how can i not show a function in header A.h that is used in a function in header B.h but not in main.cpp C++?

Question

so I have two header file (A.h and B.h) and i include B.h in the main.cpp file

//A.h

void foo()
{
    //do something
}

//B.h
#include "A.h"

void foo1()
{
    foo();
    //do something else
}

//main.cpp
#include "B.h"

int main()
{
    foo1();
}

in my testings i haven't found a way to hide foo() in main i should also mention that the functions foo() and foo1() are helper function but i want that the only way i can use foo() is when i include directly A.h is there a way to do this?

Answer 1

Simple solution: Don't define (implement) functions in header files, only declare them. Define them in source files.

Then you would have e.g. a header file A.h:

void foo();

A source file A.cpp:

void foo()
{
    // Do foo stuff...
}

And a B.h header file:

void bar();

And a B.cpp source file:

#include "A.h"

void bar()
{
    // Do bar stuff

    // Call foo
    foo();

    // Do more bar stuff
}

Then finally the main source file where you only include B.h:

#include "B.h"

int main()
{
    bar();

    // Can't call foo, as it's not declared
}

Answer 2

is there a way to do this?

Yes, you can make use of headers files and source files(.cpp) as shown below.

A.h

#ifndef A_H
#define A_H
//this is a declaration
void foo();
#endif

A.cpp

#include "A.h"
//this is the implementation
void foo()
{
    //do something
}

B.h

#ifndef B_H
#define B_H
//this is a declaration
void foo1();
#endif

B.cpp

#include "A.h"

//this is implementation
void foo1()
{
    foo();
    //do something else
}

main.cpp

//main.cpp
#include "B.h"

int main()
{
    foo1();
}

Working demo

Note

It is recommended that we should use header guards in header files.