What happens to a variable of a member function having same name as that of a private data member of the same class?

Question

When i compile the code below i don't get any error and on debugging it initializes the class data member a of class abc to zero. Can someone just tell me how is the compiler differentiating between the two. I dont see it happening in runtime.

//A function friendly to two classes (finding maximum of objects of 2 classes(one data member in class)
#include <iostream>
#include <conio.h>
using namespace std;

class abc; //Forward Declaration
class xyz
{
  int x;
  public :
  void inivalue(float);
  friend float max(xyz,abc);
};

class abc
{
  int a;
  public :
  void inivalue(float);
  friend float max(xyz,abc);
};

void xyz::inivalue(float y)
{
  x=y;
}

void abc::inivalue(float a)
{
  a=a;
}

float max(xyz m,abc n)
{
  if(m.x > n.a)
  return m.x;

  else
  return n.a;
}

int main()
{
  system("cls");
  xyz o1;
  abc o2;
  o1.inivalue(10);
  o2.inivalue(20);
  cout<<"The maximum of 2 classes is : "<<max(o1,o2)<<endl;
}

Its also pretty unfriendly to someone trying to read your code if it ever gets any more complex than what you have. — Bobby Tables, Oct 19 '20 at 17:11
Helpful reading: [Shadowing variables](https://stackoverflow.com/questions/19621785/shadowing-variables) — user4581301, Oct 19 '20 at 17:14
Your compiler can warn you about shadowed variables. In short turn on all warnings. Treat warnings like errors (it will pay off in the long run). — Martin York, Oct 19 '20 at 19:42

Gary Strivin' · Accepted Answer · 2020-10-19T17:24:36.617

0

That's called "variable shadowing".

When you do that, the local variable a "shadows" the class variable. The compiler will use the local variable, so in the inivalue function of the class abc you're just setting the parameter value to itself.

The a member of the class is unitialized when it is used in the max and the code will result in Undefined Behaviour.

edited Oct 19 '20 at 17:24

answered Oct 19 '20 at 17:19

Gary Strivin'

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What happens to a variable of a member function having same name as that of a private data member of the same class?

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