Sigstack and BSD 4.2

[William L. Sebok]

> Allowing for the elegance of the new signaling mechanism, what on
> earth  can  you do with the alternate signal stack? I have looked
> at the documentation, examined  the  listings  and  while  I  can
> understand how they are implemented, I, as yet, haven't been able
> to understand why I need them.

> Ron McDaniels

There is one thing for which I plan to use the signal stack mechanism.  One
of the conditions one might want to handle within a program is stack overflow.
Ordinarily this condition causes a Segmentation violation.  However, with a
stack invalid because of overflow it is impossible to catch the segmention
violation signal.
  I am including such a signal stack in the BSD 4.2 incarnation of my Forth
compiler for the Vax.  This compiler wants to catch all (or almost all) signals,
returning the appropriate error message, clearing stacks and going back to
the main command interpreter.  It thus acts as a self-contained programming
environment.
-- 
Bill Sebok			Princeton University, Astrophysics
{allegra,akgua,burl,cbosgd,decvax,ihnp4,kpno,princeton,vax135}!astrovax!wls