Merge branch 'ew/hashmap'

Code clean-up of the hashmap API, both users and implementation.

* ew/hashmap:
  hashmap_entry: remove first member requirement from docs
  hashmap: remove type arg from hashmap_{get,put,remove}_entry
  OFFSETOF_VAR macro to simplify hashmap iterators
  hashmap: introduce hashmap_free_entries
  hashmap: hashmap_{put,remove} return hashmap_entry *
  hashmap: use *_entry APIs for iteration
  hashmap_cmp_fn takes hashmap_entry params
  hashmap_get{,_from_hash} return "struct hashmap_entry *"
  hashmap: use *_entry APIs to wrap container_of
  hashmap_get_next returns "struct hashmap_entry *"
  introduce container_of macro
  hashmap_put takes "struct hashmap_entry *"
  hashmap_remove takes "const struct hashmap_entry *"
  hashmap_get takes "const struct hashmap_entry *"
  hashmap_add takes "struct hashmap_entry *"
  hashmap_get_next takes "const struct hashmap_entry *"
  hashmap_entry_init takes "struct hashmap_entry *"
  packfile: use hashmap_entry in delta_base_cache_entry
  coccicheck: detect hashmap_entry.hash assignment
  diff: use hashmap_entry_init on moved_entry.ent

31 files changed, 667 insertions, 381 deletions

diff --git a/attr.c b/attr.c
index d02d081e28..11f19b541c 100644
--- a/attr.c
+++ b/attr.c
@@ -62,7 +62,7 @@ static struct attr_hashmap g_attr_hashmap;
 
 /* The container for objects stored in "struct attr_hashmap" */
 struct attr_hash_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	const char *key; /* the key; memory should be owned by value */
 	size_t keylen; /* length of the key */
 	void *value; /* the stored value */
@@ -70,12 +70,14 @@ struct attr_hash_entry {
 
 /* attr_hashmap comparison function */
 static int attr_hash_entry_cmp(const void *unused_cmp_data,
-			       const void *entry,
-			       const void *entry_or_key,
+			       const struct hashmap_entry *eptr,
+			       const struct hashmap_entry *entry_or_key,
 			       const void *unused_keydata)
 {
-	const struct attr_hash_entry *a = entry;
-	const struct attr_hash_entry *b = entry_or_key;
+	const struct attr_hash_entry *a, *b;
+
+	a = container_of(eptr, const struct attr_hash_entry, ent);
+	b = container_of(entry_or_key, const struct attr_hash_entry, ent);
 	return (a->keylen != b->keylen) || strncmp(a->key, b->key, a->keylen);
 }
 
@@ -98,10 +100,10 @@ static void *attr_hashmap_get(struct attr_hashmap *map,
 	if (!map->map.tablesize)
 		attr_hashmap_init(map);
 
-	hashmap_entry_init(&k, memhash(key, keylen));
+	hashmap_entry_init(&k.ent, memhash(key, keylen));
 	k.key = key;
 	k.keylen = keylen;
-	e = hashmap_get(&map->map, &k, NULL);
+	e = hashmap_get_entry(&map->map, &k, ent, NULL);
 
 	return e ? e->value : NULL;
 }
@@ -117,12 +119,12 @@ static void attr_hashmap_add(struct attr_hashmap *map,
 		attr_hashmap_init(map);
 
 	e = xmalloc(sizeof(struct attr_hash_entry));
-	hashmap_entry_init(e, memhash(key, keylen));
+	hashmap_entry_init(&e->ent, memhash(key, keylen));
 	e->key = key;
 	e->keylen = keylen;
 	e->value = value;
 
-	hashmap_add(&map->map, e);
+	hashmap_add(&map->map, &e->ent);
 }
 
 struct all_attrs_item {
@@ -161,12 +163,12 @@ static void all_attrs_init(struct attr_hashmap *map, struct attr_check *check)
 	if (size != check->all_attrs_nr) {
 		struct attr_hash_entry *e;
 		struct hashmap_iter iter;
-		hashmap_iter_init(&map->map, &iter);
 
 		REALLOC_ARRAY(check->all_attrs, size);
 		check->all_attrs_nr = size;
 
-		while ((e = hashmap_iter_next(&iter))) {
+		hashmap_for_each_entry(&map->map, &iter, e,
+					ent /* member name */) {
 			const struct git_attr *a = e->value;
 			check->all_attrs[a->attr_nr].attr = a;
 		}
diff --git a/blame.c b/blame.c
index 6596d8de88..29770e5c81 100644
--- a/blame.c
+++ b/blame.c
@@ -417,14 +417,15 @@ static void get_fingerprint(struct fingerprint *result,
 		/* Ignore whitespace pairs */
 		if (hash == 0)
 			continue;
-		hashmap_entry_init(entry, hash);
+		hashmap_entry_init(&entry->entry, hash);
 
-		found_entry = hashmap_get(&result->map, entry, NULL);
+		found_entry = hashmap_get_entry(&result->map, entry,
+						/* member name */ entry, NULL);
 		if (found_entry) {
 			found_entry->count += 1;
 		} else {
 			entry->count = 1;
-			hashmap_add(&result->map, entry);
+			hashmap_add(&result->map, &entry->entry);
 			++entry;
 		}
 	}
@@ -432,7 +433,7 @@ static void get_fingerprint(struct fingerprint *result,
 
 static void free_fingerprint(struct fingerprint *f)
 {
-	hashmap_free(&f->map, 0);
+	hashmap_free(&f->map);
 	free(f->entries);
 }
 
@@ -449,10 +450,10 @@ static int fingerprint_similarity(struct fingerprint *a, struct fingerprint *b)
 	struct hashmap_iter iter;
 	const struct fingerprint_entry *entry_a, *entry_b;
 
-	hashmap_iter_init(&b->map, &iter);
-
-	while ((entry_b = hashmap_iter_next(&iter))) {
-		if ((entry_a = hashmap_get(&a->map, entry_b, NULL))) {
+	hashmap_for_each_entry(&b->map, &iter, entry_b,
+				entry /* member name */) {
+		entry_a = hashmap_get_entry(&a->map, entry_b, entry, NULL);
+		if (entry_a) {
 			intersection += entry_a->count < entry_b->count ?
 					entry_a->count : entry_b->count;
 		}
@@ -470,10 +471,12 @@ static void fingerprint_subtract(struct fingerprint *a, struct fingerprint *b)
 
 	hashmap_iter_init(&b->map, &iter);
 
-	while ((entry_b = hashmap_iter_next(&iter))) {
-		if ((entry_a = hashmap_get(&a->map, entry_b, NULL))) {
+	hashmap_for_each_entry(&b->map, &iter, entry_b,
+				entry /* member name */) {
+		entry_a = hashmap_get_entry(&a->map, entry_b, entry, NULL);
+		if (entry_a) {
 			if (entry_a->count <= entry_b->count)
-				hashmap_remove(&a->map, entry_b, NULL);
+				hashmap_remove(&a->map, &entry_b->entry, NULL);
 			else
 				entry_a->count -= entry_b->count;
 		}
diff --git a/builtin/describe.c b/builtin/describe.c
index 90feab1120..b6df81d8d0 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -63,19 +63,22 @@ static const char *prio_names[] = {
 };
 
 static int commit_name_neq(const void *unused_cmp_data,
-			   const void *entry,
-			   const void *entry_or_key,
+			   const struct hashmap_entry *eptr,
+			   const struct hashmap_entry *entry_or_key,
 			   const void *peeled)
 {
-	const struct commit_name *cn1 = entry;
-	const struct commit_name *cn2 = entry_or_key;
+	const struct commit_name *cn1, *cn2;
+
+	cn1 = container_of(eptr, const struct commit_name, entry);
+	cn2 = container_of(entry_or_key, const struct commit_name, entry);
 
 	return !oideq(&cn1->peeled, peeled ? peeled : &cn2->peeled);
 }
 
 static inline struct commit_name *find_commit_name(const struct object_id *peeled)
 {
-	return hashmap_get_from_hash(&names, oidhash(peeled), peeled);
+	return hashmap_get_entry_from_hash(&names, oidhash(peeled), peeled,
+						struct commit_name, entry);
 }
 
 static int replace_name(struct commit_name *e,
@@ -122,8 +125,8 @@ static void add_to_known_names(const char *path,
 		if (!e) {
 			e = xmalloc(sizeof(struct commit_name));
 			oidcpy(&e->peeled, peeled);
-			hashmap_entry_init(e, oidhash(peeled));
-			hashmap_add(&names, e);
+			hashmap_entry_init(&e->entry, oidhash(peeled));
+			hashmap_add(&names, &e->entry);
 			e->path = NULL;
 		}
 		e->tag = tag;
@@ -329,8 +332,8 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst)
 		struct commit_name *n;
 
 		init_commit_names(&commit_names);
-		n = hashmap_iter_first(&names, &iter);
-		for (; n; n = hashmap_iter_next(&iter)) {
+		hashmap_for_each_entry(&names, &iter, n,
+					entry /* member name */) {
 			c = lookup_commit_reference_gently(the_repository,
 							   &n->peeled, 1);
 			if (c)
diff --git a/builtin/difftool.c b/builtin/difftool.c
index 16eb8b70ea..c280e682b2 100644
--- a/builtin/difftool.c
+++ b/builtin/difftool.c
@@ -125,12 +125,15 @@ struct working_tree_entry {
 };
 
 static int working_tree_entry_cmp(const void *unused_cmp_data,
-				  const void *entry,
-				  const void *entry_or_key,
+				  const struct hashmap_entry *eptr,
+				  const struct hashmap_entry *entry_or_key,
 				  const void *unused_keydata)
 {
-	const struct working_tree_entry *a = entry;
-	const struct working_tree_entry *b = entry_or_key;
+	const struct working_tree_entry *a, *b;
+
+	a = container_of(eptr, const struct working_tree_entry, entry);
+	b = container_of(entry_or_key, const struct working_tree_entry, entry);
+
 	return strcmp(a->path, b->path);
 }
 
@@ -145,12 +148,14 @@ struct pair_entry {
 };
 
 static int pair_cmp(const void *unused_cmp_data,
-		    const void *entry,
-		    const void *entry_or_key,
+		    const struct hashmap_entry *eptr,
+		    const struct hashmap_entry *entry_or_key,
 		    const void *unused_keydata)
 {
-	const struct pair_entry *a = entry;
-	const struct pair_entry *b = entry_or_key;
+	const struct pair_entry *a, *b;
+
+	a = container_of(eptr, const struct pair_entry, entry);
+	b = container_of(entry_or_key, const struct pair_entry, entry);
 
 	return strcmp(a->path, b->path);
 }
@@ -161,14 +166,14 @@ static void add_left_or_right(struct hashmap *map, const char *path,
 	struct pair_entry *e, *existing;
 
 	FLEX_ALLOC_STR(e, path, path);
-	hashmap_entry_init(e, strhash(path));
-	existing = hashmap_get(map, e, NULL);
+	hashmap_entry_init(&e->entry, strhash(path));
+	existing = hashmap_get_entry(map, e, entry, NULL);
 	if (existing) {
 		free(e);
 		e = existing;
 	} else {
 		e->left[0] = e->right[0] = '\0';
-		hashmap_add(map, e);
+		hashmap_add(map, &e->entry);
 	}
 	strlcpy(is_right ? e->right : e->left, content, PATH_MAX);
 }
@@ -179,12 +184,14 @@ struct path_entry {
 };
 
 static int path_entry_cmp(const void *unused_cmp_data,
-			  const void *entry,
-			  const void *entry_or_key,
+			  const struct hashmap_entry *eptr,
+			  const struct hashmap_entry *entry_or_key,
 			  const void *key)
 {
-	const struct path_entry *a = entry;
-	const struct path_entry *b = entry_or_key;
+	const struct path_entry *a, *b;
+
+	a = container_of(eptr, const struct path_entry, entry);
+	b = container_of(entry_or_key, const struct path_entry, entry);
 
 	return strcmp(a->path, key ? key : b->path);
 }
@@ -234,8 +241,8 @@ static void changed_files(struct hashmap *result, const char *index_path,
 	while (!strbuf_getline_nul(&buf, fp)) {
 		struct path_entry *entry;
 		FLEX_ALLOC_STR(entry, path, buf.buf);
-		hashmap_entry_init(entry, strhash(buf.buf));
-		hashmap_add(result, entry);
+		hashmap_entry_init(&entry->entry, strhash(buf.buf));
+		hashmap_add(result, &entry->entry);
 	}
 	fclose(fp);
 	if (finish_command(&diff_files))
@@ -461,12 +468,13 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 
 			/* Avoid duplicate working_tree entries */
 			FLEX_ALLOC_STR(entry, path, dst_path);
-			hashmap_entry_init(entry, strhash(dst_path));
-			if (hashmap_get(&working_tree_dups, entry, NULL)) {
+			hashmap_entry_init(&entry->entry, strhash(dst_path));
+			if (hashmap_get(&working_tree_dups, &entry->entry,
+					NULL)) {
 				free(entry);
 				continue;
 			}
-			hashmap_add(&working_tree_dups, entry);
+			hashmap_add(&working_tree_dups, &entry->entry);
 
 			if (!use_wt_file(workdir, dst_path, &roid)) {
 				if (checkout_path(rmode, &roid, dst_path,
@@ -530,8 +538,8 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	 * temporary file to both the left and right directories to show the
 	 * change in the recorded SHA1 for the submodule.
 	 */
-	hashmap_iter_init(&submodules, &iter);
-	while ((entry = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(&submodules, &iter, entry,
+				entry /* member name */) {
 		if (*entry->left) {
 			add_path(&ldir, ldir_len, entry->path);
 			ensure_leading_directories(ldir.buf);
@@ -549,8 +557,8 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	 * shows only the link itself, not the contents of the link target.
 	 * This loop replicates that behavior.
 	 */
-	hashmap_iter_init(&symlinks2, &iter);
-	while ((entry = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(&symlinks2, &iter, entry,
+				entry /* member name */) {
 		if (*entry->left) {
 			add_path(&ldir, ldir_len, entry->path);
 			ensure_leading_directories(ldir.buf);
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 58a74de42a..dbec4df92b 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -127,10 +127,15 @@ struct anonymized_entry {
 };
 
 static int anonymized_entry_cmp(const void *unused_cmp_data,
-				const void *va, const void *vb,
+				const struct hashmap_entry *eptr,
+				const struct hashmap_entry *entry_or_key,
 				const void *unused_keydata)
 {
-	const struct anonymized_entry *a = va, *b = vb;
+	const struct anonymized_entry *a, *b;
+
+	a = container_of(eptr, const struct anonymized_entry, hash);
+	b = container_of(entry_or_key, const struct anonymized_entry, hash);
+
 	return a->orig_len != b->orig_len ||
 		memcmp(a->orig, b->orig, a->orig_len);
 }
@@ -149,10 +154,10 @@ static const void *anonymize_mem(struct hashmap *map,
 	if (!map->cmpfn)
 		hashmap_init(map, anonymized_entry_cmp, NULL, 0);
 
