Fix compilation with GCC 10, defaulting to -fno-common. solve issue #52

main.c

@@ -37,6 +37,8 @@ const char *copyright;
 extern char *optarg;
 extern int optind;
 
+int trace_flag = 0;
+
 void usage()
 {
     fprintf(stderr, "DMR Config, Version %s, %s\n", version, copyright);

radio.h

@@ -139,9 +139,9 @@ extern unsigned char radio_mem[];
 //
 // File descriptor of serial port with programming cable attached.
 //
-int radio_port;
+extern int radio_port;
 
 //
 // Read/write progress counter.
 //
-int radio_progress;
+extern int radio_progress;

util.h

@@ -35,7 +35,7 @@ extern const char *copyright;
 //
 // Trace data i/o via the serial port.
 //
-int trace_flag;
+extern int trace_flag;
 
 //
 // Print data in hex format.