diff --git a/apply.c b/apply.c
index 749b515ffc..93ca590b71 100644
--- a/apply.c
+++ b/apply.c
@@ -3232,7 +3232,7 @@ static int apply_binary_fragment(struct apply_state *state,
 				 struct patch *patch)
 {
 	struct fragment *fragment = patch->fragments;
-	unsigned long len;
+	size_t len;
 	void *dst;
 
 	if (!fragment)
@@ -3321,7 +3321,7 @@ static int apply_binary(struct apply_state *state,
 	if (odb_has_object(the_repository->objects, &oid, 0)) {
 		/* We already have the postimage */
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		char *result;
 
 		result = odb_read_object(the_repository->objects, &oid,
@@ -3384,7 +3384,7 @@ static int read_blob_object(struct strbuf *buf, const struct object_id *oid, uns
 		strbuf_addf(buf, "Subproject commit %s\n", oid_to_hex(oid));
 	} else {
 		enum object_type type;
-		unsigned long sz;
+		size_t sz;
 		char *result;
 
 		result = odb_read_object(the_repository->objects, oid,
@@ -3611,7 +3611,7 @@ static int load_preimage(struct apply_state *state,
 
 static int resolve_to(struct image *image, const struct object_id *result_id)
 {
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	char *data;
 
diff --git a/archive.c b/archive.c
index 51229107a5..59790be986 100644
--- a/archive.c
+++ b/archive.c
@@ -87,7 +87,7 @@ static void *object_file_to_archive(const struct archiver_args *args,
 				    const struct object_id *oid,
 				    unsigned int mode,
 				    enum object_type *type,
-				    unsigned long *sizep)
+				    size_t *sizep)
 {
 	void *buffer;
 	const struct commit *commit = args->convert ? args->commit : NULL;
@@ -158,7 +158,7 @@ static int write_archive_entry(const struct object_id *oid, const char *base,
 	write_archive_entry_fn_t write_entry = c->write_entry;
 	int err;
 	const char *path_without_prefix;
-	unsigned long size;
+	size_t size;
 	void *buffer;
 	enum object_type type;
 
diff --git a/attr.c b/attr.c
index 75369547b3..c61472a4e6 100644
--- a/attr.c
+++ b/attr.c
@@ -768,7 +768,7 @@ static struct attr_stack *read_attr_from_blob(struct index_state *istate,
 					      const char *path, unsigned flags)
 {
 	struct object_id oid;
-	unsigned long sz;
+	size_t sz;
 	enum object_type type;
 	void *buf;
 	unsigned short mode;
diff --git a/bisect.c b/bisect.c
index e29d1cbc64..94c7028d2a 100644
--- a/bisect.c
+++ b/bisect.c
@@ -154,7 +154,7 @@ static void show_list(const char *debug, int counted, int nr,
 		struct commit *commit = p->item;
 		unsigned commit_flags = commit->object.flags;
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		char *buf = odb_read_object(the_repository->objects,
 					    &commit->object.oid, &type,
 					    &size);
diff --git a/blame.c b/blame.c
index 977cbb7097..126e232416 100644
--- a/blame.c
+++ b/blame.c
@@ -1041,10 +1041,13 @@ static void fill_origin_blob(struct diff_options *opt,
 		    textconv_object(opt->repo, o->path, o->mode,
 				    &o->blob_oid, 1, &file->ptr, &file_size))
 			;
-		else
+		else {
+			size_t file_size_st = 0;
 			file->ptr = odb_read_object(the_repository->objects,
 						    &o->blob_oid, &type,
-						    &file_size);
+						    &file_size_st);
+			file_size = cast_size_t_to_ulong(file_size_st);
+		}
 		file->size = file_size;
 
 		if (!file->ptr)
@@ -2869,10 +2872,14 @@ void setup_scoreboard(struct blame_scoreboard *sb,
 		    textconv_object(sb->repo, sb->path, o->mode, &o->blob_oid, 1, (char **) &sb->final_buf,
 				    &sb->final_buf_size))
 			;
-		else
+		else {
+			size_t final_buf_size_st = 0;
 			sb->final_buf = odb_read_object(the_repository->objects,
 							&o->blob_oid, &type,
-							&sb->final_buf_size);
+							&final_buf_size_st);
+			sb->final_buf_size =
+				cast_size_t_to_ulong(final_buf_size_st);
+		}
 
 		if (!sb->final_buf)
 			die(_("cannot read blob %s for path %s"),
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 446d649904..0374e6069a 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -84,7 +84,7 @@ static char *replace_idents_using_mailmap(char *object_buf, size_t *size)
 
 static int filter_object(const char *path, unsigned mode,
 			 const struct object_id *oid,
-			 char **buf, unsigned long *size)
+			 char **buf, size_t *size)
 {
 	enum object_type type;
 
@@ -120,7 +120,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
 	struct object_id oid;
 	enum object_type type;
 	char *buf;
-	unsigned long size;
+	size_t size;
 	struct object_context obj_context = {0};
 	struct object_info oi = OBJECT_INFO_INIT;
 	unsigned flags = OBJECT_INFO_LOOKUP_REPLACE;
@@ -166,7 +166,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
 		if (use_mailmap && (type == OBJ_COMMIT || type == OBJ_TAG)) {
 			size_t s = size;
 			buf = replace_idents_using_mailmap(buf, &s);
-			size = cast_size_t_to_ulong(s);
+			size = s;
 		}
 
 		printf("%"PRIuMAX"\n", (uintmax_t)size);
@@ -188,9 +188,15 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
 		break;
 
 	case 'c':
-		if (textconv_object(the_repository, path, obj_context.mode,
-				    &oid, 1, &buf, &size))
+	{
+		unsigned long size_ul = 0;
+		int textconv_ret = textconv_object(the_repository, path,
+						   obj_context.mode, &oid, 1,
+						   &buf, &size_ul);
+		size = size_ul;
+		if (textconv_ret)
 			break;
+	}
 		/* else fallthrough */
 
 	case 'p':
@@ -219,7 +225,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
 		if (use_mailmap) {
 			size_t s = size;
 			buf = replace_idents_using_mailmap(buf, &s);
-			size = cast_size_t_to_ulong(s);
+			size = s;
 		}
 
 		/* otherwise just spit out the data */
@@ -266,7 +272,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
 		if (use_mailmap) {
 			size_t s = size;
 			buf = replace_idents_using_mailmap(buf, &s);
-			size = cast_size_t_to_ulong(s);
+			size = s;
 		}
 		break;
 	}
@@ -288,7 +294,7 @@ cleanup:
 struct expand_data {
 	struct object_id oid;
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 	unsigned short mode;
 	off_t disk_size;
 	const char *rest;
@@ -404,7 +410,7 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
 			fflush(stdout);
 		if (opt->transform_mode) {
 			char *contents;
-			unsigned long size;
+			size_t size;
 
 			if (!data->rest)
 				die("missing path for '%s'", oid_to_hex(oid));
@@ -416,9 +422,12 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
 					    oid_to_hex(oid), data->rest);
 			} else if (opt->transform_mode == 'c') {
 				enum object_type type;
-				if (!textconv_object(the_repository,
-						     data->rest, 0100644, oid,
-						     1, &contents, &size))
+				unsigned long size_ul = 0;
+				if (textconv_object(the_repository,
+						    data->rest, 0100644, oid,
+						    1, &contents, &size_ul))
+					size = size_ul;
+				else
 					contents = odb_read_object(the_repository->objects,
 								   oid, &type, &size);
 				if (!contents)
@@ -434,7 +443,7 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
 	}
 	else {
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		void *contents;
 
 		contents = odb_read_object(the_repository->objects, oid,
@@ -445,7 +454,7 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
 		if (use_mailmap) {
 			size_t s = size;
 			contents = replace_idents_using_mailmap(contents, &s);
-			size = cast_size_t_to_ulong(s);
+			size = s;
 		}
 
 		if (type != data->type)
@@ -554,7 +563,7 @@ static void batch_object_write(const char *obj_name,
 			if (!buf)
 				die(_("unable to read %s"), oid_to_hex(&data->oid));
 			buf = replace_idents_using_mailmap(buf, &s);
-			data->size = cast_size_t_to_ulong(s);
+			data->size = s;
 
 			free(buf);
 		}
diff --git a/builtin/difftool.c b/builtin/difftool.c
index 35e363c05f..e702b70fa3 100644
--- a/builtin/difftool.c
+++ b/builtin/difftool.c
@@ -319,7 +319,7 @@ static char *get_symlink(struct repository *repo,
 		data = strbuf_detach(&link, NULL);
 	} else {
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		data = odb_read_object(repo->objects, oid, &type, &size);
 		if (!data)
 			die(_("could not read object %s for symlink %s"),
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 2eb43a28da..0be43104dc 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -317,7 +317,10 @@ static void export_blob(const struct object_id *oid)
 		object = (struct object *)lookup_blob(the_repository, oid);
 		eaten = 0;
 	} else {
-		buf = odb_read_object(the_repository->objects, oid, &type, &size);
+		size_t size_st = 0;
+		buf = odb_read_object(the_repository->objects, oid, &type,
+				      &size_st);
+		size = cast_size_t_to_ulong(size_st);
 		if (!buf)
 			die(_("could not read blob %s"), oid_to_hex(oid));
 		if (check_object_signature(the_repository, oid, buf, size,
@@ -880,7 +883,7 @@ static char *anonymize_tag(void)
 
