Cygwin: fork: reserve dynloaded dll areas earlier

In dll_crt0_0, both threadinterface->Init and sigproc_init allocate
windows object handles using unpredictable memory regions, which may
collide with dynamically loaded dlls when they were relocated.

winsup/cygwin/dcrt0.cc

@@ -632,6 +632,12 @@ child_info_fork::handle_fork ()
 
   if (fixup_mmaps_after_fork (parent))
     api_fatal ("recreate_mmaps_after_fork_failed");
+
+  /* We need to occupy the address space for dynamically loaded dlls
+     before we allocate any dynamic object, or we may end up with
+     error "address space needed by <dll> is already occupied"
+     for no good reason (seen with some relocated dll). */
+  dlls.reserve_space ();
 }
 
 bool

winsup/cygwin/fork.cc

@@ -136,12 +136,6 @@ frok::child (volatile char * volatile here)
 {
   HANDLE& hParent = ch.parent;
 
-  /* NOTE: Logically this belongs in dll_list::load_after_fork, but by
-     doing it here, before the first sync_with_parent, we can exploit
-     the existing retry mechanism in hopes of getting a more favorable
-     address space layout next time. */
-  dlls.reserve_space ();
-
   sync_with_parent ("after longjmp", true);
   debug_printf ("child is running.  pid %d, ppid %d, stack here %p",
 		myself->pid, myself->ppid, __builtin_frame_address (0));