[v2,2/2] sample: rust: print: Add sampe code for Arc printing

  This both demonstrates the usage of different print format in Rust and
serves as a selftest for the `Display` and `Debug` implementation of
`Arc` and its friends.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Finn Behrens <fin@nyantec.com>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
---
 samples/rust/rust_print.rs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
  

On Tue,  7 Feb 2023 10:52:16 -0800
Boqun Feng <boqun.feng@gmail.com> wrote:

> This both demonstrates the usage of different print format in Rust and
> serves as a selftest for the `Display` and `Debug` implementation of
> `Arc` and its friends.
> 
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
> Reviewed-by: Finn Behrens <fin@nyantec.com>
> Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
>  samples/rust/rust_print.rs | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/samples/rust/rust_print.rs b/samples/rust/rust_print.rs
> index 8b39d9cef6d1..165a8d7b1c07 100644
> --- a/samples/rust/rust_print.rs
> +++ b/samples/rust/rust_print.rs
> @@ -15,6 +15,30 @@ module! {
>  
>  struct RustPrint;
>  
> +fn arc_print() -> Result {
> +    use kernel::sync::*;
> +
> +    let a = Arc::try_new(1)?;
> +    let b = UniqueArc::try_new("hello, world")?;
> +
> +    // Prints the value of data in `a`.
> +    pr_info!("{}", a);
> +
> +    // Uses ":?" to print debug fmt of `b`.
> +    pr_info!("{:?}", b);
> +
> +    let a: Arc<&str> = b.into();
> +    let c = a.clone();
> +
> +    // Uses `dbg` to print, will move `c`.
> +    dbg!(c);
> +
> +    // Prints debug fmt with pretty-print "#" and number-in-hex "x".
> +    pr_info!("{:#x?}", a);
> +
> +    Ok(())
> +}
> +
>  impl kernel::Module for RustPrint {
>      fn init(_module: &'static ThisModule) -> Result<Self> {
>          pr_info!("Rust printing macros sample (init)\n");
> @@ -43,6 +67,8 @@ impl kernel::Module for RustPrint {
>          pr_cont!(" is {}", "continued");
>          pr_cont!(" with {}\n", "args");
>  
> +        arc_print()?;
> +
>          Ok(RustPrint)
>      }
>  }
  

Boqun Feng <boqun.feng@gmail.com> writes:

> This both demonstrates the usage of different print format in Rust and
> serves as a selftest for the `Display` and `Debug` implementation of
> `Arc` and its friends.
>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
> Reviewed-by: Finn Behrens <fin@nyantec.com>
> Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
> ---

Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>


>  samples/rust/rust_print.rs | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>
> diff --git a/samples/rust/rust_print.rs b/samples/rust/rust_print.rs
> index 8b39d9cef6d1..165a8d7b1c07 100644
> --- a/samples/rust/rust_print.rs
> +++ b/samples/rust/rust_print.rs
> @@ -15,6 +15,30 @@ module! {
>  
>  struct RustPrint;
>  
> +fn arc_print() -> Result {
> +    use kernel::sync::*;
> +
> +    let a = Arc::try_new(1)?;
> +    let b = UniqueArc::try_new("hello, world")?;
> +
> +    // Prints the value of data in `a`.
> +    pr_info!("{}", a);
> +
> +    // Uses ":?" to print debug fmt of `b`.
> +    pr_info!("{:?}", b);
> +
> +    let a: Arc<&str> = b.into();
> +    let c = a.clone();
> +
> +    // Uses `dbg` to print, will move `c`.
> +    dbg!(c);
> +
> +    // Prints debug fmt with pretty-print "#" and number-in-hex "x".
> +    pr_info!("{:#x?}", a);
> +
> +    Ok(())
> +}
> +
>  impl kernel::Module for RustPrint {
>      fn init(_module: &'static ThisModule) -> Result<Self> {
>          pr_info!("Rust printing macros sample (init)\n");
> @@ -43,6 +67,8 @@ impl kernel::Module for RustPrint {
>          pr_cont!(" is {}", "continued");
>          pr_cont!(" with {}\n", "args");
>  
> +        arc_print()?;
> +
>          Ok(RustPrint)
>      }
>  }
  

On Tue, Feb 7, 2023 at 7:52 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> +    // Uses `dbg` to print, will move `c`.
> +    dbg!(c);

Perhaps:

    // Uses `dbg` to print, will move `c` (for temporary debugging purposes).
    dbg!(c);

To make it clear it is not meant to be usually committed into the tree.

> +    // Prints debug fmt with pretty-print "#" and number-in-hex "x".
> +    pr_info!("{:#x?}", a);

Apparently, `:#x?` is a bit of an accident: `#` means "alternate"
form, but it turns out it applies to both `x` and `?`, i.e. it is not
that `#` alone implies pretty-printing.

Given the above and that there are improvements under discussion
upstream, perhaps we could avoid giving details for the moment and
just say what it does as a whole, e.g.

