diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
index 9d27a984e0..b4a3285db1 100644
--- a/cmd/zdb/zdb.c
+++ b/cmd/zdb/zdb.c
@@ -734,13 +734,19 @@ dump_ddt(ddt_t *ddt, enum ddt_type type, enum ddt_class class)
 static void
 dump_all_ddts(spa_t *spa)
 {
-	ddt_histogram_t ddh_total = { 0 };
-	ddt_stat_t dds_total = { 0 };
+	ddt_histogram_t ddh_total;
+	ddt_stat_t dds_total;
+	enum zio_checksum c;
+	enum ddt_type type;
+	enum ddt_class class;
 
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	bzero(&ddh_total, sizeof (ddt_histogram_t));
+	bzero(&dds_total, sizeof (ddt_stat_t));
+
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		ddt_t *ddt = spa->spa_ddt[c];
-		for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-			for (enum ddt_class class = 0; class < DDT_CLASSES;
+		for (type = 0; type < DDT_TYPES; type++) {
+			for (class = 0; class < DDT_CLASSES;
 			    class++) {
 				dump_ddt(ddt, type, class);
 			}
diff --git a/cmd/zpool/zpool_main.c b/cmd/zpool/zpool_main.c
index 992e4a8a7f..ccb13d44ba 100644
--- a/cmd/zpool/zpool_main.c
+++ b/cmd/zpool/zpool_main.c
@@ -2176,7 +2176,7 @@ get_interval_count(int *argcp, char **argv, unsigned long *iv,
     unsigned long *cnt)
 {
 	unsigned long interval = 0, count = 0;
-	int argc = *argcp, errno;
+	int argc = *argcp;
 
 	/*
 	 * Determine if the last argument is an integer or a pool name
@@ -3216,7 +3216,7 @@ print_scan_status(pool_scan_stat_t *ps)
 	 */
 	if (ps->pss_state == DSS_FINISHED) {
 		uint64_t minutes_taken = (end - start) / 60;
-		char *fmt;
+		char *fmt = NULL;
 
 		if (ps->pss_func == POOL_SCAN_SCRUB) {
 			fmt = gettext("scrub repaired %s in %lluh%um with "
diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 47b360721a..97211e01e7 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -1995,6 +1995,8 @@ ztest_io(ztest_ds_t *zd, uint64_t object, uint64_t offset)
 	case ZTEST_IO_SETATTR:
 		(void) ztest_setattr(zd, object);
 		break;
+	default:
+		break;
 	}
 
 	umem_free(data, blocksize);
@@ -5373,7 +5375,7 @@ print_time(hrtime_t t, char *timebuf)
 }
 
 static nvlist_t *
-make_random_props()
+make_random_props(void)
 {
 	nvlist_t *props;
 
diff --git a/lib/libzfs/libzfs_sendrecv.c b/lib/libzfs/libzfs_sendrecv.c
index eaa7d9a31c..9073f47a26 100644
--- a/lib/libzfs/libzfs_sendrecv.c
+++ b/lib/libzfs/libzfs_sendrecv.c
@@ -1235,7 +1235,7 @@ zfs_send(zfs_handle_t *zhp, const char *fromsnap, const char *tosnap,
 	if (flags.dedup) {
 		featureflags |= (DMU_BACKUP_FEATURE_DEDUP |
 		    DMU_BACKUP_FEATURE_DEDUPPROPS);
-		if (err = pipe(pipefd)) {
+		if ((err = pipe(pipefd))) {
 			zfs_error_aux(zhp->zfs_hdl, strerror(errno));
 			return (zfs_error(zhp->zfs_hdl, EZFS_PIPEFAILED,
 			    errbuf));
@@ -1243,7 +1243,7 @@ zfs_send(zfs_handle_t *zhp, const char *fromsnap, const char *tosnap,
 		dda.outputfd = outfd;
 		dda.inputfd = pipefd[1];
 		dda.dedup_hdl = zhp->zfs_hdl;
-		if (err = pthread_create(&tid, NULL, cksummer, &dda)) {
+		if ((err = pthread_create(&tid, NULL, cksummer, &dda))) {
 			(void) close(pipefd[0]);
 			(void) close(pipefd[1]);
 			zfs_error_aux(zhp->zfs_hdl, strerror(errno));
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 3e570f3964..2424ee974b 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -1453,10 +1453,11 @@ arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
 static void
 arc_hdr_destroy(arc_buf_hdr_t *hdr)
 {
+	l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
+
 	ASSERT(refcount_is_zero(&hdr->b_refcnt));
 	ASSERT3P(hdr->b_state, ==, arc_anon);
 	ASSERT(!HDR_IO_IN_PROGRESS(hdr));
-	l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
 
 	if (l2hdr != NULL) {
 		boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
diff --git a/module/zfs/bplist.c b/module/zfs/bplist.c
index 066ccc6b1e..5d1cf7e763 100644
--- a/module/zfs/bplist.c
+++ b/module/zfs/bplist.c
@@ -58,7 +58,7 @@ bplist_iterate(bplist_t *bpl, bplist_itor_t *func, void *arg, dmu_tx_t *tx)
 	bplist_entry_t *bpe;
 
