Fwd: Re: re bug 638959: gmp multiarch support - why not -dev too?

[Wookey]

+++ Wookey [2012-05-22 11:04 +0100]:
> Steve M. Robbins <steve at sumost.ca> wrote
> On Mon, May 21, 2012 at 05:23:28PM +0100, Wookey wrote:
> >I just noticed that
> >http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=638959 was closed but
> >only libgmp10 libgmpxx4ldbl were made Multi-Arch: same. The -dev part
> >of the patch was missed out.
> >
> >What was the reason for this?
> 
> My understanding at the time was that you couldn't make -dev packages
> multi-arch.  I believe I received some advice to this effect at the
> time but I can't find it now.

That was wrong, or at least confused. There are sometimes extra
difficulties making -dev packages M-A: same, but it's generally a good
thing, and certainly desirable for any -dev package used by anything
that might ever be cross-built. 

> Even if this is not a general prohibition, the wiki [1] does say this:
> 
>     Although Debian policy currently doesn't allow -dev packages with
>     headers which vary across architectures to be Multi-Arch: same,

That's out of date. I'll fix that. 

> and each -dev has its own architecture-dependent <gmp-arch.h> file.

OK. So that is an example of the "sometimes extra difficulties"

Just move it to /usr/include/$DEB_HOST_MULTIARCH/gmp-arch.h
(Then check that stuff still builds against it properly). The
multiarch include dir should still be in the compiler system path so
unless the building package overrides the header paths it will be
found automatically. 

> >libgmp-dev is a build-dep of 75 packages, and because the build-arch
> >version gets installed with the toolchain it is often not possible to
> >install the host-arch version unless libgmp-dev is M-A: same.
> 
> I don't understand the issue.

If libgmp-dev:amd64 is installed you can't install libgmp-dev:armel in
order to cross-build an armel package that build-depends on libgmp,
unless libgmp-dev is M-A:same.

This affects quite a few packages.

I'm happy to help out with testing. 

Wookey