busctl: add and use strcmp_ptr()

In member_compare_func(), it compares interface, type and name of
members.  But as it can contain NULL pointer, it needs to check them
before calling strcmp().  So make it as a separate strcmp_ptr
function (named after streq_ptr) so that it can be used by others.

Also let streq_ptr() to use it in order to make the code simpler.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/test/test-util.c b/src/test/test-util.c
index f43433baa1..7a1a4b6df2 100644
--- a/src/test/test-util.c
+++ b/src/test/test-util.c
@@ -2083,6 +2083,18 @@ static void test_tempfn(void) {
         free(ret);
 }
 
+static void test_strcmp_ptr(void) {
+        assert_se(strcmp_ptr(NULL, NULL) == 0);
+        assert_se(strcmp_ptr("", NULL) > 0);
+        assert_se(strcmp_ptr("foo", NULL) > 0);
+        assert_se(strcmp_ptr(NULL, "") < 0);
+        assert_se(strcmp_ptr(NULL, "bar") < 0);
+        assert_se(strcmp_ptr("foo", "bar") > 0);
+        assert_se(strcmp_ptr("bar", "baz") < 0);
+        assert_se(strcmp_ptr("foo", "foo") == 0);
+        assert_se(strcmp_ptr("", "") == 0);
+}
+
 int main(int argc, char *argv[]) {
         log_parse_environment();
         log_open();
@@ -2169,6 +2181,7 @@ int main(int argc, char *argv[]) {
         test_shell_maybe_quote();
         test_parse_mode();
         test_tempfn();
+        test_strcmp_ptr();
 
         return 0;
 }