 static void handle_tag(const char *name, struct tag *tag)
 {
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	char *buf;
 	const char *tagger, *tagger_end, *message;
diff --git a/builtin/fast-import.c b/builtin/fast-import.c
index 070a5af3e4..aa656c5195 100644
--- a/builtin/fast-import.c
+++ b/builtin/fast-import.c
@@ -1241,6 +1241,8 @@ static void *gfi_unpack_entry(
 	unsigned long *sizep)
 {
 	enum object_type type;
+	size_t size_st = 0;
+	void *data;
 	struct packed_git *p = all_packs[oe->pack_id];
 	if (p == pack_data && p->pack_size < (pack_size + the_hash_algo->rawsz)) {
 		/* The object is stored in the packfile we are writing to
@@ -1262,7 +1264,10 @@ static void *gfi_unpack_entry(
 		 */
 		p->pack_size = pack_size + the_hash_algo->rawsz;
 	}
-	return unpack_entry(the_repository, p, oe->idx.offset, &type, sizep);
+	data = unpack_entry(the_repository, p, oe->idx.offset, &type, &size_st);
+	if (sizep)
+		*sizep = cast_size_t_to_ulong(size_st);
+	return data;
 }
 
 static void load_tree(struct tree_entry *root)
@@ -1288,7 +1293,10 @@ static void load_tree(struct tree_entry *root)
 			die(_("can't load tree %s"), oid_to_hex(oid));
 	} else {
 		enum object_type type;
-		buf = odb_read_object(the_repository->objects, oid, &type, &size);
+		size_t size_st = 0;
+		buf = odb_read_object(the_repository->objects, oid, &type,
+				      &size_st);
+		size = cast_size_t_to_ulong(size_st);
 		if (!buf || type != OBJ_TREE)
 			die(_("can't load tree %s"), oid_to_hex(oid));
 	}
@@ -2557,7 +2565,7 @@ static void note_change_n(const char *p, struct branch *b, unsigned char *old_fa
 			die(_("mark :%" PRIuMAX " not a commit"), commit_mark);
 		oidcpy(&commit_oid, &commit_oe->idx.oid);
 	} else if (!repo_get_oid(the_repository, p, &commit_oid)) {
-		unsigned long size;
+		size_t size;
 		char *buf = odb_read_object_peeled(the_repository->objects,
 						   &commit_oid, OBJ_COMMIT, &size,
 						   &commit_oid);
@@ -2624,10 +2632,12 @@ static void parse_from_existing(struct branch *b)
 		oidclr(&b->branch_tree.versions[1].oid, the_repository->hash_algo);
 	} else {
 		unsigned long size;
+		size_t size_st = 0;
 		char *buf;
 
 		buf = odb_read_object_peeled(the_repository->objects, &b->oid,
-					     OBJ_COMMIT, &size, &b->oid);
+					     OBJ_COMMIT, &size_st, &b->oid);
+		size = cast_size_t_to_ulong(size_st);
 		parse_from_commit(b, buf, size);
 		free(buf);
 	}
@@ -2719,7 +2729,7 @@ static struct hash_list *parse_merge(unsigned int *count)
 				die(_("mark :%" PRIuMAX " not a commit"), idnum);
 			oidcpy(&n->oid, &oe->idx.oid);
 		} else if (!repo_get_oid(the_repository, from, &n->oid)) {
-			unsigned long size;
+			size_t size;
 			char *buf = odb_read_object_peeled(the_repository->objects,
 							   &n->oid, OBJ_COMMIT,
 							   &size, &n->oid);
@@ -3327,7 +3337,10 @@ static void cat_blob(struct object_entry *oe, struct object_id *oid)
 	char *buf;
 
 	if (!oe || oe->pack_id == MAX_PACK_ID) {
-		buf = odb_read_object(the_repository->objects, oid, &type, &size);
+		size_t size_st = 0;
+		buf = odb_read_object(the_repository->objects, oid, &type,
+				      &size_st);
+		size = cast_size_t_to_ulong(size_st);
 	} else {
 		type = oe->type;
 		buf = gfi_unpack_entry(oe, &size);
@@ -3435,8 +3448,10 @@ static struct object_entry *dereference(struct object_entry *oe,
 		buf = gfi_unpack_entry(oe, &size);
 	} else {
 		enum object_type unused;
+		size_t size_st = 0;
 		buf = odb_read_object(the_repository->objects, oid,
-				      &unused, &size);
+				      &unused, &size_st);
+		size = cast_size_t_to_ulong(size_st);
 	}
 	if (!buf)
 		die(_("can't load object %s"), oid_to_hex(oid));
diff --git a/builtin/fsck.c b/builtin/fsck.c
index 248f8ff5a0..76b723f36d 100644
--- a/builtin/fsck.c
+++ b/builtin/fsck.c
@@ -724,7 +724,7 @@ static int fsck_loose(const struct object_id *oid, const char *path,
 	struct for_each_loose_cb *data = cb_data;
 	struct object *obj;
 	enum object_type type = OBJ_NONE;
-	unsigned long size;
+	size_t size;
 	void *contents = NULL;
 	int eaten;
 	struct object_info oi = OBJECT_INFO_INIT;
diff --git a/builtin/grep.c b/builtin/grep.c
index 6a09571903..26b85479ca 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -520,7 +520,7 @@ static int grep_submodule(struct grep_opt *opt,
 		enum object_type object_type;
 		struct tree_desc tree;
 		void *data;
-		unsigned long size;
+		size_t size;
 		struct strbuf base = STRBUF_INIT;
 
 		obj_read_lock();
@@ -573,7 +573,7 @@ static int grep_cache(struct grep_opt *opt,
 			enum object_type type;
 			struct tree_desc tree;
 			void *data;
-			unsigned long size;
+			size_t size;
 
 			data = odb_read_object(the_repository->objects, &ce->oid,
 					       &type, &size);
@@ -666,7 +666,7 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
 			enum object_type type;
 			struct tree_desc sub;
 			void *data;
-			unsigned long size;
+			size_t size;
 
 			data = odb_read_object(the_repository->objects,
 					       &entry.oid, &type, &size);
@@ -730,7 +730,7 @@ static void collect_blob_oids_for_tree(struct repository *repo,
 			enum object_type type;
 			struct tree_desc sub_tree;
 			void *data;
-			unsigned long size;
+			size_t size;
 
 			data = odb_read_object(repo->objects, &entry.oid,
 					       &type, &size);
@@ -764,7 +764,7 @@ static void collect_blob_oids_for_treeish(struct grep_opt *opt,
 {
 	struct tree_desc tree;
 	void *data;
-	unsigned long size;
+	size_t size;
 	struct strbuf base = STRBUF_INIT;
 	int len;
 
@@ -841,7 +841,7 @@ static int grep_object(struct grep_opt *opt, const struct pathspec *pathspec,
 	if (obj->type == OBJ_COMMIT || obj->type == OBJ_TREE) {
 		struct tree_desc tree;
 		void *data;
-		unsigned long size;
+		size_t size;
 		struct strbuf base;
 		int hit, len;
 
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 0793dc595c..f396658468 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -71,7 +71,7 @@ struct base_data {
 	/* Not initialized by make_base(). */
 	struct list_head list;
 	void *data;
-	unsigned long size;
+	size_t size;
 };
 
 /*
@@ -258,7 +258,7 @@ static unsigned check_object(struct object *obj)
 		return 0;
 
 	if (!(obj->flags & FLAG_CHECKED)) {
-		unsigned long size;
+		size_t size;
 		int type = odb_read_object_info(the_repository->objects,
 						&obj->oid, &size);
 		if (type <= 0)
@@ -905,7 +905,7 @@ static void sha1_object(const void *data, struct object_entry *obj_entry,
 	if (collision_test_needed) {
 		void *has_data;
 		enum object_type has_type;
-		unsigned long has_size;
+		size_t has_size;
 		read_lock();
 		has_type = odb_read_object_info(the_repository->objects, oid, &has_size);
 		if (has_type < 0)
@@ -1048,7 +1048,7 @@ static struct base_data *resolve_delta(struct object_entry *delta_obj,
 {
 	void *delta_data, *result_data;
 	struct base_data *result;
-	unsigned long result_size;
+	size_t result_size;
 
 	if (show_stat) {
 		int i = delta_obj - objects;
@@ -1515,7 +1515,7 @@ static void fix_unresolved_deltas(struct hashfile *f)
 		struct ref_delta_entry *d = sorted_by_pos[i];
 		enum object_type type;
 		void *data;
-		unsigned long size;
+		size_t size;
 
 		if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
 			continue;
diff --git a/builtin/log.c b/builtin/log.c
index e464b30af4..d027ce1e0b 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -613,7 +613,7 @@ static int show_blob_object(const struct object_id *oid, struct rev_info *rev, c
 
 static int show_tag_object(const struct object_id *oid, struct rev_info *rev)
 {
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	char *buf = odb_read_object(the_repository->objects, oid, &type, &size);
 	unsigned long offset = 0;
diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index 12d5d828ff..f30507215a 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -256,7 +256,7 @@ static void expand_objectsize(struct repository *repo, struct strbuf *line,
 	size_t len;
 
 	if (type == OBJ_BLOB) {
-		unsigned long size;
+		size_t size;
 		if (odb_read_object_info(repo->objects, oid, &size) < 0)
 			die(_("could not get object info about '%s'"),
 			    oid_to_hex(oid));
diff --git a/builtin/ls-tree.c b/builtin/ls-tree.c
index 57846911ce..46edaffc2e 100644
--- a/builtin/ls-tree.c
+++ b/builtin/ls-tree.c
@@ -32,7 +32,7 @@ static void expand_objectsize(struct strbuf *line, const struct object_id *oid,
 	size_t len;
 
 	if (type == OBJ_BLOB) {
-		unsigned long size;
+		size_t size;
 		if (odb_read_object_info(the_repository->objects, oid, &size) < 0)
 			die(_("could not get object info about '%s'"),
 			    oid_to_hex(oid));
@@ -220,7 +220,7 @@ static int show_tree_long(const struct object_id *oid, struct strbuf *base,
 		return early;
 
 	if (type == OBJ_BLOB) {
-		unsigned long size;
+		size_t size;
 		if (odb_read_object_info(the_repository->objects, oid, &size) == OBJ_BAD)
 			xsnprintf(size_text, sizeof(size_text), "BAD");
 		else
diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index 312b595d1e..49f41e520f 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -69,7 +69,7 @@ static const char *explanation(struct merge_list *entry)
 	return "removed in remote";
 }
 
