From d74e60b6a76b8f577366586e0c485986aa0e5874 Mon Sep 17 00:00:00 2001
From: KLuka <luka.krajger@gmail.com>
Date: Fri, 21 Aug 2015 18:07:26 +0200
Subject: [PATCH] Added system logging for important errors

* Messages with "fatal" or "error" log level are now also passed to
  syslogd service with help of vsyslog() function.
* On systems that use syslog service, these messages will be available
  in default system log files like /var/log/syslog or /var/log/messages.
---
 configure.ac      |  7 +++++--
 logging/logging.c | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index c64b1a6..9a7b1ab 100644
--- a/configure.ac
+++ b/configure.ac
@@ -29,8 +29,8 @@ dnl Overwrite default archiver flags.
 AC_SUBST(AR_FLAGS, [cr])
 
 dnl Check for header files that do not exist on all platforms
-AC_CHECK_HEADERS([libutil.h pthread.h pty.h strings.h sys/prctl.h sys/uio.h  \
-                  util.h utmp.h utmpx.h])
+AC_CHECK_HEADERS([libutil.h pthread.h pty.h strings.h syslog.h sys/prctl.h \
+                  sys/uio.h util.h utmp.h utmpx.h])
 
 dnl Most systems require linking against libutil.so in order to get login_tty()
 AC_CHECK_FUNCS(login_tty, [],
@@ -41,6 +41,9 @@ AC_CHECK_FUNCS(login_tty, [],
 dnl Use strlcat() instead of strncat() to avoid spurious warnings
 AC_CHECK_FUNCS([strlcat])
 
+dnl Use vsyslog() for logging important error messages
+AC_CHECK_FUNCS([vsyslog])
+
 dnl Prefer thread-safe functions, if available
 AC_CHECK_FUNCS([getgrgid_r getgrnam_r gethostbyname_r getpwnam_r getpwuid_r  \
                 openpty strcasestr getresuid getresgid setresuid setresgid ])
diff --git a/logging/logging.c b/logging/logging.c
index 0b81e7b..fb78bfa 100644
--- a/logging/logging.c
+++ b/logging/logging.c
@@ -52,6 +52,19 @@
 
 #include "logging/logging.h"
 
+#ifdef HAVE_SYSLOG_H
+# include <syslog.h>
+# ifndef HAVE_VSYSLOG
+static void vsyslog(int priority, const char *fmt, va_list ap) {
+  char *s = vStringPrintf(NULL, fmt, ap);
+  if (s) {
+    syslog(priority, "%s", s);
+    free(s);
+  }
+}
+# endif
+#endif
+
 static int verbosity = MSG_DEFAULT;
 
 static void debugMsg(int level, const char *fmt, va_list ap) {
@@ -86,6 +99,9 @@ void error(const char *fmt, ...) {
   va_list ap;
   va_start(ap, fmt);
   debugMsg(MSG_ERROR, fmt, ap);
+#ifdef HAVE_SYSLOG_H
+  vsyslog(LOG_ERR, fmt, ap);
+#endif
   va_end(ap);
 }
 
@@ -100,6 +116,10 @@ void fatal(const char *fmt, ...) {
   va_list ap;
   va_start(ap, fmt);
   debugMsg(MSG_QUIET, fmt, ap);
+#ifdef HAVE_SYSLOG_H
+  vsyslog(LOG_CRIT, fmt, ap);
+  syslog(LOG_CRIT, "Aborting...");
+#endif
   va_end(ap);
   _exit(1);
 }