[PATCH v2 3/3] log: Add vlogmsg()

[David Gibson <david@gibson.dropbear.id.au>]

Currently logmsg() is only available as a variadic function.  This is fine
for normal use, but is awkward if we ever want to write wrappers around it
which (for example) add standardised prefix information.  To allow that,
add a vlogmsg() function which takes a va_list instead, and implement
logmsg() in terms of it.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 log.c | 25 ++++++++++++++++---------
 log.h |  1 +
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/log.c b/log.c
index fd33f64..95c4fa4 100644
--- a/log.c
+++ b/log.c
@@ -47,11 +47,10 @@ int		log_to_stdout;		/* Print to stdout instead of stderr */
 
 #define BEFORE_DAEMON		(setlogmask(0) == LOG_MASK(LOG_EMERG))
 
-void logmsg(int pri, const char *format, ...)
+void vlogmsg(int pri, const char *format, va_list ap)
 {
 	FILE *out = log_to_stdout ? stdout : stderr;
 	struct timespec tp;
-	va_list args;
 
 	if (setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) {
 		clock_gettime(CLOCK_REALTIME, &tp);
@@ -61,24 +60,32 @@ void logmsg(int pri, const char *format, ...)
 	}
 
 	if ((LOG_MASK(LOG_PRI(pri)) & log_mask) || BEFORE_DAEMON) {
-		va_start(args, format);
+		va_list ap2;
+
+		va_copy(ap2, ap); /* Don't clobber ap, we need it again */
 		if (log_file != -1)
-			logfile_write(pri, format, args);
+			logfile_write(pri, format, ap2);
 		else if (!(setlogmask(0) & LOG_MASK(LOG_DEBUG)))
-			passt_vsyslog(pri, format, args);
-		va_end(args);
+			passt_vsyslog(pri, format, ap2);
 	}
 
 	if ((setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) ||
 	    (BEFORE_DAEMON && !(log_opt & LOG_PERROR))) {
-		va_start(args, format);
-		(void)vfprintf(out, format, args);
-		va_end(args);
+		(void)vfprintf(out, format, ap);
 		if (format[strlen(format)] != '\n')
 			fprintf(out, "\n");
 	}
 }
 
+void logmsg(int pri, const char *format, ...)
+{
+	va_list ap;
+
+	va_start(ap, format);
+	vlogmsg(pri, format, ap);
+	va_end(ap);
+}
+
 /* Prefixes for log file messages, indexed by priority */
 const char *logfile_prefix[] = {
 	NULL, NULL, NULL,	/* Unused: LOG_EMERG, LOG_ALERT, LOG_CRIT */
diff --git a/log.h b/log.h
index df72f9a..9c38182 100644
--- a/log.h
+++ b/log.h
@@ -12,6 +12,7 @@
 #define LOGFILE_CUT_RATIO		30	/* When full, cut ~30% size */
 #define LOGFILE_SIZE_MIN		(5UL * MAX(BUFSIZ, PAGE_SIZE))
 
+void vlogmsg(int pri, const char *format, va_list ap);
 void logmsg(int pri, const char *format, ...)
 	__attribute__((format(printf, 2, 3)));
 
-- 
@@ -12,6 +12,7 @@
 #define LOGFILE_CUT_RATIO		30	/* When full, cut ~30% size */
 #define LOGFILE_SIZE_MIN		(5UL * MAX(BUFSIZ, PAGE_SIZE))
 
+void vlogmsg(int pri, const char *format, va_list ap);
 void logmsg(int pri, const char *format, ...)
 	__attribute__((format(printf, 2, 3)));
 
-- 
2.41.0