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Bug#373193: About #373193

> > - add option to dpkg-buildpackage not to use gccross
> I'd like to understand how that works first. dpkg-cross's
> dpkg-buildpackage wrapper uses gccross if -a arch != $build has been
> requested? dpkg-bp calls configure with (possibly implicit) --host
> $build --build $build? dpkg-bp calls rules with CC=gccross? And gccross
> pretends to be $build's native compiler, but calls the cross-compiler
> and rewrites the -I / -L paths accordingly? Please correct me if
> anything is wrong.

dpkg-buildpackage from dpkg-cross just sets DEB_HOST_* variables in 
cross-compilation case, the rest is done by normal dpkg-buildpackage.

Gccross is substituted similar to tools like distcc or ccache - by 
prepending to PATH a directory that has symlinks to gccross named "gcc", 
"g++", "$target-gcc", "$target-g++" and similar. Those are prepared by 
dpkg-cross version of dpkg-buildpackage.
When started, gccross checks command line, replaces paths from -I and -L 
args if those don't point to cross-compilation dirs, and calls next 
argv[0] in path.

> My understanding is that gccross is a good short-term solution, and in
> the long-term all packages should be cross-build aware and use the right
> tools themselves. In fact, my package is configured with
> --host=$(DEB_HOST_GNU_TYPE) --build=$(DEB_BUILD_GNU_TYPE), so make
> should already call the right compiler with the right paths.

It's not that easy. Also issues that come from xxx-config and other scripts 
that print compiler arguments should be addressed. It is solvable e.g. by 
creating alternate versions of such scripts at 'dpkg-cross -b' stage and 
forcing those to PATH at cross-compile time, but that needs to be 
implemented and checked.

> So, with my current understanding, I think even further, there should be
> a mechanism (an option, environment variable, whatever) to *enable*
> using gccross. It should be disabled by default since compliant packages
> don't need it.
> What do you think?

See above. I still agree with Raphael (gccross author) that this should be 
enabled by default - at least until (almost) all debian packages will 
cross-compile without it.


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