Questions about __thread for NSS modules

[Roland McGrath]

> My question is: is this possible at all in NSS modules like libnss_nis.so?

Sure.  

> Do I need to link against libpthread? 

No.

> My first try ends in a unresolved "__tls_get_addr" symbol when I try to
> link the module.

I'll assume that's actually ___tls_get_addr if you're on x86.
This suggests your dynamic linker is not built with TLS support.
It defines that symbol.