Fixing slapo-nops (ITS#8759)

[manu@netbsd.org (Emmanuel Dreyfus)]

Hello

Following ITS#8759, I am looking for ideas about how to fix slapo-nops.

This overlays suppress nilpotent operations that replace an attribute
values by the same values.  The code is in
contrib/slapd-modules/nops/nops.c

The problem is that slapo-nops assumes it can free the nilpotent struct
Modifications after removing them from the list, but for instande
slapo-memberof uses struct Modifications allocated on the stack.

Not freeing in slapo-nops is not a fix, since unlinked struct
Modifications will not be freed anywhere else, and we will get a memory
leak. 

Would it make sense to add a SLAP_MOD_ONSTACK flag in struct
Modification's sm_flags so that we can tell the difference? Any other
idea?

-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu@netbsd.org