Re: Strange problems with data-tests.el

[Eli Zaretskii]

> From: Paul Eggert <address@hidden>
> Cc: address@hidden
> Date: Sun, 12 Aug 2018 15:43:14 -0700
> 
> I suspect that it's only bad luck that exposed the problem, that is, that the 
> recent bignum or misc changes triggered the bug only because they caused GCC 
> to 
> optimize in a different way.

No, it didn't happen because of the bignum merge.  I found a 26.0.90
pretest that was built with -Og, and sure enough, the problem is there
as well.  And when I installed your patch in that version and
recompiled, the problem went away.

So I think this is a relatively old bug, and we should backport it to
the emacs-26 branch.  WDYT?

> In theory if we're unlucky the bug could recur, since GCC doesn't
> make promises in this area. However, I changed arithcompare in such
> a way that GCC would have to be pretty perverse to cause the problem
> to resurface, and similarly for other C compilers.

Thanks.