      RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_constructor                RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_destructor                 RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_malloc                     RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_noinline                   RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_noreturn                   RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_packed                     RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_pure                       RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_returns_twice              RUBY3_COMPILER_SINCE(SunPro, 5, 10, 0)
+# define RUBY3_HAS_ATTRIBUTE_vector_size                RUBY3_COMPILER_SINCE(SunPro, 5, 10, 0)
+# define RUBY3_HAS_ATTRIBUTE_visibility                 RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+# define RUBY3_HAS_ATTRIBUTE_weak                       RUBY3_COMPILER_SINCE(SunPro, 5,  9, 0)
+
+#elif defined (_MSC_VER)
+# define RUBY3_HAS_ATTRIBUTE(_) 0
+# /* Fallback below doesn't work: see win32/Makefile.sub */
+
+#else
+# /* Take config.h definition when available. */
+# define RUBY3_HAS_ATTRIBUTE(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_ATTRIBUTE_, _)
+# ifdef ALWAYS_INLINE
+#  define RUBY3_HAS_ATTRIBUTE_always_inline
+# endif
+# ifdef FUNC_CDECL
+#  define RUBY3_HAS_ATTRIBUTE_cdecl
+# endif
+# ifdef CONSTFUNC
+#  define RUBY3_HAS_ATTRIBUTE_const
+# endif
+# ifdef DEPRECATED
+#  define RUBY3_HAS_ATTRIBUTE_deprecated
+# endif
+# ifdef ERRORFUNC
+#  define RUBY3_HAS_ATTRIBUTE_error
+# endif
+# ifdef FUNC_FASTCALL
+#  define RUBY3_HAS_ATTRIBUTE_fastcall
+# endif
+# ifdef PUREFUNC
+#  define RUBY3_HAS_ATTRIBUTE_pure
+# endif
+# ifdef NO_ADDRESS_SAFETY_ANALYSIS
+#  define RUBY3_HAS_ATTRIBUTE_no_address_safety_analysis
+# endif
+# ifdef NO_SANITIZE
+#  define RUBY3_HAS_ATTRIBUTE_no_sanitize
+# endif
+# ifdef NO_SANITIZE_ADDRESS
+#  define RUBY3_HAS_ATTRIBUTE_no_sanitize_address
+# endif
+# ifdef NOINLINE
+#  define RUBY3_HAS_ATTRIBUTE_noinline
+# endif
+# ifdef RUBY3_FUNC_NONNULL
+#  define RUBY3_HAS_ATTRIBUTE_nonnull
+# endif
+# ifdef NORETURN
+#  define RUBY3_HAS_ATTRIBUTE_noreturn
+# endif
+# ifdef FUNC_OPTIMIZED
+#  define RUBY3_HAS_ATTRIBUTE_optimize
+# endif
+# ifdef FUNC_STDCALL
+#  define RUBY3_HAS_ATTRIBUTE_stdcall
+# endif
+# ifdef MAYBE_UNUSED
+#  define RUBY3_HAS_ATTRIBUTE_unused
+# endif
+# ifdef WARN_UNUSED_RESULT
+#  define RUBY3_HAS_ATTRIBUTE_warn_unused_result
+# endif
+# ifdef WARNINGFUNC
+#  define RUBY3_HAS_ATTRIBUTE_warning
+# endif
+# ifdef WEAK
+#  define RUBY3_HAS_ATTRIBUTE_weak
+# endif
+#endif
diff --git a/include/ruby/3/has/builtin.h b/include/ruby/3/has/builtin.h
new file mode 100644
index 0000000000..51e1875b72
--- /dev/null
+++ b/include/ruby/3/has/builtin.h
@@ -0,0 +1,90 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_BUILTIN.
