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

[Benno Lossin]

On 14.08.24 18:59, Danilo Krummrich wrote:
> On Wed, Aug 14, 2024 at 04:21:38PM +0000, Benno Lossin wrote:
>> On 12.08.24 20:22, Danilo Krummrich wrote:
>>> +    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`?
> 
> Because I need `raw_ptr` in the else case below.

But you can just return early above? I would prefer the check be done
before `self.0` is called.

---
Cheers,
Benno