list-objects-filter: add and use initializers

In 7e2619d8ff (list_objects_filter_options: plug leak of filter_spec
strings, 2022-09-08), we noted that the filter_spec string_list was
inconsistent in how it handled memory ownership of strings stored in the
list. The fix there was a bit of a band-aid to set the "strdup_strings"
variable right before adding anything.

That works OK, and it lets the users of the API continue to
zero-initialize the struct. But it makes the code a bit hard to follow
and accident-prone, as any other spots appending the filter_spec need to
think about whether to set the strdup_strings value, too (there's one
such spot in partial_clone_get_default_filter_spec(), which is probably
a possible memory leak).

So let's do that full cleanup now. We'll introduce a
LIST_OBJECTS_FILTER_INIT macro and matching function, and use them as
appropriate (though it is for the "_options" struct, this matches the
corresponding list_objects_filter_release() function).

This is harder than it seems! Many other structs, like
git_transport_data, embed the filter struct. So they need to initialize
it themselves even if the rest of the enclosing struct is OK with
zero-initialization. I found all of the relevant spots by grepping
manually for declarations of list_objects_filter_options. And then doing
so recursively for structs which embed it, and ones which embed those,
and so on.

I'm pretty sure I got everything, but there's no change that would alert
the compiler if any topics in flight added new declarations. To catch
this case, we now double-check in the parsing function that things were
initialized as expected and BUG() if appropriate.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -72,7 +72,7 @@ static struct string_list option_optional_reference = STRING_LIST_INIT_NODUP;
 static int option_dissociate;
 static int max_jobs = -1;
 static struct string_list option_recurse_submodules = STRING_LIST_INIT_NODUP;
-static struct list_objects_filter_options filter_options;
+static struct list_objects_filter_options filter_options = LIST_OBJECTS_FILTER_INIT;
 static int option_filter_submodules = -1;    /* unspecified */
 static int config_filter_submodules = -1;    /* unspecified */
 static struct string_list server_options = STRING_LIST_INIT_NODUP;

builtin/fetch-pack.c

@@ -62,6 +62,7 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 	packet_trace_identity("fetch-pack");
 
 	memset(&args, 0, sizeof(args));
+	list_objects_filter_init(&args.filter_options);
 	args.uploadpack = "git-upload-pack";
 
 	for (i = 1; i < argc && *argv[i] == '-'; i++) {

builtin/fetch.c

@@ -80,7 +80,7 @@ static int recurse_submodules_cli = RECURSE_SUBMODULES_DEFAULT;
 static int recurse_submodules_default = RECURSE_SUBMODULES_ON_DEMAND;
 static int shown_url = 0;
 static struct refspec refmap = REFSPEC_INIT_FETCH;
-static struct list_objects_filter_options filter_options;
+static struct list_objects_filter_options filter_options = LIST_OBJECTS_FILTER_INIT;
 static struct string_list server_options = STRING_LIST_INIT_DUP;
 static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
 static int fetch_write_commit_graph = -1;

builtin/submodule--helper.c

@@ -1754,7 +1754,8 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 {
 	int dissociate = 0, quiet = 0, progress = 0, require_init = 0;
 	struct module_clone_data clone_data = MODULE_CLONE_DATA_INIT;
-	struct list_objects_filter_options filter_options;
+	struct list_objects_filter_options filter_options =
+		LIST_OBJECTS_FILTER_INIT;
 
 	struct option module_clone_options[] = {
 		OPT_STRING(0, "prefix", &clone_data.prefix,
@@ -1796,7 +1797,6 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 		NULL
 	};
 
-	memset(&filter_options, 0, sizeof(filter_options));
 	argc = parse_options(argc, argv, prefix, module_clone_options,
 			     git_submodule_helper_usage, 0);
 
@@ -2581,7 +2581,8 @@ static int module_update(int argc, const char **argv, const char *prefix)
 {
 	struct pathspec pathspec;
 	struct update_data opt = UPDATE_DATA_INIT;
-	struct list_objects_filter_options filter_options;
+	struct list_objects_filter_options filter_options =
+		LIST_OBJECTS_FILTER_INIT;
 	int ret;
 
 	struct option module_update_options[] = {
@@ -2639,7 +2640,6 @@ static int module_update(int argc, const char **argv, const char *prefix)
 	update_clone_config_from_gitmodules(&opt.max_jobs);
 	git_config(git_update_clone_config, &opt.max_jobs);
 
