hashmap: fix iterators to not skip entries

Currently, the HASHMAP iterators stop at the first NULL entry in a
hashmap. This is non-obvious and breaks users like sd-device, which
legitimately store NULL values in a hashmap.

Fix all the iterators by taking a pointer to the value storage, instead of
returning it. The iterators now return a boolean that tells whether the
end of the list was reached.

Current users of HASHMAP_FOREACH() are *NOT* changed to explicitly check
for NULL. If it turns out, there were users that inserted NULL into
hashmaps, but didn't properly check for it during iteration, then we
really want to find those and fix them.

1 files changed, 10 insertions, 17 deletions

diff --git a/src/basic/hashmap.h b/src/basic/hashmap.h
index a03ee5812a..5723f09ca9 100644
--- a/src/basic/hashmap.h
+++ b/src/basic/hashmap.h
@@ -65,6 +65,7 @@ typedef struct {
 } Iterator;
 
 #define _IDX_ITERATOR_FIRST (UINT_MAX - 1)
+#define _IDX_ITERATOR_NIL (UINT_MAX)
 #define ITERATOR_FIRST ((Iterator) { .idx = _IDX_ITERATOR_FIRST, .next_key = NULL })
 
 typedef unsigned long (*hash_func_t)(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]);
@@ -296,12 +297,12 @@ static inline unsigned ordered_hashmap_buckets(OrderedHashmap *h) {
         return internal_hashmap_buckets(HASHMAP_BASE(h));
 }
 
-void *internal_hashmap_iterate(HashmapBase *h, Iterator *i, const void **key);
-static inline void *hashmap_iterate(Hashmap *h, Iterator *i, const void **key) {
-        return internal_hashmap_iterate(HASHMAP_BASE(h), i, key);
+bool internal_hashmap_iterate(HashmapBase *h, Iterator *i, void **value, const void **key);
+static inline bool hashmap_iterate(Hashmap *h, Iterator *i, void **value, const void **key) {
+        return internal_hashmap_iterate(HASHMAP_BASE(h), i, value, key);
 }
-static inline void *ordered_hashmap_iterate(OrderedHashmap *h, Iterator *i, const void **key) {
-        return internal_hashmap_iterate(HASHMAP_BASE(h), i, key);
+static inline bool ordered_hashmap_iterate(OrderedHashmap *h, Iterator *i, void **value, const void **key) {
+        return internal_hashmap_iterate(HASHMAP_BASE(h), i, value, key);
 }
 
 void internal_hashmap_clear(HashmapBase *h);
@@ -386,24 +387,16 @@ static inline char **ordered_hashmap_get_strv(OrderedHashmap *h) {
  * It is safe to remove the current entry.
  */
 #define HASHMAP_FOREACH(e, h, i) \
-        for ((i) = ITERATOR_FIRST, (e) = hashmap_iterate((h), &(i), NULL); \
-             (e); \
-             (e) = hashmap_iterate((h), &(i), NULL))
+        for ((i) = ITERATOR_FIRST; hashmap_iterate((h), &(i), (void**)&(e), NULL); )
 
 #define ORDERED_HASHMAP_FOREACH(e, h, i) \
-        for ((i) = ITERATOR_FIRST, (e) = ordered_hashmap_iterate((h), &(i), NULL); \
-             (e); \
-             (e) = ordered_hashmap_iterate((h), &(i), NULL))
+        for ((i) = ITERATOR_FIRST; ordered_hashmap_iterate((h), &(i), (void**)&(e), NULL); )
 
 #define HASHMAP_FOREACH_KEY(e, k, h, i) \
-        for ((i) = ITERATOR_FIRST, (e) = hashmap_iterate((h), &(i), (const void**) &(k)); \
-             (e); \
-             (e) = hashmap_iterate((h), &(i), (const void**) &(k)))
+        for ((i) = ITERATOR_FIRST; hashmap_iterate((h), &(i), (void**)&(e), (const void**) &(k)); )
 
 #define ORDERED_HASHMAP_FOREACH_KEY(e, k, h, i) \
-        for ((i) = ITERATOR_FIRST, (e) = ordered_hashmap_iterate((h), &(i), (const void**) &(k)); \
-             (e); \
-             (e) = ordered_hashmap_iterate((h), &(i), (const void**) &(k)))
+        for ((i) = ITERATOR_FIRST; ordered_hashmap_iterate((h), &(i), (void**)&(e), (const void**) &(k)); )
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(Hashmap*, hashmap_free);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Hashmap*, hashmap_free_free);