diff --git a/Makefile b/Makefile
index 133390f17..00e563c11 100644
--- a/Makefile
+++ b/Makefile
@@ -100,7 +100,7 @@ export PROTOUFIX DEFINES
 DEFINES			+= -D_FILE_OFFSET_BITS=64
 DEFINES			+= -D_GNU_SOURCE
 
-WARNINGS		:= -Wall -Wformat-security -Wdeclaration-after-statement
+WARNINGS		:= -Wall -Wformat-security -Wdeclaration-after-statement -Wstrict-prototypes
 
 CFLAGS-GCOV		:= --coverage -fno-exceptions -fno-inline -fprofile-update=atomic
 export CFLAGS-GCOV
diff --git a/criu/config.c b/criu/config.c
index e5d42efe4..73c62f5bb 100644
--- a/criu/config.c
+++ b/criu/config.c
@@ -853,7 +853,7 @@ bad_arg:
 	return 1;
 }
 
-int check_options()
+int check_options(void)
 {
 	if (opts.tcp_established_ok)
 		pr_info("Will dump/restore TCP connections\n");
diff --git a/criu/cr-check.c b/criu/cr-check.c
index 729b2dc38..17dd29b42 100644
--- a/criu/cr-check.c
+++ b/criu/cr-check.c
@@ -51,7 +51,7 @@
 #include "restorer.h"
 #include "uffd.h"
 
-static char *feature_name(int (*func)());
+static char *feature_name(int (*func)(void));
 
 static int check_tty(void)
 {
@@ -513,7 +513,7 @@ static int check_ipc(void)
 	return -1;
 }
 
-static int check_sigqueuinfo()
+static int check_sigqueuinfo(void)
 {
 	siginfo_t info = { .si_code = 1 };
 
@@ -960,7 +960,7 @@ static int clone_cb(void *_arg) {
 	exit(0);
 }
 
-static int check_clone_parent_vs_pid()
+static int check_clone_parent_vs_pid(void)
 {
 	struct clone_arg ca;
 	pid_t pid;
@@ -1447,7 +1447,7 @@ static int check_external_net_ns(void)
 
 struct feature_list {
 	char *name;
-	int (*func)();
+	int (*func)(void);
 };
 
 static struct feature_list feature_list[] = {
@@ -1517,7 +1517,7 @@ int check_add_feature(char *feat)
 	return -1;
 }
 
-static char *feature_name(int (*func)())
+static char *feature_name(int (*func)(void))
 {
 	struct feature_list *fl;
 
diff --git a/criu/cr-dump.c b/criu/cr-dump.c
index 4b5a01cfd..88323af92 100644
--- a/criu/cr-dump.c
+++ b/criu/cr-dump.c
@@ -1439,7 +1439,7 @@ err_cure_imgset:
 
 static int alarm_attempts = 0;
 
-bool alarm_timeouted() {
+bool alarm_timeouted(void) {
 	return alarm_attempts > 0;
 }
 
@@ -1456,7 +1456,7 @@ static void alarm_handler(int signo)
 	BUG();
 }
 
-static int setup_alarm_handler()
+static int setup_alarm_handler(void)
 {
 	struct sigaction sa = {
 		.sa_handler	= alarm_handler,
diff --git a/criu/cr-restore.c b/criu/cr-restore.c
index b920ce262..687cd6c68 100644
--- a/criu/cr-restore.c
+++ b/criu/cr-restore.c
@@ -182,13 +182,13 @@ static int __restore_wait_inprogress_tasks(int participants)
 	return 0;
 }
 
-static int restore_wait_inprogress_tasks()
+static int restore_wait_inprogress_tasks(void)
 {
 	return __restore_wait_inprogress_tasks(0);
 }
 
 /* Wait all tasks except the current one */
-static int restore_wait_other_tasks()
+static int restore_wait_other_tasks(void)
 {
 	int participants, stage;
 
@@ -1587,7 +1587,7 @@ static void restore_pgid(void)
 		futex_set_and_wake(&rsti(current)->pgrp_set, 1);
 }
 
-static int __legacy_mount_proc()
+static int __legacy_mount_proc(void)
 {
 	char proc_mountpoint[] = "/tmp/crtools-proc.XXXXXX";
 	int fd;
@@ -1941,7 +1941,7 @@ static int catch_tasks(bool root_seized, enum trace_flags *flag)
 	return 0;
 }
 
