the margo_bulk_free() function doesn't have a mid (margo instance) argument
Unlike most other margo functions (most notably the margo_bulk_create() function that is naturally paired with margo_bulk_free()), margo_bulk_free() does not have a margo instance argument.
This makes it impossible to associate activity (e.g. diagnostic counters) in that function with the corresponding margo instance.
There might not be any reasonable way to fix it; the API function is widely used.