bug#22308: intermittent problem generating autoloads

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Date: Mon, 04 Jan 2016 20:35:03 -0500
> 
> There is some kind of heisenbug that shows up with autoload generation
> from time-to-time. It occurs in non-parallel builds (so a parallel make
> problem is not the cause).
> 
> See some examples:
> 
> http://lists.gnu.org/archive/html/emacs-devel/2015-11/msg01610.html
>   GEN      loaddefs.el
>     End of file during parsing 
> 
> http://hydra.nixos.org/build/29135353/log/raw
>   GEN      calendar/diary-loaddefs.el
>   Loading macroexp.elc...
>   cal-julian.el:0:0: error: end-of-file: nil
>   make[3]: *** [calendar/diary-loaddefs.el] Error 255

When that happens, do you see binary null bytes in the autoloads file?

> (The above error persisted for two builds, then went away for no
> apparent reason.)

This stopped happening for me since the undo issues were fixed on the
emacs-25 branch.  I thought that was what fixed these.

I cannot debug this unless it happens again.