The R_getgroups service checks the high-order bit of the input group count. See Group_count under Parameters for more information.

The GIDs are not explicitly added to or deleted from the supplemental group list. A GID is in this list if the user was a member of the group when the user's ACEE was created through a RACROUTE REQUEST=VERIFY request and if the GID was assigned to the group before the initUSP service was performed for the process.