#include <iostream>

void funkcja(double **wsk) {
    delete *wsk;
    *wsk = nullptr;
}

int main(int argc, char **argv) {
    double *a;
    a = new double;

    funkcja(&a);

    a == nullptr ? std::cout << "null\n" : std::cout << "not null\n";

    return 0;
}