Question

I know I shouldn’t use Dev-C++ but it’s mandatory in school so I can’t do anything about it.

Topic is pointers in C/C++ and a bug occurred while measuring the length of an integer array. See the code below:

// POINTER
# include<iostream>
# include<string.h>

using namespace std;

int main(){
    //neues Feld anlegen
    int *a = new int[5];

    a[0] = 12;
    a[1] = 5;
    a[2] = 43;
    a[3] = -12;
    a[4] = 100;
    // Feld füllen

    for(int i = 0; i<sizeof(a);i++){
            cout<<a[i]<<"\n"<<endl;
            }
    cout<<sizeof(a);
    system("pause");
    return 0;

}

The sizeof() returns 4 and not 5…Any ideas?

Answer 1

It is not a bug because its returning the size of a itself (which is of type int* – 4 bytes on a 32 bit build), not the length of the array.

Please note – others say that the size is dependent on the operating system, which is half-true. It really depends on the build. sizeof is a compile-time construct.