Unable to build 5.1-rc* Kernel

[saski4711]

Hi,

it seems that any Kernel 5.1-rc* won't compile on my current Gentoo:

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/usr/include/libelf/gelf.h:25:5: error: "__LIBELF_INTERNAL__" is not defined, evaluates to 0 [-Werror=undef]
 #if __LIBELF_INTERNAL__
     ^~~~~~~~~~~~~~~~~~~
In file included from elf.h:22,
                 from check.h:22,
                 from orc_gen.c:22:

I can work around this with:

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CFLAGS="-Wno-error=undef"

however I cannot install/build Virtualbox:

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This system is currently not set up to build kernel modules.
Please install the Linux kernel "header" files matching the current kernel

I suspect the linux-headers is too old (5.0). What can I do?

Cheers

[fedeliallalinea]

What can I do?

Waiting official release of this kernel version?

[saski4711]

What can I do?

Waiting official release of this kernel version?

Yeah I was hoping for a somewhat quicker solution

[toralf]

I suspect the linux-headers is too old (5.0). What can I do?

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echo "~sys-kernel/linux-headers-5.0" >> /etc/portage/package.accept_keywords/<your file>

?

[saski4711]

I suspect the linux-headers is too old (5.0). What can I do?

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echo "~sys-kernel/linux-headers-5.0" >> /etc/portage/package.accept_keywords/<your file>

?

Thanks. Switched back to 5.0 official.

[ShinyDoofy]

This change was introduced via commit 056d28d1 (via this GitHub issue.

I've had the same initial error message when compiling the 5.1 kernel. A possible solution is indicated here:

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emerge --deselect dev-libs/libelf
emerge -v virtual/libelf

That did the trick for me to get the kernel compiled. Maybe it helps somebody else as well

[pleasantatk]

I temporarily removed pkgconf and it worked.

Rationale / reason this works: https://github.com/NixOS/nixpkgs/issues/59929

tl;dr: recent upstream linux commit switched detection of libelf to pkgconfig, so it's being included via -I instead of -isystem. As a result, certain flags which were previously ignored due to -isystem are now combining with otherwise minor issues in the header file to result in catastrophe.

As I mentioned there, I'm planning on submitting a fix to the broken headers upstream, which will remove the real problem entirely.

Removing pkgconf manually using `emerge -C pkgconf`, building the kernel, and then reinstalling pkgconf seems to be the best solution ATM.

[saski4711]

This issue is still there. I wonder why this isn't hitting more pepole using gentoo. Anyway the best workaround IMHO is to tell GCC not to treat a warning as an error:

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CFLAGS="-Wno-error=undef" make bzImage

[risa2000]

I just got it when compiling the recent stable vanilla (5.2.4). I used the workaround suggested by @ShinyDoofy above and it went well.

[Mappy]

I'm getting this error with the 5.2.8 kernel. Temporarily removing pkgconf works but I would rather not do that during every kernel upgrade.