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From: Arnd Bergmann <arnd@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	 Masahiro Yamada <masahiroy@kernel.org>,
	llvm@lists.linux.dev,  Jonathan Corbet <corbet@lwn.net>,
	Federico Vaga <federico.vaga@vaga.pv.it>,
	Alex Shi <alexs@kernel.org>,  Hu Haowen <src.res@email.cn>,
	Michal Marek <michal.lkml@markovi.net>,
	 Nick Desaulniers <ndesaulniers@google.com>,
	 "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-doc-tw-discuss@lists.sourceforge.net,
	 Linux ARM <linux-arm-kernel@lists.infradead.org>,
	 intel-gfx <intel-gfx@lists.freedesktop.org>,
	 dri-devel <dri-devel@lists.freedesktop.org>,
	greybus-dev@lists.linaro.org,  linux-staging@lists.linux.dev,
	linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH] Kbuild: remove -std=gnu89 from compiler arguments
Date: Mon, 28 Feb 2022 09:07:03 +0100	[thread overview]
Message-ID: <CAK8P3a3Lv_uSXt9yf-9iOV3hZgV7KvwZjL-gbLTLRgo0UOQguw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whWbENRz-vLY6vpESDLj6kGUTKO3khGtVfipHqwewh2HQ@mail.gmail.com>

On Sun, Feb 27, 2022 at 11:36 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> And I don't want somebody with a newer compiler version to not notice
> that he or she ended up using a c17 feature, just because _that_
> compiler supported it, and then other people get build errors because
> their compilers use gnu11 instead by default.
>
> Put another way: I see absolutely no upside to allowing different
> users using higher/lower versions of the standard. There are only
> downsides.
>
> If gnu11 is supported by gcc-5.1 and up, and all the relevant clang
> versions, then let's just pick that.

Ok, changed my patch to -gnu11 now.

> And if there are any possible future advantages to gnu17 (or eventual
> gnu2x versions), let's document those, so that we can say "once our
> compiler version requirements go up sufficiently, we'll move to gnuXX
> because we want to take advantage of YY".
>
> Please?

I think all of the options here are equally bad: picking gnu11 means
we use a non-standard default for anything other than gcc-5 and
may get surprised again in the future when we want to change to
a newer version; -std=gnu1x would work as an alias for gnu17 in
all versions including gcc-5 but is already marked as 'deprecated'
in the gcc documentation; and using -std=gnu17 for modern compilers
requires a workaround for gcc-7 and earlier.

Regarding new features from gcc-2x, I think we already use
most of what is listed in https://en.wikipedia.org/wiki/C2x, as
those are all GNU extensions that are valid in modern gnu89 as
well. Newly added features seem to only depend on the compiler
version, e.g. #elifdef works in both clang-13 and gcc-12 with
any -std=gnu?? argument, so picking an earlier standard won't
stop people from breaking the build with older compilers.

         Arnd

WARNING: multiple messages have this Message-ID
From: Arnd Bergmann <arnd@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Michal Marek <michal.lkml@markovi.net>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>,
	linux-staging@lists.linux.dev,
	Masahiro Yamada <masahiroy@kernel.org>,
	llvm@lists.linux.dev, Nick Desaulniers <ndesaulniers@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	greybus-dev@lists.linaro.org, Alex Shi <alexs@kernel.org>,
	Federico Vaga <federico.vaga@vaga.pv.it>,
	Hu Haowen <src.res@email.cn>,
	linux-btrfs <linux-btrfs@vger.kernel.org>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	linux-doc-tw-discuss@lists.sourceforge.net,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Subject: Re: [PATCH] Kbuild: remove -std=gnu89 from compiler arguments
Date: Mon, 28 Feb 2022 09:07:03 +0100	[thread overview]
Message-ID: <CAK8P3a3Lv_uSXt9yf-9iOV3hZgV7KvwZjL-gbLTLRgo0UOQguw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whWbENRz-vLY6vpESDLj6kGUTKO3khGtVfipHqwewh2HQ@mail.gmail.com>

On Sun, Feb 27, 2022 at 11:36 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> And I don't want somebody with a newer compiler version to not notice
> that he or she ended up using a c17 feature, just because _that_
> compiler supported it, and then other people get build errors because
> their compilers use gnu11 instead by default.
>
> Put another way: I see absolutely no upside to allowing different
> users using higher/lower versions of the standard. There are only
> downsides.
>
> If gnu11 is supported by gcc-5.1 and up, and all the relevant clang
> versions, then let's just pick that.

Ok, changed my patch to -gnu11 now.