+ */
+#include "ruby/3/config.h"
+#include "ruby/3/compiler_since.h"
+#include "ruby/3/token_paste.h"
+
+/** Wraps (or simulates) `__has_builtin`. */
+#if defined(RUBY3_HAS_BUILTIN)
+# /* Take that. */
+
+#elif defined(__has_builtin)
+# define RUBY3_HAS_BUILTIN(_) __has_builtin(_)
+
+#elif RUBY3_COMPILER_IS(GCC)
+# /* :FIXME: Historically  GCC has had  tons of builtins, but  it implemented
+#  * __has_builtin  only  since  GCC  10.   This section  can  be  made  more
+#  * granular. */
+# /* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66970 */
+# define RUBY3_HAS_BUILTIN(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_BUILTIN_, _)
+# define RUBY3_HAS_BUILTIN___builtin_add_overflow      RUBY3_COMPILER_SINCE(GCC, 5, 1, 0)
+# define RUBY3_HAS_BUILTIN___builtin_alloca            RUBY3_COMPILER_SINCE(GCC, 0, 0, 0)
+# define RUBY3_HAS_BUILTIN___builtin_alloca_with_align RUBY3_COMPILER_SINCE(GCC, 6, 1, 0)
+# /* See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624 for bswap16. */
+# define RUBY3_HAS_BUILTIN___builtin_bswap16           RUBY3_COMPILER_SINCE(GCC, 4, 8, 0)
+# define RUBY3_HAS_BUILTIN___builtin_bswap32           RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_bswap64           RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_clz               RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_clzl              RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_clzll             RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_constant_p        RUBY3_COMPILER_SINCE(GCC, 2,95, 3)
+# define RUBY3_HAS_BUILTIN___builtin_ctz               RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_ctzl              RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_ctzll             RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_expect            RUBY3_COMPILER_SINCE(GCC, 3, 0, 0)
+# define RUBY3_HAS_BUILTIN___builtin_mul_overflow      RUBY3_COMPILER_SINCE(GCC, 5, 1, 0)
+# define RUBY3_HAS_BUILTIN___builtin_mul_overflow_p    RUBY3_COMPILER_SINCE(GCC, 7, 0, 0)
+# define RUBY3_HAS_BUILTIN___builtin_popcount          RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_popcountl         RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_popcountll        RUBY3_COMPILER_SINCE(GCC, 3, 6, 0)
+# define RUBY3_HAS_BUILTIN___builtin_sub_overflow      RUBY3_COMPILER_SINCE(GCC, 5, 1, 0)
+# define RUBY3_HAS_BUILTIN___builtin_unreachable       RUBY3_COMPILER_SINCE(GCC, 4, 5, 0)
+# /* Note that "0, 0, 0" might be inaccurate. */
+
+#elif RUBY3_COMPILER_IS(MSVC)
+# /* MSVC has UNREACHABLE, but that is not __builtin_unreachable. */
+# define RUBY3_HAS_BUILTIN(_) 0
+
+#else
+# /* Take config.h definition when available */
+# define RUBY3_HAS_BUILTIN(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_BUILTIN_, _)
