From: Masahiro Yamada <masahiroy@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: stable <stable@vger.kernel.org>,
Matthias Maennich <maennich@google.com>,
Michal Marek <michal.lkml@markovi.net>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH] Makefile: add -fuse-ld=lld to KBUILD_HOSTLDFLAGS when LLVM=1
Date: Sat, 22 Aug 2020 14:13:38 +0900 [thread overview]
Message-ID: <CAK7LNAQO9sKw=7RLPSnsChddrwNCc_si-XgSDQcGHTSxeq4_Pg@mail.gmail.com> (raw)
In-Reply-To: <20200820220955.3325555-1-ndesaulniers@google.com>
On Fri, Aug 21, 2020 at 7:10 AM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> While moving Android kernels over to use LLVM=1, we observe the failure
> when building in a hermetic docker image:
> HOSTCC scripts/basic/fixdep
> clang: error: unable to execute command: Executable "ld" doesn't exist!
>
> The is because the build of the host utility fixdep builds the fixdep
> executable in one step by invoking the compiler as the driver, rather
> than individual compile then link steps.
>
> Clang when configured from source defaults to use the system's linker,
> and not LLVM's own LLD, unless the CMake config
> -DCLANG_DEFAULT_LINKER='lld' is set when configuring a build of clang
> itself.
>
> Don't rely on the compiler's implicit default linker; be explicit.
I do not understand this patch.
The host compiler should be able to link executables
without any additional settings.
So, can you link a hello world program
in your docker?
masahiro@zoe:~$ cat test.c
#include <stdio.h>
int main(void)
{
printf("helloworld\n");
return 0;
}
masahiro@zoe:~$ clang test.c
If this fails, your environment is broken.
Just do -DCLANG_DEFAULT_LINKER='lld'
if you know GNU ld is missing in your docker environment.
> Cc: stable@vger.kernel.org
> Fixes: commit a0d1c951ef08 ("kbuild: support LLVM=1 to switch the default tools to Clang/LLVM")
> Reported-by: Matthias Maennich <maennich@google.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/Makefile b/Makefile
> index def590b743a9..b4e93b228a26 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -436,6 +436,7 @@ OBJDUMP = llvm-objdump
> READELF = llvm-readelf
> OBJSIZE = llvm-size
> STRIP = llvm-strip
> +KBUILD_HOSTLDFLAGS += -fuse-ld=lld
> else
> CC = $(CROSS_COMPILE)gcc
> LD = $(CROSS_COMPILE)ld
> --
> 2.28.0.297.g1956fa8f8d-goog
>
> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200820220955.3325555-1-ndesaulniers%40google.com.
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2020-08-22 5:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-20 22:09 [PATCH] Makefile: add -fuse-ld=lld to KBUILD_HOSTLDFLAGS when LLVM=1 Nick Desaulniers
2020-08-20 22:20 ` Nathan Chancellor
2020-08-22 5:13 ` Masahiro Yamada [this message]
2020-09-02 22:40 ` Nick Desaulniers
2020-09-03 1:45 ` Masahiro Yamada
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