From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 2 Apr 2019 16:41:12 +0000 (-0400)
Subject: Fix: logging: log_add_time() save/restore errno
X-Git-Url: http://git.efficios.com/?p=lttng-tools.git;a=commitdiff_plain;h=9f1053713656f28d01552540067b8887546a574c

Fix: logging: log_add_time() save/restore errno

The debugging logging macros (e.g. DBG()) are used as printf in the
lttng-tools source files. The printf() implementation does not alter the
errno value, so the fact that log_add_time() (through clock_gettime())
can alter errno is unexpected. For instance, adding a logging statement
for debugging purposes within a function for which errno is expected to
stay unchanged on return will change the behavior between execution with
-vvv and non-verbose.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/src/common/error.c b/src/common/error.c
index c79ce5713..a13320f68 100644
--- a/src/common/error.c
+++ b/src/common/error.c
@@ -20,6 +20,7 @@
 #include <inttypes.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 
 #include <lttng/lttng-error.h>
 #include <common/common.h>
@@ -45,6 +46,7 @@ const char *log_add_time(void)
 	struct tm tm, *res;
 	struct timespec tp;
 	time_t now;
+	int errsv = errno;
 
 	ret = lttng_clock_gettime(CLOCK_REALTIME, &tp);
 	if (ret < 0) {
@@ -65,10 +67,12 @@ const char *log_add_time(void)
 		goto error;
 	}
 
+	errno = errsv;
 	return URCU_TLS(error_log_time).str;
 
 error:
 	/* Return an empty string on error so logging is not affected. */
+	errno = errsv;
 	return "";
 }