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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

Indirection Operator: *

* cast-expression

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.

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