linux-kernel - Re: [GIT PULL] MM updates for 6.14-rc1

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Message-ID: <CAFULd4Z2eSJhE0qF0QEtsb-7zoOMKH=KvvrfK0M5UozLw_TYUA@mail.gmail.com>
Date: Sun, 26 Jan 2025 20:46:46 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Miguel Ojeda <ojeda@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, 
	mm-commits@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] MM updates for 6.14-rc1

On Sun, Jan 26, 2025 at 7:30 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:

> That does seem to work, but I'd admittedly be happier if we could just
> find some way to dynamically disable/enable __typeof_unqual__ based on
> which compiler is used, rather than make it a config option. So that
> bindgen would not see it, but a recent enough C compiler would.
>
> We already use '__has_attribute()' for some of these things. There's a
> '__has_extension()' thing that comes from clang but that gcc also
> supports.
>
> But I can't find the list of extensions that that model supports, and
> I guess typeof_unqual isn't on that list if I find it.
>
> In the absence of something _clean_ like that, can we just do it in
> <linux/compiler-xyz.h> instead? IOW, not use the CONFIG_xyz tests for
> this at all, but do something like
>
>   /*
>    * bindgen uses LLVM even if our C compiler is gcc, so we cannot
>    * rely on CONFIG_CC_HAS_TYPEOF_UNQUAL
>    */
>   #if __clang_major__ >= 19
>   # define CC_HAS_TYPEOF_UNQUAL 1
>   #endif
>
> in <linux/compiler-clang.h> and the gcc version check for gcc (I don't
> know when __typeof_unqual__ made it)?

It is available in gcc-14.

Uros.