Bug#846970: Patch to document Build-Indep-Architecture field

[Ian Jackson <ijackson@chiark.greenend.org.uk>]

Sean Whitton writes ("Bug#846970: Patch to document Build-Indep-Architecture field"):
> > +``Build-Indep-Architecture``
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +
> > +Specification of architectures on which the architecture-independent
> > +binary packages are known to be buildable and/or not buildable.  If
> > +this field is not specified, it defaults to ``any``, matching all
> > +Debian machine architectures.  If specified, it should be either
> > +
> > +-  A unique single word identifying a Debian machine architecture as
> > +   described in :ref:`s-arch-spec`.
> > +
> > +-  An architecture wildcard identifying a set of Debian machine
> > +   architectures, see :ref:`s-arch-wildcard-spec`.
> > +
> > +This header is useful in the rare case where architecture-independent
> > +packages cannot be built on all architectures for reasons outside the
> > +maintainer's control.
> > +
> > +Although the syntax of the field permits it, you should avoid
> > +specifying that the package can be built on only a single
> > +architecture.  This provides flexibility to the administrators of
> > +autobuilder infrastructure.

I'm afraid I don't understand this.

AFAICT from reading s-arch-spec and s-arch-wildcard-spec and looking
at the output of dpkg-architecture -L, the above syntax specification
permits, with our current arch list, only Build-Indep-Architecture
field contents of the following four forms:

    amd64              (FSVO amd64)              doc says don't do this
    kfreebsd-any       (FSVO kfreebsd)           useful but niche
    kfreebsd-amd64     (FSVO kfreebsd & amd64)   doc says don't do this
    any-amd64          (FSVO amd64               not very useful
    any                                          the default

So there is no good use for this field.  Furthermore, the things that
people actually want to be able to say ("some x86 machine", "something
mostly 32-bit", "something mostly 64-bit", "not freebsd") are not
expressable.

I think the result is surely going to be that people write "amd64"
because that "makes their thing work", and anyone who complains about
that will be asked by the maintainer to please suggest a better
option.

Ian.

-- 
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