 	mutex_enter(&bpl->bpl_lock);
-	while (bpe = list_head(&bpl->bpl_list)) {
+	while ((bpe = list_head(&bpl->bpl_list))) {
 		list_remove(&bpl->bpl_list, bpe);
 		mutex_exit(&bpl->bpl_lock);
 		func(arg, &bpe->bpe_blk, tx);
diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index 1a9ff752db..c7fc62a3a4 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -108,9 +108,9 @@ dbuf_find(dnode_t *dn, uint8_t level, uint64_t blkid)
 {
 	dbuf_hash_table_t *h = &dbuf_hash_table;
 	objset_t *os = dn->dn_objset;
-	uint64_t obj = dn->dn_object;
-	uint64_t hv = DBUF_HASH(os, obj, level, blkid);
-	uint64_t idx = hv & h->hash_table_mask;
+	uint64_t obj;
+	uint64_t hv;
+	uint64_t idx;
 	dmu_buf_impl_t *db;
 
 	obj = dn->dn_object;
@@ -2337,7 +2337,7 @@ dbuf_write_ready(zio_t *zio, arc_buf_t *buf, void *vdb)
 
 #ifdef ZFS_DEBUG
 	if (db->db_blkid == DMU_SPILL_BLKID) {
-		dnode_t *dn = db->db_dnode;
+		ASSERTV(dnode_t *dn = db->db_dnode);
 		ASSERT(dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR);
 		ASSERT(!(BP_IS_HOLE(db->db_blkptr)) &&
 		    db->db_blkptr == &dn->dn_phys->dn_spill);
@@ -2416,7 +2416,7 @@ dbuf_write_done(zio_t *zio, arc_buf_t *buf, void *vdb)
 
 #ifdef ZFS_DEBUG
 	if (db->db_blkid == DMU_SPILL_BLKID) {
-		dnode_t *dn = db->db_dnode;
+		ASSERTV(dnode_t *dn = db->db_dnode);
 		ASSERT(dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR);
 		ASSERT(!(BP_IS_HOLE(db->db_blkptr)) &&
 		    db->db_blkptr == &dn->dn_phys->dn_spill);
diff --git a/module/zfs/ddt.c b/module/zfs/ddt.c
index cd4e8476c2..7420173cc9 100644
--- a/module/zfs/ddt.c
+++ b/module/zfs/ddt.c
@@ -446,11 +446,15 @@ ddt_histogram_empty(const ddt_histogram_t *ddh)
 void
 ddt_get_dedup_object_stats(spa_t *spa, ddt_object_t *ddo_total)
 {
+	enum zio_checksum c;
+	enum ddt_type type;
+	enum ddt_class class;
+
 	/* Sum the statistics we cached in ddt_object_sync(). */
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		ddt_t *ddt = spa->spa_ddt[c];
-		for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-			for (enum ddt_class class = 0; class < DDT_CLASSES;
+		for (type = 0; type < DDT_TYPES; type++) {
+			for (class = 0; class < DDT_CLASSES;
 			    class++) {
 				ddt_object_t *ddo =
 				    &ddt->ddt_object_stats[type][class];
@@ -474,10 +478,14 @@ ddt_get_dedup_object_stats(spa_t *spa, ddt_object_t *ddo_total)
 void
 ddt_get_dedup_histogram(spa_t *spa, ddt_histogram_t *ddh)
 {
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	enum zio_checksum c;
+	enum ddt_type type;
+	enum ddt_class class;
+
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		ddt_t *ddt = spa->spa_ddt[c];
-		for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-			for (enum ddt_class class = 0; class < DDT_CLASSES;
+		for (type = 0; type < DDT_TYPES; type++) {
+			for (class = 0; class < DDT_CLASSES;
 			    class++) {
 				ddt_histogram_add(ddh,
 				    &ddt->ddt_histogram_cache[type][class]);
@@ -650,9 +658,10 @@ ddt_alloc(const ddt_key_t *ddk)
 static void
 ddt_free(ddt_entry_t *dde)
 {
-	ASSERT(!dde->dde_loading);
 	int p;
 
+	ASSERT(!dde->dde_loading);
+
 	for (p = 0; p < DDT_PHYS_TYPES; p++)
 		ASSERT(dde->dde_lead_zio[p] == NULL);
 
@@ -741,6 +750,8 @@ ddt_prefetch(spa_t *spa, const blkptr_t *bp)
 {
 	ddt_t *ddt;
 	ddt_entry_t dde;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	if (!BP_GET_DEDUP(bp))
 		return;
@@ -753,8 +764,8 @@ ddt_prefetch(spa_t *spa, const blkptr_t *bp)
 	ddt = ddt_select(spa, bp);
 	ddt_key_fill(&dde.dde_key, bp);
 
-	for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-		for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+	for (type = 0; type < DDT_TYPES; type++) {
+		for (class = 0; class < DDT_CLASSES; class++) {
 			ddt_object_prefetch(ddt, type, class, &dde);
 		}
 	}
@@ -812,15 +823,20 @@ ddt_table_free(ddt_t *ddt)
 void
 ddt_create(spa_t *spa)
 {
+	enum zio_checksum c;
+
 	spa->spa_dedup_checksum = ZIO_DEDUPCHECKSUM;
 
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++)
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++)
 		spa->spa_ddt[c] = ddt_table_alloc(spa, c);
 }
 
 int
 ddt_load(spa_t *spa)
 {
+	enum zio_checksum c;
+	enum ddt_type type;
+	enum ddt_class class;
 	int error;
 
 	ddt_create(spa);
@@ -832,10 +848,10 @@ ddt_load(spa_t *spa)
 	if (error)
 		return (error == ENOENT ? 0 : error);
 
