[pitaj]

The APIs do tell you how many bytes are actually allocated. For instance, in the following

    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>;

You can get the length of the returned byte slice (`[u8]`) to know how many bytes were actually allocated.

[tialaramex]

That's the (nightly) Allocator::allocate, but the API we were looking at is (stable) GlobalAlloc::alloc

Yes I'm aware that I can ask how long a slice is.

[pitaj]

Ah gotcha. Yeah `GlobalAlloc` is known to be non-ideal. Hopefully we can get a better API soon.