bug#9273: 23.3; malloc initialization should (sometimes) happen at runtime

[Ken Brown]

On 8/12/2011 7:33 AM, Eli Zaretskii wrote:
> > Date: Fri, 12 Aug 2011 06:10:35 -0400
> > From: Ken Brown<kbrown@cornell.edu>
> > CC: "9273@debbugs.gnu.org"<9273@debbugs.gnu.org>
> >
> > On 8/12/2011 2:54 AM, Eli Zaretskii wrote:
> > > > Date: Thu, 11 Aug 2011 17:45:41 -0400
> > > > From: Ken Brown<kbrown@cornell.edu>
> > > > CC: "9273@debbugs.gnu.org"<9273@debbugs.gnu.org>
> > > >
> > > > The problem was that realloc got called on memory that had been
> > > > allocated prior to dumping, and the malloc information that was used
> > > > then had disappeared.
> > >
> > > Can you show the code which called realloc on that memory?  I'm
> > > surprised that Emacs does that, but perhaps I'm missing something.
> >
> > Here's the code that I stumbled across (as a result of a SEGV).  I
> > haven't checked to see if there are other examples.  From terminal.c:
> >
> > /* Deletes the bootstrap terminal device.
> >      Called through delete_terminal_hook. */
> >
> > static void
> > delete_initial_terminal (struct terminal *terminal)
> > {
> >     if (terminal != initial_terminal)
> >       abort ();
> >
> >     delete_terminal (terminal);
> >     initial_terminal = NULL;
> > }
>
> delete_terminal doesn't call realloc, it just calls xfree.

Maybe I mis-remembered where the call to realloc is.  I'll reproduce it 
later and let you know.  (I don't have time at the moment.)  But I 
assure you that I did a backtrace showing that realloc was called on 
something related to terminals.

> Do the problems with the Cygwin build go away if the call to
> delete_terminal is commented out?

No.  At the very least, I have to force reinitialization of malloc. 
Otherwise the BLOCK macro yields wrong results that lead to infinite 
looping or crashing.  After reinitialization, I have to be able to 
handle calls to free() on memory allocated prior to dumping.  Probably 
it's OK to just ignore such calls.  If I can also take care of calls to 
realloc too, everything will be OK.

Ken