treewide: Cleanup free() calls.

It's perfectly fine to call free(NULL).  Take advantage of that to
simplify the code.  Use the safer CONST_CAST way of "unconsting"
pointers we pass to free while we're at it.

Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Mark Michelson <mmichels@redhat.com>

controller/ovn-controller.c

@@ -688,9 +688,7 @@ add_pending_ct_zone_entry(struct shash *pending_ct_zones,
      */
     struct ct_zone_pending_entry *existing =
         shash_replace(pending_ct_zones, name, pending);
-    if (existing) {
-        free(existing);
-    }
+    free(existing);
 }
 
 static bool
@@ -6099,12 +6097,8 @@ main(int argc, char *argv[])
 
     ovs_feature_support_destroy();
     free(ovs_remote);
-    if (file_system_id) {
-        free(file_system_id);
-    }
-    if (cli_system_id) {
-        free(cli_system_id);
-    }
+    free(file_system_id);
+    free(cli_system_id);
     ovn_exit_args_finish(&exit_args);
     unixctl_server_destroy(unixctl);
     service_stop();

controller/pinctrl.c

@@ -1282,10 +1282,7 @@ fill_ipv6_prefix_state(struct ovsdb_idl_txn *ovnsb_idl_txn,
         struct ipv6_prefixd_state *pfd;
 
         if (!smap_get_bool(&pb->options, "ipv6_prefix", false)) {
-            pfd = shash_find_and_delete(&ipv6_prefixd, pb->logical_port);
-            if (pfd) {
-                free(pfd);
-            }
+            free(shash_find_and_delete(&ipv6_prefixd, pb->logical_port));
             continue;
         }
 

controller/vif-plug.c

@@ -142,15 +142,9 @@ destroy_port_ctx(struct vif_plug_port_ctx *ctx)
 {
     smap_destroy(&ctx->vif_plug_port_ctx_in.lport_options);
     smap_destroy(&ctx->vif_plug_port_ctx_in.iface_options);
-    if (ctx->vif_plug_port_ctx_in.lport_name) {
-        free((char *)ctx->vif_plug_port_ctx_in.lport_name);
-    }
-    if (ctx->vif_plug_port_ctx_in.iface_name) {
-        free((char *)ctx->vif_plug_port_ctx_in.iface_name);
-    }
-    if (ctx->vif_plug_port_ctx_in.iface_type) {
-        free((char *)ctx->vif_plug_port_ctx_in.iface_type);
-    }
+    free(CONST_CAST(char *, ctx->vif_plug_port_ctx_in.lport_name));
+    free(CONST_CAST(char *, ctx->vif_plug_port_ctx_in.iface_name));
+    free(CONST_CAST(char *, ctx->vif_plug_port_ctx_in.iface_type));
     /* Note that data associated with ctx->vif_plug_port_ctx_out must be
      * destroyed by the plug provider implementation with a call to
      * vif_plug_port_ctx_destroy prior to calling this function */

lib/expr.c

@@ -179,17 +179,13 @@ expr_combine(enum expr_type type, struct expr *a, struct expr *b)
         } else {
             ovs_list_push_back(&a->andor, &b->node);
         }
-        if (a->as_name) {
-            free(a->as_name);
-            a->as_name = NULL;
-        }
+        free(a->as_name);
+        a->as_name = NULL;
         return a;
     } else if (b->type == type) {
         ovs_list_push_front(&b->andor, &a->node);
-        if (b->as_name) {
-            free(b->as_name);
-            b->as_name = NULL;
-        }
+        free(b->as_name);
+        b->as_name = NULL;
         return b;
     } else {
         struct expr *e = expr_create_andor(type);
@@ -879,12 +875,10 @@ parse_constant(struct expr_context *ctx, struct expr_constant_set *cs,
                                 sizeof *cs->values);
     }
 
-    if (cs->as_name) {
-        /* Combining other values to the constant set that is tracking an
-         * address set, so untrack it. */
-        free(cs->as_name);
-        cs->as_name = NULL;
-    }
+    /* Combining other values to the constant set that is tracking an
+     * address set, so untrack it. */
+    free(cs->as_name);
+    cs->as_name = NULL;
 
     if (ctx->lexer->token.type == LEX_T_TEMPLATE) {
         lexer_error(ctx->lexer, "Unexpanded template.");

lib/ovn-parallel-hmap.c

@@ -427,10 +427,8 @@ ovn_update_hashrow_locks(struct hmap *lflows, struct hashrow_locks *hrl)
 {
     int i;
     if (hrl->mask != lflows->mask) {
-        if (hrl->row_locks) {
-            free(hrl->row_locks);
-        }
-        hrl->row_locks = xcalloc(sizeof(struct ovs_mutex), lflows->mask + 1);
+        hrl->row_locks = xrealloc(hrl->row_locks,
+                                  sizeof *hrl->row_locks * (lflows->mask + 1));
         hrl->mask = lflows->mask;
         for (i = 0; i <= lflows->mask; i++) {
             ovs_mutex_init(&hrl->row_locks[i]);

northd/ipam.c

@@ -44,7 +44,7 @@ void
 destroy_ipam_info(struct ipam_info *info)
 {
     bitmap_free(info->allocated_ipv4s);
-    free((char *) info->id);
+    free(CONST_CAST(char *, info->id));
 }
 
 bool