-static int clear_breakpoints()
+static int clear_breakpoints(void)
 {
 	struct pstree_item *item;
 	int ret = 0, i;
diff --git a/criu/cr-service.c b/criu/cr-service.c
index 549b3368b..279016bcd 100644
--- a/criu/cr-service.c
+++ b/criu/cr-service.c
@@ -1278,7 +1278,7 @@ static void reap_worker(int signo)
 	}
 }
 
-static int setup_sigchld_handler()
+static int setup_sigchld_handler(void)
 {
 	struct sigaction action;
 
@@ -1295,7 +1295,7 @@ static int setup_sigchld_handler()
 	return 0;
 }
 
-static int restore_sigchld_handler()
+static int restore_sigchld_handler(void)
 {
 	struct sigaction action;
 
diff --git a/criu/crtools.c b/criu/crtools.c
index 700fad994..9b6e94809 100644
--- a/criu/crtools.c
+++ b/criu/crtools.c
@@ -47,7 +47,7 @@
 #include "setproctitle.h"
 #include "sysctl.h"
 
-void flush_early_log_to_stderr() __attribute__((destructor));
+void flush_early_log_to_stderr(void) __attribute__((destructor));
 
 void flush_early_log_to_stderr(void)
 {
diff --git a/criu/fault-injection.c b/criu/fault-injection.c
index 4128814d5..4b0650008 100644
--- a/criu/fault-injection.c
+++ b/criu/fault-injection.c
@@ -3,7 +3,7 @@
 
 enum faults fi_strategy;
 
-int fault_injection_init()
+int fault_injection_init(void)
 {
 	char *val;
 	int start;
diff --git a/criu/include/cr_options.h b/criu/include/cr_options.h
index 2c1451e86..c5af33186 100644
--- a/criu/include/cr_options.h
+++ b/criu/include/cr_options.h
@@ -158,7 +158,7 @@ extern struct cr_options opts;
 char *rpc_cfg_file;
 
 extern int parse_options(int argc, char **argv, bool *usage_error, bool *has_exec_cmd, int state);
-extern int check_options();
-extern void init_opts();
+extern int check_options(void);
+extern void init_opts(void);
 
 #endif /* __CR_OPTIONS_H__ */
diff --git a/criu/include/lsm.h b/criu/include/lsm.h
index 3b8271282..a41915a4c 100644
--- a/criu/include/lsm.h
+++ b/criu/include/lsm.h
@@ -39,7 +39,7 @@ extern int lsm_check_opts(void);
 #ifdef CONFIG_HAS_SELINUX
 int dump_xattr_security_selinux(int fd, FdinfoEntry *e);
 int run_setsockcreatecon(FdinfoEntry *e);
-int reset_setsockcreatecon();
+int reset_setsockcreatecon(void);
 #else
 static inline int dump_xattr_security_selinux(int fd, FdinfoEntry *e) {
 	return 0;
@@ -47,7 +47,7 @@ static inline int dump_xattr_security_selinux(int fd, FdinfoEntry *e) {
 static inline int run_setsockcreatecon(FdinfoEntry *e) {
 	return 0;
 }
-static inline int reset_setsockcreatecon() {
+static inline int reset_setsockcreatecon(void) {
 	return 0;
 }
 #endif
diff --git a/criu/include/mount.h b/criu/include/mount.h
index d9b375f5d..8bf19b266 100644
--- a/criu/include/mount.h
+++ b/criu/include/mount.h
@@ -96,7 +96,7 @@ extern int collect_binfmt_misc(void);
 static inline int collect_binfmt_misc(void) { return 0; }
 #endif
 
-extern struct mount_info *mnt_entry_alloc();
+extern struct mount_info *mnt_entry_alloc(void);
 extern void mnt_entry_free(struct mount_info *mi);
 
 extern int __mntns_get_root_fd(pid_t pid);
diff --git a/criu/include/net.h b/criu/include/net.h
index 9976f6eb0..0a556f3da 100644
--- a/criu/include/net.h
+++ b/criu/include/net.h
@@ -31,7 +31,7 @@ extern int collect_net_namespaces(bool for_dump);
 
 extern int network_lock(void);
 extern void network_unlock(void);
-extern int network_lock_internal();
+extern int network_lock_internal(void);
 
 extern struct ns_desc net_ns_desc;
 