-	hashmap_entry_init(&key, memhash(orig, *len));
+	hashmap_entry_init(&key.hash, memhash(orig, *len));
 	key.orig = orig;
 	key.orig_len = *len;
-	ret = hashmap_get(map, &key, NULL);
+	ret = hashmap_get_entry(map, &key, hash, NULL);
 
 	if (!ret) {
 		ret = xmalloc(sizeof(*ret));
@@ -161,7 +166,7 @@ static const void *anonymize_mem(struct hashmap *map,
 		ret->orig_len = *len;
 		ret->anon = generate(orig, len);
 		ret->anon_len = *len;
-		hashmap_put(map, ret);
+		hashmap_put(map, &ret->hash);
 	}
 
 	*len = ret->anon_len;
diff --git a/builtin/fetch.c b/builtin/fetch.c
index b0f9473489..ef731631c2 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -264,20 +264,21 @@ static void create_fetch_oidset(struct ref **head, struct oidset *out)
 }
 
 struct refname_hash_entry {
-	struct hashmap_entry ent; /* must be the first member */
+	struct hashmap_entry ent;
 	struct object_id oid;
 	int ignore;
 	char refname[FLEX_ARRAY];
 };
 
 static int refname_hash_entry_cmp(const void *hashmap_cmp_fn_data,
-				  const void *e1_,
-				  const void *e2_,
+				  const struct hashmap_entry *eptr,
+				  const struct hashmap_entry *entry_or_key,
 				  const void *keydata)
 {
-	const struct refname_hash_entry *e1 = e1_;
-	const struct refname_hash_entry *e2 = e2_;
+	const struct refname_hash_entry *e1, *e2;
 
+	e1 = container_of(eptr, const struct refname_hash_entry, ent);
+	e2 = container_of(entry_or_key, const struct refname_hash_entry, ent);
 	return strcmp(e1->refname, keydata ? keydata : e2->refname);
 }
 
@@ -289,9 +290,9 @@ static struct refname_hash_entry *refname_hash_add(struct hashmap *map,
 	size_t len = strlen(refname);
 
 	FLEX_ALLOC_MEM(ent, refname, refname, len);
-	hashmap_entry_init(ent, strhash(refname));
+	hashmap_entry_init(&ent->ent, strhash(refname));
 	oidcpy(&ent->oid, oid);
-	hashmap_add(map, ent);
+	hashmap_add(map, &ent->ent);
 	return ent;
 }
 
@@ -380,7 +381,7 @@ static void find_non_local_tags(const struct ref *refs,
 		item = refname_hash_add(&remote_refs, ref->name, &ref->old_oid);
 		string_list_insert(&remote_refs_list, ref->name);
 	}
-	hashmap_free(&existing_refs, 1);
+	hashmap_free_entries(&existing_refs, struct refname_hash_entry, ent);
 
 	/*
 	 * We may have a final lightweight tag that needs to be
@@ -398,8 +399,10 @@ static void find_non_local_tags(const struct ref *refs,
 	for_each_string_list_item(remote_ref_item, &remote_refs_list) {
 		const char *refname = remote_ref_item->string;
 		struct ref *rm;
+		unsigned int hash = strhash(refname);
 
-		item = hashmap_get_from_hash(&remote_refs, strhash(refname), refname);
+		item = hashmap_get_entry_from_hash(&remote_refs, hash, refname,
+					struct refname_hash_entry, ent);
 		if (!item)
 			BUG("unseen remote ref?");
 
@@ -413,7 +416,7 @@ static void find_non_local_tags(const struct ref *refs,
 		**tail = rm;
 		*tail = &rm->next;
 	}
-	hashmap_free(&remote_refs, 1);
+	hashmap_free_entries(&remote_refs, struct refname_hash_entry, ent);
 	string_list_clear(&remote_refs_list, 0);
 	oidset_clear(&fetch_oids);
 }
@@ -532,17 +535,18 @@ static struct ref *get_ref_map(struct remote *remote,
 		if (rm->peer_ref) {
 			const char *refname = rm->peer_ref->name;
 			struct refname_hash_entry *peer_item;
+			unsigned int hash = strhash(refname);
 
-			peer_item = hashmap_get_from_hash(&existing_refs,
-							  strhash(refname),
-							  refname);
+			peer_item = hashmap_get_entry_from_hash(&existing_refs,
+						hash, refname,
+						struct refname_hash_entry, ent);
 			if (peer_item) {
 				struct object_id *old_oid = &peer_item->oid;
 				oidcpy(&rm->peer_ref->old_oid, old_oid);
 			}
 		}
 	}
-	hashmap_free(&existing_refs, 1);
+	hashmap_free_entries(&existing_refs, struct refname_hash_entry, ent);
 
 	return ref_map;
 }
diff --git a/config.c b/config.c
index eef4f4f1bb..e7052b3977 100644
--- a/config.c
+++ b/config.c
@@ -1856,9 +1856,9 @@ static struct config_set_element *configset_find_element(struct config_set *cs,
 	if (git_config_parse_key(key, &normalized_key, NULL))
 		return NULL;
 
-	hashmap_entry_init(&k, strhash(normalized_key));
+	hashmap_entry_init(&k.ent, strhash(normalized_key));
 	k.key = normalized_key;
-	found_entry = hashmap_get(&cs->config_hash, &k, NULL);
+	found_entry = hashmap_get_entry(&cs->config_hash, &k, ent, NULL);
 	free(normalized_key);
 	return found_entry;
 }
@@ -1877,10 +1877,10 @@ static int configset_add_value(struct config_set *cs, const char *key, const cha
 	 */
 	if (!e) {
 		e = xmalloc(sizeof(*e));
-		hashmap_entry_init(e, strhash(key));
+		hashmap_entry_init(&e->ent, strhash(key));
 		e->key = xstrdup(key);
 		string_list_init(&e->value_list, 1);
-		hashmap_add(&cs->config_hash, e);
+		hashmap_add(&cs->config_hash, &e->ent);
 	}
 	si = string_list_append_nodup(&e->value_list, xstrdup_or_null(value));
 
@@ -1908,12 +1908,14 @@ static int configset_add_value(struct config_set *cs, const char *key, const cha
 }
 
 static int config_set_element_cmp(const void *unused_cmp_data,
-				  const void *entry,
-				  const void *entry_or_key,
+				  const struct hashmap_entry *eptr,
+				  const struct hashmap_entry *entry_or_key,
 				  const void *unused_keydata)
 {
-	const struct config_set_element *e1 = entry;
-	const struct config_set_element *e2 = entry_or_key;
+	const struct config_set_element *e1, *e2;
+
+	e1 = container_of(eptr, const struct config_set_element, ent);
+	e2 = container_of(entry_or_key, const struct config_set_element, ent);
 
 	return strcmp(e1->key, e2->key);
 }
@@ -1934,12 +1936,12 @@ void git_configset_clear(struct config_set *cs)
 	if (!cs->hash_initialized)
 		return;
 
-	hashmap_iter_init(&cs->config_hash, &iter);
-	while ((entry = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(&cs->config_hash, &iter, entry,
+				ent /* member name */) {
 		free(entry->key);
 		string_list_clear(&entry->value_list, 1);
 	}
-	hashmap_free(&cs->config_hash, 1);
+	hashmap_free_entries(&cs->config_hash, struct config_set_element, ent);
 	cs->hash_initialized = 0;
 	free(cs->list.items);
 	cs->list.nr = 0;
diff --git a/contrib/coccinelle/hashmap.cocci b/contrib/coccinelle/hashmap.cocci
new file mode 100644
index 0000000000..d69e120ccf
--- /dev/null
+++ b/contrib/coccinelle/hashmap.cocci
@@ -0,0 +1,16 @@
+@ hashmap_entry_init_usage @
+expression E;
+struct hashmap_entry HME;
+@@
+- HME.hash = E;
++ hashmap_entry_init(&HME, E);
+
+@@
+identifier f !~ "^hashmap_entry_init$";
+expression E;
+struct hashmap_entry *HMEP;
+@@
+  f(...) {<...
+- HMEP->hash = E;
++ hashmap_entry_init(HMEP, E);
+  ...>}
diff --git a/diff.c b/diff.c
index 8fb57b73ef..afe4400a60 100644
--- a/diff.c
+++ b/diff.c
@@ -933,16 +933,18 @@ static int cmp_in_block_with_wsd(const struct diff_options *o,
 }
 
 static int moved_entry_cmp(const void *hashmap_cmp_fn_data,
-			   const void *entry,
-			   const void *entry_or_key,
+			   const struct hashmap_entry *eptr,
+			   const struct hashmap_entry *entry_or_key,
 			   const void *keydata)
 {
 	const struct diff_options *diffopt = hashmap_cmp_fn_data;
-	const struct moved_entry *a = entry;
-	const struct moved_entry *b = entry_or_key;
+	const struct moved_entry *a, *b;
 	unsigned flags = diffopt->color_moved_ws_handling
 			 & XDF_WHITESPACE_FLAGS;
 
+	a = container_of(eptr, const struct moved_entry, ent);
+	b = container_of(entry_or_key, const struct moved_entry, ent);
+
 	if (diffopt->color_moved_ws_handling &
 	    COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE)
 		/*
@@ -964,8 +966,9 @@ static struct moved_entry *prepare_entry(struct diff_options *o,
 	struct moved_entry *ret = xmalloc(sizeof(*ret));
 	struct emitted_diff_symbol *l = &o->emitted_symbols->buf[line_no];
 	unsigned flags = o->color_moved_ws_handling & XDF_WHITESPACE_FLAGS;
+	unsigned int hash = xdiff_hash_string(l->line, l->len, flags);
 
-	ret->ent.hash = xdiff_hash_string(l->line, l->len, flags);
+	hashmap_entry_init(&ret->ent, hash);
 	ret->es = l;
 	ret->next_line = NULL;
 
@@ -1002,7 +1005,7 @@ static void add_lines_to_move_detection(struct diff_options *o,
 		if (prev_line && prev_line->es->s == o->emitted_symbols->buf[n].s)
 			prev_line->next_line = key;
 
-		hashmap_add(hm, key);
+		hashmap_add(hm, &key->ent);
 		prev_line = key;
 	}
 }
@@ -1018,7 +1021,7 @@ static void pmb_advance_or_null(struct diff_options *o,
 		struct moved_entry *prev = pmb[i].match;
 		struct moved_entry *cur = (prev && prev->next_line) ?
 				prev->next_line : NULL;
-		if (cur && !hm->cmpfn(o, cur, match, NULL)) {
+		if (cur && !hm->cmpfn(o, &cur->ent, &match->ent, NULL)) {
 			pmb[i].match = cur;
 		} else {
 			pmb[i].match = NULL;
@@ -1035,7 +1038,7 @@ static void pmb_advance_or_null_multi_match(struct diff_options *o,
 	int i;
 	char *got_match = xcalloc(1, pmb_nr);
 
-	for (; match; match = hashmap_get_next(hm, match)) {
+	hashmap_for_each_entry_from(hm, match, ent) {
 		for (i = 0; i < pmb_nr; i++) {
 			struct moved_entry *prev = pmb[i].match;
 			struct moved_entry *cur = (prev && prev->next_line) ?
@@ -1143,13 +1146,13 @@ static void mark_color_as_moved(struct diff_options *o,
 		case DIFF_SYMBOL_PLUS:
 			hm = del_lines;
 			key = prepare_entry(o, n);
-			match = hashmap_get(hm, key, NULL);
+			match = hashmap_get_entry(hm, key, ent, NULL);
 			free(key);
 			break;
 		case DIFF_SYMBOL_MINUS:
 			hm = add_lines;
 			key = prepare_entry(o, n);
-			match = hashmap_get(hm, key, NULL);
+			match = hashmap_get_entry(hm, key, ent, NULL);
 			free(key);
 			break;
 		default:
@@ -1188,7 +1191,7 @@ static void mark_color_as_moved(struct diff_options *o,
 			 * The current line is the start of a new block.
 			 * Setup the set of potential blocks.
 			 */
-			for (; match; match = hashmap_get_next(hm, match)) {
+			hashmap_for_each_entry_from(hm, match, ent) {
 				ALLOC_GROW(pmb, pmb_nr + 1, pmb_alloc);
 				if (o->color_moved_ws_handling &
 				    COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE) {
@@ -6230,8 +6233,10 @@ static void diff_flush_patch_all_file_pairs(struct diff_options *o)
 			if (o->color_moved == COLOR_MOVED_ZEBRA_DIM)
 				dim_moved_lines(o);
 
-			hashmap_free(&add_lines, 1);
-			hashmap_free(&del_lines, 1);
+			hashmap_free_entries(&add_lines, struct moved_entry,
+						ent);
+			hashmap_free_entries(&del_lines, struct moved_entry,
+						ent);
 		}
 
 		for (i = 0; i < esm.nr; i++)
diff --git a/diffcore-rename.c b/diffcore-rename.c
index 9042936aba..531d7adeaf 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -274,18 +274,17 @@ static int find_identical_files(struct hashmap *srcs,
 				struct diff_options *options)
 {
 	int renames = 0;
-
 	struct diff_filespec *target = rename_dst[dst_index].two;
 	struct file_similarity *p, *best = NULL;
 	int i = 100, best_score = -1;
+	unsigned int hash = hash_filespec(options->repo, target);
 
 	/*
 	 * Find the best source match for specified destination.
 	 */
-	p = hashmap_get_from_hash(srcs,
-				  hash_filespec(options->repo, target),
-				  NULL);
-	for (; p; p = hashmap_get_next(srcs, p)) {
+	p = hashmap_get_entry_from_hash(srcs, hash, NULL,
+					struct file_similarity, entry);
+	hashmap_for_each_entry_from(srcs, p, entry) {
 		int score;
 		struct diff_filespec *source = p->filespec;
 
@@ -329,8 +328,8 @@ static void insert_file_table(struct repository *r,
 	entry->index = index;
 	entry->filespec = filespec;
 
-	hashmap_entry_init(entry, hash_filespec(r, filespec));
-	hashmap_add(table, entry);
+	hashmap_entry_init(&entry->entry, hash_filespec(r, filespec));
+	hashmap_add(table, &entry->entry);
 }
 
 /*
@@ -359,7 +358,7 @@ static int find_exact_renames(struct diff_options *options)
 		renames += find_identical_files(&file_table, i, options);
 
 	/* Free the hash data structure and entries */
-	hashmap_free(&file_table, 1);
+	hashmap_free_entries(&file_table, struct file_similarity, entry);
 
 	return renames;
 }
diff --git a/git-compat-util.h b/git-compat-util.h
index a8b5854e27..8b8b29a867 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1313,4 +1313,42 @@ void unleak_memory(const void *ptr, size_t len);
  */
 #include "banned.h"
 
+/*
+ * container_of - Get the address of an object containing a field.
+ *
+ * @ptr: pointer to the field.
+ * @type: type of the object.
+ * @member: name of the field within the object.
+ */
+#define container_of(ptr, type, member) \
+	((type *) ((char *)(ptr) - offsetof(type, member)))
+
+/*
+ * helper function for `container_of_or_null' to avoid multiple
+ * evaluation of @ptr
+ */
+static inline void *container_of_or_null_offset(void *ptr, size_t offset)
+{
+	return ptr ? (char *)ptr - offset : NULL;
+}
+
+/*
+ * like `container_of', but allows returned value to be NULL
+ */
+#define container_of_or_null(ptr, type, member) \
+	(type *)container_of_or_null_offset(ptr, offsetof(type, member))
+
+/*
+ * like offsetof(), but takes a pointer to a a variable of type which
+ * contains @member, instead of a specified type.
+ * @ptr is subject to multiple evaluation since we can't rely on __typeof__
+ * everywhere.
+ */
+#if defined(__GNUC__) /* clang sets this, too */
+#define OFFSETOF_VAR(ptr, member) offsetof(__typeof__(*ptr), member)
+#else /* !__GNUC__ */
+#define OFFSETOF_VAR(ptr, member) \
+	((uintptr_t)&(ptr)->member - (uintptr_t)(ptr))
+#endif /* !__GNUC__ */
+
 #endif
diff --git a/hashmap.c b/hashmap.c
index d42f01ff5a..39c13110bc 100644
--- a/hashmap.c
+++ b/hashmap.c
@@ -140,8 +140,8 @@ static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
 }
 
 static int always_equal(const void *unused_cmp_data,
-			const void *unused1,
-			const void *unused2,
+			const struct hashmap_entry *unused1,
+			const struct hashmap_entry *unused2,
 			const void *unused_keydata)
 {
 	return 0;
@@ -171,41 +171,49 @@ void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
 	map->do_count_items = 1;
 }
 
-void hashmap_free(struct hashmap *map, int free_entries)
+void hashmap_free_(struct hashmap *map, ssize_t entry_offset)
 {
 	if (!map || !map->table)
 		return;
-	if (free_entries) {
+	if (entry_offset >= 0) { /* called by hashmap_free_entries */
 		struct hashmap_iter iter;
 		struct hashmap_entry *e;
+
 		hashmap_iter_init(map, &iter);
 		while ((e = hashmap_iter_next(&iter)))
-			free(e);
+			/*
+			 * like container_of, but using caller-calculated
+			 * offset (caller being hashmap_free_entries)
+			 */
+			free((char *)e - entry_offset);
 	}
 	free(map->table);
 	memset(map, 0, sizeof(*map));
 }
 
-void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)
+struct hashmap_entry *hashmap_get(const struct hashmap *map,
+				const struct hashmap_entry *key,
+				const void *keydata)
 {
 	return *find_entry_ptr(map, key, keydata);
 }
 
-void *hashmap_get_next(const struct hashmap *map, const void *entry)
+struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
+			const struct hashmap_entry *entry)
 {
-	struct hashmap_entry *e = ((struct hashmap_entry *) entry)->next;
+	struct hashmap_entry *e = entry->next;
 	for (; e; e = e->next)
 		if (entry_equals(map, entry, e, NULL))
 			return e;
 	return NULL;
 }
 
-void hashmap_add(struct hashmap *map, void *entry)
+void hashmap_add(struct hashmap *map, struct hashmap_entry *entry)
 {
 	unsigned int b = bucket(map, entry);
 
 	/* add entry */
-	((struct hashmap_entry *) entry)->next = map->table[b];
+	entry->next = map->table[b];
 	map->table[b] = entry;
 
 	/* fix size and rehash if appropriate */
@@ -216,7 +224,9 @@ void hashmap_add(struct hashmap *map, void *entry)
 	}
 }
 
-void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)
+struct hashmap_entry *hashmap_remove(struct hashmap *map,
+					const struct hashmap_entry *key,
+					const void *keydata)
 {
 	struct hashmap_entry *old;
 	struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
@@ -238,7 +248,8 @@ void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)
 	return old;
 }
 
-void *hashmap_put(struct hashmap *map, void *entry)
+struct hashmap_entry *hashmap_put(struct hashmap *map,
+				struct hashmap_entry *entry)
 {
 	struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
 	hashmap_add(map, entry);
@@ -252,7 +263,7 @@ void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
 	iter->next = NULL;
 }
 
-void *hashmap_iter_next(struct hashmap_iter *iter)
+struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter)
 {
 	struct hashmap_entry *current = iter->next;
 	for (;;) {
@@ -275,10 +286,15 @@ struct pool_entry {
 };
 
 static int pool_entry_cmp(const void *unused_cmp_data,
-			  const struct pool_entry *e1,
-			  const struct pool_entry *e2,
-			  const unsigned char *keydata)
+			  const struct hashmap_entry *eptr,
+			  const struct hashmap_entry *entry_or_key,
+			  const void *keydata)
 {
+	const struct pool_entry *e1, *e2;
+
+	e1 = container_of(eptr, const struct pool_entry, ent);
+	e2 = container_of(entry_or_key, const struct pool_entry, ent);
+
 	return e1->data != keydata &&
 	       (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
 }
@@ -290,18 +306,18 @@ const void *memintern(const void *data, size_t len)
 
 	/* initialize string pool hashmap */
 	if (!map.tablesize)
-		hashmap_init(&map, (hashmap_cmp_fn) pool_entry_cmp, NULL, 0);
+		hashmap_init(&map, pool_entry_cmp, NULL, 0);
 
 	/* lookup interned string in pool */
-	hashmap_entry_init(&key, memhash(data, len));
+	hashmap_entry_init(&key.ent, memhash(data, len));
 	key.len = len;
-	e = hashmap_get(&map, &key, data);
+	e = hashmap_get_entry(&map, &key, ent, data);
 	if (!e) {
 		/* not found: create it */
 		FLEX_ALLOC_MEM(e, data, data, len);
-		hashmap_entry_init(e, key.ent.hash);
+		hashmap_entry_init(&e->ent, key.ent.hash);
 		e->len = len;
-		hashmap_add(&map, e);
+		hashmap_add(&map, &e->ent);
 	}
 	return e->data;
 }
diff --git a/hashmap.h b/hashmap.h
index 8424911566..bd2701549f 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -13,7 +13,7 @@
  *
  * struct hashmap map;
  * struct long2string {
- *     struct hashmap_entry ent; // must be the first member!
+ *     struct hashmap_entry ent;
  *     long key;
  *     char value[FLEX_ARRAY];   // be careful with allocating on stack!
  * };
@@ -21,12 +21,16 @@
  * #define COMPARE_VALUE 1
  *
  * static int long2string_cmp(const void *hashmap_cmp_fn_data,
- *                            const struct long2string *e1,
- *                            const struct long2string *e2,
+ *                            const struct hashmap_entry *eptr,
+ *                            const struct hashmap_entry *entry_or_key,
  *                            const void *keydata)
  * {
  *     const char *string = keydata;
  *     unsigned flags = *(unsigned *)hashmap_cmp_fn_data;
+ *     const struct long2string *e1, *e2;
+ *
+ *     e1 = container_of(eptr, const struct long2string, ent);
+ *     e2 = container_of(entry_or_key, const struct long2string, ent);
  *
  *     if (flags & COMPARE_VALUE)
  *         return e1->key != e2->key ||
@@ -41,54 +45,58 @@
  *     char value[255], action[32];
  *     unsigned flags = 0;
  *
- *     hashmap_init(&map, (hashmap_cmp_fn) long2string_cmp, &flags, 0);
+ *     hashmap_init(&map, long2string_cmp, &flags, 0);
  *
  *     while (scanf("%s %ld %s", action, &key, value)) {
  *
  *         if (!strcmp("add", action)) {
  *             struct long2string *e;
  *             FLEX_ALLOC_STR(e, value, value);
- *             hashmap_entry_init(e, memhash(&key, sizeof(long)));
+ *             hashmap_entry_init(&e->ent, memhash(&key, sizeof(long)));
  *             e->key = key;
- *             hashmap_add(&map, e);
+ *             hashmap_add(&map, &e->ent);
  *         }
  *
  *         if (!strcmp("print_all_by_key", action)) {
  *             struct long2string k, *e;
- *             hashmap_entry_init(&k, memhash(&key, sizeof(long)));
+ *             hashmap_entry_init(&k->ent, memhash(&key, sizeof(long)));
  *             k.key = key;
  *
  *             flags &= ~COMPARE_VALUE;
- *             e = hashmap_get(&map, &k, NULL);
+ *             e = hashmap_get_entry(&map, &k, ent, NULL);
  *             if (e) {
  *                 printf("first: %ld %s\n", e->key, e->value);
- *                 while ((e = hashmap_get_next(&map, e)))
+ *                 while ((e = hashmap_get_next_entry(&map, e,
+ *                                              struct long2string, ent))) {
  *                     printf("found more: %ld %s\n", e->key, e->value);
+ *                 }
  *             }
  *         }
  *
  *         if (!strcmp("has_exact_match", action)) {
  *             struct long2string *e;
  *             FLEX_ALLOC_STR(e, value, value);
- *             hashmap_entry_init(e, memhash(&key, sizeof(long)));
+ *             hashmap_entry_init(&e->ent, memhash(&key, sizeof(long)));
  *             e->key = key;
  *
  *             flags |= COMPARE_VALUE;
- *             printf("%sfound\n", hashmap_get(&map, e, NULL) ? "" : "not ");
+ *             printf("%sfound\n",
+ *                    hashmap_get(&map, &e->ent, NULL) ? "" : "not ");
  *             free(e);
  *         }
  *
  *         if (!strcmp("has_exact_match_no_heap_alloc", action)) {
  *             struct long2string k;
- *             hashmap_entry_init(&k, memhash(&key, sizeof(long)));
+ *             hashmap_entry_init(&k->ent, memhash(&key, sizeof(long)));
  *             k.key = key;
  *
  *             flags |= COMPARE_VALUE;
- *             printf("%sfound\n", hashmap_get(&map, &k, value) ? "" : "not ");
+ *             printf("%sfound\n",
+ *                    hashmap_get(&map, &k->ent, value) ? "" : "not ");
  *         }
  *
  *         if (!strcmp("end", action)) {
- *             hashmap_free(&map, 1);
+ *             hashmap_free_entries(&map, struct long2string, ent);
  *             break;
  *         }
  *     }
@@ -133,7 +141,7 @@ static inline unsigned int oidhash(const struct object_id *oid)
 
