linux-kernel - [PATCH v2 2/2] coredump: add __printf attribute to cn

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Date:	Fri, 15 May 2015 10:29:35 +0800
From:	Nicolas Iooss <nicolas.iooss_linux@....org>
To:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	linux-kernel@...r.kernel.org,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Nicolas Iooss <nicolas.iooss_linux@....org>
Subject: [PATCH v2 2/2] coredump: add __printf attribute to cn_*printf functions

This allows detecting improper format string at build time, like:

  fs/coredump.c:225:5: warning: format '%ld' expects argument of type
  'long int', but argument 3 has type 'int' [-Wformat=]
       err = cn_printf(cn, "%ld", cprm->siginfo->si_signo);
       ^

As si_signo is always an int, the format should be %d here.

Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
---
 fs/coredump.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 833a57bc856c..e52e0064feac 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -70,7 +70,8 @@ static int expand_corename(struct core_name *cn, int size)
 	return 0;
 }
 
-static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg)
+static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
+				     va_list arg)
 {
 	int free, need;
 	va_list arg_copy;
@@ -93,7 +94,7 @@ again:
 	return -ENOMEM;
 }
 
-static int cn_printf(struct core_name *cn, const char *fmt, ...)
+static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
 {
 	va_list arg;
 	int ret;
@@ -105,7 +106,8 @@ static int cn_printf(struct core_name *cn, const char *fmt, ...)
 	return ret;
 }
 
-static int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
+static __printf(2, 3)
+int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 {
 	int cur = cn->used;
 	va_list arg;
@@ -225,7 +227,8 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
 				break;
 			/* signal that caused the coredump */
 			case 's':
-				err = cn_printf(cn, "%ld", cprm->siginfo->si_signo);
+				err = cn_printf(cn, "%d",
+						cprm->siginfo->si_signo);
 				break;
 			/* UNIX time of coredump */
 			case 't': {
-- 
2.4.0

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