Arduino IDE compiler error multiple definition

I have a problem in compiling my arduino sketch.

I get these error:

C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:6: multiple definition of `Bit_Array::Bit_Array(unsigned long)'
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp\bit_array.cpp.o:C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:6: first defined here
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp\Master_Controller_modbus_RTU.cpp.o: In function `Bit_Array::~Bit_Array()':
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:18: multiple definition of `Bit_Array::~Bit_Array()'
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp\bit_array.cpp.o:C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:18: first defined here
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp\Master_Controller_modbus_RTU.cpp.o: In function `Bit_Array::~Bit_Array()':
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:18: multiple definition of `Bit_Array::~Bit_Array()'
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp\bit_array.cpp.o:C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:18: first defined here
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp\Master_Controller_modbus_RTU.cpp.o: In function `Bit_Array::Set_Value_MSB(unsigned char, unsigned long, unsigned char)':
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:26: multiple definition of `Bit_Array::Set_Value_MSB(unsigned char, unsigned long, unsigned char)'
C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp\bit_array.cpp.o:C:\Users\FRANCE~1\AppData\Local\Temp\build8652217817452966608.tmp/bit_array.cpp:26: first defined here
collect2.exe: error: ld returned 1 exit status
Errore durante la compilazione

This means that I've defined more than one time my Constructor, destructor and methods. I'm a little bit confused because I've defined it only one time, as you can see.

bit_array.h

#ifndef bit_array
#define bit_array

// includo il supporto per le funzioni base dell'arduino
#if defined(ARDUINO) && ARDUINO >= 100
  #include "Arduino.h"
#else
  #include "WProgram.h"
  #include <pins_arduino.h>
#endif


#include<cstdint> // libreria per supporto tipo uint8_t in C++ standard (arduino lo conosce, ma voglio fare la libreria cross-plattform)

class Bit_Array
    {
     private:
        unsigned long N_Elementi;                 // Numero di bit della memoria effettivamente utilizzati (es 15 bit occupano 2byte, ma solo i primi 15bit hanno significato). 
        uint8_t* Array;                           // array di uint8_t. Ogni uint8_t verrà interpretato come una sequenza di 8 bool
        unsigned long Dimensione;                 // Dimensione (in byte) della memoria puntata da Array. Deve essere allocata una quantità di memoria pari a upper_bound(N_elementi/8)

     public:
        Bit_Array(const unsigned long Number_of_Elements);
        ~Bit_Array();

        // Getters
        uint8_t Get_Value_MSB(const unsigned long Inizio, const uint8_t Lunghezza ) const;
        uint8_t Get_Value_LSB(const unsigned long Inizio, const uint8_t Lunghezza ) const;           // Implementazione futura

        // Setters
        void Set_Value_MSB(const uint8_t B, const unsigned long Inizio, const uint8_t Lunghezza);
        void Set_Value_LSB(const uint8_t B, const unsigned long Inizio, const uint8_t Lunghezza);    // Implementazione futura
        void Print() const; 
    };

#endif

bit_array.cpp

#include "bit_array.h"

Bit_Array::Bit_Array(const unsigned long Number_of_Elements)
    {
      if(Number_of_Elements <= 0)
            {Array=NULL;}        // non alloco la memoria
      else
            {
             N_Elementi = Number_of_Elements;
             Dimensione = (unsigned long) (( (double)Number_of_Elements/8.0 ) + 0.5);   // alloco una quantità di memoria sufficiente a memoriazzare i Number_of_Elements. La memoria viene allocata con granularità di byte, quindi devo allocare Number_of_Elements/8 byte e poi arrotondare per eccesso

            }
    }

Bit_Array::~Bit_Array()
    {if(Array!=NULL)
        {delete Array;
         Array=NULL;}
     }


 void Bit_Array::Set_Value_MSB(const uint8_t B, const unsigned long Inizio, const uint8_t Lunghezza)
    {

    }

In main I only

#include "bit_array.cpp"

The same thing happen with all other my method.

Using DevC++ IDE, i can successfully compile the code, so I think that the problem is related to Arduino IDE.

Thank you very much for you help, I wish you a nice day

Solution

I would advice you to have a look at this article, for a better understanding of the include directive.

C++ programs are built in a two stage process. First, each source file is compiled on its own. The compiler generates intermediate files for each compiled source file. These intermediate files are often called object files -- but they are not to be confused with objects in your code. Once all the files have been individually compiled, it then links all the object files together, which generates the final binary (the program).

Even though MyClass is declared in your program, it is not declared in main.cpp, and therefore when you compile main.cpp you get that error.

This is where header files come in. Header files allow you to make the interface visible to other .cpp files

So indeed, you need to include the header file, not the source. Hope this helps.