Hey,
Thanks for your help :) > 1. Bindings create wrappers for C pointers—e.g., with > ‘pointer->device’. If several C functions return a pointer P, you > must make sure to return always the same wrapper and not create a > new one. Agreed. > > ‘pointer->device!’ attempts to do that but I think it’s bogus: it > uses a weak-value hash table, where the value is the wrapper. So > if the wrapper disappears before the underlying C object, then the > pointer is called and bad things ensue. I'm not sure to understand how could the wrapper disappear before the underlying C object? We are only exposing <device> records to the Guile-Parted users so my assumption is that when <device> goes out of scope, the pointer it wraps can be freed, but I'm maybe missing something? > ‘define-wrapped-pointer-type’ in Guile is meant to help with these > things (info "(guile) Void Pointers and Byte Access"). We can’t > use it directly here because we’re using bytestructures and all > that. Turns out, the "wrap" procedure defined in define-wrapped-pointer-type is a clone of pointer->device! except that it doesn't set a finalizer. Regarding object lifetime, I wrote a small memo in 2019 here: https://issues.guix.gnu.org/36402#11. We have three weak hash tables in Guile-Parted: %devices: To make sure that we do not set multiple finalizers on the same pointers. %disk-devices: So that a device always outlives its disks. %partition-disks: So that a disk always outlives its partitions. This means that as far as I can tell we are OK regarding your second point about "aggregation relations". Mathieu
