-----Original Message-----
From: Amit Prakash Shukla <amitpraka...@marvell.com>
Sent: Friday, September 2, 2022 8:36 PM
To: Maxime Coquelin <maxime.coque...@redhat.com>; Chenbo Xia
<chenbo....@intel.com>
Cc: dev@dpdk.org; Jerin Jacob Kollanukkaran <jer...@marvell.com>;
sta...@dpdk.org; ruifeng.w...@arm.com; Amit Prakash Shukla
<amitpraka...@marvell.com>
Subject: [PATCH v3] vhost: compilation fix for GCC-12
GCC-12 complains about the possible use of un-initialized array. At compile
time it seems like it is not able to evaluate the size as it involves run-time
variable and at compile time it seems like gcc assumes value of "size" variable
to be zero which makes gcc-12 to jump the while loop.
"size = pkt->pkt_len + sizeof(struct virtio_net_hdr_mrg_rxbuf);"
As part of the fix, "while (){}" is replaced by "do {} while()" which make the
compiler to generate a code in which buf_vec will never be used un-
initialized.
../lib/vhost/virtio_net.c:941:35: error:
'buf_vec[0].buf_len' may be used uninitialized
[-Werror=maybe-uninitialized]
941 | buf_len = buf_vec[vec_idx].buf_len;
| ~~~~~~~~~~~~~~~~^~~~~~~~
../lib/vhost/virtio_net.c: In function 'virtio_dev_rx_packed':
../lib/vhost/virtio_net.c:1285:27: note: 'buf_vec' declared here
1285 | struct buf_vector buf_vec[BUF_VECTOR_MAX];
| ^~~~~~~
cc1: all warnings being treated as errors
Fixes: 93520085efda ("vhost: add packed ring single enqueue")
Cc: sta...@dpdk.org
Signed-off-by: Amit Prakash Shukla <amitpraka...@marvell.com>
---
v2:
- Changes for code review suggestion
v3:
- Added a description
lib/vhost/virtio_net.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
b3d954aab4..9b77d3d10f 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -1069,7 +1069,7 @@ vhost_enqueue_single_packed(struct virtio_net
*dev,
else
max_tries = 1;
- while (size > 0) {
+ do {
/*
* if we tried all available ring items, and still
* can't get enough buf, it means something abnormal @@ -
1097,7 +1097,7 @@ vhost_enqueue_single_packed(struct virtio_net *dev,
avail_idx += desc_count;
if (avail_idx >= vq->size)
avail_idx -= vq->size;
- }
+ } while (size > 0);
if (mbuf_to_desc(dev, vq, pkt, buf_vec, nr_vec, num_buffers, false)
< 0)
return -1;
@@ -1574,7 +1574,7 @@ vhost_enqueue_async_packed(struct virtio_net
*dev,
else
max_tries = 1;
- while (size > 0) {
+ do {
/*
* if we tried all available ring items, and still
* can't get enough buf, it means something abnormal @@ -
1601,7 +1601,7 @@ vhost_enqueue_async_packed(struct virtio_net *dev,
avail_idx += desc_count;
if (avail_idx >= vq->size)
avail_idx -= vq->size;
- }
+ } while (size > 0);
if (unlikely(mbuf_to_desc(dev, vq, pkt, buf_vec, nr_vec,
*nr_buffers, true) < 0))
return -1;
--
2.25.1
