Fix subsequent cmake runs when using multi-arch

[Rohan Garg]

Running cmake a second time on a project when using multi-arch seems to be broken without this patch in Ubuntu.

NB: This is a patch to a patch :)

[Dimitri John Ledkov (xnox)]

How to reproduce this? and what do you mean by running a second time?

Cause, mutliarch file only kicks in when environmental variables are set correctly pointing at cross-arch build/host combination and otherwise does nothing and defaults to a normal native compilation.

Imho this patch should not be required, and multiarch file should not be used as a normal cmake toolchain file.

[Aleix Pol (aleixpol-kde)]

log that reproduces the error:
mkdir build; cd build; cmake ..; cmake ..

The second time that it's configured cmake doesn't need to detect the platform anymore so CMakeDetermineSystem.cmake isn't called anymore as it calls the Platform file directly.

[Aleix Pol (aleixpol-kde)]

Ping?

[Michael Terry (mterry)]

So I am also unsure of what exactly your scenario is (what the reproduction steps are).

Without any environment variables, cross compiling isn't used, so this bug isn't hit. It's only when you set environment variables to use cross compilers that you might hit this scenario. But if you look at, for example, dpkg-cross(1), it recommends setting:

        export CC=$(DEB_HOST_GNU_TYPE)-gcc
        export CXX=$(DEB_HOST_GNU_TYPE)-g++
        export CMAKE_TOOLCHAIN_FILE=/etc/dpkg-cross/cmake/CMakeCross.txt

Thus manually setting CMAKE_TOOLCHAIN_FILE seems to be a standard part of the documentation. What steps are you using to cross compile?

[Dimitri John Ledkov (xnox)]

On 22 December 2015 at 17:05, Michael Terry <email address hidden> wrote:
> So I am also unsure of what exactly your scenario is (what the
> reproduction steps are).
>
> Without any environment variables, cross compiling isn't used, so this
> bug isn't hit. It's only when you set environment variables to use
> cross compilers that you might hit this scenario. But if you look at,
> for example, dpkg-cross(1), it recommends setting:
>
> export CC=$(DEB_HOST_GNU_TYPE)-gcc
> export CXX=$(DEB_HOST_GNU_TYPE)-g++
> export CMAKE_TOOLCHAIN_FILE=/etc/dpkg-cross/cmake/CMakeCross.txt
>
> Thus manually setting CMAKE_TOOLCHAIN_FILE seems to be a standard part
> of the documentation. What steps are you using to cross compile?

that's for debian.

i've patched ubuntu cmake toolchain files to be sensitive to
DEB_HOST|BUILD_ARCH and thus not requiring any special variables to be
exported. This enabled cross-compilation of most cmake projects and
debian packages out of the box on ubuntu, e.g. in chroots such as
prepared with mk-sbuild and/or click chroot without any modifications
to build rules.

As per debian policy, one should be able to build projects twice in a
row, if and only if a full clean is done in between. e.g.
./debian/rules build clean build -> should work, and it does work with
these patches.

I'm not sure what bug is hit and why. Because one should purge all of
build dir to get cmake caches to its senses =0

--
Regards,

Dimitri.

[Sebastien Bacher (seb128)]

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[Launchpad Janitor (janitor)]

[Expired for cmake (Ubuntu) because there has been no activity for 60 days.]