Yes, this is a PPC.

I did as you suggested, and built the non-gencgc version, and the bug went away.

So it looks like there is a bug lurking in PPC gencgc

Thanks.  I guess I'll have to stick with the old stop n'copy collector.

Should I edit the internals page and put a warning up?

http://sbcl-internals.cliki.net/Garbage%20Collection

Many thanks
Jan

On Tue, Apr 29, 2008 at 12:00 PM, Nikodemus Siivola <nikodemus@random-state.net> wrote:
On Wed, Apr 30, 2008 at 12:33 AM, J. T.K. <jetmonk@gmail.com> wrote:
> Hello,
>
> I ran into persistent crashes on Mac OS X that threw me into LDB.
> A stripped down program is attached, with documentation. My guess is
> some kind of GC glitch.
>
> Basically, a loop with structure-copying and a bit of math causes a fatal
>  LDB error. The numerical types of some arguments have to be of a particular
> type (as documented), and structs have to be copied in a loop, probably to
> generate garbage.

This is PPC, right? At least I cannot reproduce this on an Intel mac.
If so, can you try with SBCL built with

(lambda (x)
 (remove :gencgc x))

in customize-target-features.lisp -- since I suspect this is a problem
with the PPC gencgc port.

Cheers,

 -- Nikodemus