// sysctl kernel.pid_max
int maxpid = 32768;
Lets look at what my Linux system that has unhide says.
# sysctl kernel.pid_max
kernel.pid_max = 131072
More code in unhide:
unsigned int proc_parent_pids[65536] ;
char *proc_tasks[65536];
char *ps_pids[65536];
char *messages_pids[65536];
char message[1000] ;
char description[1000] ;
int ps_count = 0 ;
This looks like it's assuming 16bit PIDs.. I won't investigate further, but it's likely to be a problem that will allow for a rootkit to bypass unhide.