Re: [akpm-mm:mm-unstable 121/130] tools/testing/selftests/kselftest.h:427:13: error: implicit declaration of function 'vasprintf'; did you mean 'vsprintf'?

[Philip Li <philip.li@intel.com>]

On Tue, Mar 31, 2026 at 11:23:41AM -0700, Andrew Morton wrote:
> On Tue, 31 Mar 2026 11:27:20 +0200 kernel test robot <lkp@intel.com> wrote:
> 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> > head:   24e341657c283c965e3bfee0baa9ed0376127973
> > commit: cc0b04b10a7b98fd8df2fd539177e94e0f83a5c3 [121/130] selftests: ksft_exit_fail_perror: support printf style arguments
> > config: arm64-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260331/202603311105.ysUeYPSZ-lkp@intel.com/config)
> > compiler: aarch64-linux-gnu-gcc (Debian 14.2.0-19) 14.2.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260331/202603311105.ysUeYPSZ-lkp@intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202603311105.ysUeYPSZ-lkp@intel.com/
> > 
> > Note: the akpm-mm/mm-unstable HEAD 24e341657c283c965e3bfee0baa9ed0376127973 builds fine.
> >       It only hurts bisectability.
> > 
> > All errors (new ones prefixed by >>):
> > 
> >    In file included from za-fork.c:12:
> >    ../../kselftest.h: In function 'ksft_exit_fail_perror':
> > >> ../../kselftest.h:427:13: error: implicit declaration of function 'vasprintf'; did you mean 'vsprintf'? [-Wimplicit-function-declaration]
> >      427 |         if (vasprintf(&buf, msg, args) == -1) {
> >          |             ^~~~~~~~~
> >          |             vsprintf
> 
> What's going on here.  vasprintf is a GNU thing, but that isn't it. 
> kselftest.h includes stdio.h directly so fine.  I don't see anything in

Sorry for the confusion, the build logic uses nolibc, which causes the wrong report.
I will do some learning to correct my knowledge for how to build the kselftests side
and update the bot.

FYI: below is the detail make command used

	aarch64-linux-gnu-gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \
	        -static -include ../../../../include/nolibc/nolibc.h \
	        -I../.. -ffreestanding -Wall tpidr2.c -o tools/testing/selftests/arm64/abi/tpidr2 -lgcc
	In file included from tpidr2.c:6:
	../../kselftest.h: In function 'ksft_exit_fail_perror':
	../../kselftest.h:427:13: error: implicit declaration of function 'vasprintf'; did you mean 'vsprintf'? [-Wimplicit-function-declaration]
	  427 |         if (vasprintf(&buf, msg, args) == -1) {
	      |             ^~~~~~~~~
	      |             vsprintf

> the later patches which could alter this, so the "only hurts
> bisectability" is inexplicable.

Sorry, you are right, this is a bug as well that the bisection does the wrong judgement,
and the same issue also in HEAD 24e341657c28 after manual check with this nolibc build.

I will look into the bug to fix it.

Thanks

> 
> I was able to reproduce this, once.  Now it's gone away.
> 
> 
> And arm64 allnoconfig is a nuisance.  Now my vmlinux build immediately
> faceplants with
> 
> ./arch/arm64/include/asm/atomic_ll_sc.h:298:9: error: unknown type name 'u128'
>   298 |         u128 full;
> 
> With the latest 15.2.0 kit from https://www.kernel.org/pub/tools/crosstool/.
> 
>