sbuild wiki page - cross compiling section query

[Phil Wyett]

Hi all,

https://wiki.debian.org/sbuild

https://wiki.debian.org/sbuild#Cross-compiling_packages


On the sbuild wiki page in the cross compiling section should we be advising
users that they need to create a chroot for the {ARCH} they wish to cross build
for and also have the relevant crossbuild-essential-{ARCH} package installed?

Regards

Phil
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[Jochen Sprickerhof]

Hi Phil,

Post by Phil Wyett
https://wiki.debian.org/sbuild
https://wiki.debian.org/sbuild#Cross-compiling_packages
On the sbuild wiki page in the cross compiling section should we be advising
users that they need to create a chroot for the {ARCH} they wish to cross build
for and also have the relevant crossbuild-essential-{ARCH} package installed?

No, why?

Cross compiling means that you need that normal build arch chroot as
initial set up. An other thing is using sbuild --arch=, that uses qemu
most of the time, where you need the arch chroot.

Cheers Jochen

[Phil Wyett]

Post by Jochen Sprickerhof
Hi Phil,

Post by Phil Wyett
https://wiki.debian.org/sbuild
https://wiki.debian.org/sbuild#Cross-compiling_packages
On the sbuild wiki page in the cross compiling section should we be advising
users that they need to create a chroot for the {ARCH} they wish to cross build
for and also have the relevant crossbuild-essential-{ARCH} package installed?

No, why?
Cross compiling means that you need that normal build arch chroot as
initial set up. An other thing is using sbuild --arch=, that uses qemu
most of the time, where you need the arch chroot.
Cheers Jochen

Hi,

Ah... Let me describe my setup.

* A VM with Debian trixie install - standard utilities plus ssh server.
* sbuild, pbuilder, piuparts and reprotest etc. installed.
* qemu is not the install.

For --host=arm64 I have to generate an arm64 chroot and install crossbuild-
essential-arm64 for crossbuilds to work.

Regards

Phil
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[Phil Wyett]

Post by Phil Wyett

Post by Jochen Sprickerhof
Hi Phil,

Post by Phil Wyett
https://wiki.debian.org/sbuild
https://wiki.debian.org/sbuild#Cross-compiling_packages
On the sbuild wiki page in the cross compiling section should we be advising
users that they need to create a chroot for the {ARCH} they wish to cross build
for and also have the relevant crossbuild-essential-{ARCH} package installed?

No, why?
Cross compiling means that you need that normal build arch chroot as
initial set up. An other thing is using sbuild --arch=, that uses qemu
most of the time, where you need the arch chroot.
Cheers Jochen

Hi,
Ah... Let me describe my setup.
* A VM with Debian trixie install - standard utilities plus ssh server.
* sbuild, pbuilder, piuparts and reprotest etc. installed.
* qemu is not the install.
For --host=arm64 I have to generate an arm64 chroot and install crossbuild-
essential-arm64 for crossbuilds to work.
Regards
Phil

Hi,

I mainly ran into issue with autopkgtest which looked for --arch (unshare
default config) and failed unless I generated the arm64 chroot.

Regards

Phil
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[Andrey Rakhmatullin]

Post by Phil Wyett
I mainly ran into issue with autopkgtest

Good.
autopkgtest and package building are separate unrelated activities.

[Jochen Sprickerhof]

Post by Phil Wyett
I mainly ran into issue with autopkgtest which looked for --arch (unshare
default config) and failed unless I generated the arm64 chroot.

sbuild passes --arch to autopkgtest as you can't run tests in a cross
compile setup. autopkgtest then uses qemu to run them. This works in
principal but is really slow so I recommend to run autopkgtest on a
native system and not via sbuild when cross compiling. Also note that
autopkgtest-virt-unshare, like sbuild, can create chroots automatically
in trixie and I would prefer to drop the chroot creation parts from the
wiki page instead at some point.

Cheers Jochen

[Jochen Sprickerhof]

Post by Phil Wyett
* A VM with Debian trixie install - standard utilities plus ssh server.

Which arch has the VM?

Post by Phil Wyett
For --host=arm64 I have to generate an arm64 chroot and install crossbuild-
essential-arm64 for crossbuilds to work.

If you want to cross build a package, i.e. your system is not arm64 and
you want to compile a package that is arm64 you need a chroot from host
system arch and sbuild will take care of the rest, no need to manually
install crossbuild-essential-arm64 or anything. Did you try that?

Cheers Jochen

[Phil Wyett]

Post by Jochen Sprickerhof

Post by Phil Wyett
* A VM with Debian trixie install - standard utilities plus ssh server.

Which arch has the VM?

Post by Phil Wyett
For --host=arm64 I have to generate an arm64 chroot and install crossbuild-
essential-arm64 for crossbuilds to work.

If you want to cross build a package, i.e. your system is not arm64 and
you want to compile a package that is arm64 you need a chroot from host
system arch and sbuild will take care of the rest, no need to manually
install crossbuild-essential-arm64 or anything. Did you try that?
Cheers Jochen

Hi,

The VM arch is amd64.

I have a build running at the moment. When it completes (probably the early
hours of tomorrow), I will clone it and perform tests to see what is and is not
required.

Regards

Phil
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[Phil Wyett]

Post by Jochen Sprickerhof

Post by Phil Wyett
* A VM with Debian trixie install - standard utilities plus ssh server.

Which arch has the VM?

Post by Phil Wyett
For --host=arm64 I have to generate an arm64 chroot and install crossbuild-
essential-arm64 for crossbuilds to work.

If you want to cross build a package, i.e. your system is not arm64 and
you want to compile a package that is arm64 you need a chroot from host
system arch and sbuild will take care of the rest, no need to manually
install crossbuild-essential-arm64 or anything. Did you try that?
Cheers Jochen

Hi Jochen and all,

Indeed, the crossbuild-essential-* were not necessary and have now been
removed.

I will be keeping the arm64 riscv64 chroots to enable autopkgtest to run
successfully with sbuild and I find the tests run extremely quickly.

Running native methods mentioned I will test on another laptop I shall make
full Debian testing. These things are not possible on my daily driver that due
to circumstance it runs Red Hat Enterprise Linux 9.x.

Regards

Phil
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[Andrey Rakhmatullin]

Post by Phil Wyett
* A VM with Debian trixie install - standard utilities plus ssh server.
* sbuild, pbuilder, piuparts and reprotest etc. installed.
* qemu is not the install.
For --host=arm64 I have to generate an arm64 chroot

No.

Post by Phil Wyett
and install crossbuild-essential-arm64 for crossbuilds to work.

Building arm64 in an arm64 chroot is not even a cross-build, you wouldn't
need crossbuild-*.

[Andrey Rakhmatullin]

Post by Phil Wyett
https://wiki.debian.org/sbuild
https://wiki.debian.org/sbuild#Cross-compiling_packages
On the sbuild wiki page in the cross compiling section should we be advising
users that they need to create a chroot for the {ARCH} they wish to cross build
for and also have the relevant crossbuild-essential-{ARCH} package installed?

Are you confusing cross-building with building in foreign chroots? The
section you linked says "To build a package for arm64 in an amd64 chroot
(as created above)".