What is _sobuf and wher is it defined?

[Guy Harris]

>I am trying to port rcs, version 3, to a Sun SPARCserver.

Get Version 4 instead.  There are some bugs in the R3 version that
prevent it from running on machines that disallow dereferencing of NULL
pointers, such as Suns of all flavors, and other bugs that prevent it
from running on machines that don't pass arguments the "conventional"
way, such as SPARC-based machines.  They are fixed in R4.

As for "_sobuf", it's an unfortunately-too-widely-known internal
variable of *some*, but not *all*, standard I/O implementations.  It's
not documented because it's an internal variable; it's used because UNIX
programmers are often undisciplined and have read the source and "know"
what's in the implementation.