linux-kernel - Re: [PATCH blktrace v2 02/22] blkparse: fix compiler warning

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Message-ID: <6eb2eab1-7a9c-4c07-a9b1-be6557247a4c@kernel.org>
Date: Wed, 1 Oct 2025 16:43:11 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Johannes Thumshirn <johannes.thumshirn@....com>,
 Jens Axboe <axboe@...nel.dk>
Cc: Steven Rostedt <rostedt@...dmis.org>,
 Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-btrace@...r.kernel.org,
 John Garry <john.g.garry@...cle.com>, Hannes Reinecke <hare@...e.de>,
 Christoph Hellwig <hch@....de>, Naohiro Aota <naohiro.aota@....com>,
 Shinichiro Kawasaki <shinichiro.kawasaki@....com>,
 Chaitanya Kulkarni <chaitanyak@...dia.com>,
 "Martin K . Petersen" <martin.petersen@...cle.com>
Subject: Re: [PATCH blktrace v2 02/22] blkparse: fix compiler warning

On 9/26/25 00:04, Johannes Thumshirn wrote:
> GCC (15.2.1) warns on about the following string truncation in blkparse.c
> 
> gcc -o blkparse.o -c -Wall -O2 -g -W -D_GNU_SOURCE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 blkparse.c
> blkparse.c: In function ‘main’:
> blkparse.c:2103:68: warning: ‘):’ directive output may be truncated writing 2 bytes into a region of size between 1 and 41 [-Wformat-truncation=]
>  2103 |                         snprintf(line, sizeof(line) - 1, "CPU%d (%s):",
>       |                                                                    ^~
> In function ‘show_device_and_cpu_stats’,
>     inlined from ‘show_stats’ at blkparse.c:3064:3,
>     inlined from ‘main’ at blkparse.c:3386:3:
> blkparse.c:2103:25: note: ‘snprintf’ output between 9 and 49 bytes into a destination of size 47
>  2103 |                         snprintf(line, sizeof(line) - 1, "CPU%d (%s):",
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  2104 |                                  j, get_dev_name(pdi, name, sizeof(name)));
>       |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> gcc -Wall -O2 -g -W -D_GNU_SOURCE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64  -o blkparse blkparse.o blkparse_fmt.o rbtree.o act_mask.o
> 
> Add two more bytes to the string in order to mitigate the compiler warning.
> 
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>

Reviewed-by: Damien Le Moal <dlemoal@...nel.org>

-- 
Damien Le Moal
Western Digital Research