@@ -47,11 +47,11 @@ extern int move_veth_to_bridge(void);
 
 extern int kerndat_link_nsid(void);
 extern int net_get_nsid(int rtsk, int fd, int *nsid);
-extern struct ns_id *net_get_root_ns();
+extern struct ns_id *net_get_root_ns(void);
 extern int kerndat_nsid(void);
 extern void check_has_netns_ioc(int fd, bool *kdat_val, const char *name);
 extern int net_set_ext(struct ns_id *ns);
-extern struct ns_id *get_root_netns();
-extern int read_net_ns_img();
+extern struct ns_id *get_root_netns(void);
+extern int read_net_ns_img(void);
 
 #endif /* __CR_NET_H__ */
diff --git a/criu/include/tls.h b/criu/include/tls.h
index aa2517887..b48e4b480 100644
--- a/criu/include/tls.h
+++ b/criu/include/tls.h
@@ -4,7 +4,7 @@
 # ifdef CONFIG_GNUTLS
 
 int tls_x509_init(int sockfd, bool is_server);
-void tls_terminate_session();
+void tls_terminate_session(void);
 
 ssize_t tls_send(const void *buf, size_t len, int flags);
 ssize_t tls_recv(void *buf, size_t len, int flags);
diff --git a/criu/kerndat.c b/criu/kerndat.c
index b0dd83135..d1afde71d 100644
--- a/criu/kerndat.c
+++ b/criu/kerndat.c
@@ -364,7 +364,7 @@ no_dt:
 }
 
 /* The page frame number (PFN) is constant for the zero page */
-static int init_zero_page_pfn()
+static int init_zero_page_pfn(void)
 {
 	void *addr;
 	int ret = 0;
@@ -429,7 +429,7 @@ static int get_task_size(void)
 	return 0;
 }
 
-static int kerndat_fdinfo_has_lock()
+static int kerndat_fdinfo_has_lock(void)
 {
 	int fd, pfd = -1, exit_code = -1, len;
 	char buf[PAGE_SIZE];
@@ -464,7 +464,7 @@ out:
 	return exit_code;
 }
 
-static int get_ipv6()
+static int get_ipv6(void)
 {
 	if (access("/proc/sys/net/ipv6", F_OK) < 0) {
 		if (errno == ENOENT) {
diff --git a/criu/lsm.c b/criu/lsm.c
index 9d7e55c11..060f10259 100644
--- a/criu/lsm.c
+++ b/criu/lsm.c
@@ -133,7 +133,7 @@ static int selinux_get_sockcreate_label(pid_t pid, char **output)
 	return 0;
 }
 
-int reset_setsockcreatecon()
+int reset_setsockcreatecon(void)
 {
 	/* Currently this only works for SELinux. */
 	if (kdat.lsm != LSMTYPE__SELINUX)
diff --git a/criu/mount.c b/criu/mount.c
index 24a8516c6..180f2a62d 100644
--- a/criu/mount.c
+++ b/criu/mount.c
@@ -2140,7 +2140,7 @@ static int restore_ext_mount(struct mount_info *mi)
 
 static char mnt_clean_path[] = "/tmp/cr-tmpfs.XXXXXX";
 
-static int mount_clean_path()
+static int mount_clean_path(void)
 {
 	/*
 	 * To make a bind mount, we need to have access to a source directory,
@@ -2167,7 +2167,7 @@ static int mount_clean_path()
 	return 0;
 }
 
-static int umount_clean_path()
+static int umount_clean_path(void)
 {
 	if (umount2(mnt_clean_path, MNT_DETACH)) {
 		pr_perror("Unable to umount %s", mnt_clean_path);
@@ -2659,7 +2659,7 @@ static int find_remap_mounts(struct mount_info *root)
 }
 
 /* Move remapped mounts to places where they have to be */
-static int fixup_remap_mounts()
+static int fixup_remap_mounts(void)
 {
 	struct mnt_remap_entry *r;
 
diff --git a/criu/namespaces.c b/criu/namespaces.c
index 57f6bdfef..21266df7c 100644
--- a/criu/namespaces.c
+++ b/criu/namespaces.c
@@ -976,7 +976,7 @@ err:
 	return exit_code;
 }
 
