Memory allocation

Question

Hi, some enlightment... Could someone...

int *ptr;
/* a block of 10 ints */
ptr = malloc(10 * sizeof(*ptr));

if (ptr != NULL) {
*(ptr + 2) = 50; /* assign 50 to third int */
}

*ptr = 40 bytes... 10*40.... 400 allocated... Ptr is null, despite...? (Ptr + 2) pointer? Ptr takes the value, index...? Tks.

Answer 1

Wait.. Already... Ignore about the ptr address... The variable itself have an address, what is not the same that pointers.. Ok..

Answer 2

I didn't understand your question

Answer 3

Which part of this code you need help with? the `if` part, the `malloc` part, the pointer arithmetic part?

Answer 4

Yes.... Despite alloc, is null? Why ptr is allocated with memory, and no your adress? And the pointer arithmetic... :) Tks in addition!

Answer 5

int *ptr;
// define a pointer of int

ptr = (int*)malloc(10 * sizeof(int));
// allocate memory block, big enough to contain 10 int value
// assign the memory block address for <ptr> variable
if (ptr != NULL)
{
// ptr will be NULL if malloc failed in allocating memory
// ptr != NULL here means memory allocation succeeded
*(ptr + 2) = 50;
// set the third int value to 50
}

Answer 6

Hi tks for ask... Some enlightment about the expression, basically.