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		ddt_t *ddt = spa->spa_ddt[c];
-		for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-			for (enum ddt_class class = 0; class < DDT_CLASSES;
+		for (type = 0; type < DDT_TYPES; type++) {
+			for (class = 0; class < DDT_CLASSES;
 			    class++) {
 				error = ddt_object_load(ddt, type, class);
 				if (error != 0 && error != ENOENT)
@@ -856,7 +872,9 @@ ddt_load(spa_t *spa)
 void
 ddt_unload(spa_t *spa)
 {
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	enum zio_checksum c;
+
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		if (spa->spa_ddt[c]) {
 			ddt_table_free(spa->spa_ddt[c]);
 			spa->spa_ddt[c] = NULL;
@@ -869,6 +887,8 @@ ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
 {
 	ddt_t *ddt;
 	ddt_entry_t dde;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	if (!BP_GET_DEDUP(bp))
 		return (B_FALSE);
@@ -880,8 +900,8 @@ ddt_class_contains(spa_t *spa, enum ddt_class max_class, const blkptr_t *bp)
 
 	ddt_key_fill(&dde.dde_key, bp);
 
-	for (enum ddt_type type = 0; type < DDT_TYPES; type++)
-		for (enum ddt_class class = 0; class <= max_class; class++)
+	for (type = 0; type < DDT_TYPES; type++)
+		for (class = 0; class <= max_class; class++)
 			if (ddt_object_lookup(ddt, type, class, &dde) == 0)
 				return (B_TRUE);
 
@@ -893,13 +913,15 @@ ddt_repair_start(ddt_t *ddt, const blkptr_t *bp)
 {
 	ddt_key_t ddk;
 	ddt_entry_t *dde;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	ddt_key_fill(&ddk, bp);
 
 	dde = ddt_alloc(&ddk);
 
-	for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-		for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+	for (type = 0; type < DDT_TYPES; type++) {
+		for (class = 0; class < DDT_CLASSES; class++) {
 			/*
 			 * We can only do repair if there are multiple copies
 			 * of the block.  For anything in the UNIQUE class,
@@ -1067,6 +1089,8 @@ ddt_sync_table(ddt_t *ddt, dmu_tx_t *tx, uint64_t txg)
 	spa_t *spa = ddt->ddt_spa;
 	ddt_entry_t *dde;
 	void *cookie = NULL;
+	enum ddt_type type;
+	enum ddt_class class;
 
 	if (avl_numnodes(&ddt->ddt_tree) == 0)
 		return;
@@ -1086,8 +1110,8 @@ ddt_sync_table(ddt_t *ddt, dmu_tx_t *tx, uint64_t txg)
 		ddt_free(dde);
 	}
 
-	for (enum ddt_type type = 0; type < DDT_TYPES; type++) {
-		for (enum ddt_class class = 0; class < DDT_CLASSES; class++) {
+	for (type = 0; type < DDT_TYPES; type++) {
+		for (class = 0; class < DDT_CLASSES; class++) {
 			if (!ddt_object_exists(ddt, type, class))
 				continue;
 			ddt_object_sync(ddt, type, class, tx);
@@ -1106,12 +1130,13 @@ ddt_sync(spa_t *spa, uint64_t txg)
 	dmu_tx_t *tx;
 	zio_t *rio = zio_root(spa, NULL, NULL,
 	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE);
+	enum zio_checksum c;
 
 	ASSERT(spa_syncing_txg(spa) == txg);
 
 	tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
 
-	for (enum zio_checksum c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
+	for (c = 0; c < ZIO_CHECKSUM_FUNCTIONS; c++) {
 		ddt_t *ddt = spa->spa_ddt[c];
 		if (ddt == NULL)
 			continue;
diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c
index fa8cf3808b..a23f6f53dc 100644
--- a/module/zfs/dmu.c
+++ b/module/zfs/dmu.c
@@ -1146,8 +1146,8 @@ dmu_sync_ready(zio_t *zio, arc_buf_t *buf, void *varg)
 {
 	dmu_sync_arg_t *dsa = varg;
 	dmu_buf_t *db = dsa->dsa_zgd->zgd_db;
-	dnode_t *dn = ((dmu_buf_impl_t *)db)->db_dnode;
 	blkptr_t *bp = zio->io_bp;
+	ASSERTV(dnode_t *dn = ((dmu_buf_impl_t *)db)->db_dnode);
 
 	if (zio->io_error == 0) {
 		if (BP_IS_HOLE(bp)) {
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index c9d2112fdf..04ac4b07c7 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -961,7 +961,6 @@ dmu_objset_write_ready(zio_t *zio, arc_buf_t *abuf, void *arg)
 	blkptr_t *bp = zio->io_bp;
 	objset_t *os = arg;
 	dnode_phys_t *dnp = &os->os_phys->os_meta_dnode;
-	ASSERTV(blkptr_t *bp_orig = &zio->io_bp_orig);
 
 	ASSERT(bp == os->os_rootbp);
 	ASSERT(BP_GET_TYPE(bp) == DMU_OT_OBJSET);
@@ -1223,7 +1222,7 @@ dmu_objset_userquota_get_ids(dnode_t *dn, boolean_t before, dmu_tx_t *tx)
 	objset_t *os = dn->dn_objset;
 	void *data = NULL;
 	dmu_buf_impl_t *db = NULL;
-	uint64_t *user, *group;
+	uint64_t *user = NULL, *group = NULL;
 	int flags = dn->dn_id_flags;
 	int error;
 	boolean_t have_spill = B_FALSE;
diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index 2cf2e8582f..daee8d44b8 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -996,6 +996,8 @@ backup_byteswap(dmu_replay_record_t *drr)
 		DO64(drr_end.drr_checksum.zc_word[3]);
 		DO64(drr_end.drr_toguid);
 		break;
+	default:
+		break;
 	}
 #undef DO64
 #undef DO32
@@ -1183,8 +1185,9 @@ restore_write_byref(struct restorearg *ra, objset_t *os,
 		ref_os = os;
 	}
 