-void free_userns_maps()
+void free_userns_maps(void)
 {
 	if (userns_entry.n_uid_map > 0) {
 		xfree(userns_entry.uid_map[0]);
diff --git a/criu/net.c b/criu/net.c
index 712837782..8e6cfaff1 100644
--- a/criu/net.c
+++ b/criu/net.c
@@ -1765,7 +1765,7 @@ static int __restore_links(struct ns_id *nsid, int *nrlinks, int *nrcreated)
 	return 0;
 }
 
-static int restore_links()
+static int restore_links(void)
 {
 	int nrcreated, nrlinks;
 	struct ns_id *nsid;
@@ -2080,7 +2080,7 @@ out:
  * iptables-restore is executed from a target userns and it may have not enough
  * rights to open /run/xtables.lock. Here we try to workaround this problem.
  */
-static int prepare_xtable_lock()
+static int prepare_xtable_lock(void)
 {
 	int fd;
 
@@ -2700,7 +2700,7 @@ err:
 	return ret;
 }
 
-int network_lock_internal()
+int network_lock_internal(void)
 {
 	char conf[] =	"*filter\n"
 				":CRIU - [0:0]\n"
@@ -2731,7 +2731,7 @@ int network_lock_internal()
 	return ret;
 }
 
-static int network_unlock_internal()
+static int network_unlock_internal(void)
 {
 	char conf[] =	"*filter\n"
 			":CRIU - [0:0]\n"
@@ -3284,7 +3284,7 @@ static int check_link_nsid(int rtsk, void *args)
 	return do_rtnl_req(rtsk, &req, sizeof(req), check_one_link_nsid, NULL, NULL, args);
 }
 
-int kerndat_link_nsid()
+int kerndat_link_nsid(void)
 {
 	int status;
 	pid_t pid;
diff --git a/criu/pstree.c b/criu/pstree.c
index 92b4167aa..19cf5ad38 100644
--- a/criu/pstree.c
+++ b/criu/pstree.c
@@ -608,7 +608,7 @@ err:
 }
 
 #define RESERVED_PIDS		300
-static int get_free_pid()
+static int get_free_pid(void)
 {
 	static struct pid *prev, *next;
 
diff --git a/criu/seize.c b/criu/seize.c
index e1e6b8195..fd314666f 100644
--- a/criu/seize.c
+++ b/criu/seize.c
@@ -194,7 +194,7 @@ static int seize_cgroup_tree(char *root_path, const char *state)
  * A freezer cgroup can contain tasks which will not be dumped
  * and we need to wait them, because the are interrupted them by ptrace.
  */
-static int freezer_wait_processes()
+static int freezer_wait_processes(void)
 {
 	int i;
 
diff --git a/criu/tls.c b/criu/tls.c
index db9cc4f5a..f7b94dee8 100644
--- a/criu/tls.c
+++ b/criu/tls.c
@@ -31,7 +31,7 @@ static gnutls_certificate_credentials_t x509_cred;
 static int tls_sk = -1;
 static int tls_sk_flags = 0;
 
-void tls_terminate_session()
+void tls_terminate_session(void)
 {
 	int ret;
 
@@ -227,7 +227,7 @@ static int tls_x509_verify_peer_cert(void)
 	return 0;
 }
 
-static int tls_handshake()
+static int tls_handshake(void)
 {
 	int ret = -1;
 	while (ret != GNUTLS_E_SUCCESS) {
@@ -241,7 +241,7 @@ static int tls_handshake()
 	return 0;
 }
 
-static int tls_x509_setup_creds()
+static int tls_x509_setup_creds(void)
 {
 	int ret;
 	char *cacert = CRIU_CACERT;
diff --git a/criu/util.c b/criu/util.c
index 3bae18ab2..1646ce1c4 100644
--- a/criu/util.c
+++ b/criu/util.c
@@ -326,7 +326,7 @@ int close_pid_proc(void)
 	return 0;
 }
 
-void close_proc()
+void close_proc(void)
 {
 	close_pid_proc();
 	close_service_fd(PROC_FD_OFF);
@@ -690,7 +690,7 @@ int cr_daemon(int nochdir, int noclose, int close_fd)
 	return 0;
 }
 
