Extract include/ruby/internal/attr/packed_struct.h

Split `PACKED_STRUCT` and `PACKED_STRUCT_UNALIGNED` macros into the
macros bellow:
* `RBIMPL_ATTR_PACKED_STRUCT_BEGIN`
* `RBIMPL_ATTR_PACKED_STRUCT_END`
* `RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN`
* `RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END`

2 files changed, 51 insertions, 10 deletions

diff --git a/include/ruby/backward/2/attributes.h b/include/ruby/backward/2/attributes.h
index 73acfc9dc0..7a1ea6b758 100644
--- a/include/ruby/backward/2/attributes.h
+++ b/include/ruby/backward/2/attributes.h
@@ -39,6 +39,7 @@
 #include "ruby/internal/attr/noinline.h"
 #include "ruby/internal/attr/nonnull.h"
 #include "ruby/internal/attr/noreturn.h"
+#include "ruby/internal/attr/packed_struct.h"
 #include "ruby/internal/attr/pure.h"
 #include "ruby/internal/attr/restrict.h"
 #include "ruby/internal/attr/returns_nonnull.h"
@@ -147,17 +148,14 @@
 #define NORETURN(x) RBIMPL_ATTR_NORETURN() x
 #define NORETURN_STYLE_NEW
 
-#ifndef PACKED_STRUCT
-# define PACKED_STRUCT(x) x
-#endif
+#undef PACKED_STRUCT
+#define PACKED_STRUCT(x) \
+    RBIMPL_ATTR_PACKED_STRUCT_BEGIN() x RBIMPL_ATTR_PACKED_STRUCT_END()
 
-#ifndef PACKED_STRUCT_UNALIGNED
-# if UNALIGNED_WORD_ACCESS
-#   define PACKED_STRUCT_UNALIGNED(x) PACKED_STRUCT(x)
-# else
-#   define PACKED_STRUCT_UNALIGNED(x) x
-# endif
-#endif
+#undef PACKED_STRUCT_UNALIGNED
+#define PACKED_STRUCT_UNALIGNED(x) \
+    RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN() x \
+    RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END()
 
 #undef RB_UNUSED_VAR
 #define RB_UNUSED_VAR(x) x RBIMPL_ATTR_MAYBE_UNUSED()
diff --git a/include/ruby/internal/attr/packed_struct.h b/include/ruby/internal/attr/packed_struct.h
new file mode 100644
index 0000000000..0678b9acc8
--- /dev/null
+++ b/include/ruby/internal/attr/packed_struct.h
@@ -0,0 +1,43 @@
+#ifndef RBIMPL_ATTR_PACKED_STRUCT_H                 /*-*-C++-*-vi:se ft=cpp:*/
+#define RBIMPL_ATTR_PACKED_STRUCT_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_PACKED_STRUCT_BEGIN,
+ *             #RBIMPL_ATTR_PACKED_STRUCT_END,
+ *             #RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN, and
+ *             #RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END.
+ */
+#include "ruby/internal/config.h"
+
+#ifndef RBIMPL_ATTR_PACKED_STRUCT_BEGIN
+# define RBIMPL_ATTR_PACKED_STRUCT_BEGIN() /* void */
+#endif
+#ifndef RBIMPL_ATTR_PACKED_STRUCT_END
+# define RBIMPL_ATTR_PACKED_STRUCT_END() /* void */
+#endif
+
+#if UNALIGNED_WORD_ACCESS
+# define RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN() RBIMPL_ATTR_PACKED_STRUCT_BEGIN()
+# define RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END() RBIMPL_ATTR_PACKED_STRUCT_END()
+#else
+# define RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_BEGIN() /* void */
+# define RBIMPL_ATTR_PACKED_STRUCT_UNALIGNED_END() /* void */
+#endif
+
+#endif