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.

5 files changed, 25 insertions, 29 deletions

diff --git a/src/basic/fdset.c b/src/basic/fdset.c
index 6101b628ec..a4823e6659 100644
--- a/src/basic/fdset.c
+++ b/src/basic/fdset.c
@@ -267,8 +267,7 @@ bool fdset_isempty(FDSet *fds) {
 int fdset_iterate(FDSet *s, Iterator *i) {
         void *p;
 
-        p = set_iterate(MAKE_SET(s), i);
-        if (!p)
+        if (!set_iterate(MAKE_SET(s), i, &p))
                 return -ENOENT;
 
         return PTR_TO_FD(p);
diff --git a/src/basic/hashmap.c b/src/basic/hashmap.c
index 20d599d04b..0ee2f3bd31 100644
--- a/src/basic/hashmap.c
+++ b/src/basic/hashmap.c
@@ -733,29 +733,33 @@ static unsigned hashmap_iterate_entry(HashmapBase *h, Iterator *i) {
                                                : hashmap_iterate_in_internal_order(h, i);
 }
 
-void *internal_hashmap_iterate(HashmapBase *h, Iterator *i, const void **key) {
+bool internal_hashmap_iterate(HashmapBase *h, Iterator *i, void **value, const void **key) {
         struct hashmap_base_entry *e;
         void *data;
         unsigned idx;
 
         idx = hashmap_iterate_entry(h, i);
         if (idx == IDX_NIL) {
+                if (value)
+                        *value = NULL;
                 if (key)
                         *key = NULL;
 
-                return NULL;
+                return false;
         }
 
         e = bucket_at(h, idx);
         data = entry_value(h, e);
+        if (value)
+                *value = data;
         if (key)
                 *key = e->key;
 
-        return data;
+        return true;
 }
 
-void *set_iterate(Set *s, Iterator *i) {
-        return internal_hashmap_iterate(HASHMAP_BASE(s), i, NULL);
+bool set_iterate(Set *s, Iterator *i, void **value) {
+        return internal_hashmap_iterate(HASHMAP_BASE(s), i, value, NULL);
 }
 
 #define HASHMAP_FOREACH_IDX(idx, h, i) \
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);
diff --git a/src/basic/ordered-set.h b/src/basic/ordered-set.h
index 766a1f2e83..6c617ab305 100644
--- a/src/basic/ordered-set.h
+++ b/src/basic/ordered-set.h
@@ -47,12 +47,12 @@ static inline bool ordered_set_isempty(OrderedSet *s) {
         return ordered_hashmap_isempty((OrderedHashmap*) s);
 }
 
-static inline void *ordered_set_iterate(OrderedSet *s, Iterator *i) {
-        return ordered_hashmap_iterate((OrderedHashmap*) s, i, NULL);
+static inline bool ordered_set_iterate(OrderedSet *s, Iterator *i, void **value) {
+        return ordered_hashmap_iterate((OrderedHashmap*) s, i, value, NULL);
 }
 
 #define ORDERED_SET_FOREACH(e, s, i)                                    \
-        for ((i) = ITERATOR_FIRST, (e) = ordered_set_iterate((s), &(i)); (e); (e) = ordered_set_iterate((s), &(i)))
+        for ((i) = ITERATOR_FIRST; ordered_set_iterate((s), &(i), (void**)&(e)); )
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(OrderedSet*, ordered_set_free);
 
diff --git a/src/basic/set.h b/src/basic/set.h
index 4dffecd39d..51e40d3a6c 100644
--- a/src/basic/set.h
+++ b/src/basic/set.h
@@ -91,7 +91,7 @@ static inline unsigned set_buckets(Set *s) {
         return internal_hashmap_buckets(HASHMAP_BASE(s));
 }
 
-void *set_iterate(Set *s, Iterator *i);
+bool set_iterate(Set *s, Iterator *i, void **value);
 
 static inline void set_clear(Set *s) {
         internal_hashmap_clear(HASHMAP_BASE(s));
@@ -125,7 +125,7 @@ int set_put_strdup(Set *s, const char *p);
 int set_put_strdupv(Set *s, char **l);
 
 #define SET_FOREACH(e, s, i) \
-        for ((i) = ITERATOR_FIRST, (e) = set_iterate((s), &(i)); (e); (e) = set_iterate((s), &(i)))
+        for ((i) = ITERATOR_FIRST; set_iterate((s), &(i), (void**)&(e)); )
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(Set*, set_free);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Set*, set_free_free);