Creating zeroed backend types might crash

[fkaa]

In some places (eg. gfxBindBufferMemory) we create a zeroed type of the backend type and mem::replace it. If the backend type has a Drop impl rust will try to drop this zeroed type which might lead to bad things.

I'm not really sure what the intent of the mem::replace call is, does anyone know?

[kvark]

I think the reason for mem::replace is that we need to move the Unbound buffer out and then get the bound buffer to put back in. Without replace you can either de-reference or unbox, which is not useful here.

But overall, we should totally not drop random zeroed content ;)