bug#61960: 30.0.50; Unexec build reliably crashes during loadup

[Konstantin Kharlamov <hi-angel@yandex.ru>]

On Sat, 2023-03-04 at 21:45 +0000, Andrea Corallo wrote:
> Konstantin Kharlamov <hi-angel@yandex.ru> writes:
> 
> > Oh, I am sorry, I posted the configuration line from the wrong emacs build.
> > It's
> > supposed to be:
> > 
> > --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib --localstatedir=/var -
> > -
> > mandir=/usr/share/man --with-gameuser=:games --with-modules --without-libotf
> > --
> > without-m17n-flt --without-gconf --with-native-compilation=yes --with-
> > xinput2 --
> > with-x-toolkit=gtk3 --without-xaw3d --with-sound=no --with-tree-sitter --
> > with-
> > unexec --without-gpm --without-compress-install 'CFLAGS=-O0 -g3'
> 
> Hi Konstantin,
> 
> maybe the crash you see is not related but native-compilation is not
> supposed to work with unexec builds.
> 
> I think we should really add a configure time error for this.  Eli could
> this change go to emacs-29?

emacs-29 haven't got the BLOCK_ALIGN change, so is unaffected.

I should note though that I'm not the reporter :)

---------------

Regarding my current findings: apparently the `unexec` has always been broken. I built it with sanitizer and found out that the variable `bss_size_growth` when doing the dump has too big size. The only difference between "before" and "after" the BLOCK_ALIGN change is that the difference "after" became quite large. It was just 440 bytes before, and became 31494584 bytes after.

However, when built with sanitizer, sanitizer catches the problem in both cases, so there's that.