Greetings!
Matt Kaufmann <[EMAIL PROTECTED]> writes:
> Thank you, Camm. Regarding #2 ("If you want to try this out in 2.6.7,
> I can send it to you."), I'd be interested in trying it out if it's
> just a bit of Lisp code that I can compile into ACL2, and include with
> later ACL2 distributions so that users don't lose their ACL2 sessions
> with C stack overflows.
>
Alas, this one requires a patch in C, albeit small. I'll endeavor to
get this into the 2.6.8pre tree.
Take care,
> Thanks --
> -- Matt
> Sender: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED], [EMAIL PROTECTED], gcl-devel@gnu.org
> From: Camm Maguire <[EMAIL PROTECTED]>
> Date: 03 May 2007 16:06:17 -0400
> X-SpamAssassin-Status: No, hits=1.3 required=5.0
> X-UTCS-Spam-Status: No, hits=-150 required=200
>
> Greetings!
>
> This stems from an overflow of the C stack, which is used in place of
> the lisp value stack when declamations are in force.
>
> 1) 2.7.0 has an enormous default C stack, so the process as written
> completes. Larger numbers run forever and start swapping. It
> has always been a question in my mind whether GCL should assume
> such things are mistakes and quit earlier, or proceed untill
> absolute exhaustion. The latter, which is the current
> behavior, is best all things considered, IMHO.
> 2) There is a simple backport from 2.7.0 which catches a continuable
> SEGFAULT error using the C routine sigaltstack. If you want to
> try this out in 2.6.7, I can send it to you. Unfortunately,
> there is as yet no easy way to distinguish between a segfault
> on the C stack and one on the heap for use in the error
> message, though I have some ideas. Please let me know if you
> consider this relevant.
> 3) If the C stack overrun happens within a GC mark, all hope is lost,
> and the current 2.7.0 behavior aborts. If you see a way to
> continue in this case I'd be most interested.
>
> Take care,
>
> Matt Kaufmann <[EMAIL PROTECTED]> writes:
>
> > Hi, Camm --
> >
> > Consider the following (integer quotient) function, which quite
> > legitimately causes the stack overflow shown:
> >
> > >(defun foo (i j)
> > (if (< i j)
> > 0
> > (+ 1 (foo (- i j) j))))
> >
> > FOO
> >
> > >(compile 'foo)
> >
> > Compiling gazonk0.lsp.
> > End of Pass 1.
> > End of Pass 2.
> > OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3
> > Finished compiling gazonk0.lsp.
> > Loading gazonk0.o
> > start address -T 0x84196e0 Finished loading gazonk0.o
> > #<compiled-function FOO>
> > NIL
> > NIL
> >
> > >(foo 1000000 1)
> >
> > Error: Value stack overflow.
> > Fast links are on: do (si::use-fast-links nil) for debugging
> > Error signalled by EVAL.
> > Broken at FOO. Type :H for Help.
> > >>
> >
> > Unfortunately, if we proclaim the function before compiling, we get a
> > seg fault instead; I wonder if you can suggest an easy patch that
> > would avoid this. Here is a log (from a new GCL session). Both
> > examples (above and below) are GCL 2.6.7 running on 32-bit linux.
> >
> > >(DECLAIM (FTYPE (FUNCTION (T T) (VALUES T)) FOO))
> >
> > NIL
> >
> > >(defun foo (i j)
> > (if (< i j)
> > 0
> > (+ 1 (foo (- i j) j))))
> >
> > FOO
> >
> > >(foo 10 1)
> >
> > 10
> >
> > >(compile 'foo)
> >
> > Compiling gazonk0.lsp.
> > End of Pass 1.
> > End of Pass 2.
> > OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3
> > Finished compiling gazonk0.lsp.
> > Loading gazonk0.o
> > start address -T 0x84196e0 Finished loading gazonk0.o
> > #<compiled-function FOO>
> > NIL
> > NIL
> >
> > >(foo 1000000 1)
> > Segmentation fault
> >
> > Thanks --
> > -- Matt
> >
> >
> >
>
> --
> Camm Maguire [EMAIL
> PROTECTED]
> ==========================================================================
> "The earth is but one country, and mankind its citizens." -- Baha'u'llah
>
>
>
--
Camm Maguire [EMAIL PROTECTED]
==========================================================================
"The earth is but one country, and mankind its citizens." -- Baha'u'llah
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