[debian-mysql] Bug#842454: default-libmysqlclient-dev is unsatisfiable for cross builds

[Johannes Schauer]

On Mon, 7 Nov 2016 18:12:41 +0100 Andreas Beckmann <anbe at debian.org> wrote:
> Right, that should be
> 
> Architecture: all
> Multi-Arch: foreign

No.

> I just verified that this is sufficient to have a package
> 
> Package: test-default-libmysqlclient-dev
> Architecture: any
> Depends:
>  default-libmysqlclient-dev,
> 
> built for i386 and install it on a amd64 chroot.

The situation you tested is not the one that breaks cross Build-Depends
involving default-libmysqlclient-dev. In the situation you painted above, the
installed default-libmysqlclient-dev package would draw in
libmariadbclient-dev-compat, libmariadbclient-dev and libmariadbclient18 all in
architecture amd64. But as explained by Helmut in his initial report, the
source packages require the development headers for the host architecture
(i386) and not for the build architecture (amd64). By marking
default-libmysqlclient-dev as Architecture:all, M-A:foreign, the affected
source packages will be able to satisfy their cross Build-Depends but they will
still not be cross-buildable because the wrong architecture mysql headers will
get installed.

> In general, how does it work to have arch:all build-depends (marked as m-a:
> foreign and depending on arch:any packages) in cross-build scenarios?
> 
> IMO it is wrong to require -dev packages to be arch:any if they could be
> arch:all + m-a:foreign.

Architecture:all packages are implicitly understood as the native architecture
which, in a cross-build scenario equals to the build architecture. Thus, if a
build dependency is Architecture:all and M-A:foreign, then all its dependencies
will also be installed for the native/build architecture. In the case of
default-libmysqlclient-dev this behaviour would make cross builds fail because
they do not need the build architecture version of the mysql libraries but the
host architecture version. Thus, default-libmysqlclient-dev needs to be able to
hand down the host architecture requirement to its dependencies. With a
M-A:foreign marking you remove this capability.

I also see no other way to solve this situation than the solution Helmut
proposed.

Thanks!

cheers, josch
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 801 bytes
Desc: signature
URL: <http://lists.alioth.debian.org/pipermail/pkg-mysql-maint/attachments/20161108/d592b346/attachment.sig>