Casting

---

Static Cast

A static cast allows casts whose types are compatible. It will catch const type casting errors at compile time.
File: static1.cpp

#include <iostream>
using namespace std ;


int main()
{
     int x1 = 10;
     float f1 = 10.5 ;
     x1 = static_cast<int>(f1);
     cout << "x1:" << x1 << endl ;

     //Undefined behavior
     //Not recommended
     const int x2 = 11 ;
     int* ptr1 = static_cast<int*>(&x2) ;
     *ptr1 = 12 ;
     cout << "x2:" << x2 << endl ;

}
$ rm a.exe ; g++ static1.cpp ; ./a.exe
static1.cpp: In function ‘int main()’:
static1.cpp:15:18: error: invalid ‘static_cast’ from type ‘const int*’ to type ‘int*’
   15 |      int* ptr1 = static_cast(&x2) ;
      |                  ^~~~~~~~~~~~~~~~~~~~~~
bash: ./a.exe: No such file or directory

The "static_cast" catches the const cast issue. However it allows
wrong inheritance casting.

File: static2.cpp

#include <iostream>
using namespace std ;

class A
{
    public:
     int x1 ;
};

class B : public A
{
    public:
     int x1B ;
};

class C : public A
{
    public:
     int x1C ;

};


int main()
{
     int x1 = 10;
     float f1 = 10.5 ;
     x1 = static_cast<int>(f1);
     cout << "x1:" << x1 << endl ;


     B bObject ;
     bObject.x1B = 22 ;
     A* aObject = &bObject  ;
     //Not valid as aObject contains bObject as the
     //underlying object
     C* cObject = static_cast<C*> (aObject) ;
     cout << cObject->x1C   << endl ;


}


$ rm a.exe ; g++ static2.cpp ; ./a.exe
x1:10
22

We notice that static_cast did not give us any compile time or
run time errors. For this type of inheritance based casting we
should use dynamic casting.