Question

I’ve this code:

#include <stdio.h>
#include <stdlib.h>
#define OUT

void getDataFromServer(OUT int** array, OUT int* size)
{
    int tmpArr[] = {0x00, 0x01, 0x02, 0x03,  0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
                        0x10, 0x11, 0x12, 0x13,  0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F};
    *size = sizeof tmpArr / sizeof(int);
    *array = tmpArr;
}

int main(void)
{
    int size = 0;
    int* dataFromServer;
    getDataFromServer(&dataFromServer, &size);

    int x;
    for (x=0; x < size; x++)
        printf("%d ", dataFromServer[x]);
    printf("\n\n");

    return 0;
}

The for loop inside the main prints garbage data.. Is this because of the OUT int** array parameter access data local to a function?

Thanks.

Answer 1

When getDataFromServer exits, all local variables are popped off of the stack. The pointer you’re using is now pointing at an area of memory that has more or less been wiped out. Either use malloc and copy the data into newly allocated memory (on the heap), or make tmpArr into a static variable.