On Tue, Apr 13, 2021 at 11:46 AM Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
>
> On Mon, Apr 12, 2021 at 5:31 PM Yonghong Song <yhs@xxxxxx> wrote:
> >
> >
> >
> > On 4/12/21 5:02 PM, Nick Desaulniers wrote:
> > > On Mon, Apr 12, 2021 at 4:58 PM Nick Desaulniers
> > > <ndesaulniers@xxxxxxxxxx> wrote:
> > >>
> > >> On Mon, Apr 12, 2021 at 7:29 AM Yonghong Song <yhs@xxxxxx> wrote:
> > >>>
> > >>> To build kernel with clang, people typically use
> > >>> make -j60 LLVM=1 LLVM_IAS=1
> > >>> LLVM_IAS=1 is not required for non-LTO build but
> > >>> is required for LTO build. In my environment,
> > >>> I am always having LLVM_IAS=1 regardless of
> > >>> whether LTO is enabled or not.
> > >>>
> > >>> After kernel is build with clang, the following command
> > >>> can be used to build selftests with clang:
> > >>> make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1
> > >>
> > >> Thank you for the series Yonghong. When I test the above command with
> > >> your series applied, I observe:
> > >> tools/include/tools/libc_compat.h:11:21: error: static declaration of
> > >> 'reallocarray' follows non-static declaration
> > >> static inline void *reallocarray(void *ptr, size_t nmemb, size_t size)
> > >> ^
> > >> /usr/include/stdlib.h:559:14: note: previous declaration is here
> > >> extern void *reallocarray (void *__ptr, size_t __nmemb, size_t __size)
> > >> ^
> > >> so perhaps the detection of
> > >> COMPAT_NEED_REALLOCARRAY/feature-reallocarray is incorrect?
> > >
> > > Is this related to _DEFAULT_SOURCE vs _GNU_SOURCE. via man 3 reallocarray:
> > > reallocarray():
> > > Since glibc 2.29:
> > > _DEFAULT_SOURCE
> > > Glibc 2.28 and earlier:
> > > _GNU_SOURCE
> > >
> >
> > You can try the following patch to see whether it works or not.
> >
> > diff --git a/tools/build/feature/test-reallocarray.c
> > b/tools/build/feature/test-reallocarray.c
> > index 8f6743e31da7..500cdeca07a7 100644
> > --- a/tools/build/feature/test-reallocarray.c
> > +++ b/tools/build/feature/test-reallocarray.c
> > @@ -1,5 +1,5 @@
> > // SPDX-License-Identifier: GPL-2.0
> > -#define _GNU_SOURCE
> > +#define _DEFAULT_SOURCE
> > #include <stdlib.h>
> >
> > int main(void)
> > @@ -7,4 +7,4 @@ int main(void)
> > return !!reallocarray(NULL, 1, 1);
> > }
> >
> > -#undef _GNU_SOURCE
> > +#undef _DEFAULT_SOURCE
>
> Yeah, I had tried that. No luck though; same error message. Even:
>
> $ cat foo.c
> #define _DEFAULT_SOURCE
> #include <stdlib.h>
> void *reallocarray(void *ptr, size_t nmemb, size_t size) { return (void*)0; };
> $ clang -c foo.c
> $ echo $?
> 0
>
> So I'm not sure precisely what's going on here. I probably have to go
> digging around to understand tools/build/feature/ anyways. With your
> v3 applied, I consistently see:
> No zlib found
> and yet, I certainly do have zlib on my host.
> https://stackoverflow.com/a/54558861
Jiri, any tips on how to debug feature detection in
tools/build/feature/Makefile?
>
> > [yhs@devbig003.ftw2 ~/work/bpf-next/tools/build]$
> >
> > > $ cd tools/testing/selftests/bpf
> > > $ grep -rn _DEFAULT_SOURCE | wc -l
> > > 0
> > > $ grep -rn _GNU_SOURCE | wc -l
> > > 37
> > > $ ldd --version | head -n1
> > > ldd (Debian GLIBC 2.31-9+build1) 2.31
> > >
>
>
>
> --
> Thanks,
> ~Nick Desaulniers
--
Thanks,
~Nick Desaulniers
