Debugging InvalidMemoryOperationError

[Sam via Digitalmars-d-learn]

On Monday, 11 July 2016 at 13:01:31 UTC, Adam D. Ruppe wrote:
> The stack trace also says this is being triggered from the 
> garbage collector. Do you have a dynamic array of RefCounted 
> objects, or one inside a class object?
>
> I'm not sure as to the nature of the bug but refcounted inside 
> a GC object isn't going to work well anyway.

I find this code:

	// FIXME: D arrays don't call element destructors when GC-d :(
         RoundBuf!CramSlice _input_queue;

Where CramSlice contains RcPtr!(cram_slice, cram_free_slice) and 
RcPtr contains a RefCounted (allowing a custom free function, 
wrapping C API - see 
https://github.com/lomereiter/sambamba/blob/master/cram/wrappers.d#L14). What exactly are the two failure modes you are alluding to?