 /*
  * struct hashmap_entry is an opaque structure representing an entry in the
- * hash table, which must be used as first member of user data structures.
+ * hash table.
  * Ideally it should be followed by an int-sized member to prevent unused
  * memory on 64-bit systems due to alignment.
  */
@@ -168,7 +176,8 @@ struct hashmap_entry {
  * The `hashmap_cmp_fn_data` entry is the pointer given in the init function.
  */
 typedef int (*hashmap_cmp_fn)(const void *hashmap_cmp_fn_data,
-			      const void *entry, const void *entry_or_key,
+			      const struct hashmap_entry *entry,
+			      const struct hashmap_entry *entry_or_key,
 			      const void *keydata);
 
 /*
@@ -223,13 +232,20 @@ void hashmap_init(struct hashmap *map,
 			 const void *equals_function_data,
 			 size_t initial_size);
 
+/* internal function for freeing hashmap */
+void hashmap_free_(struct hashmap *map, ssize_t offset);
+
 /*
- * Frees a hashmap structure and allocated memory.
- *
- * If `free_entries` is true, each hashmap_entry in the map is freed as well
- * using stdlibs free().
+ * Frees a hashmap structure and allocated memory, leaves entries undisturbed
  */
-void hashmap_free(struct hashmap *map, int free_entries);
+#define hashmap_free(map) hashmap_free_(map, -1)
+
+/*
+ * Frees @map and all entries.  @type is the struct type of the entry
+ * where @member is the hashmap_entry struct used to associate with @map
+ */
+#define hashmap_free_entries(map, type, member) \
+	hashmap_free_(map, offsetof(type, member));
 
 /* hashmap_entry functions */
 
@@ -244,9 +260,9 @@ void hashmap_free(struct hashmap *map, int free_entries);
  * your structure was allocated with xmalloc(), you can just free(3) it,
  * and if it is on stack, you can just let it go out of scope).
  */
-static inline void hashmap_entry_init(void *entry, unsigned int hash)
+static inline void hashmap_entry_init(struct hashmap_entry *e,
+					unsigned int hash)
 {
-	struct hashmap_entry *e = entry;
 	e->hash = hash;
 	e->next = NULL;
 }
@@ -286,8 +302,9 @@ static inline unsigned int hashmap_get_size(struct hashmap *map)
  * If an entry with matching hash code is found, `key` and `keydata` are passed
  * to `hashmap_cmp_fn` to decide whether the entry matches the key.
  */
-void *hashmap_get(const struct hashmap *map, const void *key,
-			 const void *keydata);
+struct hashmap_entry *hashmap_get(const struct hashmap *map,
+				const struct hashmap_entry *key,
+				const void *keydata);
 
 /*
  * Returns the hashmap entry for the specified hash code and key data,
@@ -301,9 +318,10 @@ void *hashmap_get(const struct hashmap *map, const void *key,
  * `entry_or_key` parameter of `hashmap_cmp_fn` points to a hashmap_entry
  * structure that should not be used in the comparison.
  */
-static inline void *hashmap_get_from_hash(const struct hashmap *map,
-					  unsigned int hash,
-					  const void *keydata)
+static inline struct hashmap_entry *hashmap_get_from_hash(
+					const struct hashmap *map,
+					unsigned int hash,
+					const void *keydata)
 {
 	struct hashmap_entry key;
 	hashmap_entry_init(&key, hash);
@@ -318,7 +336,8 @@ static inline void *hashmap_get_from_hash(const struct hashmap *map,
  * `entry` is the hashmap_entry to start the search from, obtained via a previous
  * call to `hashmap_get` or `hashmap_get_next`.
  */
-void *hashmap_get_next(const struct hashmap *map, const void *entry);
+struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
+			const struct hashmap_entry *entry);
 
 /*
  * Adds a hashmap entry. This allows to add duplicate entries (i.e.
@@ -327,7 +346,7 @@ void *hashmap_get_next(const struct hashmap *map, const void *entry);
  * `map` is the hashmap structure.
  * `entry` is the entry to add.
  */
-void hashmap_add(struct hashmap *map, void *entry);
+void hashmap_add(struct hashmap *map, struct hashmap_entry *entry);
 
 /*
  * Adds or replaces a hashmap entry. If the hashmap contains duplicate
@@ -337,7 +356,20 @@ void hashmap_add(struct hashmap *map, void *entry);
  * `entry` is the entry to add or replace.
  * Returns the replaced entry, or NULL if not found (i.e. the entry was added).
  */
-void *hashmap_put(struct hashmap *map, void *entry);
+struct hashmap_entry *hashmap_put(struct hashmap *map,
+				struct hashmap_entry *entry);
+
+/*
+ * Adds or replaces a hashmap entry contained within @keyvar,
+ * where @keyvar is a pointer to a struct containing a
+ * "struct hashmap_entry" @member.
+ *
+ * Returns the replaced pointer which is of the same type as @keyvar,
+ * or NULL if not found.
+ */
+#define hashmap_put_entry(map, keyvar, member) \
+	container_of_or_null_offset(hashmap_put(map, &(keyvar)->member), \
+				OFFSETOF_VAR(keyvar, member))
 
 /*
  * Removes a hashmap entry matching the specified key. If the hashmap contains
@@ -346,8 +378,24 @@ void *hashmap_put(struct hashmap *map, void *entry);
  *
  * Argument explanation is the same as in `hashmap_get`.
  */
-void *hashmap_remove(struct hashmap *map, const void *key,
-		const void *keydata);
+struct hashmap_entry *hashmap_remove(struct hashmap *map,
+					const struct hashmap_entry *key,
+					const void *keydata);
+
+/*
+ * Removes a hashmap entry contained within @keyvar,
+ * where @keyvar is a pointer to a struct containing a
+ * "struct hashmap_entry" @member.
+ *
+ * See `hashmap_get` for an explanation of @keydata
+ *
+ * Returns the replaced pointer which is of the same type as @keyvar,
+ * or NULL if not found.
+ */
+#define hashmap_remove_entry(map, keyvar, member, keydata) \
+	container_of_or_null_offset( \
+			hashmap_remove(map, &(keyvar)->member, keydata), \
+			OFFSETOF_VAR(keyvar, member))
 
 /*
  * Returns the `bucket` an entry is stored in.
@@ -370,10 +418,10 @@ struct hashmap_iter {
 void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter);
 
 /* Returns the next hashmap_entry, or NULL if there are no more entries. */
-void *hashmap_iter_next(struct hashmap_iter *iter);
+struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter);
 
 /* Initializes the iterator and returns the first entry, if any. */
-static inline void *hashmap_iter_first(struct hashmap *map,
+static inline struct hashmap_entry *hashmap_iter_first(struct hashmap *map,
 		struct hashmap_iter *iter)
 {
 	hashmap_iter_init(map, iter);
@@ -381,6 +429,64 @@ static inline void *hashmap_iter_first(struct hashmap *map,
 }
 
 /*
+ * returns the first entry in @map using @iter, where the entry is of
+ * @type (e.g. "struct foo") and @member is the name of the
+ * "struct hashmap_entry" in @type
+ */
+#define hashmap_iter_first_entry(map, iter, type, member) \
+	container_of_or_null(hashmap_iter_first(map, iter), type, member)
+
+/* internal macro for hashmap_for_each_entry */
+#define hashmap_iter_next_entry_offset(iter, offset) \
+	container_of_or_null_offset(hashmap_iter_next(iter), offset)
+
+/* internal macro for hashmap_for_each_entry */
+#define hashmap_iter_first_entry_offset(map, iter, offset) \
+	container_of_or_null_offset(hashmap_iter_first(map, iter), offset)
+
+/*
+ * iterate through @map using @iter, @var is a pointer to a type
+ * containing a @member which is a "struct hashmap_entry"
+ */
+#define hashmap_for_each_entry(map, iter, var, member) \
+	for (var = hashmap_iter_first_entry_offset(map, iter, \
+						OFFSETOF_VAR(var, member)); \
+		var; \
+		var = hashmap_iter_next_entry_offset(iter, \
+						OFFSETOF_VAR(var, member)))
+
+/*
+ * returns a pointer of type matching @keyvar, or NULL if nothing found.
+ * @keyvar is a pointer to a struct containing a
+ * "struct hashmap_entry" @member.
+ */
+#define hashmap_get_entry(map, keyvar, member, keydata) \
+	container_of_or_null_offset( \
+				hashmap_get(map, &(keyvar)->member, keydata), \
+				OFFSETOF_VAR(keyvar, member))
+
+#define hashmap_get_entry_from_hash(map, hash, keydata, type, member) \
+	container_of_or_null(hashmap_get_from_hash(map, hash, keydata), \
+				type, member)
+/*
+ * returns the next equal pointer to @var, or NULL if not found.
+ * @var is a pointer of any type containing "struct hashmap_entry"
+ * @member is the name of the "struct hashmap_entry" field
+ */
+#define hashmap_get_next_entry(map, var, member) \
+	container_of_or_null_offset(hashmap_get_next(map, &(var)->member), \
+				OFFSETOF_VAR(var, member))
+
+/*
+ * iterate @map starting from @var, where @var is a pointer of @type
+ * and @member is the name of the "struct hashmap_entry" field in @type
+ */
+#define hashmap_for_each_entry_from(map, var, member) \
+	for (; \
+		var; \
+		var = hashmap_get_next_entry(map, var, member))
+
+/*
  * Disable item counting and automatic rehashing when adding/removing items.
  *
  * Normally, the hashmap keeps track of the number of items in the map
diff --git a/merge-recursive.c b/merge-recursive.c
index e86571c91b..42be7c9960 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -45,14 +45,16 @@ struct path_hashmap_entry {
 };
 
 static int path_hashmap_cmp(const void *cmp_data,
-			    const void *entry,
-			    const void *entry_or_key,
+			    const struct hashmap_entry *eptr,
+			    const struct hashmap_entry *entry_or_key,
 			    const void *keydata)
 {
-	const struct path_hashmap_entry *a = entry;
-	const struct path_hashmap_entry *b = entry_or_key;
+	const struct path_hashmap_entry *a, *b;
 	const char *key = keydata;
 
+	a = container_of(eptr, const struct path_hashmap_entry, e);
+	b = container_of(entry_or_key, const struct path_hashmap_entry, e);
+
 	if (ignore_case)
 		return strcasecmp(a->path, key ? key : b->path);
 	else
@@ -75,7 +77,7 @@ static unsigned int path_hash(const char *path)
  *                       in get_directory_renames() for details
  */
 struct dir_rename_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	char *dir;
 	unsigned non_unique_new_dir:1;
 	struct strbuf new_dir;
@@ -89,18 +91,20 @@ static struct dir_rename_entry *dir_rename_find_entry(struct hashmap *hashmap,
 
 	if (dir == NULL)
 		return NULL;
-	hashmap_entry_init(&key, strhash(dir));
+	hashmap_entry_init(&key.ent, strhash(dir));
 	key.dir = dir;
-	return hashmap_get(hashmap, &key, NULL);
+	return hashmap_get_entry(hashmap, &key, ent, NULL);
 }
 
 static int dir_rename_cmp(const void *unused_cmp_data,
-			  const void *entry,
-			  const void *entry_or_key,
+			  const struct hashmap_entry *eptr,
+			  const struct hashmap_entry *entry_or_key,
 			  const void *unused_keydata)
 {
-	const struct dir_rename_entry *e1 = entry;
-	const struct dir_rename_entry *e2 = entry_or_key;
+	const struct dir_rename_entry *e1, *e2;
+
+	e1 = container_of(eptr, const struct dir_rename_entry, ent);
+	e2 = container_of(entry_or_key, const struct dir_rename_entry, ent);
 
 	return strcmp(e1->dir, e2->dir);
 }
@@ -113,7 +117,7 @@ static void dir_rename_init(struct hashmap *map)
 static void dir_rename_entry_init(struct dir_rename_entry *entry,
 				  char *directory)
 {
-	hashmap_entry_init(entry, strhash(directory));
+	hashmap_entry_init(&entry->ent, strhash(directory));
 	entry->dir = directory;
 	entry->non_unique_new_dir = 0;
 	strbuf_init(&entry->new_dir, 0);
@@ -121,7 +125,7 @@ static void dir_rename_entry_init(struct dir_rename_entry *entry,
 }
 
 struct collision_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	char *target_file;
 	struct string_list source_files;
 	unsigned reported_already:1;
@@ -132,22 +136,27 @@ static struct collision_entry *collision_find_entry(struct hashmap *hashmap,
 {
 	struct collision_entry key;
 
-	hashmap_entry_init(&key, strhash(target_file));
+	hashmap_entry_init(&key.ent, strhash(target_file));
 	key.target_file = target_file;
-	return hashmap_get(hashmap, &key, NULL);
+	return hashmap_get_entry(hashmap, &key, ent, NULL);
 }
 
-static int collision_cmp(void *unused_cmp_data,
-			 const struct collision_entry *e1,
-			 const struct collision_entry *e2,
+static int collision_cmp(const void *unused_cmp_data,
+			 const struct hashmap_entry *eptr,
+			 const struct hashmap_entry *entry_or_key,
 			 const void *unused_keydata)
 {
+	const struct collision_entry *e1, *e2;
+
+	e1 = container_of(eptr, const struct collision_entry, ent);
+	e2 = container_of(entry_or_key, const struct collision_entry, ent);
+
 	return strcmp(e1->target_file, e2->target_file);
 }
 
 static void collision_init(struct hashmap *map)
 {
-	hashmap_init(map, (hashmap_cmp_fn) collision_cmp, NULL, 0);
+	hashmap_init(map, collision_cmp, NULL, 0);
 }
 
 static void flush_output(struct merge_options *opt)
@@ -464,8 +473,8 @@ static int save_files_dirs(const struct object_id *oid,
 	strbuf_addstr(base, path);
 
