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Re: Bootstrappable Debian - proposal of needed changes

On Wed, Jan 16, 2013 at 03:40:52PM +0000, Neil Williams wrote:
> On Wed, 16 Jan 2013 13:50:17 +0000
> Ian Jackson <ijackson@chiark.greenend.org.uk> wrote:
> > Is it possible that packages might only cross build for certain
> > targets ?  Or only for certain hosts ?

In my reply I'm going to use autoconf terminology, so host =>
architecture built for, and target => only relevant when talking about
cross-tools themselves.  (Not everyone likes this terminology, but it is
widespread and autoconf tends to do a better job than virtually any
other build system at supporting cross-building so I tend to end up
preferring its terms.)

> For certain host architectures: yes, definitely. Any source package
> which includes assembly (there are more than most people expect) and any
> package which then has a build dependency on a binary package
> built from the source package(s) containing assembly and so on.

Such packages would typically fail to build natively for the
architecture in question too.  I think it's more interesting to consider
cases where, of the set of architectures on which a package can be built
natively, it can cross-build to some of those host architectures but not

However, I can't think of any such packages right now, although no doubt
anything is possible; at least, it seems to me to be rare enough not to
be worth inventing metadata for.  I suspect that most such instances
will be where packages only cross-build to "similar enough"
architectures, e.g. where you happen to have a multilib toolchain
available, so amd64 to i386, or perhaps architectures with the same bit
length and/or endianness.  In other words, such bugs would be a function
of the combination of build and host architectures, rather than just of
the host architecture.  (I haven't run into many of these, since I
cross-build from amd64 to armhf and they're fairly different.)

Neil, can you think of any packages that meet this stricter criterion?

Colin Watson                                       [cjwatson@debian.org]

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