-static void *result(struct merge_list *entry, unsigned long *size)
+static void *result(struct merge_list *entry, size_t *size)
 {
 	enum object_type type;
 	struct blob *base, *our, *their;
@@ -96,7 +96,7 @@ static void *result(struct merge_list *entry, unsigned long *size)
 			   base, our, their, size);
 }
 
-static void *origin(struct merge_list *entry, unsigned long *size)
+static void *origin(struct merge_list *entry, size_t *size)
 {
 	enum object_type type;
 	while (entry) {
@@ -119,7 +119,7 @@ static int show_outf(void *priv UNUSED, mmbuffer_t *mb, int nbuf)
 
 static void show_diff(struct merge_list *entry)
 {
-	unsigned long size;
+	size_t size;
 	mmfile_t src, dst;
 	xpparam_t xpp;
 	xdemitconf_t xecfg;
diff --git a/builtin/mktag.c b/builtin/mktag.c
index f40264a878..37c17e6beb 100644
--- a/builtin/mktag.c
+++ b/builtin/mktag.c
@@ -50,7 +50,7 @@ static int verify_object_in_tag(struct object_id *tagged_oid, int *tagged_type)
 {
 	int ret;
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 	void *buffer;
 	const struct object_id *repl;
 
diff --git a/builtin/notes.c b/builtin/notes.c
index 9af602bdd7..962df867c8 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -150,7 +150,7 @@ static int list_each_note(const struct object_id *object_oid,
 
 static void copy_obj_to_fd(int fd, const struct object_id *oid)
 {
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	char *buf = odb_read_object(the_repository->objects, oid, &type, &size);
 	if (buf) {
@@ -313,7 +313,7 @@ static int parse_reuse_arg(const struct option *opt, const char *arg, int unset)
 	char *value;
 	struct object_id object;
 	enum object_type type;
-	unsigned long len;
+	size_t len;
 
 	BUG_ON_OPT_NEG(unset);
 
@@ -721,7 +721,7 @@ static int append_edit(int argc, const char **argv, const char *prefix,
 
 	if (note && !edit) {
 		/* Append buf to previous note contents */
-		unsigned long size;
+		size_t size;
 		enum object_type type;
 		struct strbuf buf = STRBUF_INIT;
 		char *prev_buf = odb_read_object(the_repository->objects, note, &type, &size);
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 8a1709a1ab..27048bbb4d 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -66,8 +66,8 @@ static inline struct object_entry *oe_delta(
 		return &pack->objects[e->delta_idx - 1];
 }
 
-static inline unsigned long oe_delta_size(struct packing_data *pack,
-					  const struct object_entry *e)
+static inline size_t oe_delta_size(struct packing_data *pack,
+				   const struct object_entry *e)
 {
 	if (e->delta_size_valid)
 		return e->delta_size_;
@@ -83,11 +83,11 @@ static inline unsigned long oe_delta_size(struct packing_data *pack,
 	return pack->delta_size[e - pack->objects];
 }
 
-unsigned long oe_get_size_slow(struct packing_data *pack,
-			       const struct object_entry *e);
+size_t oe_get_size_slow(struct packing_data *pack,
+			const struct object_entry *e);
 
-static inline unsigned long oe_size(struct packing_data *pack,
-				    const struct object_entry *e)
+static inline size_t oe_size(struct packing_data *pack,
+			     const struct object_entry *e)
 {
 	if (e->size_valid)
 		return e->size_;
@@ -145,7 +145,7 @@ static inline void oe_set_delta_sibling(struct packing_data *pack,
 
 static inline void oe_set_size(struct packing_data *pack,
 			       struct object_entry *e,
-			       unsigned long size)
+			       size_t size)
 {
 	if (size < pack->oe_size_limit) {
 		e->size_ = size;
@@ -159,7 +159,7 @@ static inline void oe_set_size(struct packing_data *pack,
 
 static inline void oe_set_delta_size(struct packing_data *pack,
 				     struct object_entry *e,
-				     unsigned long size)
+				     size_t size)
 {
 	if (size < pack->oe_delta_size_limit) {
 		e->delta_size_ = size;
@@ -356,14 +356,17 @@ static void *get_delta(struct object_entry *entry)
 	unsigned long size, base_size, delta_size;
 	void *buf, *base_buf, *delta_buf;
 	enum object_type type;
+	size_t size_st = 0, base_size_st = 0;
 
 	buf = odb_read_object(the_repository->objects, &entry->idx.oid,
-			      &type, &size);
+			      &type, &size_st);
+	size = cast_size_t_to_ulong(size_st);
 	if (!buf)
 		die(_("unable to read %s"), oid_to_hex(&entry->idx.oid));
 	base_buf = odb_read_object(the_repository->objects,
 				   &DELTA(entry)->idx.oid, &type,
-				   &base_size);
+				   &base_size_st);
+	base_size = cast_size_t_to_ulong(base_size_st);
 	if (!base_buf)
 		die("unable to read %s",
 		    oid_to_hex(&DELTA(entry)->idx.oid));
@@ -455,7 +458,7 @@ static int check_pack_inflate(struct packed_git *p,
 		struct pack_window **w_curs,
 		off_t offset,
 		off_t len,
-		unsigned long expect)
+		size_t expect)
 {
 	git_zstream stream;
 	unsigned char fakebuf[4096], *in;
@@ -498,7 +501,7 @@ static void copy_pack_data(struct hashfile *f,
 
 static inline int oe_size_greater_than(struct packing_data *pack,
 				       const struct object_entry *lhs,
-				       unsigned long rhs)
+				       size_t rhs)
 {
 	if (lhs->size_valid)
 		return lhs->size_ > rhs;
@@ -530,9 +533,11 @@ static unsigned long write_no_reuse_object(struct hashfile *f, struct object_ent
 			type = st->type;
 			size = st->size;
 		} else {
+			size_t size_st = 0;
 			buf = odb_read_object(the_repository->objects,
 					      &entry->idx.oid, &type,
-					      &size);
+					      &size_st);
+			size = cast_size_t_to_ulong(size_st);
 			if (!buf)
 				die(_("unable to read %s"),
 				    oid_to_hex(&entry->idx.oid));
@@ -673,8 +678,7 @@ static off_t write_reuse_object(struct hashfile *f, struct object_entry *entry,
 	datalen -= entry->in_pack_header_size;
 
 	if (!pack_to_stdout && p->index_version == 1 &&
-	    check_pack_inflate(p, &w_curs, offset, datalen,
-			       cast_size_t_to_ulong(entry_size))) {
+	    check_pack_inflate(p, &w_curs, offset, datalen, entry_size)) {
 		error(_("corrupt packed object for %s"),
 		      oid_to_hex(&entry->idx.oid));
 		unuse_pack(&w_curs);
@@ -1940,6 +1944,7 @@ static struct pbase_tree_cache *pbase_tree_get(const struct object_id *oid)
 	struct pbase_tree_cache *ent, *nent;
 	void *data;
 	unsigned long size;
+	size_t size_st = 0;
 	enum object_type type;
 	int neigh;
 	int my_ix = pbase_tree_cache_ix(oid);
@@ -1967,7 +1972,8 @@ static struct pbase_tree_cache *pbase_tree_get(const struct object_id *oid)
 	/* Did not find one.  Either we got a bogus request or
 	 * we need to read and perhaps cache.
 	 */
-	data = odb_read_object(the_repository->objects, oid, &type, &size);
+	data = odb_read_object(the_repository->objects, oid, &type, &size_st);
+	size = cast_size_t_to_ulong(size_st);
 	if (!data)
 		return NULL;
 	if (type != OBJ_TREE) {
@@ -2122,13 +2128,15 @@ static void add_preferred_base(struct object_id *oid)
 	struct pbase_tree *it;
 	void *data;
 	unsigned long size;
+	size_t size_st = 0;
 	struct object_id tree_oid;
 
 	if (window <= num_preferred_base++)
 		return;
 
 	data = odb_read_object_peeled(the_repository->objects, oid,
-				      OBJ_TREE, &size, &tree_oid);
+				      OBJ_TREE, &size_st, &tree_oid);
+	size = cast_size_t_to_ulong(size_st);
 	if (!data)
 		return;
 
@@ -2240,7 +2248,7 @@ static void prefetch_to_pack(uint32_t object_index_start) {
 
 static void check_object(struct object_entry *entry, uint32_t object_index)
 {
-	unsigned long canonical_size;
+	size_t canonical_size;
 	enum object_type type;
 	struct object_info oi = {.typep = &type, .sizep = &canonical_size};
 
