Re: variables in scopes

[Roland McGrath <roland at redhat dot com>]

> Note that most of this complication is associated with pointer/struct
> traversal.  dtrace's answer to this is to allow typed pointers to be
> an additional script-side data type.  Maybe we should consider this.

Can you elaborate/clarify exactly what this means and looks like?  Does
that mean systemtap language having variables whose type is "pointer to
type foobar in the kernel context"?  In using language constructs, even
function-style ones, one should consider the exception case.  That is, I
think that for safety the only sane thing is to have the probe code use
runtime macros that do the pointer fetches with fault recovery, in case a
probe tries to dereference a pointer that's gone bad or whatever.  So the
runtime magic (some optimized macros, zero overhead) might have an error
return instead of yielding the value.  The generated code, and the meaning
of the language constructs, will have to take that possibility into account
and have a plan for bailing out.