From 9f870a11218d0bc6364d6b333fd878106746adf9 Mon Sep 17 00:00:00 2001
From: Robert Norris <rw_norris@hotmail.com>
Date: Sun, 5 Mar 2017 18:43:33 +0000
Subject: OS syslog compatibility fallback.

Mainly for Windows systems which doesn't have syslog().

Implement simple fallback to print to stderr,
 rather than a more complicated use of Windows Event Log.

Also basic fallbacks for openlog() and closelog() which
 don't really do anything.

TESTED:
Functions build on Windows cross build
'scons build-all check' passes on Linux

Signed-off-by: Fred Wright <fw@fwright.net>
---
 SConstruct  |  2 +-
 gpxlogger.c |  1 -
 os_compat.c | 30 ++++++++++++++++++++++++++++++
 os_compat.h | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/SConstruct b/SConstruct
index f443184d..a39912fd 100644
--- a/SConstruct
+++ b/SConstruct
@@ -761,7 +761,7 @@ else:
             announce("You do not have the endian.h header file. RTCM V2 support disabled.")
             env["rtcm104v2"] = False
 
-    for hdr in ("sys/un", "sys/socket", "sys/select", "netdb", "netinet/in", "netinet/ip", "arpa/inet", "termios", "winsock2"):
+    for hdr in ("sys/un", "sys/socket", "sys/select", "netdb", "netinet/in", "netinet/ip", "arpa/inet", "syslog", "termios", "winsock2"):
         if config.CheckHeader(hdr + ".h"):
             confdefs.append("#define HAVE_%s_H 1\n" % hdr.replace("/","_").upper())
         else:
diff --git a/gpxlogger.c b/gpxlogger.c
index d93d527b..141b7486 100644
--- a/gpxlogger.c
+++ b/gpxlogger.c
@@ -7,7 +7,6 @@
 #include <stdlib.h>
 #include <stdbool.h>
 #include <string.h>
-#include <syslog.h>
 #include <math.h>
 #include <time.h>
 #include <errno.h>
diff --git a/os_compat.c b/os_compat.c
index fa4d85b2..8c117379 100644
--- a/os_compat.c
+++ b/os_compat.c
@@ -130,6 +130,36 @@ int os_daemon(int nochdir, int noclose)
 
 /* Provide BSD strlcat()/strlcpy() on platforms that don't have it */
 
+#ifndef HAVE_SYSLOG_H
+#include "compiler.h"
+#include <stdarg.h>
+#include <stdio.h>
+/*
+ * Minimal syslog() fallback to print to stderr
+ *
+ */
+PRINTF_FUNC(2, 3) void syslog(int priority UNUSED, const char *format, ...)
+{
+  /* ATM ignore priority (i.e. don't even both prepending to output) */
+  char buf[BUFSIZ];
+  va_list ap;
+  va_start(ap, format);
+  /* Always append a new line to the message */
+  (void)vsnprintf(buf, sizeof(buf) - 2, format, ap);
+  (void)fprintf(stderr, "%s\n", buf);
+  va_end(ap);
+}
+
+void openlog (const char *__ident UNUSED, int __option UNUSED, int __facility UNUSED)
+{
+  (void)fprintf(stderr, "Warning openlog() not available\n");
+}
+
+void closelog (void)
+{
+}
+#endif /* !HAVE_SYSLOG_H */
+
 /*
  * These versions use memcpy and strlen() because they are often
  * heavily optimized down to assembler level. Thus, likely to be
diff --git a/os_compat.h b/os_compat.h
index 00e56559..9321809f 100644
--- a/os_compat.h
+++ b/os_compat.h
@@ -57,6 +57,38 @@ int clock_gettime(clockid_t, struct timespec *);
 
 int os_daemon(int nochdir, int noclose);
 
+
+#ifdef HAVE_SYSLOG_H
+#include <syslog.h>
+#else
+/*
+ * Substitutes for syslog functions
+ *  (only subset of defines used by gpsd components listed)
+ *
+ */
+/* Copy of syslog.h defines when otherwise not available */
+/* priorities (these are ordered) */
+#define	LOG_EMERG	0	/* system is unusable */
+#define	LOG_ALERT	1	/* action must be taken immediately */
+#define	LOG_CRIT	2	/* critical conditions */
+#define	LOG_ERR		3	/* error conditions */
+#define	LOG_WARNING	4	/* warning conditions */
+#define	LOG_NOTICE	5	/* normal but significant condition */
+#define	LOG_INFO	6	/* informational */
+#define	LOG_DEBUG	7	/* debug-level messages */
+/* Option flags for openlog */
+#define	LOG_PID		0x01	/* log the pid with each message */
+#define	LOG_PERROR	0x20	/* log to stderr as well */
+/* facility codes */
+#define	LOG_USER	(1<<3)	/* random user-level messages */
+#define	LOG_DAEMON	(3<<3)	/* system daemons */
+
+void syslog(int priority, const char *format, ...);
+void openlog(const char *__ident, int __option, int __facility);
+void closelog(void);
+#endif /* !HAVE_SYSLOG_H */
+
+
 /* Provide BSD strlcat()/strlcpy() on platforms that don't have it */
 
 #ifndef HAVE_STRLCAT
-- 
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