Hello, The rule of thumb is too never confuse and avoid mixing:
* untraced pointers (ptr T) * traced pointers (ref T) * stack objects If you want to store the address of a stack object, you are screwed immediatly when the function where your object is defined returns. So you have to copy it. If you want to store the address (I mean casting the ref to a pointer) of a traced object (ref), it is exactly the same problem: the nim GC (ARC) will detect when your object is no longer referenced and dealloc it (for example when your function returns !). It is possible to tell the GC to not do that with GC_ref and GC_unref, but this is not a really good practice. Your best bet is either : * to create and store your objects as ref (no conversion to pointers) * to use directly pointers and manage memory yourself (with all the risks it implies). We generally use that kind of idiom : cast[ptr MyObject](https://forum.nim-lang.org/alloc0\(sizeof MyObject\)) And I you want to share your data with C functions, it depends on what C will do, if C will store the pointer, it is unsafe to pass a ref object or the adress of a stack object.
