linux-kernel - Re: [PATCH 2/2] include/linux/typecheck.h: Zero initialize dummy variables

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=whL8rmneKbrXpccouEN1LYDtEX3L6xTr20rkn7O_XT4uw@mail.gmail.com>
Date: Thu, 1 May 2025 16:28:25 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Masahiro Yamada <masahiroy@...nel.org>, 
	Nicolas Schier <nicolas.schier@...ux.dev>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, patches@...ts.linux.dev, 
	stable@...r.kernel.org, Linux Kernel Functional Testing <lkft@...aro.org>, 
	Marcus Seyfarth <m.seyfarth@...il.com>
Subject: Re: [PATCH 2/2] include/linux/typecheck.h: Zero initialize dummy variables

On Thu, 1 May 2025 at 16:00, Nathan Chancellor <nathan@...nel.org> wrote:
>
> +({     type __dummy = {}; \
> +       typeof(x) __dummy2 = {}; \

I'm actually surprised that this doesn't cause warnings in itself.

The types in question are not necessarily compound types, and can be
simple types like 'int'.

The fact that you can write

       int x = {};

without the compiler screaming bloody murder about that insanity blows
my mind, but it does seem to be valid C (*).

How long has that been valid? Because this is certainly new to the
kernel, and sparse does complain about this initializer.

So honestly, this will just cause endless sparse warnings instead. I
think disabling this warning for now is likely the right thing to do.

                Linus

(*) Yes, the empty initializer is new in C23, but we've used that in
the kernel for non-scalar objects for a long time.