Question

void ParticleGeneratorController::generate() {
    for( unsigned i = 0; i < generators.size(); i++) {
        ParticleGenerator generator = *generators[i];
        generator.update();
    }
}

Seems to call a copy constructor or something, but I didn’t define one. I only have an explicit default constructor.

https://github.com/ChrisLundquist/Waveform/blob/master/src/models/particle_generator.h

Given my above code, by test fails. https://github.com/ChrisLundquist/Waveform/blob/master/spec/controllers/particle_generator_controller_spec.cpp#L21

When written as

void ParticleGeneratorController::generate() {
    for( unsigned i = 0; i < generators.size(); i++) {
        generators[i]->update();
    }
}

The test passes.

Why is the copy constructor called in the first implementation? How is it generated by the compiler?

Answer 1

This line causes the copy:

ParticleGenerator generator = *generators[i];

If no copy constructor (or assignment operator) is explicitly specified, the compiler automatically generates one. If you wish to prevent copying of an object you can declare, and not define, the copy constructor and assignment operator as private:

ParticleGenerator
{
public:

private:
    ParticleGenerator(const ParticleGenerator&);
    ParticleGenerator& operator=(const ParticleGenerator&);
};