Getting two different result for pow() function on two different Linux OS

Question

Here is my code

#include<stdio.h>
#include<math.h>

void main(void)
{
    printf("pow as double: %lf\n\r", pow(2,32));
    printf("pow as long int: %ld\n\r", ((long int)pow(2,32)));
}

I compiled the code on 2 different Linux OS. (gcc powfn.c -o powfn)

On VirtualBox Ubuntu, I got the following result

pow as double: 4294967296.000000  
pow as long int: 4294967296

On Debian GNU/Linux 8 OS running on a Znyq ARM Cortex A9 processor, I got the following result

pow as double: 4294967296.000000
pow as long int: 2147483647  

What is going on? Why the two different results?

Answer 1

It's highly likely the two processors have different sizes for the same data types. You can test it by compiling and running this code on both machines:

#include <stdio.h>
int main()
{
    int integerType;
    long int longIntType;
    float floatType;
    double doubleType;
    char charType;

    // Sizeof operator is used to evaluate the size of a variable
    printf("Size of int: %ld bytes\n",sizeof(integerType));
    printf("Size of long int: %ld bytes\n",sizeof(longIntType));
    printf("Size of float: %ld bytes\n",sizeof(floatType));
    printf("Size of double: %ld bytes\n",sizeof(doubleType));
    printf("Size of char: %ld byte\n",sizeof(charType));

    return 0;
}

Here is the result of running the program on a Wandboard with Cortex-A9 and Ubuntu 15.10:

wandboard:~$ ./test.exe
Size of int: 4 bytes
Size of long int: 4 bytes
Size of float: 4 bytes
Size of double: 8 bytes
Size of char: 1 byte