nss/nsswitch.c should dlopen() the NSS modules with RTLD_DEEPBIND so that the
application symbols will not interfere with symbols the NSS module is using.

A practical example (pointed out by Michael Meeks) is nss_ldap + Thunderbird
failing, since both use incompatible LDAP libraries with some symbols clashing;
nss_ldap will use the Thunderbird LDAP library symbols in preference to these of
its own library, resulting in a crash. Deepbinding should solve this problem,
and I can think of no bad side-effects (in sane situations).

------- Additional Comment #1 From Mike Frysinger 2008-12-29 20:44 -------

i tried merging this into the Gentoo glibc package, but things went badly for
mozilla users.  feel like having a look ?

http://bugs.gentoo.org/252302

------- Additional Comment #2 From Petr Baudis 2010-06-11 14:01 -------

By now, plenty of bad side-effects popped up mainly due to the fact that custom
malloc() overrides do not work - the NSS module will ignore them, but will try
to free() pointers allocated by glibc using the overriden malloc(). It's
probably best to require NSS modules not to pollute namespace.