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Date:   Wed, 17 May 2023 19:09:28 +0100
From:   Gary Guo <gary@garyguo.net>
To:     Alice Ryhl <aliceryhl@google.com>
Cc:     nmi@metaspace.dk, alex.gaynor@gmail.com, alice@ryhl.io,
        benno.lossin@proton.me, bjorn3_gh@protonmail.com,
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        ojeda@kernel.org, patches@lists.linux.dev,
        rust-for-linux@vger.kernel.org, wedsonaf@gmail.com,
        yakoyoku@gmail.com
Subject: Re: [PATCH v2] rust: str: add conversion from `CStr` to `CString`
Message-ID: <20230517190928.08cfa0d5.gary@garyguo.net>
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On Tue, 16 May 2023 11:12:02 +0000
Alice Ryhl <aliceryhl@google.com> wrote:

> Andreas Hindborg <nmi@metaspace.dk> writes:
> > Alice Ryhl <alice@ryhl.io> writes:  
> >> On 5/8/23 13:41, Gary Guo wrote:  
> >>> On Wed,  3 May 2023 14:10:16 +0000
> >>> Alice Ryhl <aliceryhl@google.com> wrote:  
> >>>> These methods can be used to copy the data in a temporary c string into
> >>>> a separate allocation, so that it can be accessed later even if the
> >>>> original is deallocated.
> >>>>
> >>>> The API in this change mirrors the standard library API for the `&str`
> >>>> and `String` types. The `ToOwned` trait is not implemented because it
> >>>> assumes that allocations are infallible.  
> >>> How about add a `TryToOwned` trait to the kernel crate and implement
> >>> that trait for `CStr` instead?  
> >>
> >> Eh, I don't think it's worth it. It doesn't give anything new to the CStr api,
> >> and I think it's rather unlikely that someone will actually need to be generic
> >> over such a trait any time soon.  
> > 
> > It is just as valid as having `From<&str>` and `ToOwned<&str>`. While it
> > does not add anything in terms of function, it carries intention. I
> > think we should consider adding it at some point.
> > 
> > BR Andreas  
> 
> Sure, I think its quite reasonable to add new traits, I just don't think
> it should be part of this patch. Adding new traits makes it a
> significantly bigger change IMO, and my changes have an actual user down
> the road.
> 
> Alice

Personally I think `CStr` to `CString` conversion should be implemented
on top of `[u8]` to `Vec<u8>` conversion. Now we have two
conversions that fit in the concept of `TryToOwned`, so a trait is
warranted.

Best,
Gary