-int is_root_user()
+int is_root_user(void)
 {
 	if (geteuid() != 0) {
 		pr_err("You need to be root to run this command\n");
diff --git a/soccr/test/tcp-conn.c b/soccr/test/tcp-conn.c
index 1a1a5bb39..e31f58e7e 100644
--- a/soccr/test/tcp-conn.c
+++ b/soccr/test/tcp-conn.c
@@ -23,7 +23,7 @@ static void pr_printf(unsigned int level, const char *fmt, ...)
 	va_end(args);
 }
 
-int main()
+int main(void)
 {
 	union libsoccr_addr addr, dst;
 	int srv, sock, clnt, rst;
diff --git a/soccr/test/tcp-constructor.c b/soccr/test/tcp-constructor.c
index 89f201000..973dbf10c 100644
--- a/soccr/test/tcp-constructor.c
+++ b/soccr/test/tcp-constructor.c
@@ -20,7 +20,7 @@ struct tcp {
 	uint16_t wscale;
 };
 
-static void usage()
+static void usage(void)
 {
 	printf(
 		"Usage: --addr ADDR -port PORT --seq SEQ --next --addr ADDR -port PORT --seq SEQ -- CMD ...\n"
diff --git a/test/others/unix-callback/unix-client.c b/test/others/unix-callback/unix-client.c
index 69808b53c..676c4adbc 100644
--- a/test/others/unix-callback/unix-client.c
+++ b/test/others/unix-callback/unix-client.c
@@ -86,7 +86,7 @@ static int check_sock(int i)
 	return 0;
 }
 
-int main()
+int main(void)
 {
 	int i, fd;
 	sigset_t set;
diff --git a/test/others/unix-callback/unix-server.c b/test/others/unix-callback/unix-server.c
index 8f32f53dd..47bebd05d 100644
--- a/test/others/unix-callback/unix-server.c
+++ b/test/others/unix-callback/unix-server.c
@@ -19,7 +19,7 @@ struct ticket *tickets;
 
 #define SK_NAME "/tmp/criu.unix.callback.test"
 
-int main()
+int main(void)
 {
 	int sk, ret, id;
 	char buf[4096];
diff --git a/test/zdtm/Makefile.inc b/test/zdtm/Makefile.inc
index 6958d128e..43763321f 100644
--- a/test/zdtm/Makefile.inc
+++ b/test/zdtm/Makefile.inc
@@ -38,7 +38,7 @@ ifeq ($(origin CC), default)
         CC := $(CROSS_COMPILE)$(HOSTCC)
 endif
 CFLAGS	+= -g -O2 -Wall -Werror -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0
-CFLAGS	+= -Wdeclaration-after-statement
+CFLAGS	+= -Wdeclaration-after-statement -Wstrict-prototypes
 CFLAGS	+= $(USERCFLAGS)
 CFLAGS	+= -D_GNU_SOURCE
 CPPFLAGS += -iquote $(LIBDIR)/arch/$(ARCH)/include
diff --git a/test/zdtm/lib/test.c b/test/zdtm/lib/test.c
index a1bdfc1b4..630476de0 100644
--- a/test/zdtm/lib/test.c
+++ b/test/zdtm/lib/test.c
@@ -71,7 +71,7 @@ static void test_fini(void)
 	unlinkat(cwd, pidfile, 0);
 }
 
-static void setup_outfile()
+static void setup_outfile(void)
 {
 	if (!access(outfile, F_OK) || errno != ENOENT) {
 		fprintf(stderr, "Output file %s appears to exist, aborting\n",
@@ -93,7 +93,7 @@ static void setup_outfile()
 		exit(1);
 }
 
-static void redir_stdfds()
+static void redir_stdfds(void)
 {
 	int nullfd;
 
@@ -346,7 +346,7 @@ void test_init(int argc, char **argv)
 	srand48(time(NULL));	/* just in case we need it */
 }
 