> And if there are any possible future advantages to gnu17 (or eventual
> gnu2x versions), let's document those, so that we can say "once our
> compiler version requirements go up sufficiently, we'll move to gnuXX
> because we want to take advantage of YY".
>
> Please?

I think all of the options here are equally bad: picking gnu11 means
we use a non-standard default for anything other than gcc-5 and
may get surprised again in the future when we want to change to
a newer version; -std=gnu1x would work as an alias for gnu17 in
all versions including gcc-5 but is already marked as 'deprecated'
in the gcc documentation; and using -std=gnu17 for modern compilers
requires a workaround for gcc-7 and earlier.

Regarding new features from gcc-2x, I think we already use
most of what is listed in https://en.wikipedia.org/wiki/C2x, as
those are all GNU extensions that are valid in modern gnu89 as
well. Newly added features seem to only depend on the compiler
version, e.g. #elifdef works in both clang-13 and gcc-12 with
any -std=gnu?? argument, so picking an earlier standard won't
stop people from breaking the build with older compilers.

         Arnd

WARNING: multiple messages have this Message-ID
From: Arnd Bergmann <arnd@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	 Masahiro Yamada <masahiroy@kernel.org>,
	llvm@lists.linux.dev,  Jonathan Corbet <corbet@lwn.net>,
	Federico Vaga <federico.vaga@vaga.pv.it>,
	Alex Shi <alexs@kernel.org>,  Hu Haowen <src.res@email.cn>,
	Michal Marek <michal.lkml@markovi.net>,
	 Nick Desaulniers <ndesaulniers@google.com>,
	 "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-doc-tw-discuss@lists.sourceforge.net,
	 Linux ARM <linux-arm-kernel@lists.infradead.org>,
	 intel-gfx <intel-gfx@lists.freedesktop.org>,
	 dri-devel <dri-devel@lists.freedesktop.org>,
	greybus-dev@lists.linaro.org,  linux-staging@lists.linux.dev,
	linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH] Kbuild: remove -std=gnu89 from compiler arguments
Date: Mon, 28 Feb 2022 09:07:03 +0100	[thread overview]
Message-ID: <CAK8P3a3Lv_uSXt9yf-9iOV3hZgV7KvwZjL-gbLTLRgo0UOQguw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whWbENRz-vLY6vpESDLj6kGUTKO3khGtVfipHqwewh2HQ@mail.gmail.com>

On Sun, Feb 27, 2022 at 11:36 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> And I don't want somebody with a newer compiler version to not notice
> that he or she ended up using a c17 feature, just because _that_
> compiler supported it, and then other people get build errors because
> their compilers use gnu11 instead by default.
>
> Put another way: I see absolutely no upside to allowing different
> users using higher/lower versions of the standard. There are only
> downsides.
>
> If gnu11 is supported by gcc-5.1 and up, and all the relevant clang
> versions, then let's just pick that.

Ok, changed my patch to -gnu11 now.

> And if there are any possible future advantages to gnu17 (or eventual
> gnu2x versions), let's document those, so that we can say "once our
> compiler version requirements go up sufficiently, we'll move to gnuXX
> because we want to take advantage of YY".
>
> Please?

I think all of the options here are equally bad: picking gnu11 means
we use a non-standard default for anything other than gcc-5 and
may get surprised again in the future when we want to change to
a newer version; -std=gnu1x would work as an alias for gnu17 in
all versions including gcc-5 but is already marked as 'deprecated'
in the gcc documentation; and using -std=gnu17 for modern compilers
requires a workaround for gcc-7 and earlier.

Regarding new features from gcc-2x, I think we already use
most of what is listed in https://en.wikipedia.org/wiki/C2x, as
those are all GNU extensions that are valid in modern gnu89 as
well. Newly added features seem to only depend on the compiler
version, e.g. #elifdef works in both clang-13 and gcc-12 with
any -std=gnu?? argument, so picking an earlier standard won't
stop people from breaking the build with older compilers.

         Arnd

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID
From: Arnd Bergmann <arnd@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Michal Marek <michal.lkml@markovi.net>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>,
	linux-staging@lists.linux.dev,
	Masahiro Yamada <masahiroy@kernel.org>,
	llvm@lists.linux.dev, Nick Desaulniers <ndesaulniers@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	greybus-dev@lists.linaro.org, Alex Shi <alexs@kernel.org>,
	Federico Vaga <federico.vaga@vaga.pv.it>,
	Hu Haowen <src.res@email.cn>,
	linux-btrfs <linux-btrfs@vger.kernel.org>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	linux-doc-tw-discuss@lists.sourceforge.net,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Subject: Re: [Intel-gfx] [PATCH] Kbuild: remove -std=gnu89 from compiler arguments
Date: Mon, 28 Feb 2022 09:07:03 +0100	[thread overview]
Message-ID: <CAK8P3a3Lv_uSXt9yf-9iOV3hZgV7KvwZjL-gbLTLRgo0UOQguw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whWbENRz-vLY6vpESDLj6kGUTKO3khGtVfipHqwewh2HQ@mail.gmail.com>

