Error definition of implicitly declared

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Hello everyone having anissue with my code today. I have created a program calculating area of square circle and rectangle. With a base class of shape. Where the UML has shape as the abstract class with public area():double, getName():string,and getDimensions:string, rectangle derived from shape with protected height, and width, and a public rectangle(h:double, w:double), followed by a derived square from rectangle with just a public square(h:double), and finally a circle derived from shape with a private radius, and a public circle(r:double).
So far have gotten far in my code yet in my shape.cpp file am getting an error on line 10 that says shape.cpp:10: error: definition of implicitly-declared ‘constexpr shape::shape()’
shape::shape()

here is a link to my complete code: https://gist.github.com/anonymous/0eedd7719a34655488fb

shape.cpp file:

#include "shape.h"
#include "circle.h"
#include "rectangle.h"
#include "square.h"
#include <QDebug>
#include <QString>
#include <iostream>
using namespace std;

shape::shape()
{

};

your help is appreciated

Compiler error: definition of implicitly-declared Class

// in the header LS7366.h
	#if !defined		DSPI_PORT						
	#define			DSPI_PORT	DSPI0	// Default DSPI port = DSPI0		
	#endif								
	#define NON_QUADRATURE	0x00
// and a whole buch of other #define lines ...
	
class	LS7366 {
private:	DSPI_PORT DSPIjack	;
and some more code lines   ;  }

// in the code file LS7366.cpp  -  Class definition
LS7366::LS7366 ( ) { }
void LS7366::begin () 	{	
and some more code lines 	; }
and some more functions defined ...
void LS7366 :: end ( ) 	{
and some more code lines ; }	

class	LS7366	{
private:	DSPI_PORT	DSPIjack	;
public:	
LS7366 ( ) ; // Forgot this line in my definition
void	begin ( ) ;
void	end (  ) ; 

With the pre-processor macro

#define sum(...) 
    _sum(sizeof((int []){ __VA_ARGS__ }) / sizeof(int), (int []){ __VA_ARGS__ })

being called with sum(1,2,3), the line is translated (a simple string substitution, replacing "__VA_ARGS__" with "1,2,3") into:

_sum(sizeof((int []){1,2,3}) / sizeof(int), (int []){1,2,3})

which is a function call to _sum() passing two things:

• the number of integers in the array {1,2,3} which is 3 (it gets this by dividing the size of the three-integer array by the size of a single integer).
• the pointer to the array itself (or a totally different array containing the same values, depending on how smart your compiler is).

All the _sum() function does is add each of the integers to s (which is initially zero) until the count runs out.

That first bullet point above bears some explanation. When you have an array of N elements defined as follows:

tType x[22];

the size of the array is sizeof(x), the size of all elements. The size of a single element of that array is sizeof(x[0]), the size of the first element, although I often prefer the sizeof(*x) variant.

So, to count the number of elements, you simply divide the total size by the size of an element, using one of the following:

sizeof(x) / sizeof(x[0])
sizeof(x) / sizeof(*x)

And, since you’ve asked for a detailed analysis of the code, here we go:

// Needed for printf().

#include <stdio.h>

// Macro to convert sum(n1,n2,...,nN) to _sum(N,n1,n2,...,nN).
// This calculates the length of the array by dividing its size by the size
//   of an int and passes both the length and array through to the new
//   function.
// __VA_ARGS__ is replaced with the entire marcro argument list, '1,2,3' in
//   this case.

#define sum(...) 
    _sum(sizeof((int []){ __VA_ARGS__ }) / sizeof(int), (int []){ __VA_ARGS__ })

// Function to take size and pointer to int array, and return sum.

int _sum (size_t count, int values[]) {
    int s = 0;                // Initial sum of zero.
    while(count--)            // Until elements exhausted (count down).
        s += values[count];   // Add each array element to accumulator.
    return s;                 // Return sum.
}

int main (void) {
    printf ("%i", sum(1, 2, 3));   // Test it with 1, 2 and 3 (should print 6).
}

#include <cstdlib>
#include <iostream>
using namespace std;

class classA
{                   
      protected:
                void setX(int a);

      private:
              int p;
};

classA:: classA()
{                      //error here.
 p = 0;
}

void classA:: setX(int a)
{
 p = a;    
}

int main()
{   
    system("PAUSE");
    return EXIT_SUCCESS;
}

class classA
{ 
      public: 
              classA();    // you forgot this!       
      protected:
                void setX(int a);

      private:
              int p;
};

class classA
{                   
      protected:
                classA(); // you were missing an explicit declaration!
                void setX(int a);

      private:
              int p;
};

classA:: classA()
{ 
 p = 0;
}

class classA
{
    // ....
    public:
       classA() ; // Missing the declaration of the default constructor.
};

class classA
{
    // ....
    public:
       classA() { p = 0;} 
};

class classA
{
    // ....
    public:
       classA():p(0) {} 
};

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