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

[Andy Green]

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 <a...@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;