-	if (err = dmu_buf_hold(ref_os, drrwbr->drr_refobject,
-	    drrwbr->drr_refoffset, FTAG, &dbp, DMU_READ_PREFETCH))
+	err = dmu_buf_hold(ref_os, drrwbr->drr_refobject,
+	    drrwbr->drr_refoffset, FTAG, &dbp, DMU_READ_PREFETCH);
+	if (err)
 		return (err);
 
 	tx = dmu_tx_create(os);
@@ -1441,7 +1444,7 @@ out:
 	if (featureflags & DMU_BACKUP_FEATURE_DEDUP) {
 		void *cookie = NULL;
 
-		while (gmep = avl_destroy_nodes(&ra.guid_to_ds_map, &cookie)) {
+		while ((gmep = avl_destroy_nodes(&ra.guid_to_ds_map, &cookie))) {
 			dsl_dataset_rele(gmep->gme_ds, &ra.guid_to_ds_map);
 			kmem_free(gmep, sizeof (guid_map_entry_t));
 		}
diff --git a/module/zfs/dmu_tx.c b/module/zfs/dmu_tx.c
index a270061388..719315d624 100644
--- a/module/zfs/dmu_tx.c
+++ b/module/zfs/dmu_tx.c
@@ -1218,7 +1218,7 @@ dmu_tx_do_callbacks(list_t *cb_list, int error)
 {
 	dmu_tx_callback_t *dcb;
 
-	while (dcb = list_head(cb_list)) {
+	while ((dcb = list_head(cb_list))) {
 		list_remove(cb_list, dcb);
 		dcb->dcb_func(dcb->dcb_data, error);
 		kmem_free(dcb, sizeof (dmu_tx_callback_t));
diff --git a/module/zfs/dmu_zfetch.c b/module/zfs/dmu_zfetch.c
index e80f3860b8..166b15916f 100644
--- a/module/zfs/dmu_zfetch.c
+++ b/module/zfs/dmu_zfetch.c
@@ -672,7 +672,7 @@ dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched)
 		ZFETCHSTAT_BUMP(zfetchstat_hits);
 	} else {
 		ZFETCHSTAT_BUMP(zfetchstat_misses);
-		if (fetched = dmu_zfetch_colinear(zf, &zst)) {
+		if ((fetched = dmu_zfetch_colinear(zf, &zst))) {
 			ZFETCHSTAT_BUMP(zfetchstat_colinear_hits);
 		} else {
 			ZFETCHSTAT_BUMP(zfetchstat_colinear_misses);
diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index d51d002308..b5935d127e 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -92,7 +92,7 @@ dsl_dataset_block_born(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx)
 	int used, compressed, uncompressed;
 	int64_t delta;
 
-	used = bp_get_dasize(tx->tx_pool->dp_spa, bp);
+	used = bp_get_dsize_sync(tx->tx_pool->dp_spa, bp);
 	compressed = BP_GET_PSIZE(bp);
 	uncompressed = BP_GET_UCSIZE(bp);
 
@@ -136,15 +136,17 @@ int
 dsl_dataset_block_kill(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx,
     boolean_t async)
 {
+	int used, compressed, uncompressed;
+
 	if (BP_IS_HOLE(bp))
 		return (0);
 
 	ASSERT(dmu_tx_is_syncing(tx));
 	ASSERT(bp->blk_birth <= tx->tx_txg);
 
-	int used = bp_get_dsize_sync(tx->tx_pool->dp_spa, bp);
-	int compressed = BP_GET_PSIZE(bp);
-	int uncompressed = BP_GET_UCSIZE(bp);
+	used = bp_get_dsize_sync(tx->tx_pool->dp_spa, bp);
+	compressed = BP_GET_PSIZE(bp);
+	uncompressed = BP_GET_UCSIZE(bp);
 
 	ASSERT(used > 0);
 	if (ds == NULL) {
@@ -1469,8 +1471,8 @@ static void
 remove_from_next_clones(dsl_dataset_t *ds, uint64_t obj, dmu_tx_t *tx)
 {
 	objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
-	uint64_t count;
 	int err;
+	ASSERTV(uint64_t count);
 
 	ASSERT(ds->ds_phys->ds_num_children >= 2);
 	err = zap_remove_int(mos, ds->ds_phys->ds_next_clones_obj, obj, tx);
@@ -1753,6 +1755,7 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, dmu_tx_t *tx)
 
 		if (dsl_dataset_is_snapshot(ds_next)) {
 			dsl_dataset_t *ds_nextnext;
+			dsl_dataset_t *hds;
 
 			/*
 			 * Update next's unique to include blocks which
@@ -1775,7 +1778,6 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, dmu_tx_t *tx)
 			ASSERT3P(ds_next->ds_prev, ==, NULL);
 
