: void *ruby_xmalloc(long size) 
    ֤ͤ malloc() Ʊ
    Ƥ˼ԤȤ
    GC ԤǤʤȤ NoMemoryError  raise 롣
    Ĥޤꤳδؿ֤֤ͤȤϾ˳ƤƤ롣