@@ -2282,7 +2290,7 @@ static void check_object(struct object_entry *entry, uint32_t object_index)
 		default:
 			/* Not a delta hence we've already got all we need. */
 			oe_set_type(entry, entry->in_pack_type);
-			SET_SIZE(entry, cast_size_t_to_ulong(in_pack_size));
+			SET_SIZE(entry, in_pack_size);
 			entry->in_pack_header_size = used;
 			if (oe_type(entry) < OBJ_COMMIT || oe_type(entry) > OBJ_BLOB)
 				goto give_up;
@@ -2336,8 +2344,8 @@ static void check_object(struct object_entry *entry, uint32_t object_index)
 		if (have_base &&
 		    can_reuse_delta(&base_ref, entry, &base_entry)) {
 			oe_set_type(entry, entry->in_pack_type);
-			SET_SIZE(entry, cast_size_t_to_ulong(in_pack_size)); /* delta size */
-			SET_DELTA_SIZE(entry, cast_size_t_to_ulong(in_pack_size));
+			SET_SIZE(entry, in_pack_size); /* delta size */
+			SET_DELTA_SIZE(entry, in_pack_size);
 
 			if (base_entry) {
 				SET_DELTA(entry, base_entry);
@@ -2360,7 +2368,8 @@ static void check_object(struct object_entry *entry, uint32_t object_index)
 			 * object size from the delta header.
 			 */
 			delta_pos = entry->in_pack_offset + entry->in_pack_header_size;
-			canonical_size = get_size_from_delta(p, &w_curs, delta_pos);
+			canonical_size = get_size_from_delta(p, &w_curs,
+							     delta_pos);
 			if (canonical_size == 0)
 				goto give_up;
 			SET_SIZE(entry, canonical_size);
@@ -2438,7 +2447,7 @@ static void drop_reused_delta(struct object_entry *entry)
 	unsigned *idx = &to_pack.objects[entry->delta_idx - 1].delta_child_idx;
 	struct object_info oi = OBJECT_INFO_INIT;
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 
 	while (*idx) {
 		struct object_entry *oe = &to_pack.objects[*idx - 1];
@@ -2716,7 +2725,7 @@ static pthread_mutex_t progress_mutex;
 
 static inline int oe_size_less_than(struct packing_data *pack,
 				    const struct object_entry *lhs,
-				    unsigned long rhs)
+				    size_t rhs)
 {
 	if (lhs->size_valid)
 		return lhs->size_ < rhs;
@@ -2739,8 +2748,8 @@ static inline void oe_set_tree_depth(struct packing_data *pack,
  * reconstruction (so non-deltas are true object sizes, but deltas
  * return the size of the delta data).
  */
-unsigned long oe_get_size_slow(struct packing_data *pack,
-			       const struct object_entry *e)
+size_t oe_get_size_slow(struct packing_data *pack,
+			const struct object_entry *e)
 {
 	struct packed_git *p;
 	struct pack_window *w_curs;
@@ -2750,7 +2759,7 @@ unsigned long oe_get_size_slow(struct packing_data *pack,
 	size_t size;
 
 	if (e->type_ != OBJ_OFS_DELTA && e->type_ != OBJ_REF_DELTA) {
-		unsigned long sz;
+		size_t sz;
 		packing_data_lock(&to_pack);
 		if (odb_read_object_info(the_repository->objects,
 					 &e->idx.oid, &sz) < 0)
@@ -2774,7 +2783,7 @@ unsigned long oe_get_size_slow(struct packing_data *pack,
 
 	unuse_pack(&w_curs);
 	packing_data_unlock(&to_pack);
-	return cast_size_t_to_ulong(size);
+	return size;
 }
 
 static int try_delta(struct unpacked *trg, struct unpacked *src,
@@ -2835,10 +2844,12 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
 
 	/* Load data if not already done */
 	if (!trg->data) {
+		size_t sz_st = 0;
 		packing_data_lock(&to_pack);
 		trg->data = odb_read_object(the_repository->objects,
 					    &trg_entry->idx.oid, &type,
-					    &sz);
+					    &sz_st);
+		sz = cast_size_t_to_ulong(sz_st);
 		packing_data_unlock(&to_pack);
 		if (!trg->data)
 			die(_("object %s cannot be read"),
@@ -2850,10 +2861,12 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
 		*mem_usage += sz;
 	}
 	if (!src->data) {
+		size_t sz_st = 0;
 		packing_data_lock(&to_pack);
 		src->data = odb_read_object(the_repository->objects,
 					    &src_entry->idx.oid, &type,
-					    &sz);
+					    &sz_st);
+		sz = cast_size_t_to_ulong(sz_st);
 		packing_data_unlock(&to_pack);
 		if (!src->data) {
 			if (src_entry->preferred_base) {
diff --git a/builtin/repo.c b/builtin/repo.c
index 71a5c1c29c..69f3626467 100644
--- a/builtin/repo.c
+++ b/builtin/repo.c
@@ -784,13 +784,14 @@ static int count_objects(const char *path UNUSED, struct oid_array *oids,
 	for (size_t i = 0; i < oids->nr; i++) {
 		struct object_info oi = OBJECT_INFO_INIT;
 		unsigned long inflated;
+		size_t inflated_st = 0;
 		struct commit *commit;
 		struct object *obj;
 		void *content;
 		off_t disk;
 		int eaten;
 
-		oi.sizep = &inflated;
+		oi.sizep = &inflated_st;
 		oi.disk_sizep = &disk;
 		oi.contentp = &content;
 
@@ -798,6 +799,7 @@ static int count_objects(const char *path UNUSED, struct oid_array *oids,
 						  OBJECT_INFO_SKIP_FETCH_OBJECT |
 						  OBJECT_INFO_QUICK) < 0)
 			continue;
+		inflated = cast_size_t_to_ulong(inflated_st);
 
 		obj = parse_object_buffer(the_repository, &oids->oid[i], type,
 					  inflated, content, &eaten);
diff --git a/builtin/tag.c b/builtin/tag.c
index d51c2e3349..06c125b53c 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -238,7 +238,7 @@ static int git_tag_config(const char *var, const char *value,
 
 static void write_tag_body(int fd, const struct object_id *oid)
 {
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	char *buf, *sp, *orig;
 	struct strbuf payload = STRBUF_INIT;
@@ -388,7 +388,7 @@ static void create_reflog_msg(const struct object_id *oid, struct strbuf *sb)
 	enum object_type type;
 	struct commit *c;
 	char *buf;
-	unsigned long size;
+	size_t size;
 	int subject_len = 0;
 	const char *subject_start;
 
diff --git a/builtin/unpack-file.c b/builtin/unpack-file.c
index 87877a9fab..387389ed49 100644
--- a/builtin/unpack-file.c
+++ b/builtin/unpack-file.c
@@ -12,7 +12,7 @@ static char *create_temp_file(struct object_id *oid)
 	static char path[50];
 	void *buf;
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 	int fd;
 
 	buf = odb_read_object(the_repository->objects, oid, &type, &size);
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index 59e9b8711e..f3849bb654 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -231,7 +231,7 @@ static int check_object(struct object *obj, enum object_type type,
 		die("object type mismatch");
 
 	if (!(obj->flags & FLAG_OPEN)) {
-		unsigned long size;
+		size_t size;
 		int type = odb_read_object_info(the_repository->objects, &obj->oid, &size);
 		if (type != obj->type || type <= 0)
 			die("object of unexpected type");
@@ -314,7 +314,7 @@ static void resolve_delta(unsigned nr, enum object_type type,
 			  void *delta, unsigned long delta_size)
 {
 	void *result;
-	unsigned long result_size;
+	size_t result_size;
 
 	result = patch_delta(base, base_size,
 			     delta, delta_size,
@@ -436,6 +436,7 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
 {
 	void *delta_data, *base;
 	unsigned long base_size;
+	size_t base_size_st = 0;
 	struct object_id base_oid;
 
 	if (type == OBJ_REF_DELTA) {
@@ -512,7 +513,8 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
 		return;
 
 	base = odb_read_object(the_repository->objects, &base_oid,
-			       &type, &base_size);
+			       &type, &base_size_st);
+	base_size = cast_size_t_to_ulong(base_size_st);
 	if (!base) {
 		error("failed to read delta-pack base object %s",
 		      oid_to_hex(&base_oid));
diff --git a/bundle.c b/bundle.c
index 42327f9739..fd2db2c837 100644
--- a/bundle.c
+++ b/bundle.c
@@ -296,7 +296,7 @@ int list_bundle_refs(struct bundle_header *header, int argc, const char **argv)
 
 static int is_tag_in_date_range(struct object *tag, struct rev_info *revs)
 {
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	char *buf = NULL, *line, *lineend;
 	timestamp_t date;
diff --git a/combine-diff.c b/combine-diff.c
index 720768ce41..fb72174918 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -325,7 +325,9 @@ static char *grab_blob(struct repository *r,
 		*size = fill_textconv(r, textconv, df, &blob);
 		free_filespec(df);
 	} else {
-		blob = odb_read_object(r->objects, oid, &type, size);
+		size_t size_st = 0;
+		blob = odb_read_object(r->objects, oid, &type, &size_st);
+		*size = cast_size_t_to_ulong(size_st);
 		if (!blob)
 			die(_("unable to read %s"), oid_to_hex(oid));
 		if (type != OBJ_BLOB)
diff --git a/commit.c b/commit.c
index f1717ccbdc..5c4a4319b5 100644
--- a/commit.c
+++ b/commit.c
@@ -395,7 +395,7 @@ const void *repo_get_commit_buffer(struct repository *r,
 	const void *ret = get_cached_commit_buffer(r, commit, sizep);
 	if (!ret) {
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		ret = odb_read_object(r->objects, &commit->object.oid, &type, &size);
 		if (!ret)
 			die("cannot read commit object %s",
@@ -404,7 +404,7 @@ const void *repo_get_commit_buffer(struct repository *r,
 			die("expected commit for %s, got %s",
 			    oid_to_hex(&commit->object.oid), type_name(type));
 		if (sizep)
-			*sizep = size;
+			*sizep = cast_size_t_to_ulong(size);
 	}
 	return ret;
 }
@@ -437,7 +437,7 @@ static inline void set_commit_tree(struct commit *c, struct tree *t)
 static void load_tree_from_commit_contents(struct repository *r, struct commit *commit)
 {
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 	char *buf;
 	const char *p;
 	struct object_id tree_oid;
@@ -604,7 +604,7 @@ int repo_parse_commit_internal(struct repository *r,
 {
 	enum object_type type;
 	void *buffer;
-	unsigned long size;
+	size_t size;
 	struct object_info oi = {
 		.typep = &type,
 		.sizep = &size,
@@ -1300,7 +1300,7 @@ static void handle_signed_tag(const struct commit *parent, struct commit_extra_h
 	struct merge_remote_desc *desc;
 	struct commit_extra_header *mergetag;
 	char *buf;
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	struct strbuf payload = STRBUF_INIT;
 	struct strbuf signature = STRBUF_INIT;
diff --git a/compat/msvc-posix.h b/compat/msvc-posix.h
index c500b8b4aa..7ce39b8d3f 100644
--- a/compat/msvc-posix.h
+++ b/compat/msvc-posix.h
@@ -16,7 +16,6 @@
 #define __attribute__(x)
 #define strcasecmp   _stricmp
 #define strncasecmp  _strnicmp
-#define ftruncate    _chsize
 #define strtoull     _strtoui64
 #define strtoll      _strtoi64
 
@@ -30,4 +29,27 @@ typedef int sigset_t;
 
 #include "mingw-posix.h"
 
+/*
+ * MSVC's `_chsize()` takes a 32-bit `long` and silently truncates files
+ * to 2 GiB. `_chsize_s()` accepts a 64-bit length but returns 0 on
+ * success or an errno value on failure, rather than the -1/errno
+ * convention POSIX `ftruncate()` callers expect. Wrap it so callers
+ * that test the return value as `< 0` or against `-1` keep working.
+ *
+ * Note: this declaration must follow `#include "mingw-posix.h"` so
+ * `off_t` resolves to `off64_t` and the parameter type matches the
+ * underlying `_chsize_s()` width.
+ */
+static inline int msvc_ftruncate(int fd, off_t length)
+{
+	int err = _chsize_s(fd, length);
+
+	if (err) {
+		errno = err;
+		return -1;
+	}
+	return 0;
+}
+#define ftruncate msvc_ftruncate
+
 #endif /* COMPAT_MSVC_POSIX_H */
diff --git a/config.c b/config.c
index 45144f73c5..6a0de86e3a 100644
--- a/config.c
+++ b/config.c
@@ -1462,7 +1462,7 @@ int git_config_from_blob_oid(config_fn_t fn,
 {
 	enum object_type type;
 	char *buf;
-	unsigned long size;
+	size_t size;
 	int ret;
 
 	buf = odb_read_object(repo->objects, oid, &type, &size);
diff --git a/delta.h b/delta.h
index fad68cfc45..eb5c6d2fdb 100644
--- a/delta.h
+++ b/delta.h
@@ -75,9 +75,9 @@ diff_delta(const void *src_buf, unsigned long src_bufsize,
  * *trg_bufsize is updated with its size.  On failure a NULL pointer is
  * returned.  The returned buffer must be freed by the caller.
  */
-void *patch_delta(const void *src_buf, unsigned long src_size,
-		  const void *delta_buf, unsigned long delta_size,
-		  unsigned long *dst_size);
+void *patch_delta(const void *src_buf, size_t src_size,
+		  const void *delta_buf, size_t delta_size,
+		  size_t *dst_size);
 
 /* the smallest possible delta size is 4 bytes */
 #define DELTA_SIZE_MIN	4
@@ -86,11 +86,8 @@ void *patch_delta(const void *src_buf, unsigned long src_size,
  * This must be called twice on the delta data buffer, first to get the
  * expected source buffer size, and again to get the target buffer size.
  */
-/*
- * Size_t variant that doesn't truncate - use for >4GB objects on Windows.
- */
-static inline size_t get_delta_hdr_size_sz(const unsigned char **datap,
-					   const unsigned char *top)
+static inline size_t get_delta_hdr_size(const unsigned char **datap,
+					const unsigned char *top)
 {
 	const unsigned char *data = *datap;
 	size_t cmd, size = 0;
@@ -104,11 +101,4 @@ static inline size_t get_delta_hdr_size_sz(const unsigned char **datap,
 	return size;
 }
 
-static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
-					       const unsigned char *top)
-{
-	size_t size = get_delta_hdr_size_sz(datap, top);
-	return cast_size_t_to_ulong(size);
-}
-
 #endif
diff --git a/diff.c b/diff.c
index 9be7582d85..2a9d0d8687 100644
--- a/diff.c
+++ b/diff.c
@@ -4595,8 +4595,9 @@ int diff_populate_filespec(struct repository *r,
 		}
 	}
 	else {
+		size_t size_st = 0;
 		struct object_info info = {
-			.sizep = &s->size
+			.sizep = &size_st
 		};
 
 		if (!(size_only || check_binary))
@@ -4618,6 +4619,7 @@ int diff_populate_filespec(struct repository *r,
 			die("unable to read %s", oid_to_hex(&s->oid));
 
 object_read:
+		s->size = cast_size_t_to_ulong(size_st);
 		if (size_only || check_binary) {
 			if (size_only)
 				return 0;
@@ -4632,6 +4634,7 @@ object_read:
 			if (odb_read_object_info_extended(r->objects, &s->oid, &info,
 							  OBJECT_INFO_LOOKUP_REPLACE))
 				die("unable to read %s", oid_to_hex(&s->oid));
+			s->size = cast_size_t_to_ulong(size_st);
 		}
 		s->should_free = 1;
 	}
diff --git a/dir.c b/dir.c
index cc1fa60f1d..8cef25cd24 100644
--- a/dir.c
+++ b/dir.c
@@ -324,7 +324,7 @@ static int do_read_blob(const struct object_id *oid, struct oid_stat *oid_stat,
 			size_t *size_out, char **data_out)
 {
 	enum object_type type;
-	unsigned long sz;
+	size_t sz;
 	char *data;
 
 	*size_out = 0;
diff --git a/entry.c b/entry.c
index cd39b963af..3087c35f9e 100644
--- a/entry.c
+++ b/entry.c
@@ -105,11 +105,9 @@ static int create_file(const char *path, unsigned int mode)
 void *read_blob_entry(const struct cache_entry *ce, size_t *size)
 {
 	enum object_type type;
-	unsigned long ul;
 	void *blob_data = odb_read_object(the_repository->objects, &ce->oid,
-					  &type, &ul);
+					  &type, size);
 
-	*size = ul;
 	if (blob_data) {
 		if (type == OBJ_BLOB)
 			return blob_data;
diff --git a/fmt-merge-msg.c b/fmt-merge-msg.c
index 45d8b20e97..14441f23ae 100644
--- a/fmt-merge-msg.c
+++ b/fmt-merge-msg.c
@@ -528,11 +528,11 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
 	for (i = 0; i < origins.nr; i++) {
 		struct object_id *oid = origins.items[i].util;
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		char *buf = odb_read_object(the_repository->objects, oid,
 					    &type, &size);
 		char *origbuf = buf;
-		unsigned long len = size;
+		size_t len = size;
 		struct signature_check sigc = { NULL };
 		struct strbuf payload = STRBUF_INIT, sig = STRBUF_INIT;
 
diff --git a/fsck.c b/fsck.c
index b4ffee6a04..94c8651c7d 100644
--- a/fsck.c
+++ b/fsck.c
@@ -1328,7 +1328,7 @@ static int fsck_blobs(struct oidset *blobs_found, struct oidset *blobs_done,
 	oidset_iter_init(blobs_found, &iter);
 	while ((oid = oidset_iter_next(&iter))) {
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		char *buf;
 
 		if (oidset_contains(blobs_done, oid))
diff --git a/grep.c b/grep.c
index 598c9cba61..733fd3a800 100644
--- a/grep.c
+++ b/grep.c
@@ -1933,9 +1933,11 @@ void grep_source_clear_data(struct grep_source *gs)
 static int grep_source_load_oid(struct grep_source *gs)
 {
 	enum object_type type;
+	size_t size_st = 0;
 
 	gs->buf = odb_read_object(gs->repo->objects, gs->identifier,
-				  &type, &gs->size);
+				  &type, &size_st);
+	gs->size = cast_size_t_to_ulong(size_st);
 	if (!gs->buf)
 		return error(_("'%s': unable to read %s"),
 			     gs->name,
diff --git a/http-push.c b/http-push.c
index 8e2248c1c0..3c23cbba27 100644
--- a/http-push.c
+++ b/http-push.c
@@ -365,7 +365,7 @@ static void start_put(struct transfer_request *request)
 	enum object_type type;
 	char hdr[50];
 	void *unpacked;
-	unsigned long len;
+	size_t len;
 	int hdrlen;
 	ssize_t size;
 	git_zstream stream;
diff --git a/list-objects-filter.c b/list-objects-filter.c
index 78316e7f90..c912ff3079 100644
--- a/list-objects-filter.c
+++ b/list-objects-filter.c
@@ -280,7 +280,7 @@ static enum list_objects_filter_result filter_blobs_limit(
 	void *filter_data_)
 {
 	struct filter_blobs_limit_data *filter_data = filter_data_;
-	unsigned long object_length;
+	size_t object_length;
 	enum object_type t;
 
 	switch (filter_situation) {
diff --git a/mailmap.c b/mailmap.c
index 3b2691781d..72b639e602 100644
--- a/mailmap.c
+++ b/mailmap.c
@@ -186,7 +186,7 @@ int read_mailmap_blob(struct repository *repo, struct string_list *map,
 {
 	struct object_id oid;
 	char *buf;
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 
 	if (!name)
diff --git a/match-trees.c b/match-trees.c
index 4216933d06..2a43c0fa1a 100644
--- a/match-trees.c
+++ b/match-trees.c
@@ -61,7 +61,7 @@ static void *fill_tree_desc_strict(struct repository *r,
 {
 	void *buffer;
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 
 	buffer = odb_read_object(r->objects, hash, &type, &size);
 	if (!buffer)
@@ -186,7 +186,7 @@ static int splice_tree(struct repository *r,
 	char *subpath;
 	int toplen;
 	char *buf;
-	unsigned long sz;
+	size_t sz;
 	struct tree_desc desc;
 	unsigned char *rewrite_here;
 	const struct object_id *rewrite_with;
diff --git a/merge-blobs.c b/merge-blobs.c
index 6fc2799417..16a75bd1e3 100644
--- a/merge-blobs.c
+++ b/merge-blobs.c
@@ -9,7 +9,7 @@
 static int fill_mmfile_blob(mmfile_t *f, struct blob *obj)
 {
 	void *buf;
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 
 	buf = odb_read_object(the_repository->objects, &obj->object.oid,
@@ -35,7 +35,7 @@ static void *three_way_filemerge(struct index_state *istate,
 				 mmfile_t *base,
 				 mmfile_t *our,
 				 mmfile_t *their,
-				 unsigned long *size)
+				 size_t *size)
 {
 	enum ll_merge_result merge_status;
 	mmbuffer_t res;
@@ -61,7 +61,7 @@ static void *three_way_filemerge(struct index_state *istate,
 
 void *merge_blobs(struct index_state *istate, const char *path,
 		  struct blob *base, struct blob *our,
-		  struct blob *their, unsigned long *size)
+		  struct blob *their, size_t *size)
 {
 	void *res = NULL;
 	mmfile_t f1, f2, common;
diff --git a/merge-blobs.h b/merge-blobs.h
index 13cf9669e5..5797517a06 100644
--- a/merge-blobs.h
+++ b/merge-blobs.h
@@ -6,6 +6,6 @@ struct index_state;
 
 void *merge_blobs(struct index_state *, const char *,
 		  struct blob *, struct blob *,
-		  struct blob *, unsigned long *);
+		  struct blob *, size_t *);
 