-void test_daemon()
+void test_daemon(void)
 {
 	futex_set_and_wake(&test_shared_state->stage, TEST_RUNNING_STAGE);
 }
diff --git a/test/zdtm/static/apparmor.c b/test/zdtm/static/apparmor.c
index 15930c761..b3a4d7549 100644
--- a/test/zdtm/static/apparmor.c
+++ b/test/zdtm/static/apparmor.c
@@ -15,7 +15,7 @@ const char *test_author	= "Tycho Andersen <tycho.andersen@canonical.com>";
 
 #define PROFILE "criu_test"
 
-int setprofile()
+int setprofile(void)
 {
 	char profile[1024];
 	int fd, len;
@@ -45,7 +45,7 @@ int setprofile()
 	return 0;
 }
 
-int checkprofile()
+int checkprofile(void)
 {
 	FILE *f;
 	char path[PATH_MAX], profile[1024];
diff --git a/test/zdtm/static/child_subreaper_and_reparent.c b/test/zdtm/static/child_subreaper_and_reparent.c
index 57943a67b..e3955d3d9 100644
--- a/test/zdtm/static/child_subreaper_and_reparent.c
+++ b/test/zdtm/static/child_subreaper_and_reparent.c
@@ -25,7 +25,7 @@ struct shared {
 	int parent_after_cr;
 } *sh;
 
-int orphan()
+int orphan(void)
 {
 	/*
 	 * Wait until reparented to the pidns init. (By waiting
@@ -45,7 +45,7 @@ int orphan()
 	return 0;
 }
 
-int helper()
+int helper(void)
 {
 	int pid;
 
@@ -59,7 +59,7 @@ int helper()
 	return 0;
 }
 
-int subreaper()
+int subreaper(void)
 {
 	int pid, ret, status;
 
diff --git a/test/zdtm/static/child_subreaper_existing_child.c b/test/zdtm/static/child_subreaper_existing_child.c
index 28e9dbb8a..8291aba08 100644
--- a/test/zdtm/static/child_subreaper_existing_child.c
+++ b/test/zdtm/static/child_subreaper_existing_child.c
@@ -24,7 +24,7 @@ struct shared {
 } *sh;
 
 
-int orphan()
+int orphan(void)
 {
 	/* Return the control back to MAIN worker to do C/R */
 	futex_set_and_wake(&sh->fstate, TEST_CRIU);
@@ -36,7 +36,7 @@ int orphan()
 	return 0;
 }
 
-int helper()
+int helper(void)
 {
 	int pid;
 
@@ -52,7 +52,7 @@ int helper()
 	return 0;
 }
 
-int subreaper()
+int subreaper(void)
 {
 	int pid, ret, status;
 
diff --git a/test/zdtm/static/dumpable02.c b/test/zdtm/static/dumpable02.c
index 024371bd8..7e2eee2d1 100644
--- a/test/zdtm/static/dumpable02.c
+++ b/test/zdtm/static/dumpable02.c
@@ -13,7 +13,7 @@
 const char *test_doc    = "Check dumpable flag handling (non-dumpable case)";
 const char *test_author = "Filipe Brandenburger <filbranden@google.com>";
 
-int dumpable_server() {
+int dumpable_server(void) {
 	char buf[256];
 	int ret;
 
diff --git a/test/zdtm/static/fdt_shared.c b/test/zdtm/static/fdt_shared.c
index 2111356f5..a84444af5 100644
--- a/test/zdtm/static/fdt_shared.c
+++ b/test/zdtm/static/fdt_shared.c
@@ -22,7 +22,7 @@ TEST_OPTION(filename, string, "file name", 1);
 #define CHILDREN 4
 static int fork_pfd[2];
 
-static void forked()
+static void forked(void)
 {
 	char c = 0;
 
@@ -32,7 +32,7 @@ static void forked()
 	}
 }
 
-static void wait_children()
+static void wait_children(void)
 {
 	int i;
 	char c;
diff --git a/test/zdtm/static/file_locks00.c b/test/zdtm/static/file_locks00.c
index 59e19cfe1..fa98a31b3 100644
--- a/test/zdtm/static/file_locks00.c
+++ b/test/zdtm/static/file_locks00.c
@@ -101,7 +101,7 @@ static int check_write_lock(int fd, int whence, off_t offset, off_t len)
 	return -1;
 }
 
