Add check to ensure -O is used with stdout

src/audio.c

@@ -458,6 +458,11 @@ int audio_open (struct audio_s *pa)
  */
 	    if (strcasecmp(pa->adev[a].adevice_out, "stdout") == 0 || strcmp(pa->adev[a].adevice_out, "-") == 0) {
 	      adev[a].g_audio_out_type = AUDIO_OUT_TYPE_STDOUT;
+	      if (!dw_printf_redirected()) {
+	        text_color_set (DW_COLOR_ERROR);
+	        dw_printf ("stdout must only be used with the -O option\n");
+	        return (-1);
+	      }
 	    } else {
 	      adev[a].g_audio_out_type = AUDIO_OUT_TYPE_SOUNDCARD;
 	    }

src/audio_win.c

@@ -354,6 +354,11 @@ int audio_open (struct audio_s *pa)
  */
 	    if (strcasecmp(pa->adev[a].adevice_out, "stdout") == 0 || strcmp(pa->adev[a].adevice_out, "-") == 0) {
 	      A->g_audio_out_type = AUDIO_OUT_TYPE_STDOUT;
+	      if (!dw_printf_redirected()) {
+	        text_color_set (DW_COLOR_ERROR);
+	        dw_printf ("stdout must only be used with the -O option\n");
+	        return (-1);
+	      }
 	      /* Change - to stdout for readability. */
 	      strlcpy (pa->adev[a].adevice_out, "stdout", sizeof(pa->adev[a].adevice_out));
 	    } else {

src/textcolor.c

@@ -388,7 +388,10 @@ int dw_printf (const char *fmt, ...)
 	return (len);
 }
 
-
+int dw_printf_redirected ()
+{
+	return g_dw_printf_dest != stdout;
+}
 
 #if TESTC
 main () 

src/textcolor.h

@@ -55,4 +55,6 @@ int dw_printf (const char *fmt, ...)
 				__attribute__((format(printf,1,2)));		/* gnu C lib. */
 #endif
 
+int dw_printf_redirected ();
+
 #endif