How t wait while one process ended with ```boost::process```?

Question

I have main program and system windows calculator. I want to run calculator from main prograM then wait while user close it and then give up control to the main program.

I try this solutions:

auto child = boost::process::child("calc.exe");
child.wait();

and

auto child = boost::process::child("calc.exe");
while (child.running()) {}

And in both ways calculator start but main process don't wait until the child closes and run farther.

How I should do this?