    // Pretty-prints the debug formatting with lower-case hexadecimal integers.
    pr_info!("{:#x?}", a);

Some links for those interested:
https://doc.rust-lang.org/std/fmt/index.html#sign0,
https://github.com/rust-lang/rust/issues/75766,
https://github.com/rust-lang/rust/pull/99138#issuecomment-1385331055
and https://github.com/rust-lang/libs-team/issues/165.

Finally, there is a small typo in the commit title. What about:

    rust: samples: print: add sample code for `Arc` printing

I can change these bits on my side if you want & agree with them, to
avoid a v3 just for this.

Thanks for these patches, Boqun!

Cheers,
Miguel
  

On Wed, Feb 08, 2023 at 04:19:04PM +0100, Miguel Ojeda wrote:
> On Tue, Feb 7, 2023 at 7:52 PM Boqun Feng <boqun.feng@gmail.com> wrote:
> >
> > +    // Uses `dbg` to print, will move `c`.
> > +    dbg!(c);
> 
> Perhaps:
> 
>     // Uses `dbg` to print, will move `c` (for temporary debugging purposes).
>     dbg!(c);
> 
> To make it clear it is not meant to be usually committed into the tree.
> 

Thanks!

> > +    // Prints debug fmt with pretty-print "#" and number-in-hex "x".
> > +    pr_info!("{:#x?}", a);
> 
> Apparently, `:#x?` is a bit of an accident: `#` means "alternate"
> form, but it turns out it applies to both `x` and `?`, i.e. it is not
> that `#` alone implies pretty-printing.
> 

Oh, good to know!

> Given the above and that there are improvements under discussion
> upstream, perhaps we could avoid giving details for the moment and
> just say what it does as a whole, e.g.
> 
>     // Pretty-prints the debug formatting with lower-case hexadecimal integers.
>     pr_info!("{:#x?}", a);
> 
> Some links for those interested:
> https://doc.rust-lang.org/std/fmt/index.html#sign0,
> https://github.com/rust-lang/rust/issues/75766,
> https://github.com/rust-lang/rust/pull/99138#issuecomment-1385331055
> and https://github.com/rust-lang/libs-team/issues/165.
> 
> Finally, there is a small typo in the commit title. What about:
> 
>     rust: samples: print: add sample code for `Arc` printing
> 

Hmm.. I'm OK with this change, but it's not a typo ;-)

I deliberately

1)	capitalize the first letter after subsystem tags in the title
	since that's kinda the rule for a few subsystems I usually work
	on, I don't have my own preference, just something I'm used to
	;-)

2)	avoid using "`" in the title to save space because title space
	is precious.

> I can change these bits on my side if you want & agree with them, to
> avoid a v3 just for this.
> 

That'll be great, thanks!

Regards,
Boqun

> Thanks for these patches, Boqun!
> 
> Cheers,
> Miguel
  

On Wed, Feb 8, 2023 at 5:34 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> Hmm.. I'm OK with this change, but it's not a typo ;-)

By typo I meant the "sampe", not the other changes -- sorry, I should
have been more clear.

> 1)      capitalize the first letter after subsystem tags in the title
>         since that's kinda the rule for a few subsystems I usually work
>         on, I don't have my own preference, just something I'm used to
>         ;-)

Yeah, I don't mind one way or the other (in fact, personally I prefer
uppercase slightly because it is a bit easier to "scan" visually to
see where it starts after the prefixes). The lowercase one is just the
one we have used so far for Rust (which I picked looking at what Linus
et al. usually do).

> 2)      avoid using "`" in the title to save space because title space
>         is precious.

I see, makes sense, thanks!

Cheers,
Miguel
  

On Wed, Feb 08, 2023 at 05:56:43PM +0100, Miguel Ojeda wrote:
> On Wed, Feb 8, 2023 at 5:34 PM Boqun Feng <boqun.feng@gmail.com> wrote:
> >
> > Hmm.. I'm OK with this change, but it's not a typo ;-)
> 
> By typo I meant the "sampe", not the other changes -- sorry, I should
> have been more clear.

Ah, good eyes! Sorry I missed that twice: one when submitting and one
you mention it's a typo ;-(


Regards,
Boqun

> 
> > 1)      capitalize the first letter after subsystem tags in the title
> >         since that's kinda the rule for a few subsystems I usually work
> >         on, I don't have my own preference, just something I'm used to
> >         ;-)
> 
> Yeah, I don't mind one way or the other (in fact, personally I prefer
> uppercase slightly because it is a bit easier to "scan" visually to
> see where it starts after the prefixes). The lowercase one is just the
> one we have used so far for Rust (which I picked looking at what Linus
> et al. usually do).
> 
> > 2)      avoid using "`" in the title to save space because title space
> >         is precious.
> 
> I see, makes sense, thanks!
> 
> Cheers,
> Miguel