Indirection Operator: *

 

The latest version of this topic can be found at Indirection Operator: *.

Syntax

* cast-expression  

Remarks

The unary indirection operator (*) dereferences a pointer; that is, it converts a pointer value to an l-value. The operand of the indirection operator must be a pointer to a type. The result of the indirection expression is the type from which the pointer type is derived. The use of the * operator in this context is different from its meaning as a binary operator, which is multiplication.

If the operand points to a function, the result is a function designator. If it points to a storage location, the result is an l-value designating the storage location.

The indirection operator may be used cumulatively to dereference pointers to pointers. For example:

// expre_Indirection_Operator.cpp  
// compile with: /EHsc  
// Demonstrate indirection operator  
#include <iostream>  
using namespace std;  
int main() {  
   int n = 5;  
   int *pn = &n;  
   int **ppn = &pn;  
  
   cout  << "Value of n:\n"  
         << "direct value: " << n << endl  
         << "indirect value: " << *pn << endl  
         << "doubly indirect value: " << **ppn << endl  
         << "address of n: " << pn << endl  
         << "address of n via indirection: " << *ppn << endl;  
}  

If the pointer value is invalid, the result is undefined. The following list includes some of the most common conditions that invalidate a pointer value.

• The pointer is a null pointer.

• The pointer specifies the address of a local item that is not visible at the time of the reference.

• The pointer specifies an address that is inappropriately aligned for the type of the object pointed to.

• The pointer specifies an address not used by the executing program.

See Also

Expressions with Unary Operators
C++ Operators
C++ Built-in Operators, Precedence and Associativity
Address-of Operator: &
Indirection and Address-of Operators