On Tue, May 07, 2013 at 10:31:10PM +0100, Wookey wrote:
> +++ Stephen Kitt [2013-05-07 14:38 +0200]:
> > Hi Wookey,
> >
> > On Tue, 7 May 2013 03:04:50 +0100, Wookey <wookey@wookware.org> wrote:
> > > (just a decision to leave arch-independent headers in /usr/include and
> > > move arch-dependent headers to /usr/include/triplet).
> >
> > Doesn't this limit us to cross-compiling only across Debian architectures? If
> > we go for a full /usr/include/triplet split (in the same way as for
> > libraries)
>
> Libraries are always different for different architectures. Only a
> fairly small subset of headers is, so you could say we are doing
> exactly the same thing for both libaries and headers:
> arch-indep stuff goes in /usr/{lib,include}
> arch-dependent stuff goes in /usr/{lib,include}/triplet
>
> But your point is taken.
>
> The tradeoff is:
> 1) (Move _all_ headers to /usr/include/triplet)
> * Much duplication of installed headers
> * Only one system include dir, which fits current build-system
> expectations
>
> 2) (Move only arch-dependent headers to /usr/include/triplet)
> * No duplication of headers
> * Two system include dirs, which may confuse/break some builds
>
> In both cases things which manage to explictly look only in '/usr/include'
> may fail to build, but much more likely for 2. I have no idea how
> much a problem this would be in practice.
> '1)', above has been reasonably well tested in Ubuntu raring, and telling the
> compiler to look in both dirs for system headers by default works
> well, but there could be issues when given paths to subdirs.
Note: #include <foo.h> will implicitly look in /usr/include/triplet
and /usr/include. You have to do something strange to fail to build.
E.g. "grep SOMETHING $dir/foo.h" in configure instead of test
compiling like macros usualy do.
So this is less of an issue than it sounds. It realy needs to be
explicitly broken to fail.
> > we could support cross-compiling to anything with the same
> > structure - I'm thinking MinGW-w64 here of course, but I imagine it would
> > apply to other targets too, some of which are supported in Debian already
> > using the /usr/triplet/include directories.
>
> The above issue is independent of the need for dpkg-architecture to know
> about an arch to use multiarch mechanism for cross-building to it. But
> that's very easy to do (An easy way to add arches in a local config
> file is something that's been mentioned before). Having mingw as an
> arch is a good idea if it isn't already.
>
> And you can still use a sysroot and non-multiarch ways of filling it
> if you prefer. I haven't really experimented with mulitarch and
> sysroot at the same time but SFAIK it should work.
>
> Wookey
MfG
Goswin