1 files changed, 85 insertions, 0 deletions
diff --git a/include/ruby/impl/core/rbasic.h b/include/ruby/impl/core/rbasic.h
new file mode 100644
index 0000000000..4f6fa576aa
--- /dev/null
+++ b/include/ruby/impl/core/rbasic.h
@@ -0,0 +1,85 @@
+#ifndef RUBY3_RBASIC_H                               /*-*-C++-*-vi:se ft=cpp:*/
+#define RUBY3_RBASIC_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  `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 struct ::RBasic.
+ */
+#include "ruby/3/attr/artificial.h"
+#include "ruby/3/attr/constexpr.h"
+#include "ruby/3/attr/forceinline.h"
+#include "ruby/3/attr/noalias.h"
+#include "ruby/3/attr/pure.h"
+#include "ruby/3/cast.h"
+#include "ruby/3/dllexport.h"
+#include "ruby/3/special_consts.h"
+#include "ruby/3/value.h"
+#include "ruby/assert.h"
+
+#define RBASIC(obj)          RUBY3_CAST((struct RBasic *)(obj))
+#define RBASIC_CLASS         RBASIC_CLASS
+#define RVALUE_EMBED_LEN_MAX RVALUE_EMBED_LEN_MAX
+
+/** @cond INTERNAL_MACRO */
+#define RUBY3_EMBED_LEN_MAX_OF(T) \
+    RUBY3_CAST((int)(sizeof(VALUE[RVALUE_EMBED_LEN_MAX]) / sizeof(T)))
+/** @endcond */
+
+enum ruby_rvalue_flags { RVALUE_EMBED_LEN_MAX = 3 };
+
+struct
+RUBY_ALIGNAS(SIZEOF_VALUE)
+RBasic {
+    VALUE flags;                /**< @see enum ::ruby_fl_type. */
+    const VALUE klass;
+
+#ifdef __cplusplus
+  public:
+    RUBY3_ATTR_CONSTEXPR(CXX11)
+    RUBY3_ATTR_ARTIFICIAL()
+    RUBY3_ATTR_FORCEINLINE()
+    RUBY3_ATTR_NOALIAS()
+    /**
+     * We need to define this explicit constructor because the field `klass` is
+     * const-qualified above,  which effectively  defines the  implicit default
+     * constructor as "deleted"  (as of C++11) --  No way but to  define one by
+     * ourselves.
+     */
+    RBasic() :
+        flags(RUBY3_VALUE_NULL),
+        klass(RUBY3_VALUE_NULL)
+    {
+    }
+#endif
+};
+
+RUBY3_SYMBOL_EXPORT_BEGIN()
+VALUE rb_obj_hide(VALUE obj);
+VALUE rb_obj_reveal(VALUE obj, VALUE klass); /* do not use this API to change klass information */
+RUBY3_SYMBOL_EXPORT_END()
+
+RUBY3_ATTR_PURE_ON_NDEBUG()
+RUBY3_ATTR_ARTIFICIAL()
+static inline VALUE
+RBASIC_CLASS(VALUE obj)
+{
+    RUBY3_ASSERT_OR_ASSUME(! RB_SPECIAL_CONST_P(obj));
+    return RBASIC(obj)->klass;
+}
+
+#endif /* RUBY3_RBASIC_H */