Flag is just an empty option

src/main.c

@@ -581,20 +581,15 @@ int main (int argc, char **argv)
 {
     gt_set_signal();
 
-    int listener = 0;
     char *host = NULL;
     char *port = "5000";
     char *dev = PACKAGE_NAME;
     char *keyfile = NULL;
     char *congestion = NULL;
     long buffer_size = GT_BUFFER_SIZE;
-    int delay = 0;
-    int multiqueue = 0;
     long ka_count = -1;
     long ka_idle = -1;
     long ka_interval = -1;
-    int version = 0;
-    int debug = 0;
 
 #ifdef TCP_INFO
     struct {
@@ -611,29 +606,32 @@ int main (int argc, char **argv)
     };
 
     struct option opts[] = {
-        { "listener",    &listener,    option_flag   },
+        { "listener",    NULL,         option_option },
         { "host",        &host,        option_str    },
         { "port",        &port,        option_str    },
         { "dev",         &dev,         option_str    },
         { "keyfile",     &keyfile,     option_str    },
         { "congestion",  &congestion,  option_str    },
-        { "delay",       &delay,       option_flag   },
-        { "multiqueue",  &multiqueue,  option_flag   },
+        { "delay",       NULL,         option_option },
+        { "multiqueue",  NULL,         option_option },
         { "keepalive",   ka_opts,      option_option },
         { "buffer-size", &buffer_size, option_long   },
-        { "debug",       &debug,       option_flag   },
-        { "version",     &version,     option_flag   },
+        { "debug",       NULL,         option_option },
+        { "version",     NULL,         option_option },
         { NULL },
     };
 
     if (option(opts, argc, argv))
         return 1;
 
-    if (version) {
+    if (option_is_set(opts, "version")) {
         gt_print(PACKAGE_STRING"\n");
         return 0;
     }
 
+    int listener = option_is_set(opts, "listener");
+    int delay = option_is_set(opts, "delay");
+    int debug = option_is_set(opts, "debug");
     int keepalive = option_is_set(opts, "keepalive");
 
     if (buffer_size < 2048) {
@@ -664,7 +662,7 @@ int main (int argc, char **argv)
     struct netio tun  = { .fd = -1 };
     struct netio sock = { .fd = -1 };
 
-    tun.fd = tun_create(dev, multiqueue);
+    tun.fd = tun_create(dev, option_is_set(opts, "multiqueue"));
 
     if (tun.fd==-1)
         return 1;

src/option.c

@@ -5,14 +5,6 @@
 
 #include "option.h"
 
-int option_flag (void *data, _unused_ int argc, _unused_ char **argv)
-{
-    const int one = 1;
-    byte_cpy(data, &one, sizeof(one));
-
-    return 0;
-}
-
 int option_str (void *data, int argc, char **argv)
 {
     if (argc<2 || !argv[1]) {
@@ -58,6 +50,9 @@ int option_is_set (struct option *opts, const char *name)
 
 int option_option (void *data, int argc, char **argv)
 {
+    if (!data)
+        return 0;
+
     struct option *opts = (struct option *)data;
 
     for (int k=0; opts[k].name; k++)
@@ -96,6 +91,9 @@ int option_option (void *data, int argc, char **argv)
 
 static int option_usage (struct option *opts, int slen)
 {
+    if (!opts)
+        return 0;
+
     int len = slen;
 
     for (int k=0; opts[k].name; k++) {
@@ -106,13 +104,11 @@ static int option_usage (struct option *opts, int slen)
 
         len += gt_print(" [%s", opts[k].name);
 
-        if (opts[k].call!=option_flag) {
         if (opts[k].call==option_option) {
             len += option_usage((struct option *)opts[k].data, len);
         } else {
             len += gt_print(" ARG");
         }
-        }
 
         len += gt_print("]");
     }

src/option.h

@@ -7,10 +7,9 @@ struct option {
     int set;
 };
 
-int option_flag   (void *, int, char **);
+int option_option (void *, int, char **);
 int option_str    (void *, int, char **);
 int option_long   (void *, int, char **);
-int option_option (void *, int, char **);
 
 int option_is_set (struct option *, const char *);
 int option        (struct option *, int, char **);