From: Will Deacon <will@kernel.org>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild@vger.kernel.org,
Nick Desaulniers <ndesaulniers@google.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
Andrew Morton <akpm@linux-foundation.org>,
Brendan Higgins <brendanhiggins@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Changbin Du <changbin.du@intel.com>,
Krzysztof Kozlowski <krzk@kernel.org>,
Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
Randy Dunlap <rdunlap@infradead.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] kconfig: unify cc-option and as-option
Date: Mon, 15 Jun 2020 11:00:08 +0100 [thread overview]
Message-ID: <20200615100007.GD2477@willie-the-truck> (raw)
In-Reply-To: <20200614144341.1077495-2-masahiroy@kernel.org>
On Sun, Jun 14, 2020 at 11:43:41PM +0900, Masahiro Yamada wrote:
> cc-option and as-option are almost the same; both pass the flag to
> $(CC). The main difference is the cc-option stops before the assemble
> stage (-S option) whereas as-option stops after it (-c option).
>
> I chose -S because it is slightly faster, but $(cc-option,-gz=zlib)
> returns a wrong result (https://lkml.org/lkml/2020/6/9/1529).
> It has been fixed by a separate patch, but using -c is more robust.
>
> However, you cannot simply replace -S with -c because the following
> code would break:
>
> depends on $(cc-option,-gsplit-dwarf)
>
> The combination of -c and -gsplit-dwarf does not accept /dev/null as
> output.
>
> $ cat /dev/null | gcc -gsplit-dwarf -S -x c - -o /dev/null
> $ echo $?
> 0
>
> $ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o /dev/null
> objcopy: Warning: '/dev/null' is not an ordinary file
> $ echo $?
> 1
>
> $ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o tmp.o
> $ echo $?
> 0
>
> There is another flag that creates an separate file based on the
> object file path:
>
> $ cat /dev/null | gcc -ftest-coverage -c -x c - -o /dev/null
> <stdin>:1: error: cannot open /dev/null.gcno
>
> So, we cannot use /dev/null to sink the output.
>
> Align the cc-option implementation with scripts/Kbuild.include.
>
> With -c option used in cc-option, as-option is unneeded.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
> arch/arm64/Kconfig | 2 +-
> lib/Kconfig.debug | 1 -
> scripts/Kconfig.include | 8 +-------
> 3 files changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 31380da53689..6eb18f45258e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1564,7 +1564,7 @@ config CC_HAS_SIGN_RETURN_ADDRESS
> def_bool $(cc-option,-msign-return-address=all)
>
> config AS_HAS_PAC
> - def_bool $(as-option,-Wa$(comma)-march=armv8.3-a)
> + def_bool $(cc-option,-Wa$(comma)-march=armv8.3-a)
For this arm64 part:
Acked-by: Will Deacon <will@kernel.org>
Will
next prev parent reply other threads:[~2020-06-15 10:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-14 14:43 [PATCH 1/2] kbuild: improve cc-option to clean up all temporary files Masahiro Yamada
2020-06-14 14:43 ` [PATCH 2/2] kconfig: unify cc-option and as-option Masahiro Yamada
2020-06-15 10:00 ` Will Deacon [this message]
2021-05-04 20:17 ` Johannes Berg
2021-05-04 20:46 ` Masahiro Yamada
2021-05-04 20:52 ` Johannes Berg
2021-05-04 21:05 ` Masahiro Yamada
2021-05-04 21:08 ` Johannes Berg
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