Code Exported C++ Referencing Max Objects, How To Replace in Code?

You would need to provide your own implementations for the genlib_buffer_* methods, according to what is needed by your application. They are all marked "// to be implemented" in the genlib.cpp file -- that's where you'd create your own implementation.

Alternatively, to avoid touching C++, you might be able to replace the [buffer] objects in your genpatcher with [data] objects. For the most part, if you have e.g. a [buffer foo] that refers to an external [buffer~ foo 500 2], you could replace it with a [data foo 0.5*samplerate 2] with no other changes needed in the genpatcher. If you needed to fill the buffer with specific data, like a wavetable, a common pattern is to use a codebox that runs once, like this:

History init(1);
if (init) {
    init = 0; // make sure this only happens once
    
    // for each frame of tbe data:
    for (i=0; i<dim(foo); i+=1) {
        // compute phase (0..1)
        phase = i/dim(foo);
        // convert to sine function:
        value = sin(phase*twopi);
        // channel 0:
        poke(foo, value, i, 0);
        // channel 1:
        poke(foo, value, i, 1);
    }
}

Example: