In file included from main.cpp:16:0:
prime_gen.h: In member function 'int PrimeNumberGenerator::GetNextPrime()':
prime_gen.h:19:5: error: expected ';' before 'return'
     return this->number;
     ^~~~~~
prime_gen.h:20:3: error: no return statement in function returning non-void [-Werror=return-type]
   }
   ^
cc1plus: all warnings being treated as errors