Re: MPS codegen

[Eli Zaretskii <eliz@gnu.org>]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: Helmut Eller <eller.helmut@gmail.com>,  acorallo@gnu.org,
>   emacs-devel@gnu.org
> Date: Sat, 15 Jun 2024 09:25:00 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >        In glibc, this function is implemented using madvise(2).
> >        However, since glibc 2.6, POSIX_MADV_DONTNEED is treated as a no-
> >        op, because the corresponding madvise(2) value, MADV_DONTNEED,
> >        has destructive semantics.
> >
> > So to do on Posix systems the same as we do on Windows, I think we
> > need to call madvise with MADV_DONTNEED, even if posix_madvise is
> > available, and also call mmap with PROT_NONE.  Do you agree?  If we do
> > that, does the GNU/Linux build still work, or does it also crash on
> > startup?
> 
> I still think we should first establish that that is indeed the problem.
> Please see my other mail.

Since you insist: I ifdef'ed away this:

  #if 0
	/* Release the commit charge for the mapping.  */
	DWORD old_prot;
	(void) VirtualProtect (mem, size, PAGE_NOACCESS, &old_prot);
  #endif

and, lo and behold, Emacs can now start without a problem.

I hope this establishes the fact that we are still accessing memory
from the "discarded" pdumper block.

Now what?