On Sun, Feb 27, 2022 at 11:36 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> And I don't want somebody with a newer compiler version to not notice
> that he or she ended up using a c17 feature, just because _that_
> compiler supported it, and then other people get build errors because
> their compilers use gnu11 instead by default.
>
> Put another way: I see absolutely no upside to allowing different
> users using higher/lower versions of the standard. There are only
> downsides.
>
> If gnu11 is supported by gcc-5.1 and up, and all the relevant clang
> versions, then let's just pick that.

Ok, changed my patch to -gnu11 now.

> And if there are any possible future advantages to gnu17 (or eventual
> gnu2x versions), let's document those, so that we can say "once our
> compiler version requirements go up sufficiently, we'll move to gnuXX
> because we want to take advantage of YY".
>
> Please?

I think all of the options here are equally bad: picking gnu11 means
we use a non-standard default for anything other than gcc-5 and
may get surprised again in the future when we want to change to
a newer version; -std=gnu1x would work as an alias for gnu17 in
all versions including gcc-5 but is already marked as 'deprecated'
in the gcc documentation; and using -std=gnu17 for modern compilers
requires a workaround for gcc-7 and earlier.

Regarding new features from gcc-2x, I think we already use
most of what is listed in https://en.wikipedia.org/wiki/C2x, as
those are all GNU extensions that are valid in modern gnu89 as
well. Newly added features seem to only depend on the compiler
version, e.g. #elifdef works in both clang-13 and gcc-12 with
any -std=gnu?? argument, so picking an earlier standard won't
stop people from breaking the build with older compilers.

         Arnd

  reply	other threads:[~2022-02-28  8:07 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-27 21:52 Arnd Bergmann
2022-02-27 21:52 ` [Intel-gfx] " Arnd Bergmann
2022-02-27 21:52 ` Arnd Bergmann
2022-02-27 21:52 ` Arnd Bergmann
2022-02-27 22:36 ` Linus Torvalds
2022-02-27 22:36   ` [Intel-gfx] " Linus Torvalds
2022-02-27 22:36   ` Linus Torvalds
2022-02-27 22:36   ` Linus Torvalds
2022-02-28  8:07   ` Arnd Bergmann [this message]
2022-02-28  8:07     ` [Intel-gfx] " Arnd Bergmann
2022-02-28  8:07     ` Arnd Bergmann
2022-02-28  8:07     ` Arnd Bergmann
2022-02-27 23:04 ` [greybus-dev] " Alex Elder
2022-02-27 23:04   ` [Intel-gfx] " Alex Elder
2022-02-27 23:04   ` Alex Elder
2022-02-27 23:04   ` Alex Elder
2022-02-27 23:11   ` Linus Torvalds
2022-02-27 23:11     ` Linus Torvalds
2022-02-27 23:11     ` Linus Torvalds
2022-02-27 23:11     ` [Intel-gfx] " Linus Torvalds
2022-02-27 23:57     ` Alex Elder
2022-02-27 23:57       ` [Intel-gfx] " Alex Elder
2022-02-27 23:57       ` Alex Elder
2022-02-27 23:57       ` Alex Elder
2022-02-28  8:11   ` Arnd Bergmann
2022-02-28  8:11     ` [Intel-gfx] " Arnd Bergmann
2022-02-28  8:11     ` Arnd Bergmann
2022-02-28  8:11     ` Arnd Bergmann
2022-02-28  0:14 ` John Stoffel
2022-02-28  0:14   ` [Intel-gfx] " John Stoffel
2022-02-28  0:14   ` John Stoffel
2022-02-28  0:14   ` John Stoffel
2022-02-28  8:11   ` Arnd Bergmann
2022-02-28  8:11     ` [Intel-gfx] " Arnd Bergmann
2022-02-28  8:11     ` Arnd Bergmann
2022-02-28  8:11     ` Arnd Bergmann
2022-02-28 12:02 ` Christoph Hellwig
2022-02-28 12:02   ` Christoph Hellwig
2022-02-28 12:02   ` [Intel-gfx] " Christoph Hellwig
2022-02-28 21:07 ` [Intel-gfx] ✗ Fi.CI.SPARSE: warning for " Patchwork
2022-02-28 21:36 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2022-03-01  6:20 ` [Intel-gfx] ✓ Fi.CI.IGT: " Patchwork

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