tools/accounting/getdelays: fix -Wformat-truncation warning in format_timespec

Reproduce with GCC 13.3.0:

  $ cd tools/accounting
  $ make

This emits:

getdelays.c: In function `format_timespec':
getdelays.c:218:67: warning: `:' directive output may be truncated writing 1 byte into a region of size between 0 and 16 [-Wformat-truncation=]
  218 |         snprintf(buffer, sizeof(buffer), "%04d-%02d-%02dT%02d:%02d:%02d",
      |
getdelays.c:218:9: note: `snprintf' output between 20 and 72 bytes into a destination of size 32

The problem is that %04d and %02d specify minimum field widths only. GCC
cannot prove that formatting tm_year + 1900 and the other struct tm
fields will always fit in the fixed 32-byte buffer, so it warns about
possible truncation.

Fix this by replacing the manual snprintf() formatting with
strftime("%Y-%m-%dT%H:%M:%S", ...). That matches the data we already have
in struct tm, keeps the intended timestamp format, and avoids the warning
when building tools/accounting with GCC.

Link: https://lore.kernel.org/87d9723e0b59d816ee2e4bd7cddd58a54c6c9f91.1776956545.git.cyyzero16@gmail.com
Signed-off-by: Yiyang Chen <cyyzero16@gmail.com>
Cc: Fan Yu <fan.yu9@zte.com.cn>
Cc: Wang Yaxin <wang.yaxin@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/accounting/getdelays.c b/tools/accounting/getdelays.c
index 368a622ca0273f1b93778a5bb3c1e8a5776e69a4..caa5fe9dd5734a0ef24dc3bc3be1393764ccfa87 100644 (file)
--- a/tools/accounting/getdelays.c
+++ b/tools/accounting/getdelays.c
@@ -241,13 +241,7 @@ static const char *format_timespec(struct __kernel_timespec *ts)
        if (localtime_r(&time_sec, &tm_info) == NULL)
                return "N/A";
 
-       snprintf(buffer, sizeof(buffer), "%04d-%02d-%02dT%02d:%02d:%02d",
-               tm_info.tm_year + 1900,
-               tm_info.tm_mon + 1,
-               tm_info.tm_mday,
-               tm_info.tm_hour,
-               tm_info.tm_min,
-               tm_info.tm_sec);
+       strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &tm_info);
 
        return buffer;
 }