hashmap: rework hashmap_clear() to be more defensive

Let's first remove an item from the hashmap and only then destroy it.
This makes sure that destructor functions can mdoify the hashtables in
their own codee and we won't be confused by that.

2 files changed, 19 insertions, 11 deletions

diff --git a/src/basic/hashmap.c b/src/basic/hashmap.c
index d0bdbe3d1..0dd9f8ddd 100644
--- a/src/basic/hashmap.c
+++ b/src/basic/hashmap.c
@@ -882,17 +882,21 @@ void internal_hashmap_clear(HashmapBase *h, free_func_t default_free_key, free_f
         free_value = h->hash_ops->free_value ?: default_free_value;
 
         if (free_key || free_value) {
-                unsigned idx;
 
-                for (idx = skip_free_buckets(h, 0); idx != IDX_NIL;
-                     idx = skip_free_buckets(h, idx + 1)) {
-                        struct hashmap_base_entry *e = bucket_at(h, idx);
+                /* If destructor calls are defined, let's destroy things defensively: let's take the item out of the
+                 * hash table, and only then call the destructor functions. If these destructors then try to unregister
+                 * themselves from our hash table a second time, the entry is already gone. */
+
+                while (internal_hashmap_size(h) > 0) {
+                        void *v, *k;
+
+                        v = internal_hashmap_first_key_and_value(h, true, &k);
 
                         if (free_key)
-                                free_key((void *) e->key);
+                                free_key(k);
 
                         if (free_value)
-                                free_value(entry_value(h, e));
+                                free_value(v);
                 }
         }
 
@@ -1475,8 +1479,8 @@ int hashmap_remove_and_replace(Hashmap *h, const void *old_key, const void *new_
         return 0;
 }
 
-void *hashmap_remove_value(Hashmap *h, const void *key, void *value) {
-        struct plain_hashmap_entry *e;
+void *internal_hashmap_remove_value(HashmapBase *h, const void *key, void *value) {
+        struct hashmap_base_entry *e;
         unsigned hash, idx;
 
         if (!h)
@@ -1487,8 +1491,8 @@ void *hashmap_remove_value(Hashmap *h, const void *key, void *value) {
         if (idx == IDX_NIL)
                 return NULL;
 
-        e = plain_bucket_at(h, idx);
-        if (e->value != value)
+        e = bucket_at(h, idx);
+        if (entry_value(h, e) != value)
                 return NULL;
 
         remove_entry(h, idx);
diff --git a/src/basic/hashmap.h b/src/basic/hashmap.h
index a330a1d49..5bf807a76 100644
--- a/src/basic/hashmap.h
+++ b/src/basic/hashmap.h
@@ -191,7 +191,11 @@ static inline void *ordered_hashmap_remove2(OrderedHashmap *h, const void *key,
         return hashmap_remove2(PLAIN_HASHMAP(h), key, rkey);
 }
 
-void *hashmap_remove_value(Hashmap *h, const void *key, void *value);
+void *internal_hashmap_remove_value(HashmapBase *h, const void *key, void *value);
+static inline void *hashmap_remove_value(Hashmap *h, const void *key, void *value) {
+        return internal_hashmap_remove_value(HASHMAP_BASE(h), key, value);
+}
+
 static inline void *ordered_hashmap_remove_value(OrderedHashmap *h, const void *key, void *value) {
         return hashmap_remove_value(PLAIN_HASHMAP(h), key, value);
 }