Re: [PATCH v5 04/26] rust: alloc: implement `Allocator` for `Kmalloc`

[Benno Lossin]

On 12.08.24 20:22, Danilo Krummrich wrote:
> +    /// # Safety
> +    ///
> +    /// This method has the same safety requirements as `Allocator::realloc`.

Please make this a link.

> +    unsafe fn call(
> +        &self,
> +        ptr: Option<NonNull<u8>>,
> +        layout: Layout,
> +        flags: Flags,
> +    ) -> Result<NonNull<[u8]>, AllocError> {
> +        let size = aligned_size(layout);
> +        let ptr = match ptr {
> +            Some(ptr) => ptr.as_ptr(),
> +            None => ptr::null(),
> +        };
> +
> +        // SAFETY: `ptr` is either NULL or valid by the safety requirements of this function.
> +        let raw_ptr = unsafe {
> +            // If `size == 0` and `ptr != NULL` the memory behind the pointer is freed.
> +            self.0(ptr.cast(), size, flags.0).cast()
> +        };
> +
> +        let ptr = if size == 0 {

Why do you do this check *after* calling `self.0`?

---
Cheers,
Benno

> +            NonNull::dangling()
> +        } else {
> +            NonNull::new(raw_ptr).ok_or(AllocError)?
> +        };
> +
> +        Ok(NonNull::slice_from_raw_parts(ptr, size))
> +    }
> +}