<unistd.h>:

lssek:   Probably should be __wur but lseek(fd,SEEK_SET,0) will succeed if
         the descriptor is fine.
lseek64: same

setuid:  will always succeed given correct privileges, so there might
         be places which don't check for it.
setreuid: same
seteuid: same
setgid:  same
setregid: same
setegid: same
setresuid: same
setresgid: same


<stdio.h>:

setvbuf:   if stream and buffer are fine and other parameters constant,
           it cannot really fail.
fseek:     see lseek
fseeko:    likewise
fgetpos:   similarly
fsetpos:   likewise


<stdlib.h>:

atexit:    it is guaranteed that a certain number of handlers can be
           registered, so some calls might need not be checked
on_exit:   same
random functions:  one might want to discard a number of results.  In any
           case, no security problem


putenv:    probably SHOULD be marked, but we'll wait a bit.
setenv:    likewise
unsetenv:  likewise
clearenv:  likewise

mbstowcs:  probably SHOULD be marked
wcstombs:  likewise

ptsname_r: probably SHOULD be marked