 #endif /* MERGE_BLOBS_H */
diff --git a/merge-ort.c b/merge-ort.c
index 544be9e466..4f6273bd51 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -3716,7 +3716,7 @@ static int read_oid_strbuf(struct merge_options *opt,
 {
 	void *buf;
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 	buf = odb_read_object(opt->repo->objects, oid, &type, &size);
 	if (!buf) {
 		path_msg(opt, ERROR_OBJECT_READ_FAILED, 0,
diff --git a/notes-cache.c b/notes-cache.c
index bf5bb1f6c1..74cef802bd 100644
--- a/notes-cache.c
+++ b/notes-cache.c
@@ -82,7 +82,7 @@ char *notes_cache_get(struct notes_cache *c, struct object_id *key_oid,
 	const struct object_id *value_oid;
 	enum object_type type;
 	char *value;
-	unsigned long size;
+	size_t size;
 
 	value_oid = get_note(&c->tree, key_oid);
 	if (!value_oid)
diff --git a/notes-merge.c b/notes-merge.c
index b9322abbcb..118cad2518 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -339,7 +339,7 @@ static void write_note_to_worktree(const struct object_id *obj,
 				   const struct object_id *note)
 {
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 	void *buf = odb_read_object(the_repository->objects, note, &type, &size);
 
 	if (!buf)
diff --git a/notes.c b/notes.c
index 8f315e2a00..ec9c2cb150 100644
--- a/notes.c
+++ b/notes.c
@@ -811,7 +811,8 @@ int combine_notes_concatenate(struct object_id *cur_oid,
 			      const struct object_id *new_oid)
 {
 	char *cur_msg = NULL, *new_msg = NULL, *buf;
-	unsigned long cur_len, new_len, buf_len;
+	unsigned long buf_len;
+	size_t cur_len, new_len;
 	enum object_type cur_type, new_type;
 	int ret;
 
@@ -875,7 +876,7 @@ static int string_list_add_note_lines(struct string_list *list,
 				      const struct object_id *oid)
 {
 	char *data;
-	unsigned long len;
+	size_t len;
 	enum object_type t;
 
 	if (is_null_oid(oid))
@@ -1282,7 +1283,8 @@ static void format_note(struct notes_tree *t, const struct object_id *object_oid
 	static const char utf8[] = "utf-8";
 	const struct object_id *oid;
 	char *msg, *msg_p;
-	unsigned long linelen, msglen;
+	unsigned long linelen;
+	size_t msglen;
 	enum object_type type;
 
 	if (!t)
diff --git a/object-file.c b/object-file.c
index 0056c369ce..6453b1d6fa 100644
--- a/object-file.c
+++ b/object-file.c
@@ -300,7 +300,7 @@ int parse_loose_header(const char *hdr, struct object_info *oi)
 	}
 
 	if (oi->sizep)
-		*oi->sizep = cast_size_t_to_ulong(size);
+		*oi->sizep = size;
 
 	/*
 	 * The length must be followed by a zero byte
@@ -932,7 +932,7 @@ int force_object_loose(struct odb_source *source,
 	struct odb_source_files *files = odb_source_files_downcast(source);
 	const struct git_hash_algo *compat = source->odb->repo->compat_hash_algo;
 	void *buf;
-	unsigned long len;
+	size_t len;
 	struct object_info oi = OBJECT_INFO_INIT;
 	struct object_id compat_oid;
 	enum object_type type;
@@ -1616,7 +1616,7 @@ int read_loose_object(struct repository *repo,
 	unsigned long mapsize;
 	git_zstream stream;
 	char hdr[MAX_HEADER_LEN];
-	unsigned long *size = oi->sizep;
+	size_t *size = oi->sizep;
 
 	fd = git_open(path);
 	if (fd >= 0)
diff --git a/object.c b/object.c
index 465902ecc6..23b84aa7e2 100644
--- a/object.c
+++ b/object.c
@@ -325,7 +325,7 @@ struct object *parse_object_with_flags(struct repository *r,
 {
 	int skip_hash = !!(flags & PARSE_OBJECT_SKIP_HASH_CHECK);
 	int discard_tree = !!(flags & PARSE_OBJECT_DISCARD_TREE);
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	int eaten;
 	const struct object_id *repl = lookup_replace_object(r, oid);
diff --git a/odb.c b/odb.c
index 965ef68e4e..7d555be09f 100644
--- a/odb.c
+++ b/odb.c
@@ -625,7 +625,7 @@ static int oid_object_info_convert(struct repository *r,
 	enum object_type type;
 	struct object_id oid, delta_base_oid;
 	struct object_info new_oi, *oi;
-	unsigned long size;
+	size_t size;
 	void *content;
 	int ret;
 
@@ -716,7 +716,7 @@ int odb_read_object_info_extended(struct object_database *odb,
 /* returns enum object_type or negative */
 int odb_read_object_info(struct object_database *odb,
 			 const struct object_id *oid,
-			 unsigned long *sizep)
+			 size_t *sizep)
 {
 	enum object_type type;
 	struct object_info oi = OBJECT_INFO_INIT;
@@ -730,7 +730,7 @@ int odb_read_object_info(struct object_database *odb,
 }
 
 int odb_pretend_object(struct object_database *odb,
-		       void *buf, unsigned long len, enum object_type type,
+		       void *buf, size_t len, enum object_type type,
 		       struct object_id *oid)
 {
 	hash_object_file(odb->repo->hash_algo, buf, len, type, oid);
@@ -744,7 +744,7 @@ int odb_pretend_object(struct object_database *odb,
 void *odb_read_object(struct object_database *odb,
 		      const struct object_id *oid,
 		      enum object_type *type,
-		      unsigned long *size)
+		      size_t *size)
 {
 	struct object_info oi = OBJECT_INFO_INIT;
 	unsigned flags = OBJECT_INFO_DIE_IF_CORRUPT | OBJECT_INFO_LOOKUP_REPLACE;
@@ -762,12 +762,12 @@ void *odb_read_object(struct object_database *odb,
 void *odb_read_object_peeled(struct object_database *odb,
 			     const struct object_id *oid,
 			     enum object_type required_type,
-			     unsigned long *size,
+			     size_t *size,
 			     struct object_id *actual_oid_return)
 {
 	enum object_type type;
 	void *buffer;
-	unsigned long isize;
+	size_t isize;
 	struct object_id actual_oid;
 
 	oidcpy(&actual_oid, oid);
diff --git a/odb.h b/odb.h
index 0030467a52..3834a0dcbf 100644
--- a/odb.h
+++ b/odb.h
@@ -228,12 +228,12 @@ struct odb_source *odb_add_to_alternates_memory(struct object_database *odb,
 void *odb_read_object(struct object_database *odb,
 		      const struct object_id *oid,
 		      enum object_type *type,
-		      unsigned long *size);
+		      size_t *size);
 
 void *odb_read_object_peeled(struct object_database *odb,
 			     const struct object_id *oid,
 			     enum object_type required_type,
-			     unsigned long *size,
+			     size_t *size,
 			     struct object_id *oid_ret);
 
 /*
@@ -245,13 +245,13 @@ void *odb_read_object_peeled(struct object_database *odb,
  * that reference it.
  */
 int odb_pretend_object(struct object_database *odb,
-		       void *buf, unsigned long len, enum object_type type,
+		       void *buf, size_t len, enum object_type type,
 		       struct object_id *oid);
 
 struct object_info {
 	/* Request */
 	enum object_type *typep;
-	unsigned long *sizep;
+	size_t *sizep;
 	off_t *disk_sizep;
 	struct object_id *delta_base_oid;
 	void **contentp;
@@ -356,7 +356,7 @@ int odb_read_object_info_extended(struct object_database *odb,
  */
 int odb_read_object_info(struct object_database *odb,
 			 const struct object_id *oid,
-			 unsigned long *sizep);
+			 size_t *sizep);
 
 enum odb_has_object_flags {
 	/* Retry packed storage after checking packed and loose storage */
diff --git a/odb/streaming.c b/odb/streaming.c
index 7602a8d5d8..20531e864c 100644
--- a/odb/streaming.c
+++ b/odb/streaming.c
@@ -157,26 +157,15 @@ static int open_istream_incore(struct odb_read_stream **out,
 		.base.read = read_istream_incore,
 	};
 	struct odb_incore_read_stream *st;
-	unsigned long size_ul;
 	int ret;
 
 	oi.typep = &stream.base.type;
-	/*
-	 * object_info.sizep is unsigned long* (32-bit on Windows), but
-	 * stream.base.size is size_t (64-bit). We use a temporary variable
-	 * because the types are incompatible. Note: this path still truncates
-	 * for >4GB objects, but large objects should use pack streaming
-	 * (packfile_store_read_object_stream) which handles size_t properly.
-	 * This incore fallback is only used for small objects or when pack
-	 * streaming is unavailable.
-	 */
-	oi.sizep = &size_ul;
+	oi.sizep = &stream.base.size;
 	oi.contentp = (void **)&stream.buf;
 	ret = odb_read_object_info_extended(odb, oid, &oi,
 					    OBJECT_INFO_DIE_IF_CORRUPT);
 	if (ret)
 		return ret;
-	stream.base.size = size_ul;
 