-static int check_file_locks()
+static int check_file_locks(void)
 {
 	int fd_0, fd_1;
 	int ret0, ret1;
diff --git a/test/zdtm/static/inotify_system.c b/test/zdtm/static/inotify_system.c
index 59f47c41c..3e6b2ad48 100644
--- a/test/zdtm/static/inotify_system.c
+++ b/test/zdtm/static/inotify_system.c
@@ -68,7 +68,7 @@ typedef struct {
 	int dir;
 } desc;
 
-void do_wait() {
+void do_wait(void) {
 	test_daemon();
 	test_waitsig();
 }
diff --git a/test/zdtm/static/maps00.c b/test/zdtm/static/maps00.c
index a6c68cd25..f2da9b975 100644
--- a/test/zdtm/static/maps00.c
+++ b/test/zdtm/static/maps00.c
@@ -123,7 +123,7 @@ static void segfault(int signo)
  * after test func should be placed check map, because size of test_func
  * is calculated as (check_map-test_func)
  */
-int test_func()
+int test_func(void)
 {
 	return 1;
 }
@@ -176,8 +176,9 @@ static int check_map(struct map *map)
 			memcpy(map->ptr,test_func, getpagesize());
 		} else {
 			if (!(map->flag & MAP_ANONYMOUS)) {
+				uint8_t funlen = (uint8_t *)check_map - (uint8_t *)test_func;
 				lseek(map->fd,0,SEEK_SET);
-				if (write(map->fd,test_func,check_map - test_func)<check_map - test_func) {
+				if (write(map->fd,test_func,funlen)<funlen) {
 					pr_perror("failed to write %s", map->filename);
 					return -1;
 				}
@@ -185,7 +186,7 @@ static int check_map(struct map *map)
 		}
 		if (!(map->flag & MAP_ANONYMOUS) || map->prot & PROT_WRITE)
 			/* Function body has been copied into the mapping */
-			((int (*)())map->ptr)();	/* perform exec access */
+			((int (*)(void))map->ptr)();	/* perform exec access */
 		else
 			/* No way to copy function body into mapping,
 			 * clear exec bit from effective protection
diff --git a/test/zdtm/static/selinux00.c b/test/zdtm/static/selinux00.c
index db8420eac..b5b3e3cc0 100644
--- a/test/zdtm/static/selinux00.c
+++ b/test/zdtm/static/selinux00.c
@@ -26,14 +26,14 @@ const char *test_author	= "Adrian Reber <areber@redhat.com>";
  */
 char state;
 
-int check_for_selinux()
+int check_for_selinux(void)
 {
 	if (access("/sys/fs/selinux", F_OK) == 0)
 		return 0;
 	return 1;
 }
 
-int setprofile()
+int setprofile(void)
 {
 	int fd, len;
 
@@ -54,7 +54,7 @@ int setprofile()
 	return 0;
 }
 
-int checkprofile()
+int checkprofile(void)
 {
 	int fd;
 	char context[1024];
@@ -83,7 +83,7 @@ int checkprofile()
 	return 0;
 }
 
-int check_sockcreate()
+int check_sockcreate(void)
 {
 	char *output = NULL;
 	FILE *f = fopen("/proc/self/attr/sockcreate", "r");
diff --git a/test/zdtm/static/selinux01.c b/test/zdtm/static/selinux01.c
index cec5980e8..cbf145d2a 100644
--- a/test/zdtm/static/selinux01.c
+++ b/test/zdtm/static/selinux01.c
@@ -28,14 +28,14 @@ const char *test_author	= "Adrian Reber <areber@redhat.com>";
  */
 char state;
 
-int check_for_selinux()
+int check_for_selinux(void)
 {
 	if (access("/sys/fs/selinux", F_OK) == 0)
 		return 0;
 	return 1;
 }
 
-int setprofile()
+int setprofile(void)
 {
 	int fd, len;
 
@@ -56,7 +56,7 @@ int setprofile()
 	return 0;
 }
 
-int set_sockcreate()
+int set_sockcreate(void)
 {
 	int fd, len;
 
@@ -77,7 +77,7 @@ int set_sockcreate()
 	return 0;
 }
 
-int check_sockcreate()
+int check_sockcreate(void)
 {
 	int fd;
 	char context[1024];
@@ -106,7 +106,7 @@ int check_sockcreate()
 	return 0;
 }
 
