dynamic array not allocating correctly

[fafner]

I need to allocate an array of unsigned chars to hold rgb data. Here's the code:

int size = vp.vres * vp.hres * 3;
std::cout << size << std::endl;
pixel_data = new uchar[size];
std::cout << sizeof(pixel_data)/sizeof(uchar) << std::endl;

This writes out:

7500
4

What am I doing wrong here? Why is the allocated space for the array so much smaller than it should be?

EDIT: uchar is just typedef unsigned char uchar;

[m4ster r0shi]

fafner wrote:

What am I doing wrong here?

Nothing. pixel_data is a pointer, not an array. sizeof(pixel_data) returns the size of a pointer, which is 4 bytes.

[fafner]

Ah, ok, I see. It's just that my program crashes because somehow there's not enough space allocated, so I thought maybe this was the cause. Oh well. Thanks anyway;)

EDIT: So how would I go about to find the actual size of the array?

[LBEaston]

Maybe sizeof(uchar[size]) for this case

[firedraco]

The size of the array would be...size >_>

[LBEaston]

Oh yeah... Kind of obvious in hindsight.

[m4ster r0shi]

If you want to check whether the crash is caused by writing
past the bounds of your array, you could do something like this:

#include <iostream>
#include <vector>
using namespace std;

template <class T>
struct DynamicArray
{
    vector<T> data;

    DynamicArray(int n):data(n) {}

    T & operator[](int i) { return data.at(i); }
};

int main()
{
    DynamicArray<int> arr(5);

    cout << arr[4] << endl;
    cout << arr[5] << endl;

    return 0;
}

http://cplusplus.com/reference/stl/vector/at/