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

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

[Yiyang Chen]

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.

Signed-off-by: Yiyang Chen <cyyzero16@gmail.com>
---
 tools/accounting/getdelays.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/tools/accounting/getdelays.c b/tools/accounting/getdelays.c
index 368a622ca027..caa5fe9dd573 100644
--- 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;
 }
-- 
2.43.0