Re: [PATCH proxmox v2 02/10] proxmox-alloc: document undefined behavior regarding custom allocs

[Robert Obkircher <r.obkircher@proxmox.com>]

> Add a new example at examples/ub.rs with tests that demonstrate
> incorrect usage & undefined behavior of custom allocations.

I don't think that it is a good idea to include a runnable example,
because it can theoretically format your hard drive, and it will likely
result in false positives from vulnerability scanners.

These examples also conflate allocation of DSTs and over-alignment to a
runtime value, which are completely separate concepts that can be
understood separately.

> 
> Add a hint in the `aware_boxed` module's docs that such an example
> exists in the crate.
> 
> Signed-off-by: Max R. Carrara <m.carrara@proxmox.com>
>
> diff --git a/proxmox-alloc/Cargo.toml b/proxmox-alloc/Cargo.toml
> index 4eeeb787..b16496f6 100644
> --- a/proxmox-alloc/Cargo.toml
> +++ b/proxmox-alloc/Cargo.toml
> @@ -11,6 +11,10 @@ repository.workspace = true
>  license.workspace = true
>  exclude.workspace = true
>  
> +[[example]]
> +crate-type = ["staticlib"]
> +name = "ub"
> +
>  [dependencies]
>  
>  [dev-dependencies]
> diff --git a/proxmox-alloc/examples/ub.rs b/proxmox-alloc/examples/ub.rs
> new file mode 100644
> index 00000000..aa97b02b
> --- /dev/null
> +++ b/proxmox-alloc/examples/ub.rs
> @@ -0,0 +1,99 @@
> +//! This example contains various tests that demonstrate [undefined behavior].
> +//! Needless to say, you should not use what's shown here in your own code.
> +//!
> +//! You can run this example's tests using the following command:
> +//!
> +//! ```text
> +//! cargo test --package proxmox-alloc --example ub
> +//! ```
> +//!
> +//! Alternatively, if you want to see what kinds of [undefined behavior] get
> +//! caught by [Miri], use the following instead:
> +//!
> +//! ```text
> +//! cargo +nightly miri nextest run --package proxmox-alloc --example ub
> +//! ```
> +//!
> +//! Note that this requires [`cargo nextest`][nextest] to be installed on your
> +//! nightly toolchain. This will guarantee that all tests are run, even if they
> +//! fail (which they do when you use Miri).
> +//!
> +//! [Miri]: https://github.com/rust-lang/miri
> +//! [nextest]: https://nexte.st/
> +//! [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
> +
> +#[cfg(test)]

This could be `#[cfg(all(test, miri))]`, but even then I don't think
miri supports something like #[should_panic] but for expected UB.

-- 
Robert Obkircher <r.obkircher@proxmox.com>