Re: xassert in dispextern.h

[David Kastrup <dak@gnu.org>]

Miles Bader <snogglethorpe@gmail.com> writes:

> The argument for disabling xassert assumes that the majority of them
> are superfluous; clearly if this _isn't_ the case then disabling
> xassert is a bad idea.

The majority of them clearly _are_ "superfluous" since they assert
assumptions occuring in the context of earlier, fixed bugs.  They are
basically superfluous until a change gets made that triggers one of
them.  They are, so to say, the poor man's regression test, and one
does not need to run those tests continuously.

> In order to demonstrate that the majority are superfluous, one has
> to actually be able to make exactly the same sort of judgement for
> each xassert -- so I'm saying, if you can make that judgement, then
> why not use it on a case-by-case basis to get the best of both
> worlds?

Because there are lots of cases.  grep in the source directory of
Emacs turns up 1430 of them.  You want to make that judgment on a
case-by-case basis?  When were we planning the release?  2007?

> If, on the other hand, it's the case that nobody can make that
> judgement for most xasserts, then nobody is in a position to say
> xassert can safely be disabled either.

That's why we are not deleting the xasserts, but turning them off by
default, and, among developers, from time to time turning them on in
order to check whether everything looks as good as last time around.

We are not talking about removing the xasserts: that would be foolish.
We are talking about not inflicting them by default on a larger
audience on which their purpose will be completely lost.  I'll second
any appeal for people _on_ _this_ _list_ to turn the asserts on, even
to run Emacs with GLYPH_DEBUG set once in a while.

But HEAD is a really bad place for such a setting, given that others
than ourselves are responsible for make-shift pseudoreleases.  I don't
want to sabotage others doing our work for us, not if it can be
avoided.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum