On Fri, Dec 9, 2011 at 3:39 PM, James Wright <james@chumsley.org> wrote:

Hi,

When I dump an SBCL core from an image that has antik loaded, I get a
memory corruption error when loading the core:
*** glibc detected *** sbcl: free(): invalid pointer: 0x0808d588 ***
This happens even with a minimal project that does nothing but load
antik; I've attached a script to reproduce the problem.

I did some investigation, and it looks like the problem is the
`*formatting-test-grid*' variable in `format-grid.lisp'. It contains
a list of grids, including some foreign arrays. Presumably the
foreign pointers in these arrays will be pointing to random/unowned
memory when the core is loaded. I've run into similar problems before
in my own code (attempting to dump a global `*rng*' variable that
contained a GSLL random number generator).

I've attached a patch that replaces the problem `defparameter' form
with a function instead. I can't find any references to this variable
in the source tree, so I assume it's just there for manual testing.

Thanks,
James

Thanks James. Indeed, *formatting-test-grid* is just a throwaway to test the formatting of grids. While a patch is OK, I would rather just not load it. However, I've long been uneasy with saved images and foreign memory; I have no confidence that what's saved will come back. Indeed, if you are seeing rng variable problems, then there is a deeper problem that can't be fixed with turning a defparameter into a function. I would like to get ideas from SBCL experts. I think the solution is likely to be implementation dependent, but that's the place to start. Can you generate a small example of your rng problem?

Liam