On Mon, May 21, 2018 at 10:01:28AM +0800, Andy Green wrote:
> /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;
> ^~~
> 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.
>
> - m->data_off -= len;
> + m->data_off = (uint16_t)(m->data_off - len);
>
> The below += or -= changes are solving the same thing.
>
> /projects/lagopus/src/dpdk/build/include/rte_mbuf.h:
> In function 'rte_pktmbuf_adj':
> /projects/lagopus/src/dpdk/build/include/rte_mbuf.h:
> 1969:17: warning: conversion from 'int' to 'uint16_t'
> {aka 'short unsigned int'} may change value [-Wconversion]
> m->data_off += len;
> ^~~
> /projects/lagopus/src/dpdk/build/include/rte_mbuf.h:
> In function 'rte_pktmbuf_chain':
> /projects/lagopus/src/dpdk/build/include/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")
> Signed-off-by: Andy Green <a...@warmcat.com>
> ---
> lib/librte_mbuf/rte_mbuf.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index a0423a548..beb104c69 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -1908,7 +1908,7 @@ 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);
>
Code change looks ok to me, again it wouldn't hurt to have a comment
explaining the absense of -=, but otherwise:
Acked-by: Bruce Richardson <bruce.richard...@intel.com>
