common: un-hardcode 'stderr' as the logging stream

It's now a global variable that's initialized to stderr
(This is prep work for eventual support of printing applications)

backend_canonselphy.c

@@ -893,7 +893,7 @@ top:
 	}
 	last_state = state;
 
-	fflush(stderr);
+	fflush(logger);
 
 	switch(state) {
 	case S_IDLE:

backend_common.c

@@ -29,7 +29,7 @@
 #include <signal.h>
 #include <strings.h>  /* For strncasecmp */
 
-#define BACKEND_VERSION "0.106"
+#define BACKEND_VERSION "0.107"
 #ifndef URI_PREFIX
 #error "Must Define URI_PREFIX"
 #endif
@@ -60,6 +60,7 @@ int ncopies = 1;
 int collate = 0;
 int test_mode = 0;
 int quiet = 0;
+FILE *logger;
 
 const char *corrtable_path = CORRTABLE_PATH;
 static int max_xfer_size = URB_XFER_SIZE;
@@ -1001,7 +1002,7 @@ for more details.\n\
 You should have received a copy of the GNU General Public License\n\
 along with this program; if not, see <https://www.gnu.org/licenses/>.\n\n";
 
-	fprintf(stderr, "%s", license);
+	fprintf(logger, "%s", license);
 }
 
 void print_help(const char *argv0, const struct dyesub_backend *backend)
@@ -1270,6 +1271,8 @@ int main (int argc, char **argv)
 	const char *backend_str = NULL;
 	int  printer_type;
 
+	logger = stderr;
+
 	/* Handle environment variables  */
 	if (getenv("BACKEND_QUIET"))
 		quiet = atoi(getenv("BACKEND_QUIET"));

backend_common.h

@@ -50,15 +50,15 @@
 #endif
 
 #define STR_LEN_MAX 64
-#define STATE( ... ) do { if (!quiet) fprintf(stderr, "STATE: " __VA_ARGS__ ); } while(0)
-#define ATTR( ... ) do { if (!quiet) fprintf(stderr, "ATTR: " __VA_ARGS__ ); } while(0)
-#define PAGE( ... ) do { if (!quiet) fprintf(stderr, "PAGE: " __VA_ARGS__ ); } while(0)
-#define DEBUG( ... ) do { if (!quiet) fprintf(stderr, "DEBUG: " __VA_ARGS__ ); } while(0)
-#define DEBUG2( ... ) do { if (!quiet) fprintf(stderr, __VA_ARGS__ ); } while(0)
-#define INFO( ... )  do { if (!quiet) fprintf(stderr, "INFO: " __VA_ARGS__ ); } while(0)
-#define WARNING( ... )  do { fprintf(stderr, "WARNING: " __VA_ARGS__ ); } while(0)
-#define ERROR( ... ) do { fprintf(stderr, "ERROR: " __VA_ARGS__ ); sleep(1); } while (0)
-#define PPD( ... ) do { fprintf(stderr, "PPD: " __VA_ARGS__ ); sleep(1); } while (0)
+#define STATE( ... ) do { if (!quiet) fprintf(logger, "STATE: " __VA_ARGS__ ); } while(0)
+#define ATTR( ... ) do { if (!quiet) fprintf(logger, "ATTR: " __VA_ARGS__ ); } while(0)
+#define PAGE( ... ) do { if (!quiet) fprintf(logger, "PAGE: " __VA_ARGS__ ); } while(0)
+#define DEBUG( ... ) do { if (!quiet) fprintf(logger, "DEBUG: " __VA_ARGS__ ); } while(0)
+#define DEBUG2( ... ) do { if (!quiet) fprintf(logger, __VA_ARGS__ ); } while(0)
+#define INFO( ... )  do { if (!quiet) fprintf(logger, "INFO: " __VA_ARGS__ ); } while(0)
+#define WARNING( ... )  do { fprintf(logger, "WARNING: " __VA_ARGS__ ); } while(0)
+#define ERROR( ... ) do { fprintf(logger, "ERROR: " __VA_ARGS__ ); sleep(1); } while (0)
+#define PPD( ... ) do { fprintf(logger, "PPD: " __VA_ARGS__ ); sleep(1); } while (0)
 
 #if (__BYTE_ORDER == __LITTLE_ENDIAN)
 #define le16_to_cpu(__x) __x
@@ -281,6 +281,7 @@ extern int collate;
 extern int test_mode;
 extern int quiet;
 extern const char *corrtable_path;
+extern FILE *logger;
 
 enum {
 	TEST_MODE_NONE = 0,

backend_kodak1400.c

@@ -456,7 +456,7 @@ top:
 		return CUPS_BACKEND_STOP;  // HOLD/CANCEL/FAILED?  XXXX parse error!
 	}
 
-	fflush(stderr);
+	fflush(logger);
 
 	switch (state) {
 	case S_IDLE:

backend_shinkos1245.c

@@ -1072,7 +1072,7 @@ top:
 
 	last_state = state;
 
-	fflush(stderr);
+	fflush(logger);
 
 	switch (state) {
 	case S_IDLE:

backend_shinkos2145.c

@@ -992,7 +992,7 @@ top:
 	}
 	last_state = state;
 
-	fflush(stderr);
+	fflush(logger);
 
 	switch (state) {
 	case S_IDLE:

backend_shinkos6145.c

@@ -1647,7 +1647,7 @@ top:
 	}
 	last_state = state;
 
-	fflush(stderr);
+	fflush(logger);
 
 	switch (state) {
 	case S_IDLE:

backend_shinkos6245.c

@@ -1231,7 +1231,7 @@ top:
 	}
 	last_state = state;
 
-	fflush(stderr);
+	fflush(logger);
 
 	switch (state) {
 	case S_IDLE: