Just like normal variables, pointers can be declared constant. There are two different ways that pointers and const can be intermixed, and they are very easy to mix up.
To declare a const pointer, use the const keyword between the asterisk and the pointer name:
|
1
2
|
int
nValue = 5;int
*const
pnPtr = &nValue; |
Just like a normal const variable, a const pointer must be initialized to a value upon declaration, and its value can not be changed. This means a const pointer will always point to the same value. In the above case, pnPtr will always point to the address of nValue. However, because the value being pointed to is still non-const, it is possible to change the value being pointed to via dereferencing the pointer:
|
1
|
*pnPtr
= 6; //
allowed, since pnPtr points to a non-const int |
It is also possible to declare a pointer to a constant variable by using the const before the data type.
|
1
2
|
int
nValue = 5;const
int
*pnPtr = &nValue; |
Note that the pointer to a constant variable does not actually have to point to a constant variable! Instead, think of it this way: a pointer to a constant variable treats the variable as constant when it is accessed through the pointer.
Thus, the following is okay:
|
1
|
nValue
= 6; //
nValue is non-const |
But the following is not:
|
1
|
*pnPtr
= 6; //
pnPtr treats its value as const |
Because a pointer to a const value is a non-const pointer, the pointer can be redirected to point at other values:
|
1
2
3
4
5
|
int
nValue = 5;int
nValue2 = 6;const
int
*pnPtr = &nValue;pnPtr
= &nValue2; //
okay |
Confused? To summarize:
Finally, it is possible to declare a const pointer to a const value:
|
1
2
|
const
int
nValue;const
int
*const
pnPtr = &nValue; |
A const pointer to a const value can not be redirected to point to another address, nor can the value it is pointing to be changed.
Const pointers are primarily used for passing variables to functions. We will discuss this further in the section on functions.
Just like normal variables,,布布扣,bubuko.com
原文：http://blog.csdn.net/u012402926/article/details/37722415