The proposal for
Multi-Arch: same
Architecture: all
Implementation approach:
Such a package is like a collection of identical .debs for all
available architectures, all marked
Multi-Arch: same
Architecture: <something>
Normally, such a .deb is treated by dpkg as if it were for the
native architecture. There should be an option to change this.
Also, such a package can be "installed" for an additional
architecture with
dpkg --package-add-arch PACKAGE:ARCH
which actually uses the same path as dpkg --install, except that
provided that the package is in `unpacked' for some ARCH2,
the package goes straight to `unpacked' for ARCH without actually
processing any .deb.
When the package is upgraded, all architectures for which it is
better than `config-files' are updated; ie, it is as if all the
.debs are processed at once.
Wrinkles:
At the moment, the reference count passed to prerm scripts is wrong
and useless. A new reference count (number of arches strictly
better than `unpacked') should be provided in a new env var and the
old one deprecated.
In mk1 of the proposal, packages marked M-A:same,Arch:all will not
be allowed to have conffiles.
I propose the following rewritten description for the M-A field (NB,
may not be true in all places - someone must check!)
The Multi-Arch field gives the packaging system information about the
kind of interfaces exposed to other packages by this package. The
packaging system uses this to control how dependencies onto this
package are interpreted.
Some packages can be installed multiple-times for different
architectures. The Multi-Arch field also declares whether this is the
case.
Multi-Arch: no
This package provides interfaces useable only by code of the same
architecture; and, it is not multi-arch coinstallable. (Or, it is
architecture-specific and has not yet been annotated -- Multi-Arch:
no is the default for non-Architecture:all packages.)
(The package satisfies dependencies only from packages of the same
architecture, or arch:all.)
Multi-Arch: same
This package provides interfaces useable only by code of the same
architecture, but to make this easier it has been made
coinstallable.
Each installed arch for this package satisfies dependencies from
other packages of the same architecture.
This is the usual marking for packages containing machine code
libraries.
When this package is Architecture: all, this means that although the
physical code in this package is architecture-independent, the
facilities it provides are useable only on certain architectures.
This can happen when this package's users and this package's
architecture-specific dependencies need to be available for the
/same/ architecture.
Most obviously, this can happen when this package is a script
language module which depends on, and is depended on by,
architecture-specific language extension modules (eg, Perl XS). An
XS module which uses this pure Perl package needs this package's
lower XS dependencies to be set up for the same architecture as the
top XS module, or it is not useable.
Multi-Arch: foreign
This package provides interfaces which are useable by code of any
architecture. (Or, it is Architecture:all and has not yet been
annotated -- Multi-Arch: foreign is the default for
Architecture:all packages.)
The packaging system will prefer to resolve dependencies on
Multi-Arch: foreign packages by installing them for a preferred
architecture, the `native' architecture.
This package is not coinstallable.
Multi-Arch: allowed
This package provides a mixture of architecture-specific and
architecture-independent interfaces.
Dependencies on this package may be marked with `:any' to indicate
that they are satisifed by any architecture version of this package
(ie, that the depending package uses an architecture-neutral
interface). If not so marked, they are only satisfied by the
package of the same architecture (ie, the depending package uses an
architecture-specific interface).
This package is not coinstallable.
Ian.