 	CALLOC_ARRAY(st, 1);
 	*st = stream;
diff --git a/pack-bitmap.c b/pack-bitmap.c
index f9af8a96bd..e8a82945cc 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -1856,7 +1856,7 @@ static void filter_bitmap_blob_none(struct bitmap_index *bitmap_git,
 static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
 				     uint32_t pos)
 {
-	unsigned long size;
+	size_t size;
 	struct object_info oi = OBJECT_INFO_INIT;
 
 	oi.sizep = &size;
@@ -1891,7 +1891,7 @@ static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
 			die(_("unable to get size of %s"), oid_to_hex(&obj->oid));
 	}
 
-	return size;
+	return cast_size_t_to_ulong(size);
 }
 
 static void filter_bitmap_blob_limit(struct bitmap_index *bitmap_git,
diff --git a/pack-check.c b/pack-check.c
index 2792f34d25..5adfb3f272 100644
--- a/pack-check.c
+++ b/pack-check.c
@@ -143,9 +143,8 @@ static int verify_packfile(struct repository *r,
 			data = NULL;
 			data_valid = 0;
 		} else {
-			unsigned long sz;
-			data = unpack_entry(r, p, entries[i].offset, &type, &sz);
-			size = sz;
+			data = unpack_entry(r, p, entries[i].offset, &type,
+					    &size);
 			data_valid = 1;
 		}
 
diff --git a/pack-objects.h b/pack-objects.h
index 83299d4732..e97e84ddcb 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -141,7 +141,7 @@ struct packing_data {
 	uint32_t index_size;
 
 	unsigned int *in_pack_pos;
-	unsigned long *delta_size;
+	size_t *delta_size;
 
 	/*
 	 * Only one of these can be non-NULL and they have different
diff --git a/packfile.c b/packfile.c
index 89366abfe3..78c389e6f3 100644
--- a/packfile.c
+++ b/packfile.c
@@ -1164,11 +1164,12 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 }
 
 /*
- * Size_t variant for >4GB delta results on Windows.
+ * Read a delta object's header at curpos in p (already inflated as needed)
+ * and return the size of the result object (the post-application target).
  */
-static size_t get_size_from_delta_sz(struct packed_git *p,
-				     struct pack_window **w_curs,
-				     off_t curpos)
+size_t get_size_from_delta(struct packed_git *p,
+			   struct pack_window **w_curs,
+			   off_t curpos)
 {
 	const unsigned char *data;
 	unsigned char delta_head[20], *in;
@@ -1215,18 +1216,10 @@ static size_t get_size_from_delta_sz(struct packed_git *p,
 	data = delta_head;
 
 	/* ignore base size */
-	get_delta_hdr_size_sz(&data, delta_head+sizeof(delta_head));
+	get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
 
 	/* Read the result size */
-	return get_delta_hdr_size_sz(&data, delta_head+sizeof(delta_head));
-}
-
-unsigned long get_size_from_delta(struct packed_git *p,
-				  struct pack_window **w_curs,
-				  off_t curpos)
-{
-	size_t size = get_size_from_delta_sz(p, w_curs, curpos);
-	return cast_size_t_to_ulong(size);
+	return get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
 }
 
 int unpack_object_header(struct packed_git *p,
@@ -1454,7 +1447,7 @@ struct delta_base_cache_entry {
 	struct delta_base_cache_key key;
 	struct list_head lru;
 	void *data;
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 };
 
@@ -1525,7 +1518,7 @@ static void detach_delta_base_cache_entry(struct delta_base_cache_entry *ent)
 }
 
 static void *cache_or_unpack_entry(struct repository *r, struct packed_git *p,
-				   off_t base_offset, unsigned long *base_size,
+				   off_t base_offset, size_t *base_size,
 				   enum object_type *type)
 {
 	struct delta_base_cache_entry *ent;
@@ -1558,8 +1551,8 @@ void clear_delta_base_cache(void)
 }
 
 static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
-				 void *base, unsigned long base_size,
-				 unsigned long delta_base_cache_limit,
+				 void *base, size_t base_size,
+				 size_t delta_base_cache_limit,
 				 enum object_type type)
 {
 	struct delta_base_cache_entry *ent;
@@ -1614,8 +1607,8 @@ static int packed_object_info_with_index_pos(struct packed_git *p, off_t obj_off
 	 * a "real" type later if the caller is interested.
 	 */
 	if (oi->contentp) {
-		*oi->contentp = cache_or_unpack_entry(p->repo, p, obj_offset, oi->sizep,
-						      &type);
+		*oi->contentp = cache_or_unpack_entry(p->repo, p, obj_offset,
+						      oi->sizep, &type);
 		if (!*oi->contentp)
 			type = OBJ_BAD;
 	} else if (oi->sizep || oi->typep || oi->delta_base_oid) {
@@ -1631,18 +1624,13 @@ static int packed_object_info_with_index_pos(struct packed_git *p, off_t obj_off
 				ret = -1;
 				goto out;
 			}
-			/*
-			 * Use size_t variant to avoid die() on >4GB deltas.
-			 * oi->sizep is unsigned long, so truncation may occur,
-			 * but streaming code uses its own size_t tracking.
-			 */
-			size = get_size_from_delta_sz(p, &w_curs, tmp_pos);
+			size = get_size_from_delta(p, &w_curs, tmp_pos);
 			if (size == 0) {
 				ret = -1;
 				goto out;
 			}
 		}
-		*oi->sizep = (unsigned long)size;
+		*oi->sizep = size;
 	}
 
 	if (oi->disk_sizep || (oi->mtimep && p->is_cruft)) {
@@ -1735,7 +1723,7 @@ int packed_object_info(struct packed_git *p, off_t obj_offset,
 static void *unpack_compressed_entry(struct packed_git *p,
 				    struct pack_window **w_curs,
 				    off_t curpos,
-				    unsigned long size)
+				    size_t size)
 {
 	int st;
 	git_zstream stream;
@@ -1790,11 +1778,11 @@ int do_check_packed_object_crc;
 struct unpack_entry_stack_ent {
 	off_t obj_offset;
 	off_t curpos;
-	unsigned long size;
+	size_t size;
 };
 
 void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
-		   enum object_type *final_type, unsigned long *final_size)
+		   enum object_type *final_type, size_t *final_size)
 {
 	struct pack_window *w_curs = NULL;
 	off_t curpos = obj_offset;
@@ -1911,7 +1899,7 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 		void *delta_data;
 		void *base = data;
 		void *external_base = NULL;
-		unsigned long delta_size, base_size = size;
+		size_t delta_size, base_size = size;
 		int i;
 		off_t base_obj_offset = obj_offset;
 
@@ -1964,10 +1952,8 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 			      (uintmax_t)curpos, p->pack_name);
 			data = NULL;
 		} else {
-			unsigned long sz;
 			data = patch_delta(base, base_size, delta_data,
-					   delta_size, &sz);
-			size = sz;
+					   delta_size, &size);
 
 			/*
 			 * We could not apply the delta; warn the user, but
diff --git a/packfile.h b/packfile.h
index 5729a37018..defb6f442c 100644
--- a/packfile.h
+++ b/packfile.h
@@ -455,9 +455,10 @@ off_t nth_packed_object_offset(const struct packed_git *, uint32_t n);
 off_t find_pack_entry_one(const struct object_id *oid, struct packed_git *);
 
 int is_pack_valid(struct packed_git *);
-void *unpack_entry(struct repository *r, struct packed_git *, off_t, enum object_type *, unsigned long *);
+void *unpack_entry(struct repository *r, struct packed_git *, off_t,
+		   enum object_type *, size_t *);
 unsigned long unpack_object_header_buffer(const unsigned char *buf, unsigned long len, enum object_type *type, size_t *sizep);
-unsigned long get_size_from_delta(struct packed_git *, struct pack_window **, off_t);
+size_t get_size_from_delta(struct packed_git *, struct pack_window **, off_t);
 int unpack_object_header(struct packed_git *, struct pack_window **, off_t *, size_t *);
 off_t get_delta_base(struct packed_git *p, struct pack_window **w_curs,
 		     off_t *curpos, enum object_type type,
diff --git a/patch-delta.c b/patch-delta.c
index b5c8594db6..42199fa956 100644
--- a/patch-delta.c
+++ b/patch-delta.c
@@ -12,13 +12,13 @@
 #include "git-compat-util.h"
 #include "delta.h"
 
