Problem with structure and organization in big c++ project

Question

I started my first big c++ project, in which I divided the functionality of the program into different files. I ran in a situation where library include each other and there was some declaration problem.

sometingh like this:

in apha.h

#pagma once
#include "betha.h"

struct alpha
{
    int data;
    betha bb;
};

int fun1(apha a);

in betha.h

#pagma once
#include "alpha.h"

struct betha
{
    double data;
    double moreData;
};

int fun2(alpha a, betha b);

I found a solution in transferring all the struct in a separate file struct.h and it works fine. but I was wondering if there was a way to have the struct in their respective libraries because it would make more sense and be easier to work with.

There are many methods to solve this, forward declarations are one of the mostly used method. https://stackoverflow.com/questions/625799/resolve-build-errors-due-to-circular-dependency-amongst-classes — crackaf, Nov 22 '21 at 13:35
Such circular dependency in code is indication of bad code design. — Marek R, Nov 22 '21 at 13:37

Vlad from Moscow · Accepted Answer · 2021-11-22T13:43:11.747

For starters it seems there are two typos in the header name

apha.h

that should be

alpha.h

and in this declaration

int fun1(apha a);

It seems you mean

int fun1(alpha a);

After including the header apha.h in a compilation unit you in fact have

struct betha
{
    double data;
    double moreData;
};

int fun2(alpha a, betha b);

struct alpha
{
    int data;
    betha bb;
};

int fun1(apha a);

As you can see the function func2 refers to the name alpha

int fun2(alpha a, betha b);

that was not yet declared.

You could use either the forward declaration

struct betha
{
    double data;
    double moreData;
};

struct alpha;

int fun2(alpha a, betha b);

or the elaborated type specifier in the function declaration

struct betha
{
    double data;
    double moreData;
};

int fun2( struct alpha a, betha b);

Problem with structure and organization in big c++ project

1 Answers1