 			/* Collapse range in this head. */
-			dsl_dataset_t *hds;
 			VERIFY3U(0, ==, dsl_dataset_hold_obj(dp,
 			    ds->ds_dir->dd_phys->dd_head_dataset_obj,
 			    FTAG, &hds));
@@ -2477,7 +2479,6 @@ struct promotearg {
 };
 
 static int snaplist_space(list_t *l, uint64_t mintxg, uint64_t *spacep);
-static boolean_t snaplist_unstable(list_t *l);
 
 static int
 dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c
index 19114ef4cb..fec52874a4 100644
--- a/module/zfs/dsl_pool.c
+++ b/module/zfs/dsl_pool.c
@@ -692,9 +692,10 @@ upgrade_dir_clones_cb(spa_t *spa, uint64_t dsobj, const char *dsname, void *arg)
 void
 dsl_pool_upgrade_dir_clones(dsl_pool_t *dp, dmu_tx_t *tx)
 {
-	ASSERT(dmu_tx_is_syncing(tx));
 	uint64_t obj;
 
+	ASSERT(dmu_tx_is_syncing(tx));
+
 	(void) dsl_dir_create_sync(dp, dp->dp_root_dir, FREE_DIR_NAME, tx);
 	VERIFY(0 == dsl_pool_open_special_dir(dp,
 	    FREE_DIR_NAME, &dp->dp_free_dir));
diff --git a/module/zfs/dsl_prop.c b/module/zfs/dsl_prop.c
index d12d05a624..af99d74153 100644
--- a/module/zfs/dsl_prop.c
+++ b/module/zfs/dsl_prop.c
@@ -413,6 +413,8 @@ dsl_prop_check_prediction(dsl_dir_t *dd, dsl_prop_setarg_t *psa)
 		case ZFS_PROP_QUOTA:
 		case ZFS_PROP_RESERVATION:
 			return;
+		default:
+			break;
 		}
 	}
 
diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c
index e402dde7c3..6f095dad8e 100644
--- a/module/zfs/dsl_scan.c
+++ b/module/zfs/dsl_scan.c
@@ -1072,6 +1072,7 @@ dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx)
 {
 	dsl_pool_t *dp = scn->scn_dp;
 	dsl_dataset_t *ds;
+	char *dsname;
 
 	VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
 
@@ -1081,7 +1082,7 @@ dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx)
 	dmu_buf_will_dirty(ds->ds_dbuf, tx);
 	dsl_scan_visit_rootbp(scn, ds, &ds->ds_phys->ds_bp, tx);
 
-	char *dsname = kmem_alloc(ZFS_MAXNAMELEN, KM_SLEEP);
+	dsname = kmem_alloc(ZFS_MAXNAMELEN, KM_SLEEP);
 	dsl_dataset_name(ds, dsname);
 	zfs_dbgmsg("scanned dataset %llu (%s) with min=%llu max=%llu; "
 	    "pausing=%u",
@@ -1644,9 +1645,9 @@ dsl_scan_scrub_cb(dsl_pool_t *dp,
 	size_t size = BP_GET_PSIZE(bp);
 	spa_t *spa = dp->dp_spa;
 	uint64_t phys_birth = BP_PHYSICAL_BIRTH(bp);
-	boolean_t needs_io;
+	boolean_t needs_io = B_FALSE;
 	int zio_flags = ZIO_FLAG_SCRUB_THREAD | ZIO_FLAG_RAW | ZIO_FLAG_CANFAIL;
-	int zio_priority;
+	int zio_priority = 0;
 	int d;
 
 	if (phys_birth <= scn->scn_phys.scn_min_txg ||
diff --git a/module/zfs/include/sys/dmu.h b/module/zfs/include/sys/dmu.h
index 83932f467a..54115a08cb 100644
--- a/module/zfs/include/sys/dmu.h
+++ b/module/zfs/include/sys/dmu.h
@@ -528,8 +528,8 @@ int dmu_xuio_add(struct xuio *uio, struct arc_buf *abuf, offset_t off,
 int dmu_xuio_cnt(struct xuio *uio);
 struct arc_buf *dmu_xuio_arcbuf(struct xuio *uio, int i);
 void dmu_xuio_clear(struct xuio *uio, int i);
-void xuio_stat_wbuf_copied();
-void xuio_stat_wbuf_nocopy();
+void xuio_stat_wbuf_copied(void);
+void xuio_stat_wbuf_nocopy(void);
 
 extern int zfs_prefetch_disable;
 
diff --git a/module/zfs/include/sys/sa.h b/module/zfs/include/sys/sa.h
index e9a96a0f95..176bb3a179 100644
--- a/module/zfs/include/sys/sa.h
+++ b/module/zfs/include/sys/sa.h
@@ -148,8 +148,8 @@ int sa_replace_all_by_template(sa_handle_t *, sa_bulk_attr_t *,
 int sa_replace_all_by_template_locked(sa_handle_t *, sa_bulk_attr_t *,
     int, dmu_tx_t *);
 boolean_t sa_enabled(objset_t *);
-void sa_cache_init();
-void sa_cache_fini();
+void sa_cache_init(void);
+void sa_cache_fini(void);
 int sa_set_sa_object(objset_t *, uint64_t);
 int sa_hdrsize(void *);
 void sa_handle_lock(sa_handle_t *);
diff --git a/module/zfs/sa.c b/module/zfs/sa.c
index 17649274dd..ccbc620494 100644
--- a/module/zfs/sa.c
+++ b/module/zfs/sa.c
@@ -393,6 +393,8 @@ sa_attr_op(sa_handle_t *hdl, sa_bulk_attr_t *bulk, int count,
 			if (error)
 				return (error);
 			break;
+		default:
+			break;
 		}
 	}
 	return (error);
@@ -637,7 +639,7 @@ sa_build_layouts(sa_handle_t *hdl, sa_bulk_attr_t *attr_desc, int attr_count,
 	int buf_space;
 	sa_attr_type_t *attrs, *attrs_start;
 	int i, lot_count;
-	int hdrsize, spillhdrsize;
+	int hdrsize, spillhdrsize = 0;
 	int used;
 	dmu_object_type_t bonustype;
 	sa_lot_t *lot;
@@ -1020,16 +1022,16 @@ sa_tear_down(objset_t *os)
 	    sizeof (sa_attr_table_t) * sa->sa_num_attrs);
 
