Hi Antoine, > AFAIU, the problem only exists with ResizableBuffer?
I think, it comes down to the memory ownership. While Buffer apparently never owns it's memory (based on the doc string), a MutableBuffer can. So if you slice a MutableBuffer, and the memory gets deallocated, you've got the same problem. Your proposed solution seems to be a safe one, we could even use shared_ptr::use_counts. But I'd rather invert the responsibility: a parent buffer can do with it's memory as it pleases, the slices get a way of checking if they are still valid. Maybe we could even include a safe cast to void*, uint8_t* and char* for the buffers (which checks buffers validity), so to discourage reusing of a stale data pointer (like the raw_data* in some ArrayBuilders). So instead of memcpy(buffer.data(), source, N) you'd just use memcpy(buffer, source, N). So the logic would basically be: a Buffer either owns it's memory or is a slice (view). If it's a slice, then it has a way of checking if it's still valid (and hasn't shrunk so the view is not valid anymore). If the slice is built with a raw pointer, then all bets are off, but we should mark such cases as super unsafe, i.e. UnsafeBuffer. Maybe I'm overthinking it, but I can imagine, that it'll come to bite us, when the code base grows. Cheers, Dimitri. On Wed, Apr 11, 2018 at 11:19 AM, Antoine Pitrou <anto...@python.org> wrote: > > Hi Dimitri, > > Le 11/04/2018 à 09:02, Dimitri Vorona a écrit : > > Hi everybody, > > > > to continue the discussion in [0]: right now this [1] can happen and the > > sliced buffer has no way to foresee or to check against it beforehand. > > > > I'd suggest to create a new class SlicedBuffer, which would reference the > > parent buffer and return it's data() pointer, insted of grabbing the > > pointer at creation. We can the parent reference a weak pointer, so the > > existing SliceBuffers don't prevent the deallocation (or maybe even have > a > > separate WeakSliceBuffer class). > > AFAIU, the problem only exists with ResizableBuffer? > > We could do the following: > > - add a new Buffer member counting the number of exports (default 0) > > - in SliceBuffer, increment the parent's number of exports > - in ~Buffer, decrement the parent's number of exports > - in PoolBuffer::Resize(), return an error if the buffer has any exports > > (this is how Python buffers work, for the record) > > What do you think? > > Regards > > Antoine. >
