bug#716: Bug in buffer-swap-text

[Jason Rumney]

Stefan Monnier wrote:
> > I can reliably get a crash without changing coding systems:
> > (progn
> >   (buffer-swap-text (generate-new-buffer "test"))
> >   (insert (make-string 128 ?a)))
> >     
> > (progn
> >   (buffer-swap-text (generate-new-buffer "test"))
> >   (garbage-collect))
> >     
>
> I cannot seem to reproduce it here, tho I'm not 100% sure how you run
> the above code.  Could you give a more detailed recipe, starting from
> "emacs -Q" and showing whether you use M-: or C-x C-e, ... ?
>   

One possible variable here is the way that buffer space is allocated. On 
Windows, it seems REL_ALLOC is defined. I presume GNU/Linux defines 
USE_MMAP_FOR_BUFFERS which would cause it to take a different code path 
around the point where we see a crash on Windows, and as Magnus Henoch 
saw on NetBSD/powerpc also (though we don't have a stack trace for that 
crash, so can't tell for sure it is crashing in the same place).

Magnus, does src/config.h have either of these constants defined on your 
NetBSD/powerpc machine? A third possibility if neither of those are 
defined is that xmalloc/xfree/xrealloc are used.