[Buildroot] BR2_FORCE_HOST_BUILD broken

[Buildroot] BR2_FORCE_HOST_BUILD broken

[Markus Mayer via buildroot]

Hi all,

The following commit[1] seems to be breaking BR2_FORCE_HOST_BUILD:

4703a7ae9176 package/xz: fix musl static build

Here is a one-liner to reproduce the problem:

$ make O=/tmp/dummy raspberrypi5_defconfig && \
    sed -i 's/# BR2_FORCE_HOST_BUILD.*/BR2_FORCE_HOST_BUILD=y/' \
    /tmp/dummy/.config  && make O=/tmp/dummy
  GEN     /tmp/dummy/Makefile
#
# configuration written to /tmp/dummy/.config
#
package/xz/xz.mk:72: *** Recursive variable
'HOST_XZ_FINAL_RECURSIVE_DEPENDENCIES' references itself (eventually).
Stop.
make: *** [Makefile:83: _all] Error 2

That means:
    1. Configure for Raspberry Pi 5 (but any target would work)
    2. Turn on BR2_FORCE_HOST_BUILD
    3. Try to build
    4. Observe circular dependency for host-xz

I haven't determined the actual circular dependency yet. Are there any
tips for narrowing this down? These circular dependencies don't seem
to be easy to track down.

Thanks,
-Markus

[1] https://github.com/buildroot/buildroot/commit/4703a7ae9176b3a9d824880ef095b1b80c123df4
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Re: [Buildroot] BR2_FORCE_HOST_BUILD broken

[Thomas Petazzoni via buildroot]

Hello,

+Fabrice in Cc.

On Mon, 5 Aug 2024 14:29:05 -0700
Markus Mayer via buildroot <buildroot@buildroot.org> wrote:

> I haven't determined the actual circular dependency yet. Are there any
> tips for narrowing this down? These circular dependencies don't seem
> to be easy to track down.

Thanks for reporting the issue. The problem is that AUTORECONF = YES
adds host-autoconf as a dependency to host-xz... but host-autoconf
extracts a .tar.xz tarball, which requires host-xz (when you have
BR2_FORCE_HOST_BUILD=y).

Since the reason why we autoreconf xz is only relevant for the target
build, I think we could use the same trick as the one I've done in the
tar package in commit 69cbb563a124002fcb3e2725c3516b502587f9cc. I.e, we
do the autoreconf only for the target variant, and not the host
variant, which requires a bit of trickery.

Fabrice, or Markus, do you want to have a look?

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] BR2_FORCE_HOST_BUILD broken

[Markus Mayer via buildroot]

On Mon, 5 Aug 2024 at 14:48, Thomas Petazzoni
<thomas.petazzoni@bootlin.com> wrote:
>
> Hello,
>
> +Fabrice in Cc.
>
> Thanks for reporting the issue. The problem is that AUTORECONF = YES
> adds host-autoconf as a dependency to host-xz... but host-autoconf
> extracts a .tar.xz tarball, which requires host-xz (when you have
> BR2_FORCE_HOST_BUILD=y).

Thanks for the explanation.

> Since the reason why we autoreconf xz is only relevant for the target
> build, I think we could use the same trick as the one I've done in the
> tar package in commit 69cbb563a124002fcb3e2725c3516b502587f9cc. I.e, we
> do the autoreconf only for the target variant, and not the host
> variant, which requires a bit of trickery.
>
> Fabrice, or Markus, do you want to have a look?

I don't mind having a look.

Regards,
-Markus
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Re: [Buildroot] BR2_FORCE_HOST_BUILD broken

[Thomas Petazzoni via buildroot]

On Mon, 5 Aug 2024 20:08:51 -0700
Markus Mayer <markus.mayer@broadcom.com> wrote:

> Patch submitted. Turns out this one seems to be a bit simpler than the
> "tar" case. In my tests there was no need for a post patch hook. Just
> setting "HOST_XZ_AUTORECONF=NO" seems to suffice.

Indeed, the tar case is different. In the tar case, we apply patches
that touch configure.ac/Makefile.am, so we have to autoreconf. The
patches are also applied when building host-tar, so if we don't do
anything, configure.ac has a newer timestamp than configure, and
therefore even with HOST_TAR_AUTORECONF = NO, and automagic-autoreconf
gets triggered at build time.

In the case of xz, we don't patch anything, it's just that the provided
configure/Makefile are slightly broken for static builds, which is
completely irrelevant for host-xz, so indeed HOST_XZ_AUTORECONF = NO is
sufficient.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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