daemon: free listen_addr before returning

We build up a string list of listen addresses from the command-line
arguments, but never free it. This causes t5811 to complain of a leak
(though curiously it seems to do so only when compiled with gcc, not
with clang).

To handle this correctly, we have to do a little refactoring:

  - there are two exit points from the main function, depending on
    whether we are entering the main loop or serving a single client
    (since rather than a traditional fork model, we re-exec ourselves
    with the extra "--serve" argument to accommodate Windows).

    We don't need --listen at all in the --serve case, of course, but it
    is passed along by the parent daemon, which simply copies all of the
    command-line options it got.

  - we just "return serve()" to run the main loop, giving us no chance
    to do any cleanup

So let's use a "ret" variable to store the return code, and give
ourselves a single exit point at the end. That gives us one place to do
cleanup.

Note that this code also uses the "use a no-dup string-list, but
allocate strings we add to it" trick, meaning string_list_clear() will
not realize it should free them. We can fix this by switching to a "dup"
string-list, but using the "append_nodup" function to add to it (this is
preferable to tweaking the strdup_strings flag before clearing, as it
puts all the subtle memory-ownership code together).

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

daemon.c

@@ -1243,19 +1243,20 @@ static int serve(struct string_list *listen_addr, int listen_port,
 int cmd_main(int argc, const char **argv)
 {
 	int listen_port = 0;
-	struct string_list listen_addr = STRING_LIST_INIT_NODUP;
+	struct string_list listen_addr = STRING_LIST_INIT_DUP;
 	int serve_mode = 0, inetd_mode = 0;
 	const char *pid_file = NULL, *user_name = NULL, *group_name = NULL;
 	int detach = 0;
 	struct credentials *cred = NULL;
 	int i;
+	int ret;
 
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 		const char *v;
 
 		if (skip_prefix(arg, "--listen=", &v)) {
-			string_list_append(&listen_addr, xstrdup_tolower(v));
+			string_list_append_nodup(&listen_addr, xstrdup_tolower(v));
 			continue;
 		}
 		if (skip_prefix(arg, "--port=", &v)) {
@@ -1437,9 +1438,9 @@ int cmd_main(int argc, const char **argv)
 			die_errno("failed to redirect stderr to /dev/null");
 	}
 
-	if (inetd_mode || serve_mode)
-		return execute();
-
+	if (inetd_mode || serve_mode) {
+		ret = execute();
+	} else {
 		if (detach) {
 			if (daemonize())
 				die("--detach not supported on this platform");
@@ -1454,5 +1455,9 @@ int cmd_main(int argc, const char **argv)
 		for (i = 1; i < argc; ++i)
 			strvec_push(&cld_argv, argv[i]);
 
-	return serve(&listen_addr, listen_port, cred);
+		ret = serve(&listen_addr, listen_port, cred);
+	}
+
+	string_list_clear(&listen_addr, 0);
+	return ret;
 }

t/t5811-proto-disable-git.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='test disabling of git-over-tcp in clone/fetch'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 . "$TEST_DIRECTORY/lib-proto-disable.sh"
 . "$TEST_DIRECTORY/lib-git-daemon.sh"