linux-kernel - [PATCH 4/4] tools lib traceevent: Fix strerror_r() use in pevent

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Date:	Wed, 22 Aug 2012 16:00:31 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: [PATCH 4/4] tools lib traceevent: Fix strerror_r() use in pevent_strerror

From: Namhyung Kim <namhyung.kim@....com>

glibc-2.16 starts to mark the function with attribute
warn_unused_result so that it can cause a build warning.

Since GNU version of strerror_r() can return a pointer to a string
without setting @buf, check the return value and copy/truncate it to
our buffer if needed.

Cc: Fredereic Weisbecker <fweisbec@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Kirill A. Shutemov <kirill@...temov.name>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/lib/traceevent/event-parse.c | 7 ++++++-
 tools/lib/traceevent/event-utils.h | 6 ++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 1373e4cf109e..f978c59f67bf 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -4809,7 +4809,12 @@ int pevent_strerror(struct pevent *pevent, enum pevent_errno errnum,
 	const char *msg;
 
 	if (errnum >= 0) {
-		strerror_r(errnum, buf, buflen);
+		msg = strerror_r(errnum, buf, buflen);
+		if (msg != buf) {
+			size_t len = strlen(msg);
+			char *c = mempcpy(buf, msg, min(buflen-1, len));
+			*c = '\0';
+		}
 		return 0;
 	}
 
diff --git a/tools/lib/traceevent/event-utils.h b/tools/lib/traceevent/event-utils.h
index 08296383d1e6..bc075006966e 100644
--- a/tools/lib/traceevent/event-utils.h
+++ b/tools/lib/traceevent/event-utils.h
@@ -39,6 +39,12 @@ void __vdie(const char *fmt, ...);
 void __vwarning(const char *fmt, ...);
 void __vpr_stat(const char *fmt, ...);
 
+#define min(x, y) ({				\
+	typeof(x) _min1 = (x);			\
+	typeof(y) _min2 = (y);			\
+	(void) (&_min1 == &_min2);		\
+	_min1 < _min2 ? _min1 : _min2; })
+
 static inline char *strim(char *string)
 {
 	char *ret;
-- 
1.7.11.4

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