In my processBlock function, I’ve simply created a vector with an initial size, which should allocate heap memory.
I just re-tried by explicitly creating the vector itself on the heap as well:
std::default_random_engine generator;
std::uniform_int_distribution<int> distribution(1,6);
int dice_roll = distribution(generator);
auto *buf = new std::vector<float>(dice_roll);
std::cout << buf->size();
delete buf;
Interesting, it seems to be that LTO in release build disables the operator new hooks.
If you run it in debug mode or with LTO turned off you should see the allocations.