 	FLEX_ALLOC_MEM(entry, path, base->buf, base->len);
-	hashmap_entry_init(entry, path_hash(entry->path));
-	hashmap_add(&opt->priv->current_file_dir_set, entry);
+	hashmap_entry_init(&entry->e, path_hash(entry->path));
+	hashmap_add(&opt->priv->current_file_dir_set, &entry->e);
 
 	strbuf_setlen(base, baselen);
 	return (S_ISDIR(mode) ? READ_TREE_RECURSIVE : 0);
@@ -743,8 +752,8 @@ static char *unique_path(struct merge_options *opt,
 	}
 
 	FLEX_ALLOC_MEM(entry, path, newpath.buf, newpath.len);
-	hashmap_entry_init(entry, path_hash(entry->path));
-	hashmap_add(&opt->priv->current_file_dir_set, entry);
+	hashmap_entry_init(&entry->e, path_hash(entry->path));
+	hashmap_add(&opt->priv->current_file_dir_set, &entry->e);
 	return strbuf_detach(&newpath, NULL);
 }
 
@@ -2013,7 +2022,7 @@ static void remove_hashmap_entries(struct hashmap *dir_renames,
 
 	for (i = 0; i < items_to_remove->nr; i++) {
 		entry = items_to_remove->items[i].util;
-		hashmap_remove(dir_renames, entry, NULL);
+		hashmap_remove(dir_renames, &entry->ent, NULL);
 	}
 	string_list_clear(items_to_remove, 0);
 }
@@ -2136,8 +2145,8 @@ static void handle_directory_level_conflicts(struct merge_options *opt,
 	struct string_list remove_from_head = STRING_LIST_INIT_NODUP;
 	struct string_list remove_from_merge = STRING_LIST_INIT_NODUP;
 
-	hashmap_iter_init(dir_re_head, &iter);
-	while ((head_ent = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_re_head, &iter, head_ent,
+				ent /* member name */) {
 		merge_ent = dir_rename_find_entry(dir_re_merge, head_ent->dir);
 		if (merge_ent &&
 		    !head_ent->non_unique_new_dir &&
@@ -2161,8 +2170,8 @@ static void handle_directory_level_conflicts(struct merge_options *opt,
 	remove_hashmap_entries(dir_re_head, &remove_from_head);
 	remove_hashmap_entries(dir_re_merge, &remove_from_merge);
 
-	hashmap_iter_init(dir_re_merge, &iter);
-	while ((merge_ent = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_re_merge, &iter, merge_ent,
+				ent /* member name */) {
 		head_ent = dir_rename_find_entry(dir_re_head, merge_ent->dir);
 		if (tree_has_path(opt->repo, merge, merge_ent->dir)) {
 			/* 2. This wasn't a directory rename after all */
@@ -2241,7 +2250,7 @@ static struct hashmap *get_directory_renames(struct diff_queue_struct *pairs)
 		if (!entry) {
 			entry = xmalloc(sizeof(*entry));
 			dir_rename_entry_init(entry, old_dir);
-			hashmap_put(dir_renames, entry);
+			hashmap_put(dir_renames, &entry->ent);
 		} else {
 			free(old_dir);
 		}
@@ -2266,8 +2275,8 @@ static struct hashmap *get_directory_renames(struct diff_queue_struct *pairs)
 	 * we set non_unique_new_dir.  Once we've determined the winner (or
 	 * that there is no winner), we no longer need possible_new_dirs.
 	 */
-	hashmap_iter_init(dir_renames, &iter);
-	while ((entry = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_renames, &iter, entry,
+				ent /* member name */) {
 		int max = 0;
 		int bad_max = 0;
 		char *best = NULL;
@@ -2370,8 +2379,9 @@ static void compute_collisions(struct hashmap *collisions,
 		if (!collision_ent) {
 			collision_ent = xcalloc(1,
 						sizeof(struct collision_entry));
-			hashmap_entry_init(collision_ent, strhash(new_path));
-			hashmap_put(collisions, collision_ent);
+			hashmap_entry_init(&collision_ent->ent,
+						strhash(new_path));
+			hashmap_put(collisions, &collision_ent->ent);
 			collision_ent->target_file = new_path;
 		} else {
 			free(new_path);
@@ -2624,12 +2634,12 @@ static struct string_list *get_renames(struct merge_options *opt,
 							     entries);
 	}
 
-	hashmap_iter_init(&collisions, &iter);
-	while ((e = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(&collisions, &iter, e,
+				ent /* member name */) {
 		free(e->target_file);
 		string_list_clear(&e->source_files, 0);
 	}
-	hashmap_free(&collisions, 1);
+	hashmap_free_entries(&collisions, struct collision_entry, ent);
 	return renames;
 }
 
@@ -2842,13 +2852,13 @@ static void initial_cleanup_rename(struct diff_queue_struct *pairs,
 	struct hashmap_iter iter;
 	struct dir_rename_entry *e;
 
-	hashmap_iter_init(dir_renames, &iter);
-	while ((e = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_renames, &iter, e,
+				ent /* member name */) {
 		free(e->dir);
 		strbuf_release(&e->new_dir);
 		/* possible_new_dirs already cleared in get_directory_renames */
 	}
-	hashmap_free(dir_renames, 1);
+	hashmap_free_entries(dir_renames, struct dir_rename_entry, ent);
 	free(dir_renames);
 
 	free(pairs->queue);
@@ -3475,7 +3485,8 @@ static int merge_trees_internal(struct merge_options *opt,
 		string_list_clear(entries, 1);
 		free(entries);
 
-		hashmap_free(&opt->priv->current_file_dir_set, 1);
+		hashmap_free_entries(&opt->priv->current_file_dir_set,
+					struct path_hashmap_entry, e);
 
 		if (clean < 0) {
 			unpack_trees_finish(opt);
diff --git a/name-hash.c b/name-hash.c
index 695908609f..ceb1d7bd6f 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -17,14 +17,16 @@ struct dir_entry {
 };
 
 static int dir_entry_cmp(const void *unused_cmp_data,
-			 const void *entry,
-			 const void *entry_or_key,
+			 const struct hashmap_entry *eptr,
+			 const struct hashmap_entry *entry_or_key,
 			 const void *keydata)
 {
-	const struct dir_entry *e1 = entry;
-	const struct dir_entry *e2 = entry_or_key;
+	const struct dir_entry *e1, *e2;
 	const char *name = keydata;
 
+	e1 = container_of(eptr, const struct dir_entry, ent);
+	e2 = container_of(entry_or_key, const struct dir_entry, ent);
+
 	return e1->namelen != e2->namelen || strncasecmp(e1->name,
 			name ? name : e2->name, e1->namelen);
 }
@@ -33,9 +35,9 @@ static struct dir_entry *find_dir_entry__hash(struct index_state *istate,
 		const char *name, unsigned int namelen, unsigned int hash)
 {
 	struct dir_entry key;
-	hashmap_entry_init(&key, hash);
+	hashmap_entry_init(&key.ent, hash);
 	key.namelen = namelen;
-	return hashmap_get(&istate->dir_hash, &key, name);
+	return hashmap_get_entry(&istate->dir_hash, &key, ent, name);
 }
 
 static struct dir_entry *find_dir_entry(struct index_state *istate,
@@ -68,9 +70,9 @@ static struct dir_entry *hash_dir_entry(struct index_state *istate,
 	if (!dir) {
 		/* not found, create it and add to hash table */
 		FLEX_ALLOC_MEM(dir, name, ce->name, namelen);
-		hashmap_entry_init(dir, memihash(ce->name, namelen));
+		hashmap_entry_init(&dir->ent, memihash(ce->name, namelen));
 		dir->namelen = namelen;
-		hashmap_add(&istate->dir_hash, dir);
+		hashmap_add(&istate->dir_hash, &dir->ent);
 
 		/* recursively add missing parent directories */
 		dir->parent = hash_dir_entry(istate, ce, namelen);
@@ -95,7 +97,7 @@ static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
 	struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
 	while (dir && !(--dir->nr)) {
 		struct dir_entry *parent = dir->parent;
-		hashmap_remove(&istate->dir_hash, dir, NULL);
+		hashmap_remove(&istate->dir_hash, &dir->ent, NULL);
 		free(dir);
 		dir = parent;
 	}
@@ -106,20 +108,23 @@ static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 	if (ce->ce_flags & CE_HASHED)
 		return;
 	ce->ce_flags |= CE_HASHED;
-	hashmap_entry_init(ce, memihash(ce->name, ce_namelen(ce)));
-	hashmap_add(&istate->name_hash, ce);
+	hashmap_entry_init(&ce->ent, memihash(ce->name, ce_namelen(ce)));
+	hashmap_add(&istate->name_hash, &ce->ent);
 
 	if (ignore_case)
 		add_dir_entry(istate, ce);
 }
 
 static int cache_entry_cmp(const void *unused_cmp_data,
-			   const void *entry,
-			   const void *entry_or_key,
+			   const struct hashmap_entry *eptr,
+			   const struct hashmap_entry *entry_or_key,
 			   const void *remove)
 {
-	const struct cache_entry *ce1 = entry;
-	const struct cache_entry *ce2 = entry_or_key;
+	const struct cache_entry *ce1, *ce2;
+
+	ce1 = container_of(eptr, const struct cache_entry, ent);
+	ce2 = container_of(entry_or_key, const struct cache_entry, ent);
+
 	/*
 	 * For remove_name_hash, find the exact entry (pointer equality); for
 	 * index_file_exists, find all entries with matching hash code and
@@ -280,10 +285,10 @@ static struct dir_entry *hash_dir_entry_with_parent_and_prefix(
 	dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash);
 	if (!dir) {
 		FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len);
-		hashmap_entry_init(dir, hash);
+		hashmap_entry_init(&dir->ent, hash);
 		dir->namelen = prefix->len;
 		dir->parent = parent;
-		hashmap_add(&istate->dir_hash, dir);
+		hashmap_add(&istate->dir_hash, &dir->ent);
 
 		if (parent) {
 			unlock_dir_mutex(lock_nr);
@@ -472,8 +477,8 @@ static void *lazy_name_thread_proc(void *_data)
 	for (k = 0; k < d->istate->cache_nr; k++) {
 		struct cache_entry *ce_k = d->istate->cache[k];
 		ce_k->ce_flags |= CE_HASHED;
-		hashmap_entry_init(ce_k, d->lazy_entries[k].hash_name);
-		hashmap_add(&d->istate->name_hash, ce_k);
+		hashmap_entry_init(&ce_k->ent, d->lazy_entries[k].hash_name);
+		hashmap_add(&d->istate->name_hash, &ce_k->ent);
 	}
 
 	return NULL;
@@ -625,7 +630,7 @@ void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 	if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))
 		return;
 	ce->ce_flags &= ~CE_HASHED;
-	hashmap_remove(&istate->name_hash, ce, ce);
+	hashmap_remove(&istate->name_hash, &ce->ent, ce);
 
 	if (ignore_case)
 		remove_dir_entry(istate, ce);
@@ -702,15 +707,15 @@ void adjust_dirname_case(struct index_state *istate, char *name)
 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 {
 	struct cache_entry *ce;
+	unsigned int hash = memihash(name, namelen);
 
 	lazy_init_name_hash(istate);
 
-	ce = hashmap_get_from_hash(&istate->name_hash,
-				   memihash(name, namelen), NULL);
-	while (ce) {
+	ce = hashmap_get_entry_from_hash(&istate->name_hash, hash, NULL,
+					 struct cache_entry, ent);
+	hashmap_for_each_entry_from(&istate->name_hash, ce, ent) {
 		if (same_name(ce, name, namelen, icase))
 			return ce;
-		ce = hashmap_get_next(&istate->name_hash, ce);
 	}
 	return NULL;
 }
@@ -721,6 +726,6 @@ void free_name_hash(struct index_state *istate)
 		return;
 	istate->name_hash_initialized = 0;
 
-	hashmap_free(&istate->name_hash, 0);
-	hashmap_free(&istate->dir_hash, 1);
+	hashmap_free(&istate->name_hash);
+	hashmap_free_entries(&istate->dir_hash, struct dir_entry, ent);
 }
diff --git a/oidmap.c b/oidmap.c
index 6d6e840d03..423aa014a3 100644
--- a/oidmap.c
+++ b/oidmap.c
@@ -2,14 +2,18 @@
 #include "oidmap.h"
 
 static int oidmap_neq(const void *hashmap_cmp_fn_data,
-		      const void *entry, const void *entry_or_key,
+		      const struct hashmap_entry *e1,
+		      const struct hashmap_entry *e2,
 		      const void *keydata)
 {
-	const struct oidmap_entry *entry_ = entry;
+	const struct oidmap_entry *a, *b;
+
+	a = container_of(e1, const struct oidmap_entry, internal_entry);
+	b = container_of(e2, const struct oidmap_entry, internal_entry);
+
 	if (keydata)
-		return !oideq(&entry_->oid, (const struct object_id *) keydata);
-	return !oideq(&entry_->oid,
-		      &((const struct oidmap_entry *) entry_or_key)->oid);
+		return !oideq(&a->oid, (const struct object_id *) keydata);
+	return !oideq(&a->oid, &b->oid);
 }
 
 void oidmap_init(struct oidmap *map, size_t initial_size)
@@ -21,7 +25,9 @@ void oidmap_free(struct oidmap *map, int free_entries)
 {
 	if (!map)
 		return;
-	hashmap_free(&map->map, free_entries);
+
+	/* TODO: make oidmap itself not depend on struct layouts */
+	hashmap_free_(&map->map, free_entries ? 0 : -1);
 }
 
 void *oidmap_get(const struct oidmap *map, const struct object_id *key)
@@ -51,5 +57,5 @@ void *oidmap_put(struct oidmap *map, void *entry)
 		oidmap_init(map, 0);
 
 	hashmap_entry_init(&to_put->internal_entry, oidhash(&to_put->oid));
-	return hashmap_put(&map->map, to_put);
+	return hashmap_put(&map->map, &to_put->internal_entry);
 }
diff --git a/oidmap.h b/oidmap.h
index 7a939461ff..c66a83ab1d 100644
--- a/oidmap.h
+++ b/oidmap.h
@@ -78,14 +78,16 @@ static inline void oidmap_iter_init(struct oidmap *map, struct oidmap_iter *iter
 
 static inline void *oidmap_iter_next(struct oidmap_iter *iter)
 {
-	return hashmap_iter_next(&iter->h_iter);
+	/* TODO: this API could be reworked to do compile-time type checks */
+	return (void *)hashmap_iter_next(&iter->h_iter);
 }
 
 static inline void *oidmap_iter_first(struct oidmap *map,
 				      struct oidmap_iter *iter)
 {
 	oidmap_iter_init(map, iter);
-	return oidmap_iter_next(iter);
+	/* TODO: this API could be reworked to do compile-time type checks */
+	return (void *)oidmap_iter_next(iter);
 }
 
