Re: [dpdk-dev] [PATCH v4 13/23] rte_mbuf.h: explicit casts to uint16 to avoid warnings

[Andy Green <andy@warmcat.com>]

On 05/17/2018 06:58 PM, Bruce Richardson wrote:
> On Mon, May 14, 2018 at 01:10:32PM +0800, Andy Green wrote:
>> Signed-off-by: Andy Green <andy@warmcat.com>
>> ---
>>   lib/librte_mbuf/rte_mbuf.h |   15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
>> index 169f3d3b0..3cd76abbc 100644
>> --- a/lib/librte_mbuf/rte_mbuf.h
>> +++ b/lib/librte_mbuf/rte_mbuf.h
>> @@ -1580,7 +1580,7 @@ static inline void rte_pktmbuf_detach(struct rte_mbuf *m)
>>   	mbuf_size = (uint32_t)sizeof(struct rte_mbuf) + priv_size;
>>   	buf_len = rte_pktmbuf_data_room_size(mp);
>>   
>> -	m->priv_size = priv_size;
>> +	m->priv_size = (uint16_t)priv_size;
>>   	m->buf_addr = (char *)m + mbuf_size;
>>   	m->buf_iova = rte_mempool_virt2iova(m) + mbuf_size;
>>   	m->buf_len = (uint16_t)buf_len;
> 
> I think a better fix for this is to change priv_size to be uint16_t. There
> is no reason for it to be a 32-bit value.

OK.

>> @@ -1905,7 +1905,7 @@ static inline char *rte_pktmbuf_prepend(struct rte_mbuf *m,
>>   	if (unlikely(len > rte_pktmbuf_headroom(m)))
>>   		return NULL;
>>   
>> -	m->data_off -= len;
>> +	m->data_off = (uint16_t)(m->data_off - len);
>>   	m->data_len = (uint16_t)(m->data_len + len);
>>   	m->pkt_len  = (m->pkt_len + len);
>>   
> 
> What is the error message here? The cast isn't wrong, it just seems like we
> shouldn't need it. I suppose it's implicit promotion being done in the
> subtraction operation.

     /projects/lagopus/src/dpdk/build/include/rte_mbuf.h:
     In function 'rte_pktmbuf_prepend':
     /projects/lagopus/src/dpdk/build/include/rte_mbuf.h:
     1908:17: warning: conversion from 'int' to 'uint16_t'
     {aka 'short unsigned int'} may change value [-Wconversion]
       m->data_off -= len;
                      ^~~

I have added all the original warnings to the patch.

-Andy

>> @@ -1966,7 +1966,7 @@ static inline char *rte_pktmbuf_adj(struct rte_mbuf *m, uint16_t len)
>>   		return NULL;
>>   
>>   	m->data_len = (uint16_t)(m->data_len - len);
>> -	m->data_off += len;
>> +	m->data_off = (uint16_t)(m->data_off + len);
>>   	m->pkt_len  = (m->pkt_len - len);
>>   	return (char *)m->buf_addr + m->data_off;
>>   }
>> @@ -2079,7 +2079,7 @@ static inline int rte_pktmbuf_chain(struct rte_mbuf *head, struct rte_mbuf *tail
>>   	cur_tail->next = tail;
>>   
>>   	/* accumulate number of segments and total length. */
>> -	head->nb_segs += tail->nb_segs;
>> +	head->nb_segs = (uint16_t)(head->nb_segs + tail->nb_segs);
>>   	head->pkt_len += tail->pkt_len;
>>   
>>   	/* pkt_len is only set in the head */
>> @@ -2109,7 +2109,8 @@ rte_validate_tx_offload(const struct rte_mbuf *m)
>>   		return 0;
>>   
>>   	if (ol_flags & PKT_TX_OUTER_IP_CKSUM)
>> -		inner_l3_offset += m->outer_l2_len + m->outer_l3_len;
>> +		inner_l3_offset += (unsigned int)(m->outer_l2_len +
>> +						  m->outer_l3_len);
>>   
>>   	/* Headers are fragmented */
>>   	if (rte_pktmbuf_data_len(m) < inner_l3_offset + m->l3_len + m->l4_len)
>> @@ -2154,7 +2155,7 @@ rte_validate_tx_offload(const struct rte_mbuf *m)
>>   static inline int
>>   rte_pktmbuf_linearize(struct rte_mbuf *mbuf)
>>   {
>> -	int seg_len, copy_len;
>> +	size_t seg_len, copy_len;
>>   	struct rte_mbuf *m;
>>   	struct rte_mbuf *m_next;
>>   	char *buffer;
>> @@ -2169,7 +2170,7 @@ rte_pktmbuf_linearize(struct rte_mbuf *mbuf)
>>   		return -1;
>>   
>>   	buffer = rte_pktmbuf_mtod_offset(mbuf, char *, mbuf->data_len);
>> -	mbuf->data_len = (uint16_t)(mbuf->pkt_len);
>> +	mbuf->data_len = (uint16_t)mbuf->pkt_len;
>>   
>>   	/* Append data from next segments to the first one */
>>   	m = mbuf->next;
>>