-	memset(&filter_options, 0, sizeof(filter_options));
 	argc = parse_options(argc, argv, prefix, module_update_options,
 			     git_submodule_helper_usage, 0);
 

bundle.h

@@ -18,6 +18,7 @@ struct bundle_header {
 { \
 	.prerequisites = STRING_LIST_INIT_DUP, \
 	.references = STRING_LIST_INIT_DUP, \
+	.filter = LIST_OBJECTS_FILTER_INIT, \
 }
 void bundle_header_init(struct bundle_header *header);
 void bundle_header_release(struct bundle_header *header);

list-objects-filter-options.c

@@ -108,7 +108,7 @@ int gently_parse_list_objects_filter(
 
 	strbuf_addf(errbuf, _("invalid filter-spec '%s'"), arg);
 
-	memset(filter_options, 0, sizeof(*filter_options));
+	list_objects_filter_init(filter_options);
 	return 1;
 }
 
@@ -223,8 +223,7 @@ static void transform_to_combine_type(
 		struct list_objects_filter_options *sub_array =
 			xcalloc(initial_sub_alloc, sizeof(*sub_array));
 		sub_array[0] = *filter_options;
-		memset(filter_options, 0, sizeof(*filter_options));
-		string_list_init_dup(&filter_options->filter_spec);
+		list_objects_filter_init(filter_options);
 		filter_options->sub = sub_array;
 		filter_options->sub_alloc = initial_sub_alloc;
 	}
@@ -255,11 +254,8 @@ void parse_list_objects_filter(
 	struct strbuf errbuf = STRBUF_INIT;
 	int parse_error;
 
-	if (!filter_options->filter_spec.strdup_strings) {
-		if (filter_options->filter_spec.nr)
-			BUG("unexpected non-allocated string in filter_spec");
-		filter_options->filter_spec.strdup_strings = 1;
-	}
+	if (!filter_options->filter_spec.strdup_strings)
+		BUG("filter_options not properly initialized");
 
 	if (!filter_options->choice) {
 		string_list_append(&filter_options->filter_spec, arg);
@@ -346,7 +342,7 @@ void list_objects_filter_release(
 	for (sub = 0; sub < filter_options->sub_nr; sub++)
 		list_objects_filter_release(&filter_options->sub[sub]);
 	free(filter_options->sub);
-	memset(filter_options, 0, sizeof(*filter_options));
+	list_objects_filter_init(filter_options);
 }
 
 void partial_clone_register(
@@ -429,3 +425,9 @@ void list_objects_filter_copy(
 	for (i = 0; i < src->sub_nr; i++)
 		list_objects_filter_copy(&dest->sub[i], &src->sub[i]);
 }
+
+void list_objects_filter_init(struct list_objects_filter_options *filter_options)
+{
+	struct list_objects_filter_options blank = LIST_OBJECTS_FILTER_INIT;
+	memcpy(filter_options, &blank, sizeof(*filter_options));
+}

list-objects-filter-options.h

@@ -69,6 +69,9 @@ struct list_objects_filter_options {
 	 */
 };
 
+#define LIST_OBJECTS_FILTER_INIT { .filter_spec = STRING_LIST_INIT_DUP }
+void list_objects_filter_init(struct list_objects_filter_options *filter_options);
+
 /*
  * Parse value of the argument to the "filter" keyword.
  * On the command line this looks like:

revision.c

@@ -1900,6 +1900,7 @@ void repo_init_revisions(struct repository *r,
 	}
 
 	init_display_notes(&revs->notes_opt);
+	list_objects_filter_init(&revs->filter);
 }
 
 static void add_pending_commit_list(struct rev_info *revs,

transport-helper.c

@@ -1286,6 +1286,8 @@ int transport_helper_init(struct transport *transport, const char *name)
 	if (getenv("GIT_TRANSPORT_HELPER_DEBUG"))
 		debug = 1;
 
+	list_objects_filter_init(&data->transport_options.filter_options);
+
 	transport->data = data;
 	transport->vtable = &vtable;
 	transport->smart_options = &(data->transport_options);

transport.c

@@ -1113,6 +1113,7 @@ struct transport *transport_get(struct remote *remote, const char *url)
 		 * will be checked individually in git_connect.
 		 */
 		struct git_transport_data *data = xcalloc(1, sizeof(*data));
+		list_objects_filter_init(&data->options.filter_options);
 		ret->data = data;
 		ret->vtable = &builtin_smart_vtable;
 		ret->smart_options = &(data->options);

upload-pack.c

@@ -141,6 +141,7 @@ static void upload_pack_data_init(struct upload_pack_data *data)
 	data->allow_filter_fallback = 1;
 	data->tree_filter_max_depth = ULONG_MAX;
 	packet_writer_init(&data->writer, 1);
+	list_objects_filter_init(&data->filter_options);
 
 	data->keepalive = 5;
 	data->advertise_sid = 0;