+# define RUBY3_HAS_BUILTIN___builtin_add_overflow      HAVE_BUILTIN___BUILTIN_ADD_OVERFLOW
+# define RUBY3_HAS_BUILTIN___builtin_alloca_with_align HAVE_BUILTIN___BUILTIN_ALLOCA_WITH_ALIGN
+# define RUBY3_HAS_BUILTIN___builtin_assume_aligned    HAVE_BUILTIN___BUILTIN_ASSUME_ALIGNED
+# define RUBY3_HAS_BUILTIN___builtin_bswap16           HAVE_BUILTIN___BUILTIN_BSWAP16
+# define RUBY3_HAS_BUILTIN___builtin_bswap32           HAVE_BUILTIN___BUILTIN_BSWAP32
+# define RUBY3_HAS_BUILTIN___builtin_bswap64           HAVE_BUILTIN___BUILTIN_BSWAP64
+# define RUBY3_HAS_BUILTIN___builtin_clz               HAVE_BUILTIN___BUILTIN_CLZ
+# define RUBY3_HAS_BUILTIN___builtin_clzl              HAVE_BUILTIN___BUILTIN_CLZL
+# define RUBY3_HAS_BUILTIN___builtin_clzll             HAVE_BUILTIN___BUILTIN_CLZLL
+# define RUBY3_HAS_BUILTIN___builtin_constant_p        HAVE_BUILTIN___BUILTIN_CONSTANT_P
+# define RUBY3_HAS_BUILTIN___builtin_ctz               HAVE_BUILTIN___BUILTIN_CTZ
+# define RUBY3_HAS_BUILTIN___builtin_ctzll             HAVE_BUILTIN___BUILTIN_CTZLL
+# define RUBY3_HAS_BUILTIN___builtin_expect            HAVE_BUILTIN___BUILTIN_EXPECT
+# define RUBY3_HAS_BUILTIN___builtin_mul_overflow      HAVE_BUILTIN___BUILTIN_MUL_OVERFLOW
+# define RUBY3_HAS_BUILTIN___builtin_mul_overflow_p    HAVE_BUILTIN___BUILTIN_MUL_OVERFLOW_P
+# define RUBY3_HAS_BUILTIN___builtin_popcount          HAVE_BUILTIN___BUILTIN_POPCOUNT
+# define RUBY3_HAS_BUILTIN___builtin_popcountll        HAVE_BUILTIN___BUILTIN_POPCOUNTLL
+# define RUBY3_HAS_BUILTIN___builtin_sub_overflow      HAVE_BUILTIN___BUILTIN_SUB_OVERFLOW
+# if defined(UNREACHABLE)
+#  define RUBY3_HAS_BUILTIN___builtin_unreachable
+# endif
+#endif
diff --git a/include/ruby/3/has/c_attribute.h b/include/ruby/3/has/c_attribute.h
new file mode 100644
index 0000000000..89186217d3
--- /dev/null
+++ b/include/ruby/3/has/c_attribute.h
@@ -0,0 +1,37 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_C_ATTRIBUTE.
+ */
+
+/** Wraps (or simulates) `__has_c_attribute`. */
+#if defined(RUBY3_HAS_C_ATTRIBUTE)
+# /* Take that. */
+
+#elif defined(__cplusplus)
+# /* Makes no sense. */
+# define RUBY3_HAS_C_ATTRIBUTE(_) 0
+
+#elif defined(__has_c_attribute)
+# define RUBY3_HAS_C_ATTRIBUTE(_) __has_c_attribute(_)
+
+#else
+# /* As  of writing  everything  that lacks  __has_c_attribute also  completely
+#  * lacks C2x attributes as well.  Might change in future? */
+# define RUBY3_HAS_C_ATTRIBUTE(_) 0
+#endif
diff --git a/include/ruby/3/has/cpp_attribute.h b/include/ruby/3/has/cpp_attribute.h
new file mode 100644
index 0000000000..83c5392200
--- /dev/null
+++ b/include/ruby/3/has/cpp_attribute.h
@@ -0,0 +1,82 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_CPP_ATTRIBUTE.
