shash, simap, smap: Add assertions to *_count functions.

This commit adds assertions in the functions `shash_count`,
`simap_count`, and `smap_count` to ensure that the corresponding input
struct pointer is not NULL.

This ensures that if the return values of `shash_sort`, `simap_sort`,
or `smap_sort` are NULL, then the following for loops would not attempt
to access the pointer, which might result in segmentation faults or
undefined behavior.

Reviewed-by: Simon Horman <simon.horman@corigine.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: James Raphael Tiovalen <jamestiotio@gmail.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

lib/shash.c

@@ -17,6 +17,7 @@
 #include <config.h>
 #include "openvswitch/shash.h"
 #include "hash.h"
+#include "util.h"
 
 static struct shash_node *shash_find__(const struct shash *,
                                        const char *name, size_t name_len,
@@ -100,6 +101,7 @@ shash_is_empty(const struct shash *shash)
 size_t
 shash_count(const struct shash *shash)
 {
+    ovs_assert(shash);
     return hmap_count(&shash->map);
 }
 

lib/simap.c

@@ -17,6 +17,7 @@
 #include <config.h>
 #include "simap.h"
 #include "hash.h"
+#include "util.h"
 
 static size_t hash_name(const char *, size_t length);
 static struct simap_node *simap_find__(const struct simap *,
@@ -84,6 +85,7 @@ simap_is_empty(const struct simap *simap)
 size_t
 simap_count(const struct simap *simap)
 {
+    ovs_assert(simap);
     return hmap_count(&simap->map);
 }
 

lib/smap.c

@@ -300,6 +300,7 @@ smap_is_empty(const struct smap *smap)
 size_t
 smap_count(const struct smap *smap)
 {
+    ovs_assert(smap);
     return hmap_count(&smap->map);
 }