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Memory allocation

Leadorn · 2002-06-25T05:20:56

Hail I have some questions about memory. If i allocate *ptaData = new int[15]; do i have a array with adresses to 16 different int locations or do i have an pointer to an array on the same memoryplace? Does it look lika this? *ptaData Pointers adress data [0] an andress to int any where [1] an andress to int any where [2] an andress to int any where Or *ptaData Pointer adress an andress to int array any were, but the array will be on the same place after an other. |----------------- | | | | |_______________________ |45 int data | |46 int data | |47 int data | |48 int data | |49 int data | |50 int data | |... in this case i goto 45 then if I want to access the next item num 46 i use ptrData[2] or ptrdata+1 (+sizeof ptrData). One last question. I want to dynamic allocate int *ipData[10](not dynamic); But if i use *ptrData = new int[10]; I allocate 10 int locations. I only want the first pointer array (*ipData) not what it is pointing to. I want the address to be NULL only a var...... *ipData [0] address NULL [1] address NULL

General and Gameplay Programming Programming

Started by Leadorn June 25, 2002 12:36 AM

12 comments, last by Leadorn 21 years, 9 months ago

nicho_tedja

122

June 25, 2002 04:18 AM

NULL == 0;
It''s not a memory address. It means empty. if you do this:

a_ptr = new int* [10];

that means you''re allocating 10 pointers to int which are not yet initialized. so, you have to initialize them again:

for (int i=0; i<10; i++)
a_ptr = new int [100];

by doing this, each pointer in a_ptr points to an array of int of size 100.

if you want to delete it, you do it in the reverse order:
for (int i=0; i<10; i++)
if (a_ptr != NULL) delete [] a_ptr; delete [] a_ptr; however, people usually do it this way: for (int i=0; i<10; i++) { if (a_ptr != NULL) { delete [] a_ptr; a_ptr = NULL; } } delete [] a_ptr; a_ptr = NULL; You don''t have to set it equal to NULL, but it''s just the good way to do it. Sometimes, you''ll also find some benefits by doing that, so it''s a good practice. <hr>My compiler generates one error message: "Doesn''t compile." -Albert Tedja-

My compiler generates one error message: "does not compile."

nicho_tedja

122

June 25, 2002 04:19 AM

i wonder...how come part of my post is in italic?? oh, i see. some parts are recognized as tags. btw, here's the complete code from the above post. some of them are removed accidentally.

    a_ptr = new int* [10];for (int i=0; i<10; i++)a_ptr[i] = new int [100];//if you want to delete it, you do it in the reverse order:for (int i=0; i<10; i++)if (a_ptr[i] != NULL) delete [] a_ptr[i];delete [] a_ptr;//however, people usually do it this way:for (int i=0; i<10; i++) {if (a_ptr[i] != NULL) {delete [] a_ptr[i];a_ptr[i] = NULL;}}delete [] a_ptr;a_ptr = NULL;

[edited by - nicho_tedja on June 25, 2002 5:23:33 AM]

[edited by - nicho_tedja on June 25, 2002 5:24:19 AM]

My compiler generates one error message: "does not compile."

SabreMan

504

June 25, 2002 04:41 AM

quote:Original post by nicho_tedja
however, people usually do it this way:

Which people? Nobody I know does it that way.

Leadorn

100

Author

June 25, 2002 05:20 AM

Why do it this way?
int **pointer_array = new int *[10];

what is the difference between them?

a_ptr = new int* [10];
that means you''re allocating 10 pointers to int which are not yet initialized. so, you have to initialize them again:

Memory allocation

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