+ */
+#include "ruby/3/compiler_is.h"
+#include "ruby/3/compiler_since.h"
+#include "ruby/3/token_paste.h"
+
+/** @cond INTERNAL_MACRO */
+#if defined(RUBY3_HAS_CPP_ATTRIBUTE0)
+# /* Take that. */
+
+#elif defined(__has_cpp_attribute)
+# define RUBY3_HAS_CPP_ATTRIBUTE0(_) __has_cpp_attribute(_)
+
+#elif RUBY3_COMPILER_IS(MSVC)
+# /* MSVC has  never updated  its __cplusplus  since forever  (unless specified
+#  * explicitly by a compiler flag).   They also lack __has_cpp_attribute until
+#  * 2019.  However, they do have attributes since 2015 or so. */
+# /* https://docs.microsoft.com/en-us/cpp/overview/visual-cpp-language-conformance */
+# define RUBY3_HAS_CPP_ATTRIBUTE0(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_CPP_ATTRIBUTE_, _)
+# define RUBY3_HAS_CPP_ATTRIBUTE_noreturn           200809 * RUBY3_COMPILER_SINCE(MSVC, 19, 00, 0)
+# define RUBY3_HAS_CPP_ATTRIBUTE_carries_dependency 200809 * RUBY3_COMPILER_SINCE(MSVC, 19, 00, 0)
+# define RUBY3_HAS_CPP_ATTRIBUTE_deprecated         201309 * RUBY3_COMPILER_SINCE(MSVC, 19, 10, 0)
+# define RUBY3_HAS_CPP_ATTRIBUTE_fallthrough        201603 * RUBY3_COMPILER_SINCE(MSVC, 19, 10, 0)
+# define RUBY3_HAS_CPP_ATTRIBUTE_maybe_unused       201603 * RUBY3_COMPILER_SINCE(MSVC, 19, 11, 0)
+# define RUBY3_HAS_CPP_ATTRIBUTE_nodiscard          201603 * RUBY3_COMPILER_SINCE(MSVC, 19, 11, 0)
+
+#elif RUBY3_COMPILER_BEFORE(Clang, 3, 6, 0)
+# /* Clang  3.6.0  introduced  __has_cpp_attribute.  Prior  to  that  following
+#  * attributes were already there. */
+# /* https://clang.llvm.org/cxx_status.html */
+# define RUBY3_HAS_CPP_ATTRIBUTE0(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_CPP_ATTRIBUTE_, _)
+# define RUBY3_HAS_CPP_ATTRIBUTE_noreturn           200809 * RUBY3_COMPILER_SINCE(Clang, 3, 3, 0)
+# define RUBY3_HAS_CPP_ATTRIBUTE_deprecated         201309 * RUBY3_COMPILER_SINCE(Clang, 3, 4, 0)
+
+#elif RUBY3_COMPILER_BEFORE(GCC, 5, 0, 0)
+# /* GCC 5+ have __has_cpp_attribute, while 4.x had following attributes. */
+# /* https://gcc.gnu.org/projects/cxx-status.html */
+# define RUBY3_HAS_CPP_ATTRIBUTE0(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_CPP_ATTRIBUTE_, _)
+# define RUBY3_HAS_CPP_ATTRIBUTE_noreturn           200809 * RUBY3_COMPILER_SINCE(GCC, 4, 8, 0)
+# define RUBY3_HAS_CPP_ATTRIBUTE_deprecated         201309 * RUBY3_COMPILER_SINCE(GCC, 4, 9, 0)
+
+#else
+# /* :FIXME:
+#  * Candidate compilers to list here:
+#  * - icpc: They have __INTEL_CXX11_MODE__.
+#  * - SunPro: Seems they support C++11.
+#  */
+# define RUBY3_HAS_CPP_ATTRIBUTE0(_) 0
+#endif
+/** @endcond */
+
+/** Wraps (or simulates) `__has_cpp_attribute`. */
+#ifdef RUBY3_HAS_CPP_ATTRIBUTE
+# /* Take that. */
+
+#elif ! defined(__cplusplus)
+# /* Makes no sense. */
+# define RUBY3_HAS_CPP_ATTRIBUTE(_) 0
+
+#else
+# /* GCC needs workarounds.  See https://gcc.godbolt.org/z/jdz3pa */
+# define RUBY3_HAS_CPP_ATTRIBUTE(_) \
+    ((RUBY3_HAS_CPP_ATTRIBUTE0(_) <= __cplusplus) ? RUBY3_HAS_CPP_ATTRIBUTE0(_) : 0)
+#endif
diff --git a/include/ruby/3/has/declspec_attribute.h b/include/ruby/3/has/declspec_attribute.h
new file mode 100644
index 0000000000..f902ef963c
--- /dev/null
+++ b/include/ruby/3/has/declspec_attribute.h
@@ -0,0 +1,48 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_DECLSPEC_ATTRIBUTE.
