diff --git a/src/socketcand.h b/src/socketcand.h
index f80739e..0c46262 100644
--- a/src/socketcand.h
+++ b/src/socketcand.h
@@ -48,12 +48,12 @@
 
 #undef DEBUG_RECEPTION
 
-void state_bcm();
-void state_raw();
-void state_isotp();
-void state_control();
+void state_bcm(void);
+void state_raw(void);
+void state_isotp(void);
+void state_control(void);
 void tcp_quickack(int s);
-void state_nobus();
+void state_nobus(void);
 
 extern int client_socket;
 extern char **interface_names;
diff --git a/src/socketcandcl.c b/src/socketcandcl.c
index 3913c76..8c761ff 100644
--- a/src/socketcandcl.c
+++ b/src/socketcandcl.c
@@ -60,17 +60,17 @@ void sigint(int signum);
 int receive_command(int socket, char *buf);
 void state_connected();
 
-int server_socket;
-int raw_socket;
-int port;
-int verbose_flag = 0;
-int cmd_index = 0;
-int more_elements = 0;
-int state, previous_state;
-char ldev[IFNAMSIZ];
-char rdev[IFNAMSIZ];
-char buf[MAXLEN];
-char cmd_buffer[MAXLEN];
+static int server_socket;
+static int raw_socket;
+static int port;
+static int verbose_flag = 0;
+static int cmd_index = 0;
+static int more_elements = 0;
+static int state, previous_state;
+static char ldev[IFNAMSIZ];
+static char rdev[IFNAMSIZ];
+static char buf[MAXLEN];
+static char cmd_buffer[MAXLEN];
 
 int main(int argc, char **argv)
 {
diff --git a/src/state_bcm.c b/src/state_bcm.c
index 84826a2..40480cf 100644
--- a/src/state_bcm.c
+++ b/src/state_bcm.c
@@ -29,7 +29,7 @@
 
 int sc = -1;
 
-void state_bcm()
+void state_bcm(void)
 {
 	int i, j, ret;
 	unsigned long long sec, usec;
diff --git a/src/state_control.c b/src/state_control.c
index 734c060..d4e7613 100644
--- a/src/state_control.c
+++ b/src/state_control.c
@@ -19,7 +19,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 
-void state_control()
+void state_control(void)
 {
 	char buf[MAXLEN];
 	int i, items;
diff --git a/src/state_isotp.c b/src/state_isotp.c
index 1efb706..0c7b251 100644
--- a/src/state_isotp.c
+++ b/src/state_isotp.c
@@ -26,7 +26,7 @@
 
 int si = -1;
 
-void state_isotp()
+void state_isotp(void)
 {
 	int i, items, ret;
 
diff --git a/src/state_raw.c b/src/state_raw.c
index 8424dbc..8b40611 100644
--- a/src/state_raw.c
+++ b/src/state_raw.c
@@ -23,17 +23,17 @@
 #include <linux/can.h>
 #include <linux/can/raw.h>
 
-int raw_socket;
-struct ifreq ifr;
-struct sockaddr_can addr;
-struct msghdr msg;
-struct can_frame frame;
-struct iovec iov;
-char ctrlmsg[CMSG_SPACE(sizeof(struct timeval)) + CMSG_SPACE(sizeof(__u32))];
-struct timeval tv;
-struct cmsghdr *cmsg;
-
-void state_raw()
+static int raw_socket;
+static struct ifreq ifr;
+static struct sockaddr_can addr;
+static struct msghdr msg;
+static struct can_frame frame;
+static struct iovec iov;
+static char ctrlmsg[CMSG_SPACE(sizeof(struct timeval)) + CMSG_SPACE(sizeof(__u32))];
+static struct timeval tv;
+static struct cmsghdr *cmsg;
+
+void state_raw(void)
 {
 	char buf[MAXLEN];
 	int i, ret, items;
diff --git a/src/statistics.c b/src/statistics.c
index 9b26348..f44ae8a 100644
--- a/src/statistics.c
+++ b/src/statistics.c
@@ -14,7 +14,7 @@
 
 int statistics_ival = 0;
 
-struct timeval last_fired;
+static struct timeval last_fired;
 
 void *statistics_loop(void *ptr)
 {