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Date: Tue, 18 Mar 2025 19:46:49 +0100
From: Danilo Krummrich <dakr@kernel.org>
To: Tamir Duberstein <tamird@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>,
	Benno Lossin <benno.lossin@proton.me>,
	Andrew Ballance <andrewjballance@gmail.com>,
	Miguel Ojeda <ojeda@kernel.org>,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Andreas Hindborg <a.hindborg@kernel.org>,
	Trevor Gross <tmgross@umich.edu>, rust-for-linux@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] rust: alloc: add `Vec::dec_len`
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In-Reply-To: <CAJ-ks9mHvjPn98mcXh3q18nB5pPH6YBj3jf1YH6510bP-mtFtQ@mail.gmail.com>

On Tue, Mar 18, 2025 at 02:28:02PM -0400, Tamir Duberstein wrote:
> On Tue, Mar 18, 2025 at 10:44 AM Alice Ryhl <aliceryhl@google.com> wrote:
> >
> > On Tue, Mar 18, 2025 at 10:12:28AM -0400, Tamir Duberstein wrote:\
> > >
> > > The methods you're describing are all on Vec, right? In other words,
> > > their usage calls for a private `dec_len` or `set_len`. As I've said
> > > repeatedly in the course of this discussion: I would prefer not to
> > > introduce `dec_len` at all here. It (or `set_len`) can be introduced
> > > in the series that adds truncate or your patch that adds clear, where
> > > its signature can be properly scrutinized in the context of an actual
> > > caller.
> >
> > Oh I did not see that you said that. Dropping patch 2 is fine with me.
> >
> > Alice
> 
> Benno, Danilo: are you both OK with this? I'll discard this patch on
> the respin and prepend the patch adding the len <= cap invariant.

I mean, the whole reason to switch set_len() to inc_len() and have a separate
dec_len() was to properly cover things like [1] and Alice' patch by having
dec_len() return the abandoned entries.

If we now only switch set_len() to inc_len() and drop dec_len() then what should
Andrew do?

Maybe we should just revert to Tamir's first proposal, i.e. keep set_len() as it
is, but make it return the abandoned entries, if any.

[1] https://lore.kernel.org/rust-for-linux/20250316111644.154602-1-andrewjballance@gmail.com/