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 $?
0
So I'm not sure precisely what's going on here. I probably have to go
digging around to understand tools/build/feature/ anyways. With your
v3 applied, I consistently see:
No zlib found
and yet, I certainly do have zlib on my host.
https://stackoverflow.com/a/54558861
> [yhs@devbig003.ftw2 ~/work/bpf-next/tools/build]$
>
> > $ 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
