process-util: make pidref_safe_fork_full() work with FORK_WAIT

(This is useful for the test case added in the next commit, where it's
kinda nice being able to use pidref_safe_fork_full() and acquiring a
pidref of the child in the child in one go. There's no other value in
this than a bit of synctactic sugar for that test. But otoh thre's no
good reason to prohibit FORK_WAIT use like this, hence either way, this
commit should be a good thing.)

diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index f48285d3d52a36ab5a72ac3ce0579c61936a56fb..1264bae3e61e111c8ad24419e2e7f0c075403491 100644 (file)
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -1783,12 +1783,16 @@ int pidref_safe_fork_full(
         pid_t pid;
         int r, q;
 
-        assert(!FLAGS_SET(flags, FORK_WAIT));
-
         r = safe_fork_full(name, stdio_fds, except_fds, n_except_fds, flags, &pid);
-        if (r < 0)
+        if (r < 0 || !ret_pid)
                 return r;
 
+        if (r > 0 && FLAGS_SET(flags, FORK_WAIT)) {
+                /* If we are in the parent and successfully waited, then the process doesn't exist anymore */
+                *ret_pid = PIDREF_NULL;
+                return r;
+        }
+
         q = pidref_set_pid(ret_pid, pid);
         if (q < 0) /* Let's not fail for this, no matter what, the process exists after all, and that's key */
                 *ret_pid = PIDREF_MAKE_FROM_PID(pid);