diff --git a/tests/zfs-tests/cmd/btree_test/btree_test.c b/tests/zfs-tests/cmd/btree_test/btree_test.c
index 8de14ff2a266..aaad4e47e464 100644
--- a/tests/zfs-tests/cmd/btree_test/btree_test.c
+++ b/tests/zfs-tests/cmd/btree_test/btree_test.c
@@ -294,6 +294,7 @@ drain_tree(zfs_btree_t *bt, char *why)
 static int
 stress_tree(zfs_btree_t *bt, char *why)
 {
+	(void) why;
 	avl_tree_t avl;
 	int_node_t *node;
 	struct timeval tp;
diff --git a/tests/zfs-tests/cmd/largest_file/largest_file.c b/tests/zfs-tests/cmd/largest_file/largest_file.c
index 00e1019cc8e4..912607640965 100644
--- a/tests/zfs-tests/cmd/largest_file/largest_file.c
+++ b/tests/zfs-tests/cmd/largest_file/largest_file.c
@@ -137,9 +137,9 @@ usage(char *name)
 	exit(1);
 }
 
-/* ARGSUSED */
 static void
 sigxfsz(int signo)
 {
+	(void) signo;
 	(void) printf("\nlargest_file: sigxfsz() caught SIGXFSZ\n");
 }
diff --git a/tests/zfs-tests/cmd/mmap_libaio/mmap_libaio.c b/tests/zfs-tests/cmd/mmap_libaio/mmap_libaio.c
index 21119ebca9d6..a02f46d91b30 100644
--- a/tests/zfs-tests/cmd/mmap_libaio/mmap_libaio.c
+++ b/tests/zfs-tests/cmd/mmap_libaio/mmap_libaio.c
@@ -52,6 +52,7 @@ do_sync_io(struct iocb *iocb)
 int
 main(int argc, char **argv)
 {
+	(void) argc;
 	char *buf;
 	int page_size = getpagesize();
 	int buf_size = strtol(argv[2], NULL, 0);
diff --git a/tests/zfs-tests/cmd/rename_dir/rename_dir.c b/tests/zfs-tests/cmd/rename_dir/rename_dir.c
index 5f80f7229462..897ec7b84148 100644
--- a/tests/zfs-tests/cmd/rename_dir/rename_dir.c
+++ b/tests/zfs-tests/cmd/rename_dir/rename_dir.c
@@ -49,7 +49,7 @@
 #include <strings.h>
 
 int
-main(int argc, char *argvp[])
+main(void)
 {
 	int i = 1;
 
diff --git a/tests/zfs-tests/cmd/rm_lnkcnt_zero_file/rm_lnkcnt_zero_file.c b/tests/zfs-tests/cmd/rm_lnkcnt_zero_file/rm_lnkcnt_zero_file.c
index e262ecefea92..f8b6e3e808bb 100644
--- a/tests/zfs-tests/cmd/rm_lnkcnt_zero_file/rm_lnkcnt_zero_file.c
+++ b/tests/zfs-tests/cmd/rm_lnkcnt_zero_file/rm_lnkcnt_zero_file.c
@@ -55,10 +55,10 @@ pickidx(void)
 	return (random() % 1000);
 }
 
-/* ARGSUSED */
 static void *
 mover(void *a)
 {
+	(void) a;
 	char buf[256];
 	int idx, len, ret;
 
@@ -75,10 +75,10 @@ mover(void *a)
 	return (NULL);
 }
 
-/* ARGSUSED */
 static void *
 cleaner(void *a)
 {
+	(void) a;
 	char buf[256];
 	int idx, len, ret;
 
diff --git a/tests/zfs-tests/cmd/xattrtest/xattrtest.c b/tests/zfs-tests/cmd/xattrtest/xattrtest.c
index 0b68126c0327..49b6629ba056 100644
--- a/tests/zfs-tests/cmd/xattrtest/xattrtest.c
+++ b/tests/zfs-tests/cmd/xattrtest/xattrtest.c
@@ -96,12 +96,12 @@ static char script[PATH_MAX] = "/bin/true";
 static char xattrbytes[XATTR_SIZE_MAX];
 
 static int
-usage(int argc, char **argv)
+usage(char *argv0)
 {
 	fprintf(stderr,
 	    "usage: %s [-hvycdrRk] [-n <nth>] [-f <files>] [-x <xattrs>]\n"
 	    "       [-s <bytes>] [-p <path>] [-t <script> ] [-o <phase>]\n",
-	    argv[0]);
+	    argv0);
 
 	fprintf(stderr,
 	    "  --help        -h           This help\n"
@@ -136,7 +136,7 @@ parse_args(int argc, char **argv)
 	while ((c = getopt_long(argc, argv, shortopts, longopts, NULL)) != -1) {
 		switch (c) {
 		case 'h':
-			return (usage(argc, argv));
+			return (usage(argv[0]));
 		case 'v':
 			verbose++;
 			break;
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_events/ereports.c b/tests/zfs-tests/tests/functional/cli_root/zpool_events/ereports.c
index f825240000f7..bff3bb1ee808 100644
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_events/ereports.c
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_events/ereports.c
@@ -146,9 +146,8 @@ ereports_dump(libzfs_handle_t *zhdl, int zevent_fd)
 	}
 }
 
-/* ARGSUSED */
 int
-main(int argc, char **argv)
+main(void)
 {
 	libzfs_handle_t *hdl;
 	int fd;
diff --git a/tests/zfs-tests/tests/functional/ctime/ctime.c b/tests/zfs-tests/tests/functional/ctime/ctime.c
index b755be2feb29..41dcf6abc9c2 100644
--- a/tests/zfs-tests/tests/functional/ctime/ctime.c
+++ b/tests/zfs-tests/tests/functional/ctime/ctime.c
@@ -303,9 +303,8 @@ static timetest_t timetest_table[] = {
 
 #define	NCOMMAND (sizeof (timetest_table) / sizeof (timetest_table[0]))
 
-/* ARGSUSED */
 int
-main(int argc, char *argv[])
+main(void)
 {
 	int i, ret, fd;
 	char *penv[] = {"TESTDIR", "TESTFILE0"};
diff --git a/tests/zfs-tests/tests/functional/hkdf/hkdf_test.c b/tests/zfs-tests/tests/functional/hkdf/hkdf_test.c
index dd23da332c9a..5fff3e09ed04 100644
--- a/tests/zfs-tests/tests/functional/hkdf/hkdf_test.c
+++ b/tests/zfs-tests/tests/functional/hkdf/hkdf_test.c
@@ -211,7 +211,7 @@ run_test(int i, hkdf_tv_t *tv)
 }
 
 int
-main(int argc, char **argv)
+main(void)
 {
 	int ret, i;
 
diff --git a/tests/zfs-tests/tests/functional/libzfs/many_fds.c b/tests/zfs-tests/tests/functional/libzfs/many_fds.c
index e09ed60eef9a..6def57c5a51a 100644
--- a/tests/zfs-tests/tests/functional/libzfs/many_fds.c
+++ b/tests/zfs-tests/tests/functional/libzfs/many_fds.c
@@ -35,9 +35,8 @@
 /*
  * Check if libzfs works with more than 255 held file handles.
  */
-/* ARGSUSED */
 int
-main(int argc, char **argv)
+main(void)
 {
 	int i;
 	struct rlimit limit;
diff --git a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_001_pos.c b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_001_pos.c
index b0c236081928..d40da0d2ba62 100644
--- a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_001_pos.c
+++ b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_001_pos.c
@@ -31,15 +31,13 @@
 static void
 fill_random(char *buf, int len)
 {
-	int i;
 	srand(time(NULL));
-	for (i = 0; i < len; i++) {
+	for (int i = 0; i < len; i++)
 		buf[i] = (char)rand();
-	}
 }
 
 int
-main(int argc, char *argv[])
+main(void)
 {
 	int i, fd;
 	char buf1[BSZ], buf2[BSZ] = {};
diff --git a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_002_pos.c b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_002_pos.c
index c92e6127d6a3..55d939abd23b 100644
--- a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_002_pos.c
+++ b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_002_pos.c
@@ -25,7 +25,7 @@
  */
 
 int
-main(int argc, char *argv[])
+main(void)
 {
 	int i, fd, ret;
 	char spath[1024], dpath[1024];
diff --git a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_003_pos.c b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_003_pos.c
index 477ef3f81948..58aa9051215e 100644
--- a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_003_pos.c
+++ b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_003_pos.c
@@ -24,7 +24,7 @@
  */
 
 int
-main(int argc, char *argv[])
+main(void)
 {
 	int i, fd;
 	char spath[1024], dpath[1024];
diff --git a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_stat_mode.c b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_stat_mode.c
index bf71d429c3fd..c72ea2bb6ad7 100644
--- a/tests/zfs-tests/tests/functional/tmpfile/tmpfile_stat_mode.c
+++ b/tests/zfs-tests/tests/functional/tmpfile/tmpfile_stat_mode.c
@@ -110,7 +110,7 @@ test_stat_mode(mode_t mask)
 }
 
 int
-main(int argc, char *argv[])
+main(void)
 {
 	fprintf(stdout, "Verify stat(2) for O_TMPFILE file considers umask.\n");