-void *patch_delta(const void *src_buf, unsigned long src_size,
-		  const void *delta_buf, unsigned long delta_size,
-		  unsigned long *dst_size)
+void *patch_delta(const void *src_buf, size_t src_size,
+		  const void *delta_buf, size_t delta_size,
+		  size_t *dst_size)
 {
 	const unsigned char *data, *top;
 	unsigned char *dst_buf, *out, cmd;
-	unsigned long size;
+	size_t size;
 
 	if (delta_size < DELTA_SIZE_MIN)
 		return NULL;
diff --git a/path-walk.c b/path-walk.c
index 94ff90bd15..edc8e736d7 100644
--- a/path-walk.c
+++ b/path-walk.c
@@ -368,7 +368,7 @@ static int walk_path(struct path_walk_context *ctx,
 		struct oid_array filtered = OID_ARRAY_INIT;
 
 		for (size_t i = 0; i < list->oids.nr; i++) {
-			unsigned long size;
+			size_t size;
 
 			if (odb_read_object_info(ctx->repo->objects,
 						 &list->oids.oid[i],
diff --git a/protocol-caps.c b/protocol-caps.c
index 35072ed60b..8858ea4489 100644
--- a/protocol-caps.c
+++ b/protocol-caps.c
@@ -50,7 +50,7 @@ static void send_info(struct repository *r, struct packet_writer *writer,
 	for_each_string_list_item (item, oid_str_list) {
 		const char *oid_str = item->string;
 		struct object_id oid;
-		unsigned long object_size;
+		size_t object_size;
 
 		if (get_oid_hex_algop(oid_str, &oid, r->hash_algo) < 0) {
 			packet_writer_error(
@@ -66,7 +66,8 @@ static void send_info(struct repository *r, struct packet_writer *writer,
 			if (odb_read_object_info(r->objects, &oid, &object_size) < 0) {
 				strbuf_addstr(&send_buffer, " ");
 			} else {
-				strbuf_addf(&send_buffer, " %lu", object_size);
+				strbuf_addf(&send_buffer, " %"PRIuMAX,
+					    (uintmax_t)object_size);
 			}
 		}
 
diff --git a/read-cache.c b/read-cache.c
index ea5f839156..9cef28d27f 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -250,7 +250,7 @@ static int ce_compare_link(const struct cache_entry *ce, size_t expected_size)
 {
 	int match = -1;
 	void *buffer;
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 	struct strbuf sb = STRBUF_INIT;
 
@@ -3464,7 +3464,7 @@ void *read_blob_data_from_index(struct index_state *istate,
 				const char *path, unsigned long *size)
 {
 	int pos, len;
-	unsigned long sz;
+	size_t sz;
 	enum object_type type;
 	void *data;
 
@@ -3492,7 +3492,7 @@ void *read_blob_data_from_index(struct index_state *istate,
 		return NULL;
 	}
 	if (size)
-		*size = sz;
+		*size = cast_size_t_to_ulong(sz);
 	return data;
 }
 
diff --git a/ref-filter.c b/ref-filter.c
index 1da4c0e60d..8ba91c72a1 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -86,7 +86,7 @@ struct ref_trailer_buf {
 static struct expand_data {
 	struct object_id oid;
 	enum object_type type;
-	unsigned long size;
+	size_t size;
 	off_t disk_size;
 	struct object_id delta_base_oid;
 	void *content;
diff --git a/reflog.c b/reflog.c
index 82337078d0..04edbe5670 100644
--- a/reflog.c
+++ b/reflog.c
@@ -154,7 +154,7 @@ static int tree_is_complete(const struct object_id *oid)
 
 	if (!tree->buffer) {
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 		void *data = odb_read_object(the_repository->objects, oid,
 					     &type, &size);
 		if (!data) {
diff --git a/rerere.c b/rerere.c
index 28a740b771..8232542585 100644
--- a/rerere.c
+++ b/rerere.c
@@ -990,7 +990,7 @@ static int handle_cache(struct index_state *istate,
 
 	while (pos < istate->cache_nr) {
 		enum object_type type;
-		unsigned long size;
+		size_t size;
 
 		ce = istate->cache[pos++];
 		if (ce_namelen(ce) != len || memcmp(ce->name, path, len))
diff --git a/submodule-config.c b/submodule-config.c
index a81897b4e0..f75997402a 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -694,7 +694,7 @@ static const struct submodule *config_from(struct submodule_cache *cache,
 		enum lookup_type lookup_type)
 {
 	struct strbuf rev = STRBUF_INIT;
-	unsigned long config_size;
+	size_t config_size;
 	char *config = NULL;
 	struct object_id oid;
 	enum object_type type;
diff --git a/t/helper/test-delta.c b/t/helper/test-delta.c
index 52ea00c937..8223a60229 100644
--- a/t/helper/test-delta.c
+++ b/t/helper/test-delta.c
@@ -21,7 +21,7 @@ int cmd__delta(int argc, const char **argv)
 	int fd;
 	struct strbuf from = STRBUF_INIT, data = STRBUF_INIT;
 	char *out_buf;
-	unsigned long out_size;
+	size_t out_size;
 
 	if (argc != 5 || (strcmp(argv[1], "-d") && strcmp(argv[1], "-p")))
 		usage(usage_str);
@@ -31,11 +31,13 @@ int cmd__delta(int argc, const char **argv)
 	if (strbuf_read_file(&data, argv[3], 0) < 0)
 		die_errno("unable to read '%s'", argv[3]);
 
-	if (argv[1][1] == 'd')
+	if (argv[1][1] == 'd') {
+		unsigned long delta_size;
 		out_buf = diff_delta(from.buf, from.len,
 				     data.buf, data.len,
-				     &out_size, 0);
-	else
+				     &delta_size, 0);
+		out_size = delta_size;
+	} else
 		out_buf = patch_delta(from.buf, from.len,
 				      data.buf, data.len,
 				      &out_size);
diff --git a/t/helper/test-pack-deltas.c b/t/helper/test-pack-deltas.c
index c493b75e02..840797cf0d 100644
--- a/t/helper/test-pack-deltas.c
+++ b/t/helper/test-pack-deltas.c
@@ -48,7 +48,8 @@ static void write_ref_delta(struct hashfile *f,
 			    struct object_id *base)
 {
 	unsigned char header[MAX_PACK_OBJECT_HEADER];
-	unsigned long size, base_size, delta_size, compressed_size, hdrlen;
+	unsigned long delta_size, compressed_size, hdrlen;
+	size_t size, base_size;
 	enum object_type type;
 	void *base_buf, *delta_buf;
 	void *buf = odb_read_object(the_repository->objects,
diff --git a/t/helper/test-partial-clone.c b/t/helper/test-partial-clone.c
index a7aab426d0..87c59108e0 100644
--- a/t/helper/test-partial-clone.c
+++ b/t/helper/test-partial-clone.c
@@ -17,7 +17,7 @@ static void object_info(const char *gitdir, const char *oid_hex)
 {
 	struct repository r;
 	struct object_id oid;
-	unsigned long size;
+	size_t size;
 	struct object_info oi = {.sizep = &size};
 	const char *p;
 
diff --git a/t/unit-tests/u-odb-inmemory.c b/t/unit-tests/u-odb-inmemory.c
index 482502ef4b..6844bfc37c 100644
--- a/t/unit-tests/u-odb-inmemory.c
+++ b/t/unit-tests/u-odb-inmemory.c
@@ -20,7 +20,7 @@ static void cl_assert_object_info(struct odb_source_inmemory *source,
 				  const char *expected_content)
 {
 	enum object_type actual_type;
-	unsigned long actual_size;
+	size_t actual_size;
 	void *actual_content;
 	struct object_info oi = {
 		.typep = &actual_type,
diff --git a/tag.c b/tag.c
index 2f12e51024..1a00ded6eb 100644
--- a/tag.c
+++ b/tag.c
@@ -49,7 +49,7 @@ int gpg_verify_tag(struct repository *r, const struct object_id *oid,
 {
 	enum object_type type;
 	char *buf;
-	unsigned long size;
+	size_t size;
 	int ret;
 
 	type = odb_read_object_info(r->objects, oid, NULL);
@@ -207,7 +207,7 @@ int parse_tag(struct repository *r, struct tag *item)
 {
 	enum object_type type;
 	void *data;
-	unsigned long size;
+	size_t size;
 	int ret;
 
 	if (item->object.parsed)
diff --git a/tree-walk.c b/tree-walk.c
index 7e1b956f27..a67f06b9eb 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -87,7 +87,7 @@ void *fill_tree_descriptor(struct repository *r,
 			   struct tree_desc *desc,
 			   const struct object_id *oid)
 {
-	unsigned long size = 0;
+	size_t size = 0;
 	void *buf = NULL;
 
 	if (oid) {
@@ -610,7 +610,7 @@ int get_tree_entry(struct repository *r,
 {
 	int retval;
 	void *tree;
-	unsigned long size;
+	size_t size;
 	struct object_id root;
 
 	tree = odb_read_object_peeled(r->objects, tree_oid, OBJ_TREE, &size, &root);
@@ -682,7 +682,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 		if (!t.buffer) {
 			void *tree;
 			struct object_id root;
-			unsigned long size;
+			size_t size;
 			tree = odb_read_object_peeled(r->objects, &current_tree_oid,
 						      OBJ_TREE, &size, &root);
 			if (!tree)
@@ -778,6 +778,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 		} else if (S_ISLNK(*mode)) {
 			/* Follow a symlink */
 			unsigned long link_len;
+			size_t link_len_st = 0;
 			size_t len;
 			char *contents, *contents_start;
 			struct dir_state *parent;
@@ -797,7 +798,8 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 
 			contents = odb_read_object(r->objects,
 						   &current_tree_oid, &type,
-						   &link_len);
+						   &link_len_st);
+			link_len = cast_size_t_to_ulong(link_len_st);
 
 			if (!contents)
 				goto done;
diff --git a/tree.c b/tree.c
index d703ab97c8..53f7395e9f 100644
--- a/tree.c
+++ b/tree.c
@@ -188,7 +188,7 @@ int repo_parse_tree_gently(struct repository *r, struct tree *item,
 {
 	 enum object_type type;
 	 void *buffer;
-	 unsigned long size;
+	 size_t size;
 
 	if (item->object.parsed)
 		return 0;
diff --git a/xdiff-interface.c b/xdiff-interface.c
index 5ee2b96d0a..db6938689f 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -179,7 +179,7 @@ int read_mmfile(mmfile_t *ptr, const char *filename)
 void read_mmblob(mmfile_t *ptr, struct object_database *odb,
 		 const struct object_id *oid)
 {
-	unsigned long size;
+	size_t size;
 	enum object_type type;
 
 	if (is_null_oid(oid)) {