-int check_sockcreate_empty()
+int check_sockcreate_empty(void)
 {
 	char *output = NULL;
 	FILE *f = fopen("/proc/self/attr/sockcreate", "r");
diff --git a/test/zdtm/static/session02.c b/test/zdtm/static/session02.c
index 37f245d2e..f5c81df16 100644
--- a/test/zdtm/static/session02.c
+++ b/test/zdtm/static/session02.c
@@ -25,7 +25,7 @@ struct process *processes;
 int nr_processes = 20;
 int current = 0;
 
-static void cleanup()
+static void cleanup(void)
 {
 	int i;
 
@@ -55,9 +55,9 @@ struct command
 	int		arg2;
 };
 
-static void handle_command();
+static void handle_command(void);
 
-static void mainloop()
+static void mainloop(void)
 {
 	while (1)
 		handle_command();
@@ -100,7 +100,7 @@ static int make_child(int id, int flags)
 	return cid;
 }
 
-static void handle_command()
+static void handle_command(void)
 {
 	int sk = processes[current].sks[0], ret, status = 0;
 	struct command cmd;
diff --git a/test/zdtm/static/session03.c b/test/zdtm/static/session03.c
index 2b3c46c32..8ca16e410 100644
--- a/test/zdtm/static/session03.c
+++ b/test/zdtm/static/session03.c
@@ -36,7 +36,7 @@ static void sigchld_handler(int signal, siginfo_t *siginfo, void *data)
 		waitpid(pid, NULL, WNOHANG);
 }
 
-static void cleanup()
+static void cleanup(void)
 {
 	int i, ret;
 
@@ -72,7 +72,7 @@ enum commands
 
 int cmd_weght[TEST_MAX] = {10, 3, 1, 10, 7};
 int sum_weight = 0;
-static int get_rnd_op()
+static int get_rnd_op(void)
 {
 	int i, m;
 	if (sum_weight == 0) {
@@ -97,9 +97,9 @@ struct command
 	int		arg2;
 };
 
-static void handle_command();
+static void handle_command(void);
 
-static void mainloop()
+static void mainloop(void)
 {
 	while (1)
 		handle_command();
@@ -142,7 +142,7 @@ static int make_child(int id, int flags)
 	return cid;
 }
 
-static void handle_command()
+static void handle_command(void)
 {
 	int sk = processes[current].sks[0], ret, status = 0;
 	struct command cmd;
diff --git a/test/zdtm/transition/netlink00.c b/test/zdtm/transition/netlink00.c
index c9b2303e8..3504a48a1 100644
--- a/test/zdtm/transition/netlink00.c
+++ b/test/zdtm/transition/netlink00.c
@@ -56,12 +56,12 @@ struct rtmsg *rtp;
 int rtl;
 struct rtattr *rtap;
 
-int send_request();
-int recv_reply();
-int form_request_add();
-int form_request_del();
-int read_reply();
-typedef int (*cmd_t)();
+int send_request(void);
+int recv_reply(void);
+int form_request_add(void);
+int form_request_del(void);
+int read_reply(void);
+typedef int (*cmd_t)(void);
 #define CMD_NUM 2
 cmd_t cmd[CMD_NUM]={form_request_add, form_request_del};
 
@@ -120,7 +120,7 @@ out:
 	return 0;
 }
 
-int send_request()
+int send_request(void)
 {
 	// create the remote address
 	// to communicate
@@ -145,7 +145,7 @@ int send_request()
 	}
 	return 0;
 }
-int recv_reply()
+int recv_reply(void)
 {
 	char *p;
 	// initialize the socket read buffer
@@ -191,7 +191,7 @@ int recv_reply()
 	return 0;
 }
 
-int read_reply()
+int read_reply(void)
 {
 	//string to hold content of the route
 	// table (i.e. one entry)
@@ -250,7 +250,7 @@ int read_reply()
 #define NLMSG_TAIL(nmsg) \
         ((struct rtattr *) (((void *) (nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len)))
 
-int form_request_del()
+int form_request_del(void)
 {
 	bzero(&req, sizeof(req));
 	req.nl.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
@@ -272,7 +272,7 @@ int form_request_del()
 	return 0;
 }
 
-int form_request_add()
+int form_request_add(void)
 {
 	int ifcn = 1; //interface number