Const keyword and pointer, const keyword pointer

Const keyword and pointer, const keyword pointer

Four cases of const and pointer combination

The four situations are as follows:

Int cons * p itself is not a constant, and p points to the address of the data is a constant

Const int * p itself is not a constant, and p points to the address of the data is a constant

Int * const p is a constant, and p points to an address space that is not a constant.

Const int * const p is a constant, and the address space pointed to by p is also a constant

 

Summary: When const is on the left side of *, it modifies the data of the address pointed by p. When const is on the right side of *, the modified p

 

When a variable is modified with const, the value of the variable can still be modified with the pointer in gcc.

Int main (void)

{
Const int a = 5;
// A = 6; // error: assignment of read-only variable 'A'
Int * p;
P = (int *) & a; // The alert height here can be eliminated by force type conversion
* P = 6;
Printf ("a = % d. \ n", a); // a = 6, the result shows that the const type variable is changed

Return 0;

}