[PATCH] event: fix warning from useless snprintf

[Van Haaren, Harry]

> From: Stephen Hemminger <stephen at networkplumber.org>
> Sent: Wednesday, April 24, 2024 4:45 AM
> To: dev at dpdk.org
> Cc: Richardson, Bruce; Stephen Hemminger; Van Haaren, Harry; Jerin Jacob
> Subject: [PATCH] event: fix warning from useless snprintf
> 
> With Gcc-14, this warning is generated:
> ../drivers/event/sw/sw_evdev.c:263:3: warning: 'snprintf' will always be truncated;
>     specified size is 12, but format string expands to at least 13 [-Wformat-truncation]
>   263 |                 snprintf(buf, sizeof(buf), "sw%d_iq_%d_rob", dev_id, i);
>       |                 ^
> 
> Yet the whole printf to the buf is unnecessary. The type string argument
> has never been implemented, and should just be NULL.  Removing the
> unnecessary snprintf, then means IQ_ROB_NAMESIZE can be removed.

I understand that today the "type" value isn't implemented, but across the DPDK codebase it
seems like others are filling in "type" to be some debug-useful name/string. If it was added
in future it'd be nice to have the ROB/IQ memory identified by name, like the rest of DPDK components.


> Fixes: 5ffb2f142d95 ("event/sw: support event queues")
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> ---
>  drivers/event/sw/iq_chunk.h | 2 --
>  drivers/event/sw/sw_evdev.c | 5 +----
>  2 files changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/event/sw/iq_chunk.h b/drivers/event/sw/iq_chunk.h
> index 7a7a8782e6..e638142dbc 100644
> --- a/drivers/event/sw/iq_chunk.h
> +++ b/drivers/event/sw/iq_chunk.h
> @@ -9,8 +9,6 @@
>  #include <stdbool.h>
>  #include <rte_eventdev.h>
> 
> -#define IQ_ROB_NAMESIZE 12

We can over-provision the temporary buffer, and solve the problem with minimal changes;
+#define IQ_ROB_NAMESIZE 64

> -
>  struct __rte_cache_aligned sw_queue_chunk {
>         struct rte_event events[SW_EVS_PER_Q_CHUNK];
>         struct sw_queue_chunk *next;
> diff --git a/drivers/event/sw/sw_evdev.c b/drivers/event/sw/sw_evdev.c
> index 1c01b069fe..19a52afc7d 100644
> --- a/drivers/event/sw/sw_evdev.c
> +++ b/drivers/event/sw/sw_evdev.c
> @@ -228,9 +228,7 @@ qid_init(struct sw_evdev *sw, unsigned int idx, int type,
>                 const struct rte_event_queue_conf *queue_conf)
>  {
>         unsigned int i;
> -       int dev_id = sw->data->dev_id;
>         int socket_id = sw->data->socket_id;
> -       char buf[IQ_ROB_NAMESIZE];
>         struct sw_qid *qid = &sw->qids[idx];
> 
>         /* Initialize the FID structures to no pinning (-1), and zero packets */
> @@ -260,8 +258,7 @@ qid_init(struct sw_evdev *sw, unsigned int idx, int type,
>                         goto cleanup;
>                 }
> 
> -               snprintf(buf, sizeof(buf), "sw%d_iq_%d_rob", dev_id, i);

There is a 2nd hidden bug here; the "i" variable iterates the ROB size, and does not represent the QID index.
Changing the "i" to "idx" solves, and prints the expected output instead:
snprintf(buf, sizeof(buf), "sw%d_iq_%d_rob", dev_id, idx);

> -               qid->reorder_buffer = rte_zmalloc_socket(buf,
> +               qid->reorder_buffer = rte_zmalloc_socket(NULL,
>                                 window_size * sizeof(qid->reorder_buffer[0]),
>                                 0, socket_id);
>                 if (!qid->reorder_buffer) {
> --
> 2.43.0

I'm happy to send a patch with the above, if that seems a good solution to you Stephen?

Regards, -Harry