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mbuf: avoid integer promotion in prepend/adj/chain

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GCC 8.1 warned:

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

        uint16_t data_off;

len (a uint16_t) is promoted to an int using -=.  Do the
subtraction explicitly and cast the result to uint16_t.

The below += or -= changes are solving the same thing.

In function 'rte_pktmbuf_adj':
rte_mbuf.h:1969:17: warning: conversion from 'int' to 'uint16_t'
{aka 'short unsigned int'} may change value [-Wconversion]
  m->data_off += len;
                 ^~~

In function 'rte_pktmbuf_chain':
rte_mbuf.h:2082:19: warning: conversion from 'int' to 'uint16_t'
{aka 'short unsigned int'} may change value [-Wconversion]
  head->nb_segs += tail->nb_segs;
                   ^~~~
Also uint16_t

        uint16_t nb_segs;         /**< Number of segments. */

Fixes: 08b563ffb1 ("mbuf: replace data pointer by an offset")
Fixes: 1a60a0daa6 ("mbuf: fix segments number type increase")
Cc: stable@dpdk.org

Signed-off-by: Andy Green <andy@warmcat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
This commit is contained in:
Andy Green 2018-05-22 09:24:42 +08:00 committed by Thomas Monjalon
parent ef5092e16b
commit 9d0b59f84e
1 changed files with 13 additions and 4 deletions
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17
lib/librte_mbuf/rte_mbuf.h
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@ -1908,7 +1908,10 @@ static inline char *rte_pktmbuf_prepend(struct rte_mbuf *m,
if (unlikely(len > rte_pktmbuf_headroom(m)))
return NULL;
m->data_off -= len;
/* NB: elaborating the subtraction like this instead of using
* -= allows us to ensure the result type is uint16_t
* avoiding compiler warnings on gcc 8.1 at least */
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);
@ -1968,8 +1971,11 @@ static inline char *rte_pktmbuf_adj(struct rte_mbuf *m, uint16_t len)
if (unlikely(len > m->data_len))
return NULL;
/* NB: elaborating the addition like this instead of using
* += allows us to ensure the result type is uint16_t
* avoiding compiler warnings on gcc 8.1 at least */
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;
}
@ -2081,8 +2087,11 @@ static inline int rte_pktmbuf_chain(struct rte_mbuf *head, struct rte_mbuf *tail
cur_tail = rte_pktmbuf_lastseg(head);
cur_tail->next = tail;
/* accumulate number of segments and total length. */
head->nb_segs += tail->nb_segs;
/* accumulate number of segments and total length.
* NB: elaborating the addition like this instead of using
* -= allows us to ensure the result type is uint16_t
* avoiding compiler warnings on gcc 8.1 at least */
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 */