Changes in value output

[PeterPea]

template<typename T>
class AClass{
public:
  AClass(){
    std::cout<<"AClass is called with "<<var<<'\n';
  }
private:
  T var;
};

int main(){
  AClass<int> m;
  return 0;
} 

Weird value of var will certainly be output but why it changes everytime I make any change in AClass ?

[cilu]

Because it's never initialize? So var's value is undefined? What do you think?

[PeterPea]

But why does it change each time I add something to the class ?

[philkr]

Because you change the alignment in memory, when you change the class.

[Hobson]

But why does it change each time I add something to the class ?

In your program var value is not initialized, and noone knows why its value is what it is. It depends on everything, like memory layout of your program, OS, and curent weather in Tokyo.

[sreehari]

In your program var value is not initialized, and noone knows why its value is what it is. It depends on everything, like memory layout of your program, OS, and curent weather in Tokyo.

......

[Mattrang]

Your mind will take you far

[exterminator]

POD types are not default initialized. You need to initialize them yourself. Had it been a non-POD type object (var) - something for which the operator<< were overloaded to work with std::cout - you would have had got the same value over and over again. Since int is a POD type - you get garbage - that could be same for the first 1 million times and never get that value ever...