Re: Test failures in --disable-multibyte

["Daniel Shahaf" <d.s@daniel.shahaf.name>]

Peter Stephenson wrote on Wed, 01 Jan 2020 18:01 +00:00:
> On Wed, 2020-01-01 at 13:44 +0000, Daniel Shahaf wrote:
> > > It's not generally expected you'll want to disable multibyte explicitly,
> > > but it tests the case you get if you have a system which doesn't have
> > > the required multibyte support.  It's not clear if zsh gets compiled on
> > > such systems now --- they won't be very common but there might be some
> > > deliberately reduced systems for low-level use.  These only need testing
> > > in a similarly limited fashion.
> > 
> > This state of affairs doesn't sound quite right.  If those codepaths
> > need testing, the test suite should be made to pass in that
> > configuration, so that bugfixes would be able to be tested for
> > unintended side effects.  With no working test suite and no known
> > users, it sounds like --disable-multibyte is _de facto_ unsupported,
> > but we are not ready to officially pull the plug on it due to the
> > possibility of it being used on a C99-less embedded system somewhere.
> > So, how about having NEWS in 5.8 say that unless someone asks us to
> > continue supporting --disable-multibyte, it will become unsupported
> > and may be removed?
> 
> You're correct, it's de facto unsupported.  The difference is largely
> whether anyone gets around to fixing it, which is hard to predict --- I
> don't think the problems are likely to be hard.  So certainly it would
> be useful to get interest.  Alas, experience suggests most people don't
> take much notice until the point where it actually stops working for
> them.  So as long as we point out there are problems, I think whatever
> takes the least number of hostages to fortune is probably the right
> thing to say.
> 
> With the changes being largely minor and even cosmetic (but they're
> certainly not all cosmetic) it probably doesn't make sense to remove
> it any time soon.  But it could rot further, so possibly a warning is
> sensible.

A build-time warning, then?  I.e., have configure warn if --disable-multibyte
is selected (manually or automatically), or perhaps use a #warning at
the C level.  It could say something to the effect of "Compiling without
multibyte support is known not to pass 'make test'.  We recommend to
rebuild with --enable-multibyte.  Alternatively, fix the test suite and
send us the patches".

This will at least make the issue known to anyone who tries to disable
multibyte support for whatever reason.