 	cookie = NULL;
-	while (layout = avl_destroy_nodes(&sa->sa_layout_hash_tree, &cookie)) {
+	while ((layout = avl_destroy_nodes(&sa->sa_layout_hash_tree, &cookie))){
 		sa_idx_tab_t *tab;
-		while (tab = list_head(&layout->lot_idx_tab)) {
+		while ((tab = list_head(&layout->lot_idx_tab))) {
 			ASSERT(refcount_count(&tab->sa_refcount));
 			sa_idx_tab_rele(os, tab);
 		}
 	}
 
 	cookie = NULL;
-	while (layout = avl_destroy_nodes(&sa->sa_layout_num_tree, &cookie)) {
+	while ((layout = avl_destroy_nodes(&sa->sa_layout_num_tree, &cookie))){
 		kmem_free(layout->lot_attrs,
 		    sizeof (sa_attr_type_t) * layout->lot_attr_count);
 		kmem_free(layout, sizeof (sa_lot_t));
@@ -1121,9 +1123,9 @@ sa_byteswap(sa_handle_t *hdl, sa_buf_type_t buftype)
 {
 	sa_hdr_phys_t *sa_hdr_phys = SA_GET_HDR(hdl, buftype);
 	dmu_buf_impl_t *db;
-	sa_os_t *sa = hdl->sa_os->os_sa;
 	int num_lengths = 1;
 	int i;
+	ASSERTV(sa_os_t *sa = hdl->sa_os->os_sa);
 
 	ASSERT(MUTEX_HELD(&sa->sa_lock));
 	if (sa_hdr_phys->sa_magic == SA_MAGIC)
@@ -1224,7 +1226,7 @@ sa_idx_tab_rele(objset_t *os, void *arg)
 static void
 sa_idx_tab_hold(objset_t *os, sa_idx_tab_t *idx_tab)
 {
-	sa_os_t *sa = os->os_sa;
+	ASSERTV(sa_os_t *sa = os->os_sa);
 
 	ASSERT(MUTEX_HELD(&sa->sa_lock));
 	(void) refcount_add(&idx_tab->sa_refcount, NULL);
@@ -1260,10 +1262,10 @@ sa_handle_get_from_db(objset_t *os, dmu_buf_t *db, void *userp,
     sa_handle_type_t hdl_type, sa_handle_t **handlepp)
 {
 	int error = 0;
-	dmu_object_info_t doi;
 	sa_handle_t *handle;
-
 #ifdef ZFS_DEBUG
+	dmu_object_info_t doi;
+
 	dmu_object_info_from_db(db, &doi);
 	ASSERT(doi.doi_bonus_type == DMU_OT_SA ||
 	    doi.doi_bonus_type == DMU_OT_ZNODE);
@@ -1302,7 +1304,7 @@ sa_handle_get(objset_t *objset, uint64_t objid, void *userp,
 	dmu_buf_t *db;
 	int error;
 
-	if (error = dmu_bonus_hold(objset, objid, NULL, &db))
+	if ((error = dmu_bonus_hold(objset, objid, NULL, &db)))
 		return (error);
 
 	return (sa_handle_get_from_db(objset, db, userp, hdl_type,
@@ -1402,8 +1404,8 @@ sa_find_idx_tab(objset_t *os, dmu_object_type_t bonustype, void *data)
 
 	/* Verify header size is consistent with layout information */
 	ASSERT(tb);
-	ASSERT(IS_SA_BONUSTYPE(bonustype) &&
-	    SA_HDR_SIZE_MATCH_LAYOUT(hdr, tb) || !IS_SA_BONUSTYPE(bonustype) ||
+	ASSERT((IS_SA_BONUSTYPE(bonustype) &&
+	    SA_HDR_SIZE_MATCH_LAYOUT(hdr, tb)) || !IS_SA_BONUSTYPE(bonustype) ||
 	    (IS_SA_BONUSTYPE(bonustype) && hdr->sa_layout_info == 0));
 
 	/*
@@ -1541,7 +1543,7 @@ sa_modify_attrs(sa_handle_t *hdl, sa_attr_type_t newattr,
 	sa_bulk_attr_t *attr_desc;
 	void *old_data[2];
 	int bonus_attr_count = 0;
-	int bonus_data_size, spill_data_size;
+	int bonus_data_size = 0, spill_data_size = 0;
 	int spill_attr_count = 0;
 	int error;
 	uint16_t length;
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index aa87a01942..98478761a3 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -1682,7 +1682,6 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
 	int orig_mode = spa->spa_mode;
 	int parse;
 	uint64_t obj;
-	int c;
 
