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From: Andy Green <andy@warmcat.com>
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Subject: [dpdk-dev] [PATCH v7 7/8] rte_mbuf.h: add and subtract explicitly
to avoid promotion
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/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 <andy@warmcat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
---
lib/librte_mbuf/rte_mbuf.h | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index 0e89a6927..e136d12b7 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -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 */