Re: [PATCH v4 15/17] kconfig: Add support for 'as-option'

From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Kristina Martsenko <kristina.martsenko@arm.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Mark Brown <broonie@kernel.org>,
	James Morse <james.morse@arm.com>,
	Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
	Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v4 15/17] kconfig: Add support for 'as-option'
Date: Thu, 23 Jan 2020 10:52:05 +0000	[thread overview]
Message-ID: <0640c3c6-8b5f-8c29-692c-a9acdda01a6c@arm.com> (raw)
In-Reply-To: <CAKv+Gu-r4d1bBNJK0BZAX=b2+SDqMztAHx+cpq1dxB2q8O1YJA@mail.gmail.com>

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On 23/01/2020 10:30, Ard Biesheuvel wrote:
> On Thu, 23 Jan 2020 at 11:22, Amit Daniel Kachhap <amit.kachhap@arm.com> wrote:
>>
>> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>>
>> Currently kconfig does not have a feature that allows to detect if the
>> used assembler supports a specific compilation option.
>>
>> Introduce 'as-option' to serve this purpose in the context of Kconfig:
>>
>>         config X
>>                 def_bool $(as-option,...)
>>
>> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
>> Cc: linux-kbuild@vger.kernel.org
>> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
>> ---
>> Changes since v3:
>> *) Changed the assembler option to -c instead of earlier -E.
>> *) Added Masahiro Acked-by.
>>
>>  scripts/Kconfig.include | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
>> index d4adfbe..c4b4424 100644
>> --- a/scripts/Kconfig.include
>> +++ b/scripts/Kconfig.include
>> @@ -31,6 +31,10 @@ cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /de
>>  # Return y if the linker supports <flag>, n otherwise
>>  ld-option = $(success,$(LD) -v $(1))
>>
>> +# $(as-option,<flag>)
>> +# Return y if the assembler supports <flag>, n otherwise
>> +as-option = $(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
> 
> Did you mean '-o /dev/null' here?
>

No /dev/zero because otherwise I get a warning that says that I am trying to
compile an object into the same file.

If I invert /dev/zero and /dev/null this trashes the compilation. It took me a
while to get the right combination.

>> +
>>  # check if $(CC) and $(LD) exist
>>  $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
>>  $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
>> --
>> 2.7.4
>>

-- 
Regards,
Vincenzo

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