[PATCH 4/7] hurd: Make _exit work during early boot-up

[Sergey Bugaev <bugaevc@gmail.com>]

If any of the early boot-up tasks calls exit () or returns from main (),
terminate it properly instead of crashing on trying to dereference
_hurd_ports and getting forcibly terminated by the kernel.

We sadly cannot make the __USEPORT macro do the check for _hurd_ports
being unset, because it evaluates to the value of the expression
provided as the second argument, and that can be of any type; so there
is no single suitable fallback value for the macro to evaluate to in
case _hurd_ports is unset. Instead, each use site that wants to care for
this case will have to do its own checking.

Checked on x86_64-gnu.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---
 sysdeps/mach/hurd/_exit.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sysdeps/mach/hurd/_exit.c b/sysdeps/mach/hurd/_exit.c
index 73957744..80cfe532 100644
--- a/sysdeps/mach/hurd/_exit.c
+++ b/sysdeps/mach/hurd/_exit.c
@@ -24,8 +24,9 @@
 void
 _hurd_exit (int status)
 {
-  /* Give the proc server our exit status.  */
-  __USEPORT (PROC, __proc_mark_exit (port, status, 0));
+  if (_hurd_ports != NULL)
+    /* Give the proc server our exit status.  */
+    __USEPORT (PROC, __proc_mark_exit (port, status, 0));
 
   /* Commit suicide.  */
   __task_terminate (__mach_task_self ());
-- 
2.40.1