The ebuild for v4l2loopback overrides CC, LD, and related environment variables to point at gcc (and related tools). This leads to compile time errors if the kernel used a different compiler (obvious example is clang, but a non-systemwide gcc may have the same issue). Reproducible: Always Steps to Reproduce: 1. Build the kernel with CC=clang + LD=ld.lld 2. Invoke CC=clang LD=ld.lld emerge media-video/v4l2loopback 3. Observe error Actual Results: The relevant section of the build log is: warning: the compiler differs from the one used to build the kernel The kernel was built by: clang version 13.0.1 You are using: x86_64-pc-linux-gnu-gcc (Gentoo 11.2.1_p20220115 p4) 11.2.1 20220115 CC [M] /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5/v4l2loopback.o x86_64-pc-linux-gnu-gcc: error: unrecognized command-line option ‘-Qunused-arguments’ ... Expected Results: Package merges cleanly The reason it can give the warning is because the built kernel sources record what compiler was used (and what options it was given). Instead of guessing, the ebuild should pull this information. It already does for the options to pass to the compiler, but not for the compiler executable itself.
I can confirm the bug too ``` >>> Verifying ebuild manifests >>> Emerging (1 of 1) media-video/v4l2loopback-0.12.5-r1::gentoo * v4l2loopback-0.12.5.tar.gz BLAKE2B SHA512 size ;-) ... [ ok ] * Determining the location of the kernel source code * Found kernel source directory: * /usr/src/linux * Found sources for kernel version: * 6.2.7-gentoo * Checking for suitable kernel configuration options ... [ ok ] >>> Unpacking source... >>> Unpacking v4l2loopback-0.12.5.tar.gz to /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work >>> Source unpacked in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work >>> Preparing source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... >>> Source prepared. >>> Configuring source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... >>> Source configured. >>> Compiling source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... ln: failed to create symbolic link 'Module.symvers': File exists * Preparing v4l2loopback module make -j16 HOSTCC=x86_64-pc-linux-gnu-gcc 'LDFLAGS=-m elf_x86_64' all Building v4l2-loopback driver... make -C /lib/modules/6.2.7-gentoo/build M=/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 modules warning: the compiler differs from the one used to build the kernel The kernel was built by: clang version 15.0.7 You are using: x86_64-pc-linux-gnu-gcc (Gentoo 12.2.1_p20230304 p13) 12.2.1 20230304 CC [M] /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5/v4l2loopback.o x86_64-pc-linux-gnu-gcc: error: unrecognized command-line option ‘-Qunused-arguments’ x86_64-pc-linux-gnu-gcc: error: unrecognized command-line option ‘-mretpoline-external-thunk’ x86_64-pc-linux-gnu-gcc: error: unrecognized command-line option ‘-fsplit-lto-unit’ x86_64-pc-linux-gnu-gcc: error: unrecognized command-line option ‘-Wformat-invalid-specifier’ x86_64-pc-linux-gnu-gcc: error: unrecognized command-line option ‘-Wformat-insufficient-args’ make[2]: *** [scripts/Makefile.build:252: /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5/v4l2loopback.o] Error 1 make[1]: *** [Makefile:2021: /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5] Error 2 make: *** [Makefile:43: v4l2loopback.ko] Error 2 * ERROR: media-video/v4l2loopback-0.12.5-r1::gentoo failed (compile phase): * emake failed * * If you need support, post the output of `emerge --info '=media-video/v4l2loopback-0.12.5-r1::gentoo'`, * the complete build log and the output of `emerge -pqv '=media-video/v4l2loopback-0.12.5-r1::gentoo'`. * The complete build log is located at '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/temp/build.log'. * The ebuild environment file is located at '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/temp/environment'. * Working directory: '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5' * S: '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5' ```
*** Bug 907552 has been marked as a duplicate of this bug. ***
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=032d9f3e8f89b760dc4d179a79128ae0490387b7 commit 032d9f3e8f89b760dc4d179a79128ae0490387b7 Author: Andrew Ammerlaan <andrewammerlaan@gentoo.org> AuthorDate: 2023-06-21 08:25:15 +0000 Commit: Andrew Ammerlaan <andrewammerlaan@gentoo.org> CommitDate: 2023-06-21 08:29:43 +0000 media-video/v4l2loopback: migrate to linux-mod-r1.eclass, EAPI bump This should also fix Bug 843053 (please confirm that it works now) Should also fix the open CVE-2022-2652, the mentioned patch is in this release Bug: https://bugs.gentoo.org/864442 Bug: https://bugs.gentoo.org/843053 Closes: https://bugs.gentoo.org/888649 Closes: https://bugs.gentoo.org/908723 Signed-off-by: Andrew Ammerlaan <andrewammerlaan@gentoo.org> media-video/v4l2loopback/Manifest | 1 + .../v4l2loopback/v4l2loopback-0.12.7.ebuild | 59 ++++++++++++++++++++++ media-video/v4l2loopback/v4l2loopback-9999.ebuild | 19 +++---- 3 files changed, 70 insertions(+), 9 deletions(-)
Yes, I can confirm the bug has been fixed, I successfully compile it with clang16
Great, Thanks for testing
