linux-kernel - Re: C aggregate passing (Rust kernel policy)

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Message-ID: <CAFJgqgSjRwOUkcC5v6wGcfQ-53oWyWW+wBg3PZ-w7vRweHekpw@mail.gmail.com>
Date: Thu, 27 Feb 2025 07:21:24 -0700
From: Ventura Jack <venturajack85@...il.com>
To: Martin Uecker <uecker@...raz.at>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Ralf Jung <post@...fj.de>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Kent Overstreet <kent.overstreet@...ux.dev>, Gary Guo <gary@...yguo.net>, airlied@...il.com, 
	boqun.feng@...il.com, david.laight.linux@...il.com, ej@...i.de, 
	gregkh@...uxfoundation.org, hch@...radead.org, hpa@...or.com, 
	ksummit@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	miguel.ojeda.sandonis@...il.com, rust-for-linux@...r.kernel.org
Subject: Re: C aggregate passing (Rust kernel policy)

On Wed, Feb 26, 2025 at 1:00 PM Martin Uecker <uecker@...raz.at> wrote:
>
> I think C++ messed up a lot (including time-travel UB, uninitialized
> variables, aliasing ules and much more), but I do not see
> the problem here.

C++26 actually changes the rules of reading uninitialized
variables from being undefined behavior to being
"erroneous behavior", for the purpose of decreasing instances
that can cause UB. Though programmers can still opt-into
the old behavior with UB, on a case by case basis, for the
sake of performance.

Best, VJ.