Hi,

Ludovic Courtès <ludo@gnu.org> skribis:

> What if ‘scm_i_vm_mark_stack’ walks the stack right before the ‘vp->fp’
> assignment?  It can determine that one of the just-assigned ‘sp[nargs]’
> is a dead slot, and thus set it to SCM_UNSPECIFIED.  Later, when we set
> ‘vp->fp’, that stack slot that we just initialized has been overwritten
> by ‘scm_i_vm_mark_stack’.  Down the road, we get something like:
>
>   Wrong type to apply: #<unspecified>

I believe the patch below solves this problem.  Also attached is a small
program that reproduces the bug (without the patch) after a couple of
minutes.

Thoughts?

The full grafting test case exposes another VM stack-corruption-looking
crash that I’m still investigating.

Ludo’.