msgpack-c: error data is not consumed

non_consume.c

#include <msgpack.h>
#include <stdio.h>
#include <assert.h>

int main(void)
{
	msgpack_unpacker* unp = msgpack_unpacker_new(100);
	msgpack_unpacked result;
	bool ret;
	char* buf;

	printf("unp:%p\n", unp);
	assert(unp);

	buf = msgpack_unpacker_buffer(unp);
	printf("buf:%p\n", buf);
	assert(buf);
	printf("cap:%d\n", msgpack_unpacker_buffer_capacity(unp));
	assert(msgpack_unpacker_buffer_capacity(unp) >= 3);

	buf[0] = 0xc0;
	buf[1] = 0xc1;
	buf[2] = 0xc0;

	msgpack_unpacker_buffer_consumed(unp, 3);

	msgpack_unpacked_init(&result);
	ret = msgpack_unpacker_next(unp, &result);
	printf("ret:%d\n", ret);
	ret = msgpack_unpacker_next(unp, &result);
	printf("ret:%d\n", ret);
	ret = msgpack_unpacker_next(unp, &result);
	printf("ret:%d\n", ret);

	msgpack_unpacked_destroy(&result);
	msgpack_unpacker_destroy(unp);
	return 0;
}