 #endif
diff --git a/packfile.c b/packfile.c
index b4c218d78e..355066de17 100644
--- a/packfile.c
+++ b/packfile.c
@@ -1343,7 +1343,7 @@ struct delta_base_cache_key {
 };
 
 struct delta_base_cache_entry {
-	struct hashmap hash;
+	struct hashmap_entry ent;
 	struct delta_base_cache_key key;
 	struct list_head lru;
 	void *data;
@@ -1363,7 +1363,7 @@ static unsigned int pack_entry_hash(struct packed_git *p, off_t base_offset)
 static struct delta_base_cache_entry *
 get_delta_base_cache_entry(struct packed_git *p, off_t base_offset)
 {
-	struct hashmap_entry entry;
+	struct hashmap_entry entry, *e;
 	struct delta_base_cache_key key;
 
 	if (!delta_base_cache.cmpfn)
@@ -1372,7 +1372,8 @@ get_delta_base_cache_entry(struct packed_git *p, off_t base_offset)
 	hashmap_entry_init(&entry, pack_entry_hash(p, base_offset));
 	key.p = p;
 	key.base_offset = base_offset;
-	return hashmap_get(&delta_base_cache, &entry, &key);
+	e = hashmap_get(&delta_base_cache, &entry, &key);
+	return e ? container_of(e, struct delta_base_cache_entry, ent) : NULL;
 }
 
 static int delta_base_cache_key_eq(const struct delta_base_cache_key *a,
@@ -1382,11 +1383,16 @@ static int delta_base_cache_key_eq(const struct delta_base_cache_key *a,
 }
 
 static int delta_base_cache_hash_cmp(const void *unused_cmp_data,
-				     const void *va, const void *vb,
+				     const struct hashmap_entry *va,
+				     const struct hashmap_entry *vb,
 				     const void *vkey)
 {
-	const struct delta_base_cache_entry *a = va, *b = vb;
+	const struct delta_base_cache_entry *a, *b;
 	const struct delta_base_cache_key *key = vkey;
+
+	a = container_of(va, const struct delta_base_cache_entry, ent);
+	b = container_of(vb, const struct delta_base_cache_entry, ent);
+
 	if (key)
 		return !delta_base_cache_key_eq(&a->key, key);
 	else
@@ -1405,7 +1411,7 @@ static int in_delta_base_cache(struct packed_git *p, off_t base_offset)
  */
 static void detach_delta_base_cache_entry(struct delta_base_cache_entry *ent)
 {
-	hashmap_remove(&delta_base_cache, ent, &ent->key);
+	hashmap_remove(&delta_base_cache, &ent->ent, &ent->key);
 	list_del(&ent->lru);
 	delta_base_cached -= ent->size;
 	free(ent);
@@ -1469,8 +1475,8 @@ static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
 
 	if (!delta_base_cache.cmpfn)
 		hashmap_init(&delta_base_cache, delta_base_cache_hash_cmp, NULL, 0);
-	hashmap_entry_init(ent, pack_entry_hash(p, base_offset));
-	hashmap_add(&delta_base_cache, ent);
+	hashmap_entry_init(&ent->ent, pack_entry_hash(p, base_offset));
+	hashmap_add(&delta_base_cache, &ent->ent);
 }
 
 int packed_object_info(struct repository *r, struct packed_git *p,
diff --git a/patch-ids.c b/patch-ids.c
index e8c150d0c9..12aa6d494b 100644
--- a/patch-ids.c
+++ b/patch-ids.c
@@ -36,14 +36,16 @@ int commit_patch_id(struct commit *commit, struct diff_options *options,
  * any significance; only that it is non-zero matters.
  */
 static int patch_id_neq(const void *cmpfn_data,
-			const void *entry,
-			const void *entry_or_key,
+			const struct hashmap_entry *eptr,
+			const struct hashmap_entry *entry_or_key,
 			const void *unused_keydata)
 {
 	/* NEEDSWORK: const correctness? */
 	struct diff_options *opt = (void *)cmpfn_data;
-	struct patch_id *a = (void *)entry;
-	struct patch_id *b = (void *)entry_or_key;
+	struct patch_id *a, *b;
+
+	a = container_of(eptr, struct patch_id, ent);
+	b = container_of(entry_or_key, struct patch_id, ent);
 
 	if (is_null_oid(&a->patch_id) &&
 	    commit_patch_id(a->commit, opt, &a->patch_id, 0, 0))
@@ -69,7 +71,7 @@ int init_patch_ids(struct repository *r, struct patch_ids *ids)
 
 int free_patch_ids(struct patch_ids *ids)
 {
-	hashmap_free(&ids->patches, 1);
+	hashmap_free_entries(&ids->patches, struct patch_id, ent);
 	return 0;
 }
 
@@ -83,7 +85,7 @@ static int init_patch_id_entry(struct patch_id *patch,
 	if (commit_patch_id(commit, &ids->diffopts, &header_only_patch_id, 1, 0))
 		return -1;
 
-	hashmap_entry_init(patch, oidhash(&header_only_patch_id));
+	hashmap_entry_init(&patch->ent, oidhash(&header_only_patch_id));
 	return 0;
 }
 
@@ -99,7 +101,7 @@ struct patch_id *has_commit_patch_id(struct commit *commit,
 	if (init_patch_id_entry(&patch, commit, ids))
 		return NULL;
 
-	return hashmap_get(&ids->patches, &patch, NULL);
+	return hashmap_get_entry(&ids->patches, &patch, ent, NULL);
 }
 
 struct patch_id *add_commit_patch_id(struct commit *commit,
@@ -116,6 +118,6 @@ struct patch_id *add_commit_patch_id(struct commit *commit,
 		return NULL;
 	}
 
-	hashmap_add(&ids->patches, key);
+	hashmap_add(&ids->patches, &key->ent);
 	return key;
 }
diff --git a/range-diff.c b/range-diff.c
index f2fc1e02c2..7fed5a3b4b 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -218,8 +218,8 @@ static void find_exact_matches(struct string_list *a, struct string_list *b)
 		util->i = i;
 		util->patch = a->items[i].string;
 		util->diff = util->patch + util->diff_offset;
-		hashmap_entry_init(util, strhash(util->diff));
-		hashmap_add(&map, util);
+		hashmap_entry_init(&util->e, strhash(util->diff));
+		hashmap_add(&map, &util->e);
 	}
 
 	/* Now try to find exact matches in b */
@@ -229,8 +229,8 @@ static void find_exact_matches(struct string_list *a, struct string_list *b)
 		util->i = i;
 		util->patch = b->items[i].string;
 		util->diff = util->patch + util->diff_offset;
-		hashmap_entry_init(util, strhash(util->diff));
-		other = hashmap_remove(&map, util, NULL);
+		hashmap_entry_init(&util->e, strhash(util->diff));
+		other = hashmap_remove_entry(&map, util, e, NULL);
 		if (other) {
 			if (other->matching >= 0)
 				BUG("already assigned!");
@@ -240,7 +240,7 @@ static void find_exact_matches(struct string_list *a, struct string_list *b)
 		}
 	}
 
-	hashmap_free(&map, 0);
+	hashmap_free(&map);
 }
 
 static void diffsize_consume(void *data, char *line, unsigned long len)
diff --git a/ref-filter.c b/ref-filter.c
index 220e9bd74a..6867e33648 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -79,17 +79,20 @@ static struct expand_data {
 } oi, oi_deref;
 
 struct ref_to_worktree_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	struct worktree *wt; /* key is wt->head_ref */
 };
 
 static int ref_to_worktree_map_cmpfnc(const void *unused_lookupdata,
-				      const void *existing_hashmap_entry_to_test,
-				      const void *key,
+				      const struct hashmap_entry *eptr,
+				      const struct hashmap_entry *kptr,
 				      const void *keydata_aka_refname)
 {
-	const struct ref_to_worktree_entry *e = existing_hashmap_entry_to_test;
-	const struct ref_to_worktree_entry *k = key;
+	const struct ref_to_worktree_entry *e, *k;
+
+	e = container_of(eptr, const struct ref_to_worktree_entry, ent);
+	k = container_of(kptr, const struct ref_to_worktree_entry, ent);
+
 	return strcmp(e->wt->head_ref,
 		keydata_aka_refname ? keydata_aka_refname : k->wt->head_ref);
 }
@@ -1565,9 +1568,10 @@ static void populate_worktree_map(struct hashmap *map, struct worktree **worktre
 			struct ref_to_worktree_entry *entry;
 			entry = xmalloc(sizeof(*entry));
 			entry->wt = worktrees[i];
-			hashmap_entry_init(entry, strhash(worktrees[i]->head_ref));
+			hashmap_entry_init(&entry->ent,
+					strhash(worktrees[i]->head_ref));
 
-			hashmap_add(map, entry);
+			hashmap_add(map, &entry->ent);
 		}
 	}
 }
@@ -1584,18 +1588,20 @@ static void lazy_init_worktree_map(void)
 
 static char *get_worktree_path(const struct used_atom *atom, const struct ref_array_item *ref)
 {
-	struct hashmap_entry entry;
+	struct hashmap_entry entry, *e;
 	struct ref_to_worktree_entry *lookup_result;
 
 	lazy_init_worktree_map();
 
 	hashmap_entry_init(&entry, strhash(ref->refname));
-	lookup_result = hashmap_get(&(ref_to_worktree_map.map), &entry, ref->refname);
+	e = hashmap_get(&(ref_to_worktree_map.map), &entry, ref->refname);
 
-	if (lookup_result)
-		return xstrdup(lookup_result->wt->path);
-	else
+	if (!e)
 		return xstrdup("");
+
+	lookup_result = container_of(e, struct ref_to_worktree_entry, ent);
+
+	return xstrdup(lookup_result->wt->path);
 }
 
 /*
@@ -2166,7 +2172,8 @@ void ref_array_clear(struct ref_array *array)
 	used_atom_cnt = 0;
 
 	if (ref_to_worktree_map.worktrees) {
-		hashmap_free(&(ref_to_worktree_map.map), 1);
+		hashmap_free_entries(&(ref_to_worktree_map.map),
+					struct ref_to_worktree_entry, ent);
 		free_worktrees(ref_to_worktree_map.worktrees);
 		ref_to_worktree_map.worktrees = NULL;
 	}
diff --git a/refs.c b/refs.c
index cd297ee4bd..1ab0bb54d3 100644
--- a/refs.c
+++ b/refs.c
@@ -1772,7 +1772,7 @@ int resolve_gitlink_ref(const char *submodule, const char *refname,
 
 struct ref_store_hash_entry
 {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 
 	struct ref_store *refs;
 
@@ -1781,11 +1781,16 @@ struct ref_store_hash_entry
 };
 
 static int ref_store_hash_cmp(const void *unused_cmp_data,
-			      const void *entry, const void *entry_or_key,
+			      const struct hashmap_entry *eptr,
+			      const struct hashmap_entry *entry_or_key,
 			      const void *keydata)
 {
-	const struct ref_store_hash_entry *e1 = entry, *e2 = entry_or_key;
-	const char *name = keydata ? keydata : e2->name;
+	const struct ref_store_hash_entry *e1, *e2;
+	const char *name;
+
+	e1 = container_of(eptr, const struct ref_store_hash_entry, ent);
+	e2 = container_of(entry_or_key, const struct ref_store_hash_entry, ent);
+	name = keydata ? keydata : e2->name;
 
 	return strcmp(e1->name, name);
 }
@@ -1796,7 +1801,7 @@ static struct ref_store_hash_entry *alloc_ref_store_hash_entry(
 	struct ref_store_hash_entry *entry;
 
 	FLEX_ALLOC_STR(entry, name, name);
-	hashmap_entry_init(entry, strhash(name));
+	hashmap_entry_init(&entry->ent, strhash(name));
 	entry->refs = refs;
 	return entry;
 }
@@ -1815,12 +1820,15 @@ static struct ref_store *lookup_ref_store_map(struct hashmap *map,
 					      const char *name)
 {
 	struct ref_store_hash_entry *entry;
+	unsigned int hash;
 
 	if (!map->tablesize)
 		/* It's initialized on demand in register_ref_store(). */
 		return NULL;
 
