In my newly created project, using QBarSet yields strange behavior that is indicative of memory corruption

I will be attaching my entire project to this issue, so that you can better inspect it.

Long story short: I made a new CMakeLists Qt Desktop project for myself in which I allocate a QBarSet object on the heap, I call the count method on it, I inject 3 double values into it and then I call the count method once again.

Both calls give me an output of 0, when, normally, it should give me an output of 0 elements followed by 3 (since I previously injected 3 values into it).

This indicates some level of memory corruption, from somewhere. Running Valgrind on the project also seems to indicate memory corruption, since it tells me that I'm doing an illegal read.

The code seems legal and innocuous. There should be no undefined behavior (or at least none that I can find myself).