core: rework cgroup path parse logic

Various cleanups, be stricter when parsing unit paths.

Most importantly: return the root slice "-.slice" when asked for slice
of paths that contain no slice component.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/shared/login-shared.c b/src/shared/login-shared.c
index 054c77503b..64650a9134 100644
--- a/src/shared/login-shared.c
+++ b/src/shared/login-shared.c
@@ -23,7 +23,9 @@
 #include "def.h"
 
 bool session_id_valid(const char *id) {
-        assert(id);
 
-        return id[0] && id[strspn(id, LETTERS DIGITS)] == '\0';
+        if (isempty(id))
+                return false;
+
+        return id[strspn(id, LETTERS DIGITS)] == '\0';
 }