 	/*
 	 * If this is an untrusted config, access the pool in read-only mode.
@@ -2712,6 +2711,7 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 	nvlist_t **spares, **l2cache;
 	uint_t nspares, nl2cache;
 	uint64_t version, obj;
+	int c;
 
 	/*
 	 * If this pool already exists, return failure.
@@ -5382,7 +5382,7 @@ spa_sync(spa_t *spa, uint64_t txg)
 		ddt_sync(spa, txg);
 		dsl_scan_sync(dp, tx);
 
-		while (vd = txg_list_remove(&spa->spa_vdev_txg_list, txg))
+		while ((vd = txg_list_remove(&spa->spa_vdev_txg_list, txg)))
 			vdev_sync(vd, txg);
 
 		if (pass == 1)
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index 5fd5beb075..3999bf7032 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -884,10 +884,9 @@ spa_vdev_config_enter(spa_t *spa)
 void
 spa_vdev_config_exit(spa_t *spa, vdev_t *vd, uint64_t txg, int error, char *tag)
 {
-	ASSERT(MUTEX_HELD(&spa_namespace_lock));
-
 	int config_changed = B_FALSE;
 
+	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 	ASSERT(txg > spa_last_synced_txg(spa));
 
 	spa->spa_pending_vdev = NULL;
diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index 8d677ee605..e1018ccc6a 100644
--- a/module/zfs/vdev.c
+++ b/module/zfs/vdev.c
@@ -1417,8 +1417,8 @@ vdev_validate(vdev_t *vd)
 void
 vdev_close(vdev_t *vd)
 {
-	ASSERTV(spa_t *spa = vd->vdev_spa);
 	vdev_t *pvd = vd->vdev_parent;
+	ASSERTV(spa_t *spa = vd->vdev_spa);
 
 	ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
 
@@ -1467,10 +1467,9 @@ vdev_hold(vdev_t *vd)
 void
 vdev_rele(vdev_t *vd)
 {
-	spa_t *spa = vd->vdev_spa;
 	int c;
 
-	ASSERT(spa_is_root(spa));
+	ASSERT(spa_is_root(vd->vdev_spa));
 	for (c = 0; c < vd->vdev_children; c++)
 		vdev_rele(vd->vdev_child[c]);
 
@@ -3075,10 +3074,10 @@ vdev_is_bootable(vdev_t *vd)
 void
 vdev_load_log_state(vdev_t *nvd, vdev_t *ovd)
 {
-	spa_t *spa = nvd->vdev_spa;
 	int c;
 
-	ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
+	ASSERT3S(spa_config_held(nvd->vdev_spa, SCL_STATE_ALL, RW_WRITER), ==,
+		 SCL_STATE_ALL);
 	ASSERT3U(nvd->vdev_guid, ==, ovd->vdev_guid);
 
 	for (c = 0; c < nvd->vdev_children; c++)
diff --git a/module/zfs/vdev_label.c b/module/zfs/vdev_label.c
index 09a958320c..e46120a362 100644
--- a/module/zfs/vdev_label.c
+++ b/module/zfs/vdev_label.c
@@ -1077,12 +1077,13 @@ vdev_label_sync_list(spa_t *spa, int l, uint64_t txg, int flags)
 	zio = zio_root(spa, NULL, NULL, flags);
 
 	for (vd = list_head(dl); vd != NULL; vd = list_next(dl, vd)) {
-		uint64_t *good_writes = kmem_zalloc(sizeof (uint64_t),
-		    KM_SLEEP);
+		uint64_t *good_writes;
+		zio_t *vio;
 
 		ASSERT(!vd->vdev_ishole);
 
-		zio_t *vio = zio_null(zio, spa, NULL,
+		good_writes = kmem_zalloc(sizeof (uint64_t), KM_SLEEP);
+		vio = zio_null(zio, spa, NULL,
 		    (vd->vdev_islog || vd->vdev_aux != NULL) ?
 		    vdev_label_sync_ignore_done : vdev_label_sync_top_done,
 		    good_writes, flags);
diff --git a/module/zfs/zap_micro.c b/module/zfs/zap_micro.c
index e121bf2e8e..aa86bdecb1 100644
--- a/module/zfs/zap_micro.c
+++ b/module/zfs/zap_micro.c
@@ -1043,12 +1043,13 @@ zap_update(objset_t *os, uint64_t zapobj, const char *name,
 {
 	zap_t *zap;
 	mzap_ent_t *mze;
-	uint64_t oldval;
 	const uint64_t *intval = val;
 	zap_name_t *zn;
 	int err;
 
 #ifdef ZFS_DEBUG
+	uint64_t oldval;
+
 	/*
 	 * If there is an old value, it shouldn't change across the
 	 * lockdir (eg, due to bprewrite's xlation).
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index d1159c453e..bc166465d2 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -1521,8 +1521,8 @@ zfs_ioc_vdev_split(zfs_cmd_t *zc)
 	if ((error = spa_open(zc->zc_name, &spa, FTAG)) != 0)
 		return (error);
 
-	if (error = get_nvlist(zc->zc_nvlist_conf, zc->zc_nvlist_conf_size,
-	    zc->zc_iflags, &config)) {
+	if ((error = get_nvlist(zc->zc_nvlist_conf, zc->zc_nvlist_conf_size,
+	    zc->zc_iflags, &config))) {
 		spa_close(spa, FTAG);
 		return (error);
 	}
@@ -1637,13 +1637,13 @@ zfs_ioc_objset_stats(zfs_cmd_t *zc)
  * local property values.
  */
 static int
-zfs_ioc_objset_recvd_props(zfs_cmd_t *zc)
+zfs_ioc_objset_recvd_props(struct file *filp, zfs_cmd_t *zc)
 {
 	objset_t *os = NULL;
 	int error;
 	nvlist_t *nv;
 
