AIX v3.1: alloca and .<symbol>

[Jon Crowcroft]

we're getting a number undefined symbols linking various programs

e.g.
1. .rusers (librpcsvc.a)
2. .alloca  (libc.a)
3. .flock (libbsd.a?)

can someone please:
a) explain the . instead of _  prefix
b) explain the manual page for alloca reference to mystirous cc/xlc
option to get the alloca symbol recogized * linked properly?
c) the missing-ness of rusers

jon