panic safety issue in impl TransformContent<S, D> for [S; (2|3|4)]

[JOE1994]

Hello 🦀 ,
we (Rust group @sslab-gatech) found a memory-safety/soundness issue in this crate while scanning Rust code on crates.io for potential vulnerabilities.

Issue Description

The issue is relevant to implementation of TransformContent<S, D> trait for [S; 2], [S; 3], and [S; 4].

basic_dsp/matrix/src/lib.rs

Lines 229 to 241 in 7375e9f

	fn transform<F>(self, mut conversion: F) -> Self::Output
	where
	F: FnMut(S) -> D,
	{
	unsafe {
	let result = [
	conversion(ptr::read(&self[0])),
	conversion(ptr::read(&self[1])),
	];
	mem::forget(self);
	result
	}
	}

basic_dsp/matrix/src/lib.rs

Lines 243 to 258 in 7375e9f

	fn transform_res<F>(self, mut conversion: F) -> TransRes<Self::Output>
	where
	F: FnMut(S) -> TransRes<D>,
	{
	unsafe {
	let mut error = None;
	let first = try_conv!(conversion(ptr::read(&self[0])), error);
	let second = try_conv!(conversion(ptr::read(&self[1])), error);
	mem::forget(self);
	match error {
	None => Ok([first, second]),
	Some(err) => Err((err, [first, second])),
	}
	}
	}

If a panic happens within conversion,
item(S) within self can be dropped twice since the ownership of the item within self is duplicated with ptr::read().

Suggested Fix

By keeping self within ManuallyDrop<_> instead of using mem::forget(),
it is possible to guard against such double drop bugs.
I will immediately submit a PR containing the suggested fix.

Thank you for checking out this issue 👍