a simple GP based C++

GOftn* children[];
1>g:\c++_gp\genetic-prog-master\genetic-prog-master\basicfunctions.h(30): warning C4200: nonstandard extension used : zero-sized array in struct/union
1>          Cannot generate copy-ctor or copy-assignment operator when UDT contains a zero-sized array

GOftn* children[1];

GOftn* retFtn;
1>g:\c++_gp\genetic-prog-master\genetic-prog-master\treegeneops.cpp(101): error C4703: potentially uninitialized local pointer variable 'retFtn' used

GOftn* retFtn=0;

//main.c 39 line,   
err = outputs[j] - (initTrees[i]->eval(inputs[j]));