From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 31 May 2017 15:12:32 +0000 (+0900)
Subject: sd-login: sd_get_machine_names(): do not return -EINVAL when output parameter is... 
X-Git-Tag: chiark/234.4-1+devuan1.1+iwj1~115
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=e9eacf18de0e1fe360469958095d9e22bc7b36b2

sd-login: sd_get_machine_names(): do not return -EINVAL when output parameter is NULL

Other functions in sd-login generally allow the output parameter to be NULL, in
which case only the number of items that would be stored in the array is returned.
Be nice and do the same here.
---

diff --git a/src/libelogind/sd-login/sd-login.c b/src/libelogind/sd-login/sd-login.c
index 7630e6265..5f90ba70c 100644
--- a/src/libelogind/sd-login/sd-login.c
+++ b/src/libelogind/sd-login/sd-login.c
@@ -942,14 +942,13 @@ _public_ int sd_get_uids(uid_t **users) {
 }
 
 _public_ int sd_get_machine_names(char ***machines) {
-        char **l = NULL, **a, **b;
+        char **l, **a, **b;
         int r;
 
-        assert_return(machines, -EINVAL);
-
         r = get_files_in_directory("/run/systemd/machines/", &l);
         if (r == -ENOENT) {
-                *machines = NULL;
+                if (machines)
+                        *machines = NULL;
                 return 0;
         }
         if (r < 0)
@@ -959,7 +958,7 @@ _public_ int sd_get_machine_names(char ***machines) {
                 r = 0;
 
                 /* Filter out the unit: symlinks */
-                for (a = l, b = l; *a; a++) {
+                for (a = b = l; *a; a++) {
                         if (startswith(*a, "unit:") || !machine_name_is_valid(*a))
                                 free(*a);
                         else {
@@ -972,7 +971,8 @@ _public_ int sd_get_machine_names(char ***machines) {
                 *b = NULL;
         }
 
-        *machines = l;
+        if (machines)
+                *machines = l;
         return r;
 }
 
diff --git a/src/libelogind/sd-login/test-login.c b/src/libelogind/sd-login/test-login.c
index 3dc797530..3eb11cf4a 100644
--- a/src/libelogind/sd-login/test-login.c
+++ b/src/libelogind/sd-login/test-login.c
@@ -251,8 +251,9 @@ static void test_login(void) {
                 assert_se(r >= 0);
                 assert_se(r == (int) strv_length(machines));
                 assert_se(buf = strv_join(machines, " "));
-
                 log_info("sd_get_machines(…) → [%i] \"%s\"", r, buf);
+
+                assert_se(sd_get_machine_names(NULL) == r);
         }
 }