[PATCH] Eliminate third argument from _JMPBUF_UNWINDS

[Roland McGrath]

> Roland McGrath <roland@hack.frob.com> writes:
> 
> > This all but ensures that when a machine adds PTR_MANGLE/PTR_DEMANGLE
> > support, or changes how it does the mangling, that the corresponding
> > update in jmpbuf-unwind.h will be forgotten.
> 
> That will not happen.

Your assertion alone does not reassure me.  
What guarantees this will not happen?

> > How is this better?
> 
> It removes a layer violation and consolidates the jmpbuf handling into
> the architecture header.  The caller must not have knowlege of the
> jmpbuf internals.

In the current scheme the caller does not have knowledge of jmp_buf
internals.  It is required to supply a function that performs PTR_DEMANGLE.
That's all it knows.  _JMPBUF_UNWINDS has the knowledge of how that
function is useful in interpreting a jmp_buf.