A reference to the reference to the normal pointer release memory
First, see a piece of code first:
#include
Using namespace std;
Void FreePtr1 (INT * P1)
{
Delete P1;
P1 = NULL;
}
Void FreePtr2 (INT * & P2)
{
Delete P2;
P2 = NULL;
}
void main ()
{
INT * p1 = new int;
* p1 = 1;
FreePTR1 (P1);
INT * p2 = new int;
* p2 = 2;
FreePTR2 (P2);
System ("pause");
}
Thinking: Can you find them different points in FreePTR1 and FreePTR2?
Second, explain the code:
#include
Using namespace std;
Void FreePtr1 (INT * P1)
{
// Not released before memory -> p1 address: 0012fddc p1 value: 003429b8, here, P1 is also a variable, since it is a variable, then it will pass the external variable P1 to the stack with the value of the value, An address is generated in the stack: 0012FDDC, of course, its value does not change still point to the pile of addresses: 003429b8.
Delete P1; / / The system reclaims the memory at address 003429b8 at the P1 value.
P1 = NULL; // Taking the NULL value of P1: 00000000, Note: The address of the P1 itself is not changed, and the value of P1 is changed.
/ / After release memory -> p1 address: 0012fddc p1 value: 00000000, after the stack, P1 is automatically considered to be invalid after the stack is out.
}
Void FreePtr2 (INT * & P2)
{
// No memory -> p2 address: 0012FEC8 P2 Value: 003429b8, P2 is a reference to a pointer, that is, reference pointed pointer, remember the characteristics of reference: Direct operation of the referenced object. Therefore, its address and value are the same as the main () function outside the stack.
DELETE P2; / / / / The pointer referenced by P2 is released, ie: the system reclaims the memory of the value 003429b8 address in the main () function.
P2 = null; // The pointer to the main () function is defined in a null value.
// Release memory -> p2 address: 0012FEC8 P2 Value: 00000000
}
void main ()
{
INT * p1 = new int;
/ / Pre-release memory -> p1 address: 0012FED4 P1 value: 003429B8
FreePTR1 (P1);
// Release memory -> p1 address: 0012FED4 P1 value: 003429B8
INT * p2 = new int;
// Release memory before -> P2 Address: 0012FEC8 P2 Value: 003429B8
FreePTR2 (P2);
/ / After release memory -> p2 address: 0012FEC8 P2 Value: 00000000
System ("pause");
This is three months later, once again picked up C start school, the above example can make the beginner (of course, I also include it), you can have a new or another understanding of the reference and pointer. Everyone said, good memory is not as bad as a mess, although it is a relatively simple question) ... ^ _ ^, if there is any difference, or personal opinion, please leave a message, thank you.
Thanks again, the Perfect Wasteman (WOLF) provides an example ...
