The instruction at "<address>" referenced memory at "<address>". The memory could not be "read."

Question

A c/c++ app throws that error, how to start to debug (better idea than adding print statements)?

Answer 1

Is the second address a very small number, like 0x00000001 or 0x00000000? If so, you probably just forgot to initialize a pointer.

In any case, standard debugging tricks apply: start isolating the problem by noticing when it happens and narrowing things down from there.