common: Improve readability and utility of MSG_*() macros

Ensures we can't dereference NULL if a logger hasn't been set, and
cleans up the MSG_*() macros for readability.

Change-Id: I9808d8fe7672613e90c705686d1eaf1e2edef38a
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>

1 files changed, 11 insertions, 0 deletions

diff --git a/common.c b/common.c
index c460815..540cec5 100644
--- a/common.c
+++ b/common.c
@@ -45,8 +45,19 @@ void mbox_log_console(int p, const char *fmt, va_list args)
 __attribute__((format(printf, 2, 3)))
 void mbox_log(int p, const char *fmt, ...)
 {
+	static bool warned = false;
 	va_list args;
 
+	if (!mbox_vlog) {
+		if (!warned) {
+			fprintf(stderr, "Logging backend not configured, "
+					"log output disabled\n");
+			warned = true;
+		}
+
+		return;
+	}
+
 	va_start(args, fmt);
 	mbox_vlog(p, fmt, args);
 	va_end(args);