CODEWITHSUNDEEP
c++
Tyler S.
Tyler S.

Reputation: 13

Multiple class definition error in C++, is something wrong with my header files?

I only declare the class once in a .hpp file and implement its member functions in another .cpp file. The .cpp and .hpp file in that order are below. I get the errors in the .cpp file. The first is on the 6th line saying 'multiple definition of complex::complex'and 'first defined here' This happens for every function, including the overloaded ctor. Am I unintentionally defining all these functions twice when I try to include their prototypes in the .hpp file?

I get no error as long as I include the .hpp file instead of the .cpp in the main file that I use the class in. How does this make any sense? How does the compiler access the .cpp file with all the function definitions?

#include <iomanip>      // For fixed, setprecision()
#include <sstream>      // For stringstream class
#include "Complex.hpp"  // For the complex class declaration


    complex::complex()
    {
        init(0,0);
    }
 
 complex::complex(double init_real, double init_imag)
 {
    init(init_real, init_imag);
 }


 double complex::get_imag()
 {
     return m_imag;
 }


    double complex::get_real()
    {
        return m_real;
    }


//--------------------------------------------------------------------------------------------------
void complex::init(double init_real, double init_imag)
    {
        m_real = init_real;
        m_imag = init_imag;
    }

void complex::set_imag(double s)
    {
        m_imag = s;
    }
-
void complex::set_real(double s)
    {
        m_real = s;
    }


std::string complex::to_string()
{
    std::stringstream sout;
    sout << std::fixed << std::setprecision(4);
    sout << "(" << get_real();
    double imag = get_imag();
    if (imag < 0) {
        sout << " - " << -imag << 'i';
    } else if (imag > 0) {
        sout << " + " << imag << 'i';
    }
    sout << ")";
    return sout.str();
}

#ifndef COMPLEX_HPP  // See the comments in the header comment block regarding these two lines.
#define COMPLEX_HPP

#include <string> // Included because we are using the string class in to_string()
class complex
{
    public:

    complex();

    complex(double , double);

    double get_imag();

    double get_real();

    void set_imag(double);

    void set_real(double);

    std::string to_string();

    private:

    void init(double , double );

    double m_real;

    double m_imag;
};

#endif

The main file where these are used: 

#include <fstream> // For ofstream class declaration
#include <iostream> // For cout, endl
#include "Complex.hpp" // So we can access the complex class declaration (hint: see Complex.cpp)
#include <string>


int main()
{
    std::string filename; filename = "complex-test.txt";
    std::ofstream...
    .
    .
    .
    return 0;
}

Upvotes: 1

Views: 269

Answers (1)

Abhinav
Abhinav

Reputation: 1490

Including a cpp file is equivalent to importing the definition in that file. That means you have a definition in cpp file where it is actually defined and the definition silently gets into the file where you include. That way the linker generates 2 copies of definition for same function and gets confused. Compile should be fine but link would cause problems. Try avoiding cpp file inside #include

Upvotes: 2

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