-	if (error = dmu_objset_hold(zc->zc_name, FTAG, &os))
+	if ((error = dmu_objset_hold(zc->zc_name, FTAG, &os)))
 		return (error);
 
 	/*
@@ -2368,8 +2368,8 @@ zfs_ioc_pool_set_props(zfs_cmd_t *zc)
 	int error;
 	nvpair_t *pair;
 
-	if (error = get_nvlist(zc->zc_nvlist_src, zc->zc_nvlist_src_size,
-	    zc->zc_iflags, &props))
+	if ((error = get_nvlist(zc->zc_nvlist_src, zc->zc_nvlist_src_size,
+	    zc->zc_iflags, &props)))
 		return (error);
 
 	/*
@@ -3090,8 +3090,8 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 
 	if (prop == ZPROP_INVAL) {
 		if (zfs_prop_user(propname)) {
-			if (err = zfs_secpolicy_write_perms(dsname,
-			    ZFS_DELEG_PERM_USERPROP, cr))
+			if ((err = zfs_secpolicy_write_perms(dsname,
+			    ZFS_DELEG_PERM_USERPROP, cr)))
 				return (err);
 			return (0);
 		}
@@ -3114,7 +3114,7 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 				return (EINVAL);
 			}
 
-			if (err = zfs_secpolicy_write_perms(dsname, perm, cr))
+			if ((err = zfs_secpolicy_write_perms(dsname, perm, cr)))
 				return (err);
 			return (0);
 		}
@@ -3198,6 +3198,8 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 				return (ENOTSUP);
 		}
 		break;
+	default:
+		break;
 	}
 
 	return (zfs_secpolicy_setprop(dsname, prop, pair, CRED()));
diff --git a/module/zfs/zfs_znode.c b/module/zfs/zfs_znode.c
index 0cd4a9771a..620ab9d5d7 100644
--- a/module/zfs/zfs_znode.c
+++ b/module/zfs/zfs_znode.c
@@ -1894,8 +1894,8 @@ zfs_obj_to_pobj(objset_t *osp, uint64_t obj, uint64_t *pobjp, int *is_xattrdir,
 	dmu_object_info_from_db(db, &doi);
 	if ((doi.doi_bonus_type != DMU_OT_SA &&
 	    doi.doi_bonus_type != DMU_OT_ZNODE) ||
-	    doi.doi_bonus_type == DMU_OT_ZNODE &&
-	    doi.doi_bonus_size < sizeof (znode_phys_t)) {
+	    (doi.doi_bonus_type == DMU_OT_ZNODE &&
+	    doi.doi_bonus_size < sizeof (znode_phys_t))) {
 		sa_buf_rele(db, FTAG);
 		return (EINVAL);
 	}
diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index 3c2b40a0c6..e35ad6f5af 100644
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -78,8 +78,6 @@ boolean_t zfs_nocacheflush = B_FALSE;
 
 static kmem_cache_t *zil_lwb_cache;
 
-static boolean_t zil_empty(zilog_t *zilog);
-
 #define	LWB_EMPTY(lwb) ((BP_GET_LSIZE(&lwb->lwb_blk) - \
     sizeof (zil_chain_t)) == (lwb->lwb_sz - lwb->lwb_nused))
 
@@ -287,6 +285,8 @@ zil_parse(zilog_t *zilog, zil_parse_blk_func_t *parse_blk_func,
 	char *lrbuf, *lrp;
 	int error = 0;
 
+	bzero(&next_blk, sizeof(blkptr_t));
+
 	/*
 	 * Old logs didn't record the maximum zh_claim_lr_seq.
 	 */
@@ -308,7 +308,7 @@ zil_parse(zilog_t *zilog, zil_parse_blk_func_t *parse_blk_func,
 	for (blk = zh->zh_log; !BP_IS_HOLE(&blk); blk = next_blk) {
 		uint64_t blk_seq = blk.blk_cksum.zc_word[ZIL_ZC_SEQ];
 		int reclen;
-		char *end;
+		char *end = NULL;
 
 		if (blk_seq > claim_blk_seq)
 			break;
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index 5df7d3b9f0..d951b68e25 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -1949,12 +1949,12 @@ static void
 zio_ddt_ditto_write_done(zio_t *zio)
 {
 	int p = DDT_PHYS_DITTO;
-	zio_prop_t *zp = &zio->io_prop;
 	blkptr_t *bp = zio->io_bp;
 	ddt_t *ddt = ddt_select(zio->io_spa, bp);
 	ddt_entry_t *dde = zio->io_private;
 	ddt_phys_t *ddp = &dde->dde_phys[p];
 	ddt_key_t *ddk = &dde->dde_key;
+	ASSERTV(zio_prop_t *zp = &zio->io_prop);
 
 	ddt_enter(ddt);
 
@@ -2171,6 +2171,8 @@ zio_dva_claim(zio_t *zio)
 static void
 zio_dva_unallocate(zio_t *zio, zio_gang_node_t *gn, blkptr_t *bp)
 {
+	int g;
+
 	ASSERT(bp->blk_birth == zio->io_txg || BP_IS_HOLE(bp));
 	ASSERT(zio->io_bp_override == NULL);