https://lists.gnu.org/archive/html/bug-bash/2017-12/msg00025.html
https://bugs.gentoo.org/644720

--- bash-4.4/jobs.c
+++ bash-4.4/jobs.c
@@ -750,7 +750,7 @@
   else
     nsize = bgpids.nalloc;
 
-  while (nsize < js.c_childmax)
+  while (nsize < (ps_index_t)js.c_childmax)
     nsize *= 2;
 
   if (bgpids.nalloc < js.c_childmax)
