linux-kernel - Re: [PATCH v10 4/5] rust: replace `kernel::c

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Message-ID: <CAJ-ks9nd6_iGK+ie-f+F0x4kwpyEGJ-kQiQGt-ffdbVN5S6kOg@mail.gmail.com>
Date: Mon, 26 May 2025 18:29:46 -0400
From: Tamir Duberstein <tamird@...il.com>
To: Benno Lossin <lossin@...nel.org>
Cc: Michal Rostecki <vadorovsky@...tonmail.com>, Miguel Ojeda <ojeda@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
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Subject: Re: [PATCH v10 4/5] rust: replace `kernel::c_str!` with C-Strings

On Mon, May 26, 2025 at 11:04 AM Benno Lossin <lossin@...nel.org> wrote:
>
> On Sat May 24, 2025 at 10:33 PM CEST, Tamir Duberstein wrote:
> > +macro_rules! c_str_avoid_literals {
>
> I don't like this name, how about `concat_to_c_str` or
> `concat_with_nul`?
>
> This macro also is useful from macros that have a normal string literal,
> but can't turn it into a `c""` one.

Uh, can you give an example? I'm not attached to the name.

>
> > +    // NB: we could write `($str:lit) => compile_error!("use a C string literal instead");` here but
> > +    // that would trigger when the literal is at the top of several macro expansions. That would be
> > +    // too limiting to macro authors, so we rely on the name as a hint instead.
> >      ($str:expr) => {{
> > -        const S: &str = concat!($str, "\0");
> > -        const C: &$crate::str::CStr = match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
> > -            Ok(v) => v,
> > -            Err(_) => panic!("string contains interior NUL"),
> > -        };
> > +        const S: &'static str = concat!($str, "\0");
> > +        const C: &'static $crate::str::CStr =
> > +            match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
>
> Why is this still our CStr?

Good question. I'll just revert all the changes here, I don't need to
touch this.

>
> > +                Ok(v) => v,
> > +                Err(err) => {
> > +                    let _: core::ffi::FromBytesWithNulError = err;
>
> Is this really necessary?

No. Reverted in v11.