Re: [PATCH 1/3 proxmox-rrd-migration-tool] use libc::c_char instead of i8 to fix mismatched type

[Maximiliano Sandoval <m.sandoval@proxmox.com>]

A small nit below.

Luke Yasuda <jing@jing.rocks> writes:

> Otherwise this fails on non-amd64 arches:
>
> error[E0308]: mismatched types
>    --> src/main.rs:374:17
>     |
> 374 |     source[0] = file.0.as_ptr();
>     |     ---------   ^^^^^^^^^^^^^^^ expected `*const i8`, found `*const u8`
>     |     |
>     |     expected due to the type of this binding
>     |
>     = note: expected raw pointer `*const i8`
>                found raw pointer `*const u8`
>
> error[E0308]: mismatched types
>    --> src/main.rs:386:13
>     |
> 381 |         let res = rrd_create_r2(
>     |                   ------------- arguments to this function are incorrect
> ...
> 386 |             source.as_mut_ptr(),
>     |             ^^^^^^^^^^^^^^^^^^^ expected `*mut *const u8`, found `*mut *const i8`
>     |
>     = note: expected raw pointer `*mut *const u8`
>                found raw pointer `*mut *const i8`
>
> Signed-off-by: Luke Yasuda <jing@jing.rocks>
> ---
>  Cargo.toml  | 1 +
>  src/main.rs | 3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/Cargo.toml b/Cargo.toml
> index 4574e32..a637278 100644
> --- a/Cargo.toml
> +++ b/Cargo.toml
> @@ -14,6 +14,7 @@ anyhow = "1"
>  pico-args = "0.5"
>  proxmox-async = "0.5"
>  crossbeam-channel = "0.5"
> +libc = "0.2"
>  
>  [build-dependencies]
>  bindgen = "0.71"
> diff --git a/src/main.rs b/src/main.rs
> index 799cde8..b2b9bbe 100644
> --- a/src/main.rs
> +++ b/src/main.rs
> @@ -8,6 +8,7 @@ use std::{
>  };
>  
>  use anyhow::{bail, Context, Error, Result};
> +use libc::c_char;
>  
>  use proxmox_rrd_migration_tool::{rrd_clear_error, rrd_create_r2, rrd_get_context, rrd_get_error};
>  
> @@ -370,7 +371,7 @@ fn do_rrd_migration(
>          bail!("refusing to migrate metrics for {resource:?} - target already exists and 'force' not set!");
>      }
>  
> -    let mut source: [*const i8; 2] = [std::ptr::null(); 2];
> +    let mut source: [*const libc::c_char; 2] = [std::ptr::null(); 2];

I would recommend to use [c_char] from the standard library here.

[c_char] https://doc.rust-lang.org/std/ffi/type.c_char.html

>      source[0] = file.0.as_ptr();
>  
>      let target_path = CString::new(target_path.to_str().unwrap()).unwrap();

-- 
Maximiliano