[PATCH 03/24] format-patch: don't leak "extra_headers" or "ref_message_ids"

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Fix two memory leaks in "struct rev_info" by freeing that memory in
cmd_format_patch(). These two are unusual special-cases in being in
the "struct rev_info", but not being "owned" by the code in
revision.c. I.e. they're members of the struct so that this code in
"builtin/log.c" can pass information code in log-tree.c.

See 20ff06805c6 (format-patch: resurrect extra headers from config,
2006-06-02) and d1566f7883f (git-format-patch: Make the second and
subsequent mails replies to the first, 2006-07-14) for the initial
introduction of "extra_headers" and "ref_message_ids".

We can count on repo_init_revisions() memset()-ing this data to 0
however, so we can count on it being either NULL or something we
allocated. In the case of "extra_headers" let's add a local "char *"
variable to hold it, to avoid the eventual cast from "const char *"
when we free() it.

While we're at it let's also move to using string_list_init_nodup()
instead of relying on calloc() implicitly coming up with the same
result. See 770fedaf9fb (string-list.[ch]: add a
string_list_init_{nodup,dup}(), 2021-07-01) for the introduction of
the string_list_init_nodup() helper. The string_list_clear() here is
redundant due to the *_nodup() initialization, but let's add it anyway
for consistency with other API use.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/log.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/builtin/log.c b/builtin/log.c
index c211d66d1d0..00846c2c8ac 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1746,6 +1746,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	struct commit *commit;
 	struct commit **list = NULL;
 	struct rev_info rev;
+	char *extra_headers = NULL;
 	struct setup_revision_opt s_r_opt;
 	int nr = 0, total, i;
 	int use_stdout = 0;
@@ -1946,7 +1947,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		strbuf_addch(&buf, '\n');
 	}
 
-	rev.extra_headers = strbuf_detach(&buf, NULL);
+	extra_headers = strbuf_detach(&buf, NULL);
+	rev.extra_headers = extra_headers;
 
 	if (from) {
 		if (split_ident_line(&rev.from_ident, from, strlen(from)))
@@ -2173,8 +2175,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		prepare_bases(&bases, base, list, nr);
 	}
 
-	if (in_reply_to || thread || cover_letter)
-		rev.ref_message_ids = xcalloc(1, sizeof(struct string_list));
+	if (in_reply_to || thread || cover_letter) {
+		rev.ref_message_ids = xmalloc(sizeof(*rev.ref_message_ids));
+		string_list_init_nodup(rev.ref_message_ids);
+	}
 	if (in_reply_to) {
 		const char *msgid = clean_message_id(in_reply_to);
 		string_list_append(rev.ref_message_ids, msgid);
@@ -2281,6 +2285,11 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	strbuf_release(&rdiff1);
 	strbuf_release(&rdiff2);
 	strbuf_release(&rdiff_title);
+	free(extra_headers);
+	if (rev.ref_message_ids) {
+		string_list_clear(rev.ref_message_ids, 0);
+		free(rev.ref_message_ids);
+	}
 	UNLEAK(rev);
 	return 0;
 }
-- 
2.35.1.1295.g6b025d3e231