Re: [PATCH v2] docs: rust: quick-start: update Ubuntu instructions

[Igor Korotin <igor.korotin@yahoo.com>]

On 4/2/25 12:26, Miguel Ojeda wrote:
> On Wed, Apr 2, 2025 at 12:48 PM Igor Korotin <igor.korotin@yahoo.com> wrote:
>>
>> +``PATH`` needs to be set when installing rust 1.80 with apt, e.g.::
>> +
>> +       PATH=/usr/lib/rust-1.80/bin:$PATH
> 
> Why does it need to be set? i.e. why not `RUSTC=...` for that one too?
> 
> In other words, why are we mixing the approaches? We can explain both,
> but mixing them seems confusing.

I checked what happens with other tools(For example rustdoc) if I define 
only
`RUSTC=rustc-1.80`. Unsurprisingly `rustdoc` remains 1.75, which is 
installed from `rustc` package, which in its turn is dependency for the 
package `bindgen-0.65`. Though I see that this mix works fine, it seems 
a little bit weird when you have one tool of version 1.80 another 1.75, 
etc. Without a doubt one can define each tool explicitly using `RUSTC`, 
`RUSTDOC`, etc. On the other hand defining `PATH` to 
`/usr/lib/rust-1.80/bin/` automatically makes build to use rust-1.80 
tools.

>> +Deb package bindgen-0.65 does not set itself as a default, thus it should be set
>> +explicitly, e.g.::
>> +
>> +       BINDGEN=bindgen-0.65
> 
> I don't think this example adds much, since we already show it below.

This was intention to explain each additional environment part of the 
overall command.

>> +       make LLVM=1 PATH=/usr/lib/rust-1.80/bin:$PATH \
>> +               RUST_LIB_SRC=/usr/src/rustc-$(rustc-1.80 --version | cut -d' ' -f2)/library \
> 
> Note that `RUST_LIB_SRC` (and `PATH`) are not needed there, i.e. those
> two can be set as environment variables.
> 
> Perhaps we could just add something like this to the existing paragraph:
> 
>      ``RUST_LIB_SRC`` needs to be set (possibly as an environment variable) ...

By adding these as part of the overall build command, I was going by 
your earlier statement that you prefer setups that minimize global changes.

> 
> Also, weren't we going to mention `RUSTDOC`, `RUSTFMT` and `CLIPPY_DRIVER`?

This one was supposed to be covered by `PATH=/usr/lib/rust-1.80/bin:$PATH`

Thanks for the review

Best Regards
Igor