help! (int*)+offset

To start off, here's my code:

Code:

// setting stuff up
std::cout.setf(std::ios::hex);
std::cout.unsetf(std::ios::dec);
int int_size = sizeof(int);

int commands = 5;
int max_bytes = 3;

int byte_array = (int)malloc(int_size*commands*max_bytes);
int* pbyte_array = &byte_array;

cout << (0x0012FF3C+(int_size*1)) << "\n\n";
	
for(int i=0x0;i<commands*max_bytes;i+=0x1)
{
	cout << pbyte_array << "\t+\t";
	cout << i*int_size << "\t=\t";
	cout << pbyte_array+(i*int_size) << "\n";
}

Okay so it compiles fine, but running gives me

Code:

12ff40

0012FF3C	+	0	=	0012FF3C
0012FF3C	+	4	=	0012FF4C
0012FF3C	+	8	=	0012FF5C
0012FF3C	+	c	=	0012FF6C
.................
0012FF3c	+	38	=	0013001C

Basically it's adding 16 each time. If I change it to

Code:

cout << pbyte_array+1

it adds 4 to the output (instead of 1 as it should). I notice if I change pbyte_array declaration to

Code:

int pbyte_array = (int)(&byte_array)

then it works fine (although the hex output becomes lowercase o_O). I have checked the output of int_size and it's 4 as it should be. If I type the address directly into the loop it does the same thing as it does with the changed pbyte_array declaration.

Basically I want a a pointer/address and the addition of an offset.
I'm running Visual C++ 2008

Thanks!

Oh and also I couldn't get arrays to work properly oddly, which is why I created this code in the first place. It kept saying it couldn't convert (int*) to (int).

sizeof(int) = 4. Since you have your array declared as type int, adding one to the pointer will take you to the next int, four bytes away. Since you add (i*int_size), you're adding 4, which means that you go four ints down the line, sixteen bytes away.

PS: int* and int aren't the same thing. What were you trying to do.

So use a type which has a size of 1 (say unsigned char), not 4 (as is the case with your ints).

Thanks, I got it working.. just changed it to

Code:

cout << pbyte_array+i << "\n";

I know they aren't the same.. which is why it confused me, I was just going

Code:

int testarray[];
testarray = new int[5];

my compiler errors are

Code:

'testarray': unknown size.
'=': cannot convert from 'int *' to 'int []'

changing it to

Code:

int[] testarray

didn't help either.. more errors

Obvious way to do that:

Code:

int testarray[5];

Way to do that for people who insist on new:

Code:

int *testarray;
testarray = new int[5];

You can't declare an array without giving it a size.

Okay thanks... I did get a warning with

Code:

int testarray[5];

though. Thanks anyway though!

You obviously don't know what pointers are and what the heap is or how to allocate memory.
When allocating on the heap, we keep track of the memory by the use of pointers.
Anyway, I suggest you stay away from pointer + n, because it's confusing and is obviously confusing you too. Use pointer[n] instead.

Originally Posted by RobotGymnast

Okay thanks... I did get a warning with

Code:

int testarray[5];

though. Thanks anyway though!

What warning?