Re: [PATCH 2/7] Compiler Attributes: use the no-underscores syntax

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	efriedma@codeaurora.org, Christopher Li <sparse@chrisli.org>,
	Kees Cook <keescook@chromium.org>, Ingo Molnar <mingo@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg KH <gregkh@linuxfoundation.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Joe Perches <joe@perches.com>,
	asmadeus@codewreck.org,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH 2/7] Compiler Attributes: use the no-underscores syntax
Date: Mon, 3 Sep 2018 08:42:26 +0200	[thread overview]
Message-ID: <CAMuHMdV2iDHTJh2PbBzzWNSYLH-hudMB5CWzEEBormGHPMegcw@mail.gmail.com> (raw)
In-Reply-To: <CANiq72mDH1hPTAuB=zmX0uiVEx_mWS-3GO26YUSKXPHRREYjjA@mail.gmail.com>

Hi Miguel,

On Sat, Sep 1, 2018 at 12:41 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
> On Sat, Sep 1, 2018 at 12:10 AM, Miguel Ojeda
> <miguel.ojeda.sandonis@gmail.com> wrote:
> > arch/parisc/boot/compressed/misc.c:#define malloc       malloc_gzip
> > include/linux/decompress/mm.h:#define malloc(a) kmalloc(a, GFP_KERNEL)
> > lib/inflate.c:#define malloc(a) kmalloc(a, GFP_KERNEL)
> > include/linux/compiler_types.h:#define noinline_for_stack noinline
> > include/linux/raid/pq.h:#define noinline __attribute__((noinline))
> > tools/include/linux/compiler.h:#define noinline
> > arch/mips/sgi-ip27/ip27-reset.c:#define noreturn while(1);
>
> A better list, searching for all attributes used anywhere in the kernel:
>
> git grep -E '^\s*#define\s+(address_space|alias|aligned|always_inline|assume_aligned|bitwise|bnd_legacy|cold|common|const|constructor|context|deprecated|designated_init|destructor|error|externally_visible|flatten|force|format|format|gnu_inline|hot|hotpatch|indirect_branch|latent_entropy|long_call|malloc|may_alias|mode|model|naked|nocast|noclone|noderef|noinline|no_instrument_function|nonnull|no_randomize_layout|noreturn|no_sanitize_address|optimize|packed|pure|randomize_layout|regparm|require_context|safe|section|syscall_linkage|target|tls_model|unused|used|user|vector_size|visibility|warning|warn_unused_result|weak)(\(|\s|$)'
>
> arch/mips/sgi-ip27/ip27-reset.c:#define noreturn while(1);
>                  /* Silence gcc.  */
> arch/parisc/boot/compressed/misc.c:#define malloc       malloc_gzip
> arch/powerpc/xmon/ansidecl.h:#define    const
> drivers/gpu/drm/nouveau/nvkm/subdev/bios/init.c:#define error(fmt,
> args...) bioslog(ERROR, fmt, ##args)
> include/linux/compiler_attributes.h:#define   noinline
> __attribute__((noinline))
> include/linux/decompress/mm.h:#define malloc(a) kmalloc(a, GFP_KERNEL)
> include/linux/raid/pq.h:#define noinline __attribute__((noinline))
> lib/inflate.c:#define malloc(a) kmalloc(a, GFP_KERNEL)
> tools/include/linux/compiler-gcc.h:#define  noinline
> __attribute__((noinline))
> tools/include/linux/compiler.h:#define noinline
> tools/testing/selftests/futex/include/logging.h:#define error(message,
> err, args...) \
>
> None of these should make a problem. And it would may avoid people
> using such common-name-macros in the future ;-)

That's very fragile.
Who knows all (current and future) attribute names by heart, and that defining
them could have such side effects?

At least "alias", "force", "format", "mode", "model", "optimize", "target" are
names I wouldn't hesitate to use as a macro name in a driver...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds