Maybe unsound in RLocal::new

[lwz23]

Hello, thank you for your contribution in this project, I am scanning the unsoundness problem in rust project.
I notice the following code:

pub struct RLocal<T: Copy> {
    old_value: T,
    variable: *mut T,
}

impl<T> RLocal<T>
where
    T: Copy,
{
    pub fn new(new_value: T, variable: *mut T) -> RLocal<T> {
        unsafe {
            let old_value = libr::get(variable);
            libr::set(variable, new_value);

            Self {
                old_value,
                variable,
            }
        }
    }
}

Considering that pub mod raii, and new is also a pub function. I assume that users can directly call this function. This potential situation could result in libr::get being called to a null pointer, and might trigger undefined behavior (UB). For safety reasons, I felt it necessary to report this issue. If you have performed checks elsewhere that ensure this is safe, please don’t take offense at my raising this issue.
I suggest Several possible fixes:

1. If there is no external usage for RLocal or new, they should not marked as pub, at least its new should not marked as pub
2. new method should add additional check for null pointer.
3. mark new method as unsafe and proper doc to let users know that they should provide valid Pointers.

[lionel-]

It's really an internal function from an internal crate (neither are meant to be used in other projects). We can make it pub(crate) for clarity.

[lwz23]

Thanks for your reply, I think maybe same problem for

ark/crates/harp/src/vector/list.rs

Line 65 in a569d6e

unsafe { *self.ptr.wrapping_add(index as usize) }

, the index ptr offset is not been varify.
and

ark/crates/ark/src/sys/unix/console.rs

Line 13 in a569d6e

pub fn console_to_utf8(x: *const c_char) -> anyhow::Result<String> {

ark/crates/ark/src/sys/windows/console.rs

Line 37 in a569d6e

let x = unsafe { CStr::from_ptr(x) };

ark/crates/harp/src/table.rs

Line 162 in 1366044

pub fn get_unchecked(&self, index: isize) -> Option<String> {

I understand that these functions are not intended for external use, but in that case it might be more appropriate to declare them as pub(crate). This will ensure that future projects on these modules will not cause possible unsound problems, thank you!

[lionel-]

Note that we have cross-crate internal dependencies too.