Clean up code for the silent lead-in on a non-syncing back end e.g. a pipe. Clean up pipe creation and initial opening and associated error messages. Fix error with warning/die messages. Tidy up some debug messages.

audio_pipe.c

@@ -51,8 +51,19 @@ static void start(__attribute__((unused)) int sample_rate,
   // "ENXIO  O_NONBLOCK | O_WRONLY is set, the named file is a FIFO, and no process has the FIFO
   // open for reading."
 
- fd = try_to_open_pipe_for_writing(pipename);
- }
+	fd = try_to_open_pipe_for_writing(pipename);
+	// we check that it's not a "real" error. From the "man 2 open" page:
+	// "ENXIO  O_NONBLOCK | O_WRONLY is set, the named file is a FIFO, and no process has the FIFO
+	// open for reading." Which is okay.
+	if ((fd == -1) && (errno != ENXIO)) {
+		char errorstring[1024];
+		strerror_r(errno, (char *)errorstring, sizeof(errorstring));
+		debug(1, "audio_pipe start -- error %d (\"%s\") opening pipe: \"%s\".", errno,
+					(char *)errorstring, pipename);
+		warn("can not open audio pipe -- error %d (\"%s\") opening pipe: \"%s\".", errno,
+					(char *)errorstring, pipename);
+	}
+}
 
 static int play(void *buf, int samples) {
   // if the file is not open, try to open it.
@@ -74,6 +85,7 @@ static int play(void *buf, int samples) {
 
 static void stop(void) {
   // Don't close the pipe just because a play session has stopped.
+
 }
 
 static int init(int argc, char **argv) {