+ */
+#include "ruby/3/compiler_since.h"
+#include "ruby/3/token_paste.h"
+
+/** Wraps (or simulates) `__has_declspec_attribute`. */
+#if defined(RUBY3_HAS_DECLSPEC_ATTRIBUTE)
+# /* Take that. */
+
+#elif defined(__has_declspec_attribute)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE(_) __has_declspec_attribute(_)
+
+#else
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE(_) RUBY3_TOKEN_PASTE(RUBY3_HAS_DECLSPEC_ATTRIBUTE_, _)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_align       RUBY3_COMPILER_SINCE(MSVC, 8, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_deprecated  RUBY3_COMPILER_SINCE(MSVC,13, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_dllexport   RUBY3_COMPILER_SINCE(MSVC, 8, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_dllimport   RUBY3_COMPILER_SINCE(MSVC, 8, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_empty_bases RUBY3_COMPILER_SINCE(MSVC,19, 0, 23918)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_noalias     RUBY3_COMPILER_SINCE(MSVC, 8, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_noinline    RUBY3_COMPILER_SINCE(MSVC,13, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_noreturn    RUBY3_COMPILER_SINCE(MSVC,11, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_nothrow     RUBY3_COMPILER_SINCE(MSVC, 8, 0, 0)
+# define RUBY3_HAS_DECLSPEC_ATTRIBUTE_restrict    RUBY3_COMPILER_SINCE(MSVC,14, 0, 0)
+# /* Note that "8, 0, 0" might be inaccurate. */
+# if ! defined(__cplusplus)
+#  /* Clang has this in both C/C++, but MSVC has this in C++ only.*/
+#  undef RUBY3_HAS_DECLSPEC_ATTRIBUTE_nothrow
+# endif
+#endif
diff --git a/include/ruby/3/has/extension.h b/include/ruby/3/has/extension.h
new file mode 100644
index 0000000000..ca3392a090
--- /dev/null
+++ b/include/ruby/3/has/extension.h
@@ -0,0 +1,33 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_EXTENSION.
+ */
+#include "ruby/3/has/feature.h"
+
+/** Wraps (or simulates) `__has_extension`. */
+#if defined(RUBY3_HAS_EXTENSION)
+# /* Take that. */
+
+#elif defined(__has_extension)
+# define RUBY3_HAS_EXTENSION(_) __has_extension(_)
+
+#else
+# /* Pre-3.0 clang had __has_feature but not __has_extension. */
+# define RUBY3_HAS_EXTENSION(_) RUBY3_HAS_FEATURE(_)
+#endif
diff --git a/include/ruby/3/has/feature.h b/include/ruby/3/has/feature.h
new file mode 100644
index 0000000000..977b8150bb
--- /dev/null
+++ b/include/ruby/3/has/feature.h
@@ -0,0 +1,31 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_FEATURE.
+ */
+
+/** Wraps (or simulates) `__has_feature`. */
+#if defined(RUBY3_HAS_FEATURE)
+# /* Take that. */
+
+#elif defined(__has_feature)
+# define RUBY3_HAS_FEATURE(_) __has_feature(_)
+
+#else
+# define RUBY3_HAS_FEATURE(_) 0
+#endif
diff --git a/include/ruby/3/has/warning.h b/include/ruby/3/has/warning.h
new file mode 100644
index 0000000000..a66d76dfa7
--- /dev/null
+++ b/include/ruby/3/has/warning.h
@@ -0,0 +1,31 @@
+/**                                                     \noop-*-C++-*-vi:ft=cpp
+ * @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  `RUBY3`   or   `ruby3`   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 #RUBY3_HAS_WARNING.
+ */
+
+/** Wraps (or simulates) `__has_warning`. */
+#if defined(RUBY3_HAS_WARNING)
+# /* Take that. */
+
+#elif defined(__has_warning)
+# define RUBY3_HAS_WARNING(_) __has_warning(_)
+
+#else
+# define RUBY3_HAS_WARNING(_) 0
+#endif