code to migrate between 2 mrb_state

gistfile1.c

#include "mruby.h"
#include "mruby/string.h"
#include "mruby/array.h"

mrb_value
migrate_simple_value(mrb_state *mrb, mrb_value v, mrb_state *mrb2)
{
  mrb_value nv;			/* new value */
  const char *s;
  int len;

  nv.tt = v.tt;
  switch (mrb_type(v)) {
  case MRB_TT_FALSE:
  case MRB_TT_TRUE:
  case MRB_TT_FIXNUM:
    nv.value.i = v.value.i;
    break;
  case MRB_TT_SYMBOL:
    nv = mrb_symbol_value(mrb_intern_str(mrb2, v));
    break;
  case MRB_TT_FLOAT:
    nv.value.f = v.value.f;
    break;
  case MRB_TT_STRING:
    {
      struct RString *str = mrb_str_ptr(v);
      
      s = str->ptr;
      len = str->len;
      nv = mrb_str_new(mrb2, s, len);
    }
    break;
  case MRB_TT_ARRAY:
    {
      struct RArray *a0, *a1;
      int i;

      a0 = mrb_ary_ptr(v);
      nv = mrb_ary_new_capa(mrb2, a0->len);
      a1 = mrb_ary_ptr(nv);
      for (i=0; i<a0->len; i++) {
	int ai = mrb_gc_arena_save(mrb2);
	a1->ptr[i] = migrate_simple_value(mrb, a0->ptr[i], mrb2);
	a1->len++;
	mrb_gc_arena_restore(mrb2, ai);
      }
    }
    break;
  default:
    mrb_raise(mrb, E_TYPE_ERROR, "cannot migrate object");
    break;
  }
  return nv;
}

そうですね。後からコピペする人のために修正しておきました。