Re: C aggregate passing (Rust kernel policy)

[henrychurchill@mailo.com]

---- Original message ----
> From: Linus Torvalds <torvalds@linux-foundation.org>
> To: Jan Engelhardt <ej@inai.de>
> Subject: Re: C aggregate passing (Rust kernel policy)
> Date: 02/21/2025 21:26:02 Europe/Paris
> Cc: David Laight <david.laight.linux@gmail.com>;
>       H. Peter Anvin <hpa@zytor.com>;
>       Greg KH <gregkh@linuxfoundation.org>;
>       Boqun Feng <boqun.feng@gmail.com>;
>       Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>;
>       Christoph Hellwig <hch@infradead.org>;
>       rust-for-linux <rust-for-linux@vger.kernel.org>;
>       David Airlie <airlied@gmail.com>;
>       linux-kernel@vger.kernel.org;
>       ksummit@lists.linux.dev
> 
> On Fri, 21 Feb 2025 at 12:06, Jan Engelhardt <ej@inai.de> 
wrote:
> >
> > >(Apart from the fact that c++ makes it hard to ensure all 
the non-class
> > >members are initialised.)
> >
> >         struct stat x{};
> >         struct stat x = {};
> >
> > all of x's members (which are scalar and thus non-class) 
are
> > initialized. The second line even works in C.
> 
> Yeah. People love to talk about "safe C", but compiler people 
have
> actively tried to make C unsafer for decades. The C 
standards
> committee has been complicit. I've ranted about the crazy C 
alias
> rules before.
> 

The unsafe subset of Rust has way stricter aliasing rules than 
C. You should read up on unsafe before touching it in Rust, it 
can get gnarly.