-	entry = hashmap_get_from_hash(map, strhash(name), name);
+	hash = strhash(name);
+	entry = hashmap_get_entry_from_hash(map, hash, name,
+					struct ref_store_hash_entry, ent);
 	return entry ? entry->refs : NULL;
 }
 
@@ -1863,10 +1871,13 @@ static void register_ref_store_map(struct hashmap *map,
 				   struct ref_store *refs,
 				   const char *name)
 {
+	struct ref_store_hash_entry *entry;
+
 	if (!map->tablesize)
 		hashmap_init(map, ref_store_hash_cmp, NULL, 0);
 
-	if (hashmap_put(map, alloc_ref_store_hash_entry(name, refs)))
+	entry = alloc_ref_store_hash_entry(name, refs);
+	if (hashmap_put(map, &entry->ent))
 		BUG("%s ref_store '%s' initialized twice", type, name);
 }
 
diff --git a/remote.c b/remote.c
index e50f7602ed..5c4666b53a 100644
--- a/remote.c
+++ b/remote.c
@@ -111,14 +111,16 @@ struct remotes_hash_key {
 };
 
 static int remotes_hash_cmp(const void *unused_cmp_data,
-			    const void *entry,
-			    const void *entry_or_key,
+			    const struct hashmap_entry *eptr,
+			    const struct hashmap_entry *entry_or_key,
 			    const void *keydata)
 {
-	const struct remote *a = entry;
-	const struct remote *b = entry_or_key;
+	const struct remote *a, *b;
 	const struct remotes_hash_key *key = keydata;
 
+	a = container_of(eptr, const struct remote, ent);
+	b = container_of(entry_or_key, const struct remote, ent);
+
 	if (key)
 		return strncmp(a->name, key->str, key->len) || a->name[key->len];
 	else
@@ -135,7 +137,7 @@ static struct remote *make_remote(const char *name, int len)
 {
 	struct remote *ret, *replaced;
 	struct remotes_hash_key lookup;
-	struct hashmap_entry lookup_entry;
+	struct hashmap_entry lookup_entry, *e;
 
 	if (!len)
 		len = strlen(name);
@@ -145,8 +147,9 @@ static struct remote *make_remote(const char *name, int len)
 	lookup.len = len;
 	hashmap_entry_init(&lookup_entry, memhash(name, len));
 
-	if ((ret = hashmap_get(&remotes_hash, &lookup_entry, &lookup)) != NULL)
-		return ret;
+	e = hashmap_get(&remotes_hash, &lookup_entry, &lookup);
+	if (e)
+		return container_of(e, struct remote, ent);
 
 	ret = xcalloc(1, sizeof(struct remote));
 	ret->prune = -1;  /* unspecified */
@@ -158,8 +161,8 @@ static struct remote *make_remote(const char *name, int len)
 	ALLOC_GROW(remotes, remotes_nr + 1, remotes_alloc);
 	remotes[remotes_nr++] = ret;
 
-	hashmap_entry_init(ret, lookup_entry.hash);
-	replaced = hashmap_put(&remotes_hash, ret);
+	hashmap_entry_init(&ret->ent, lookup_entry.hash);
+	replaced = hashmap_put_entry(&remotes_hash, ret, ent);
 	assert(replaced == NULL);  /* no previous entry overwritten */
 	return ret;
 }
diff --git a/remote.h b/remote.h
index 83e885672b..0e1d2b245b 100644
--- a/remote.h
+++ b/remote.h
@@ -14,7 +14,7 @@ enum {
 };
 
 struct remote {
-	struct hashmap_entry ent;  /* must be first */
+	struct hashmap_entry ent;
 
 	const char *name;
 	int origin, configured_in_repo;
diff --git a/revision.c b/revision.c
index 0fc0b425f6..0e39b2b8a5 100644
--- a/revision.c
+++ b/revision.c
@@ -108,30 +108,34 @@ struct path_and_oids_entry {
 };
 
 static int path_and_oids_cmp(const void *hashmap_cmp_fn_data,
-			     const struct path_and_oids_entry *e1,
-			     const struct path_and_oids_entry *e2,
+			     const struct hashmap_entry *eptr,
+			     const struct hashmap_entry *entry_or_key,
 			     const void *keydata)
 {
+	const struct path_and_oids_entry *e1, *e2;
+
+	e1 = container_of(eptr, const struct path_and_oids_entry, ent);
+	e2 = container_of(entry_or_key, const struct path_and_oids_entry, ent);
+
 	return strcmp(e1->path, e2->path);
 }
 
 static void paths_and_oids_init(struct hashmap *map)
 {
-	hashmap_init(map, (hashmap_cmp_fn) path_and_oids_cmp, NULL, 0);
+	hashmap_init(map, path_and_oids_cmp, NULL, 0);
 }
 
 static void paths_and_oids_clear(struct hashmap *map)
 {
 	struct hashmap_iter iter;
 	struct path_and_oids_entry *entry;
-	hashmap_iter_init(map, &iter);
 
-	while ((entry = (struct path_and_oids_entry *)hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(map, &iter, entry, ent /* member name */) {
 		oidset_clear(&entry->trees);
 		free(entry->path);
 	}
 
-	hashmap_free(map, 1);
+	hashmap_free_entries(map, struct path_and_oids_entry, ent);
 }
 
 static void paths_and_oids_insert(struct hashmap *map,
@@ -142,18 +146,19 @@ static void paths_and_oids_insert(struct hashmap *map,
 	struct path_and_oids_entry key;
 	struct path_and_oids_entry *entry;
 
-	hashmap_entry_init(&key, hash);
+	hashmap_entry_init(&key.ent, hash);
 
 	/* use a shallow copy for the lookup */
 	key.path = (char *)path;
 	oidset_init(&key.trees, 0);
 
-	if (!(entry = (struct path_and_oids_entry *)hashmap_get(map, &key, NULL))) {
+	entry = hashmap_get_entry(map, &key, ent, NULL);
+	if (!entry) {
 		entry = xcalloc(1, sizeof(struct path_and_oids_entry));
-		hashmap_entry_init(entry, hash);
+		hashmap_entry_init(&entry->ent, hash);
 		entry->path = xstrdup(key.path);
 		oidset_init(&entry->trees, 16);
-		hashmap_put(map, entry);
+		hashmap_put(map, &entry->ent);
 	}
 
 	oidset_insert(&entry->trees, oid);
@@ -236,8 +241,7 @@ void mark_trees_uninteresting_sparse(struct repository *r,
 		add_children_by_path(r, tree, &map);
 	}
 
-	hashmap_iter_init(&map, &map_iter);
-	while ((entry = hashmap_iter_next(&map_iter)))
+	hashmap_for_each_entry(&map, &map_iter, entry, ent /* member name */)
 		mark_trees_uninteresting_sparse(r, &entry->trees);
 
 	paths_and_oids_clear(&map);
diff --git a/sequencer.c b/sequencer.c
index 5670bd7e7a..9d5964fd81 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -4397,9 +4397,14 @@ struct labels_entry {
 	char label[FLEX_ARRAY];
 };
 
-static int labels_cmp(const void *fndata, const struct labels_entry *a,
-		      const struct labels_entry *b, const void *key)
+static int labels_cmp(const void *fndata, const struct hashmap_entry *eptr,
+		      const struct hashmap_entry *entry_or_key, const void *key)
 {
+	const struct labels_entry *a, *b;
+
+	a = container_of(eptr, const struct labels_entry, entry);
+	b = container_of(entry_or_key, const struct labels_entry, entry);
+
 	return key ? strcmp(a->label, key) : strcmp(a->label, b->label);
 }
 
@@ -4495,8 +4500,8 @@ static const char *label_oid(struct object_id *oid, const char *label,
 	}
 
 	FLEX_ALLOC_STR(labels_entry, label, label);
-	hashmap_entry_init(labels_entry, strihash(label));
-	hashmap_add(&state->labels, labels_entry);
+	hashmap_entry_init(&labels_entry->entry, strihash(label));
+	hashmap_add(&state->labels, &labels_entry->entry);
 
 	FLEX_ALLOC_STR(string_entry, string, label);
 	oidcpy(&string_entry->entry.oid, oid);
@@ -4531,7 +4536,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 
 	oidmap_init(&commit2todo, 0);
 	oidmap_init(&state.commit2label, 0);
-	hashmap_init(&state.labels, (hashmap_cmp_fn) labels_cmp, NULL, 0);
+	hashmap_init(&state.labels, labels_cmp, NULL, 0);
 	strbuf_init(&state.buf, 32);
 
 	if (revs->cmdline.nr && (revs->cmdline.rev[0].flags & BOTTOM)) {
@@ -4726,7 +4731,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 
 	oidmap_free(&commit2todo, 1);
 	oidmap_free(&state.commit2label, 1);
-	hashmap_free(&state.labels, 1);
+	hashmap_free_entries(&state.labels, struct labels_entry, entry);
 	strbuf_release(&state.buf);
 
 	return 0;
@@ -5097,9 +5102,15 @@ struct subject2item_entry {
 };
 
 static int subject2item_cmp(const void *fndata,
-			    const struct subject2item_entry *a,
-			    const struct subject2item_entry *b, const void *key)
+			    const struct hashmap_entry *eptr,
+			    const struct hashmap_entry *entry_or_key,
+			    const void *key)
 {
+	const struct subject2item_entry *a, *b;
+
+	a = container_of(eptr, const struct subject2item_entry, entry);
+	b = container_of(entry_or_key, const struct subject2item_entry, entry);
+
 	return key ? strcmp(a->subject, key) : strcmp(a->subject, b->subject);
 }
 
@@ -5132,8 +5143,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list)
 	 * In that case, last[i] will indicate the index of the latest item to
 	 * be moved to appear after the i'th.
 	 */
-	hashmap_init(&subject2item, (hashmap_cmp_fn) subject2item_cmp,
-		     NULL, todo_list->nr);
+	hashmap_init(&subject2item, subject2item_cmp, NULL, todo_list->nr);
 	ALLOC_ARRAY(next, todo_list->nr);
 	ALLOC_ARRAY(tail, todo_list->nr);
 	ALLOC_ARRAY(subjects, todo_list->nr);
@@ -5176,8 +5186,11 @@ int todo_list_rearrange_squash(struct todo_list *todo_list)
 					break;
 			}
 
-			if ((entry = hashmap_get_from_hash(&subject2item,
-							   strhash(p), p)))
+			entry = hashmap_get_entry_from_hash(&subject2item,
+						strhash(p), p,
+						struct subject2item_entry,
+						entry);
+			if (entry)
 				/* found by title */
 				i2 = entry->i;
 			else if (!strchr(p, ' ') &&
@@ -5211,8 +5224,9 @@ int todo_list_rearrange_squash(struct todo_list *todo_list)
 						strhash(subject), subject)) {
 			FLEX_ALLOC_MEM(entry, subject, subject, subject_len);
 			entry->i = i;
-			hashmap_entry_init(entry, strhash(entry->subject));
-			hashmap_put(&subject2item, entry);
+			hashmap_entry_init(&entry->entry,
+					strhash(entry->subject));
+			hashmap_put(&subject2item, &entry->entry);
 		}
 	}
 
@@ -5246,7 +5260,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list)
 	for (i = 0; i < todo_list->nr; i++)
 		free(subjects[i]);
 	free(subjects);
-	hashmap_free(&subject2item, 1);
+	hashmap_free_entries(&subject2item, struct subject2item_entry, entry);
 
 	clear_commit_todo_item(&commit_todo);
 
diff --git a/sub-process.c b/sub-process.c
index 3f4af93555..1b1af9dcbd 100644
--- a/sub-process.c
+++ b/sub-process.c
@@ -6,12 +6,14 @@
 #include "pkt-line.h"
 
 int cmd2process_cmp(const void *unused_cmp_data,
-		    const void *entry,
-		    const void *entry_or_key,
+		    const struct hashmap_entry *eptr,
+		    const struct hashmap_entry *entry_or_key,
 		    const void *unused_keydata)
 {
-	const struct subprocess_entry *e1 = entry;
-	const struct subprocess_entry *e2 = entry_or_key;
+	const struct subprocess_entry *e1, *e2;
+
+	e1 = container_of(eptr, const struct subprocess_entry, ent);
+	e2 = container_of(entry_or_key, const struct subprocess_entry, ent);
 
 	return strcmp(e1->cmd, e2->cmd);
 }
@@ -20,9 +22,9 @@ struct subprocess_entry *subprocess_find_entry(struct hashmap *hashmap, const ch
 {
 	struct subprocess_entry key;
 
-	hashmap_entry_init(&key, strhash(cmd));
+	hashmap_entry_init(&key.ent, strhash(cmd));
 	key.cmd = cmd;
-	return hashmap_get(hashmap, &key, NULL);
+	return hashmap_get_entry(hashmap, &key, ent, NULL);
 }
 
 int subprocess_read_status(int fd, struct strbuf *status)
@@ -58,7 +60,7 @@ void subprocess_stop(struct hashmap *hashmap, struct subprocess_entry *entry)
 	kill(entry->process.pid, SIGTERM);
 	finish_command(&entry->process);
 
-	hashmap_remove(hashmap, entry, NULL);
+	hashmap_remove(hashmap, &entry->ent, NULL);
 }
 
 static void subprocess_exit_handler(struct child_process *process)
@@ -96,7 +98,7 @@ int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, co
 		return err;
 	}
 
-	hashmap_entry_init(entry, strhash(cmd));
+	hashmap_entry_init(&entry->ent, strhash(cmd));
 
 	err = startfn(entry);
 	if (err) {
@@ -105,7 +107,7 @@ int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, co
 		return err;
 	}
 
-	hashmap_add(hashmap, entry);
+	hashmap_add(hashmap, &entry->ent);
 	return 0;
 }
 
diff --git a/sub-process.h b/sub-process.h
index 5c182fad98..e85f21fa1a 100644
--- a/sub-process.h
+++ b/sub-process.h
@@ -24,7 +24,7 @@
 
 /* Members should not be accessed directly. */
 struct subprocess_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	const char *cmd;
 	struct child_process process;
 };
@@ -43,8 +43,8 @@ struct subprocess_capability {
 
 /* Function to test two subprocess hashmap entries for equality. */
 int cmd2process_cmp(const void *unused_cmp_data,
-		    const void *e1,
-		    const void *e2,
+		    const struct hashmap_entry *e,
+		    const struct hashmap_entry *entry_or_key,
 		    const void *unused_keydata);
 
 /*
diff --git a/submodule-config.c b/submodule-config.c
index 4264ee216f..401a9b2382 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -38,24 +38,28 @@ enum lookup_type {
 };
 
 static int config_path_cmp(const void *unused_cmp_data,
-			   const void *entry,
-			   const void *entry_or_key,
+			   const struct hashmap_entry *eptr,
+			   const struct hashmap_entry *entry_or_key,
 			   const void *unused_keydata)
 {
-	const struct submodule_entry *a = entry;
-	const struct submodule_entry *b = entry_or_key;
+	const struct submodule_entry *a, *b;
+
+	a = container_of(eptr, const struct submodule_entry, ent);
+	b = container_of(entry_or_key, const struct submodule_entry, ent);
 
 	return strcmp(a->config->path, b->config->path) ||
 	       !oideq(&a->config->gitmodules_oid, &b->config->gitmodules_oid);
 }
 
 static int config_name_cmp(const void *unused_cmp_data,
-			   const void *entry,
-			   const void *entry_or_key,
+			   const struct hashmap_entry *eptr,
+			   const struct hashmap_entry *entry_or_key,
 			   const void *unused_keydata)
 {
-	const struct submodule_entry *a = entry;
-	const struct submodule_entry *b = entry_or_key;
+	const struct submodule_entry *a, *b;
+
+	a = container_of(eptr, const struct submodule_entry, ent);
+	b = container_of(entry_or_key, const struct submodule_entry, ent);
 
 	return strcmp(a->config->name, b->config->name) ||
 	       !oideq(&a->config->gitmodules_oid, &b->config->gitmodules_oid);
@@ -95,12 +99,12 @@ static void submodule_cache_clear(struct submodule_cache *cache)
 	 * allocation of struct submodule entries. Each is allocated by
 	 * their .gitmodules blob sha1 and submodule name.
 	 */
-	hashmap_iter_init(&cache->for_name, &iter);
-	while ((entry = hashmap_iter_next(&iter)))
+	hashmap_for_each_entry(&cache->for_name, &iter, entry,
+				ent /* member name */)
 		free_one_config(entry);
 
-	hashmap_free(&cache->for_path, 1);
-	hashmap_free(&cache->for_name, 1);
+	hashmap_free_entries(&cache->for_path, struct submodule_entry, ent);
+	hashmap_free_entries(&cache->for_name, struct submodule_entry, ent);
 	cache->initialized = 0;
 	cache->gitmodules_read = 0;
 }
@@ -123,9 +127,9 @@ static void cache_put_path(struct submodule_cache *cache,
 	unsigned int hash = hash_oid_string(&submodule->gitmodules_oid,
 					    submodule->path);
 	struct submodule_entry *e = xmalloc(sizeof(*e));
-	hashmap_entry_init(e, hash);
+	hashmap_entry_init(&e->ent, hash);
 	e->config = submodule;
-	hashmap_put(&cache->for_path, e);
+	hashmap_put(&cache->for_path, &e->ent);
 }
 
 static void cache_remove_path(struct submodule_cache *cache,
@@ -135,9 +139,9 @@ static void cache_remove_path(struct submodule_cache *cache,
 					    submodule->path);
 	struct submodule_entry e;
 	struct submodule_entry *removed;
-	hashmap_entry_init(&e, hash);
+	hashmap_entry_init(&e.ent, hash);
 	e.config = submodule;
-	removed = hashmap_remove(&cache->for_path, &e, NULL);
+	removed = hashmap_remove_entry(&cache->for_path, &e, ent, NULL);
 	free(removed);
 }
 
@@ -147,9 +151,9 @@ static void cache_add(struct submodule_cache *cache,
 	unsigned int hash = hash_oid_string(&submodule->gitmodules_oid,
 					    submodule->name);
 	struct submodule_entry *e = xmalloc(sizeof(*e));
-	hashmap_entry_init(e, hash);
+	hashmap_entry_init(&e->ent, hash);
 	e->config = submodule;
-	hashmap_add(&cache->for_name, e);
+	hashmap_add(&cache->for_name, &e->ent);
 }
 
 static const struct submodule *cache_lookup_path(struct submodule_cache *cache,
@@ -163,10 +167,10 @@ static const struct submodule *cache_lookup_path(struct submodule_cache *cache,
 	oidcpy(&key_config.gitmodules_oid, gitmodules_oid);
 	key_config.path = path;
 
-	hashmap_entry_init(&key, hash);
+	hashmap_entry_init(&key.ent, hash);
 	key.config = &key_config;
 
-	entry = hashmap_get(&cache->for_path, &key, NULL);
+	entry = hashmap_get_entry(&cache->for_path, &key, ent, NULL);
 	if (entry)
 		return entry->config;
 	return NULL;
@@ -183,10 +187,10 @@ static struct submodule *cache_lookup_name(struct submodule_cache *cache,
 	oidcpy(&key_config.gitmodules_oid, gitmodules_oid);
 	key_config.name = name;
 
-	hashmap_entry_init(&key, hash);
+	hashmap_entry_init(&key.ent, hash);
 	key.config = &key_config;
 
-	entry = hashmap_get(&cache->for_name, &key, NULL);
+	entry = hashmap_get_entry(&cache->for_name, &key, ent, NULL);
 	if (entry)
 		return entry->config;
 	return NULL;
@@ -550,7 +554,9 @@ static const struct submodule *config_from(struct submodule_cache *cache,
 		struct hashmap_iter iter;
 		struct submodule_entry *entry;
 
-		entry = hashmap_iter_first(&cache->for_name, &iter);
+		entry = hashmap_iter_first_entry(&cache->for_name, &iter,
+						struct submodule_entry,
+						ent /* member name */);
 		if (!entry)
 			return NULL;
 		return entry->config;
diff --git a/t/helper/test-hashmap.c b/t/helper/test-hashmap.c
index aaf17b0ddf..f38706216f 100644
--- a/t/helper/test-hashmap.c
+++ b/t/helper/test-hashmap.c
@@ -5,6 +5,7 @@
 
 struct test_entry
 {
+	int padding; /* hashmap entry no longer needs to be the first member */
 	struct hashmap_entry ent;
 	/* key and value as two \0-terminated strings */
 	char key[FLEX_ARRAY];
@@ -16,15 +17,17 @@ static const char *get_value(const struct test_entry *e)
 }
 
 static int test_entry_cmp(const void *cmp_data,
-			  const void *entry,
-			  const void *entry_or_key,
+			  const struct hashmap_entry *eptr,
+			  const struct hashmap_entry *entry_or_key,
 			  const void *keydata)
 {
 	const int ignore_case = cmp_data ? *((int *)cmp_data) : 0;
-	const struct test_entry *e1 = entry;
-	const struct test_entry *e2 = entry_or_key;
+	const struct test_entry *e1, *e2;
 	const char *key = keydata;
 
+	e1 = container_of(eptr, const struct test_entry, ent);
+	e2 = container_of(entry_or_key, const struct test_entry, ent);
+
 	if (ignore_case)
 		return strcasecmp(e1->key, key ? key : e2->key);
 	else
@@ -37,7 +40,7 @@ static struct test_entry *alloc_test_entry(unsigned int hash,
 	size_t klen = strlen(key);
 	size_t vlen = strlen(value);
 	struct test_entry *entry = xmalloc(st_add4(sizeof(*entry), klen, vlen, 2));
-	hashmap_entry_init(entry, hash);
+	hashmap_entry_init(&entry->ent, hash);
 	memcpy(entry->key, key, klen + 1);
 	memcpy(entry->key + klen + 1, value, vlen + 1);
 	return entry;
@@ -103,11 +106,11 @@ static void perf_hashmap(unsigned int method, unsigned int rounds)
 
 			/* add entries */
 			for (i = 0; i < TEST_SIZE; i++) {
-				hashmap_entry_init(entries[i], hashes[i]);
-				hashmap_add(&map, entries[i]);
+				hashmap_entry_init(&entries[i]->ent, hashes[i]);
+				hashmap_add(&map, &entries[i]->ent);
 			}
 
-			hashmap_free(&map, 0);
+			hashmap_free(&map);
 		}
 	} else {
 		/* test map lookups */
@@ -116,8 +119,8 @@ static void perf_hashmap(unsigned int method, unsigned int rounds)
 		/* fill the map (sparsely if specified) */
 		j = (method & TEST_SPARSE) ? TEST_SIZE / 10 : TEST_SIZE;
 		for (i = 0; i < j; i++) {
-			hashmap_entry_init(entries[i], hashes[i]);
-			hashmap_add(&map, entries[i]);
+			hashmap_entry_init(&entries[i]->ent, hashes[i]);
+			hashmap_add(&map, &entries[i]->ent);
 		}
 
 		for (j = 0; j < rounds; j++) {
@@ -127,7 +130,7 @@ static void perf_hashmap(unsigned int method, unsigned int rounds)
 			}
 		}
 
-		hashmap_free(&map, 0);
+		hashmap_free(&map);
 	}
 }
 
@@ -179,7 +182,7 @@ int cmd__hashmap(int argc, const char **argv)
 			entry = alloc_test_entry(hash, p1, p2);
 
 			/* add to hashmap */
-			hashmap_add(&map, entry);
+			hashmap_add(&map, &entry->ent);
 
 		} else if (!strcmp("put", cmd) && p1 && p2) {
 
@@ -187,43 +190,44 @@ int cmd__hashmap(int argc, const char **argv)
 			entry = alloc_test_entry(hash, p1, p2);
 
 			/* add / replace entry */
-			entry = hashmap_put(&map, entry);
+			entry = hashmap_put_entry(&map, entry, ent);
 
 			/* print and free replaced entry, if any */
 			puts(entry ? get_value(entry) : "NULL");
 			free(entry);
 
 		} else if (!strcmp("get", cmd) && p1) {
-
 			/* lookup entry in hashmap */
-			entry = hashmap_get_from_hash(&map, hash, p1);
+			entry = hashmap_get_entry_from_hash(&map, hash, p1,
+							struct test_entry, ent);
 
 			/* print result */
 			if (!entry)
 				puts("NULL");
-			while (entry) {
+			hashmap_for_each_entry_from(&map, entry, ent)
 				puts(get_value(entry));
-				entry = hashmap_get_next(&map, entry);
-			}
 
 		} else if (!strcmp("remove", cmd) && p1) {
 
 			/* setup static key */
 			struct hashmap_entry key;
+			struct hashmap_entry *rm;
 			hashmap_entry_init(&key, hash);
 
 			/* remove entry from hashmap */
-			entry = hashmap_remove(&map, &key, p1);
+			rm = hashmap_remove(&map, &key, p1);
+			entry = rm ? container_of(rm, struct test_entry, ent)
+					: NULL;
 
 			/* print result and free entry*/
 			puts(entry ? get_value(entry) : "NULL");
 			free(entry);
 
 		} else if (!strcmp("iterate", cmd)) {
-
 			struct hashmap_iter iter;
-			hashmap_iter_init(&map, &iter);
-			while ((entry = hashmap_iter_next(&iter)))
+
+			hashmap_for_each_entry(&map, &iter, entry,
+						ent /* member name */)
 				printf("%s %s\n", entry->key, get_value(entry));
 
 		} else if (!strcmp("size", cmd)) {
@@ -258,6 +262,6 @@ int cmd__hashmap(int argc, const char **argv)
 	}
 
 	strbuf_release(&line);
-	hashmap_free(&map, 1);
+	hashmap_free_entries(&map, struct test_entry, ent);
 	return 0;
 }
diff --git a/t/helper/test-lazy-init-name-hash.c b/t/helper/test-lazy-init-name-hash.c
index b99a37080d..cd1b4c9736 100644
--- a/t/helper/test-lazy-init-name-hash.c
+++ b/t/helper/test-lazy-init-name-hash.c
@@ -41,17 +41,13 @@ static void dump_run(void)
 			die("non-threaded code path used");
 	}
 
-	dir = hashmap_iter_first(&the_index.dir_hash, &iter_dir);
-	while (dir) {
+	hashmap_for_each_entry(&the_index.dir_hash, &iter_dir, dir,
+				ent /* member name */)
 		printf("dir %08x %7d %s\n", dir->ent.hash, dir->nr, dir->name);
-		dir = hashmap_iter_next(&iter_dir);
-	}
 
-	ce = hashmap_iter_first(&the_index.name_hash, &iter_cache);
-	while (ce) {
+	hashmap_for_each_entry(&the_index.name_hash, &iter_cache, ce,
+				ent /* member name */)
 		printf("name %08x %s\n", ce->ent.hash, ce->name);
-		ce = hashmap_iter_next(&iter_cache);
-	}
 
 	discard_cache();
 }