如果表示形式相同，则表示大小相同.

If the representations are the same, that implies that the sizes are the same.

C标准的第6.2.6.1p2节状态:

存储在任何其他对象类型的非位字段对象中的值[ed.不是未签名的字符]由 n×CHAR_BIT 位组成，其中 n 是对象的大小该类型(以字节为单位).该值可以复制到一个类型的对象中 unsigned char [n] (例如，通过 memcpy )；结果字节集为称为值的对象表示形式.位字段由 m 位组成，其中 m 是指定的大小对于位域.对象表示形式是该位字段包含 m 位，该位包含该位字段.相同的Tw o值(NaN除外)对象表示比较相等，但比较的值相等可能具有不同的对象表示形式.

Values stored in non-bit-field objects of any other object type [ed. not unsigned char] consist of n×CHAR_BIT bits, where n is the size of an object of that type, in bytes. The value may be copied into an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is called the object representation of the value. Values stored in bit-fields consist of m bits, where m is the size specified for the bit-field. The object representation is the set of m bits the bit-field comprises in the addressable storage unit holding it. Tw o values (other than NaNs) with the same object representation compare equal, but values that compare equal may have different object representations.

作为示例，gcc下的 int 和 short 都使用二进制补码，但是它们没有相同的对象表示形式，因为一个是4个字节，另一个是是2个字节.

As an example, an int and a short under gcc both use two's complement but they don't have the same object representation because one is 4 bytes and the other is 2 bytes.