inline structures data type for mruby (MRB_TT_INLINE) (fix #3237)

Inline structures have no instance variables, no finalizer, and offer as much space as possible in RBASIC object. This means 24 bytes on 64-bit platforms and 12 bytes on 32-bit platforms.
mruby-inline-struct gem is only provided for testing.

src/class.c

@@ -14,6 +14,7 @@
 #include <mruby/variable.h>
 #include <mruby/error.h>
 #include <mruby/data.h>
+#include <mruby/inline.h>
 
 KHASH_DEFINE(mt, mrb_sym, struct RProc*, TRUE, kh_int_hash_func, kh_int_hash_equal)
 
@@ -491,6 +492,7 @@ to_sym(mrb_state *mrb, mrb_value ss)
     b:      Boolean        [mrb_bool]
     n:      Symbol         [mrb_sym]
     d:      Data           [void*,mrb_data_type const] 2nd argument will be used to check data type so it won't be modified
+    I:      Inline struct  [void*]
     &:      Block          [mrb_value]
     *:      rest argument  [mrb_value*,mrb_int]   Receive the rest of the arguments as an array.
     |:      optional                              Next argument of '|' and later are optional.
@@ -702,6 +704,24 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
         }
       }
       break;
+    case 'I':
+      {
+        void* *p;
+        mrb_value ss;
+
+        p = va_arg(ap, void**);
+        if (i < argc) {
+          ss = ARGV[arg_i];
+          if (mrb_type(ss) != MRB_TT_INLINE)
+          {
+            mrb_raisef(mrb, E_TYPE_ERROR, "%S is not inline struct", ss);
+          }
+          *p = mrb_inline_ptr(ss);
+          arg_i++;
+          i++;
+        }
+      }
+      break;
     case 'f':
       {
         mrb_float *p;

src/etc.c

@@ -139,6 +139,7 @@ mrb_obj_id(mrb_value obj)
   case MRB_TT_EXCEPTION:
   case MRB_TT_FILE:
   case MRB_TT_DATA:
+  case MRB_TT_INLINE:
   default:
     return MakeID(mrb_ptr(obj));
   }

src/kernel.c

@@ -11,6 +11,7 @@
 #include <mruby/string.h>
 #include <mruby/variable.h>
 #include <mruby/error.h>
+#include <mruby/inline.h>
 
 typedef enum {
   NOEX_PUBLIC    = 0x00,
@@ -301,6 +302,9 @@ init_copy(mrb_state *mrb, mrb_value dest, mrb_value obj)
     case MRB_TT_EXCEPTION:
       mrb_iv_copy(mrb, dest, obj);
       break;
+    case MRB_TT_INLINE:
+      mrb_inline_copy(dest, obj);
+      break;
 
     default:
       break;

src/object.c

@@ -348,7 +348,7 @@ mrb_check_convert_type(mrb_state *mrb, mrb_value val, enum mrb_vtype type, const
 {
   mrb_value v;
 
-  if (mrb_type(val) == type && type != MRB_TT_DATA) return val;
+  if (mrb_type(val) == type && type != MRB_TT_DATA && type != MRB_TT_INLINE) return val;
   v = convert_type(mrb, val, tname, method, FALSE);
   if (mrb_nil_p(v) || mrb_type(v) != type) return mrb_nil_value();
   return v;
@@ -390,7 +390,7 @@ mrb_check_type(mrb_state *mrb, mrb_value x, enum mrb_vtype t)
   enum mrb_vtype xt;
 
   xt = mrb_type(x);
-  if ((xt != t) || (xt == MRB_TT_DATA)) {
+  if ((xt != t) || (xt == MRB_TT_DATA) || (xt == MRB_TT_INLINE)) {
     while (type->type < MRB_TT_MAXDEFINE) {
       if (type->type == t) {
         const char *etype;