Error in Bubble sort. Getting an input wrong - c

Question

I have the following source and when I execute it the values are getting their signs changed. I am not able to find out where I am going wrong. Any suggestions is helpful
Code
#include <stdio.h>
#include <stdlib.h>
int arrsort(int *arr, int size);
int display(int *arr, int size);
int main()
{
int s_o_1=0, s_o_2=0;
int i; //index for arrays
int a[s_o_1],b[s_o_2];
printf("enter the size of the first array\n");
scanf("%d",&s_o_1);
printf("Enter the values of the first array\n");
for (i=0;i<s_o_1;i++)
{
scanf("%d",&a[i]);
}
printf("enter the size of the second array\n");
scanf("%d",&s_o_2);
printf("Enter the values of the second array\n");
for (i=0;i<s_o_2;i++)
{
scanf("%d",&b[i]);
}
//sort the first array
arrsort(a,s_o_1);
printf("The sorted first array is\n");
display(a,s_o_1);
//sort the second array
arrsort(b,s_o_2);
printf("The sorted second array is\n");
display(b,s_o_2);
}
int arrsort(int *arr, int size)
{
int temp; //for holding the temp value
int i; //for indexing
int j;
for(j=0;j<size;j++)
{
for(i=0;i<size;i++)
{
if(arr[i]>arr[i+1])
{
temp=arr[i];
arr[i]=arr[i+1];
arr[i+1]=temp;
}
}
}
}
int display(int *arr, int size)
{
int i; //array index
for (i=0;i<size;i++)
{
printf("%d\t",i);
}
printf("\n");
for (i=0;i<size;i++)
{
printf("%d\t",arr[i]);
}
printf("\n");
}
Output
enter the size of the first array
5
Enter the values of the first array
1 5 -10 -15 3
enter the size of the second array
5
Enter the values of the second array
-3 -5 15 9 10
The sorted first array is
0 1 2 3 4
-15 -10 3 5 10
The sorted second array is
0 1 2 3 4
-15 -10 -5 -3 9

Answer 1

The problem is the array declaration:
int s_o_1=0, s_o_2=0;
int i; //index for arrays
int a[s_o_1],b[s_o_2];
The arrays are probably declared with size 0. Either declare with an appropriate maximum size, or declare after reading the sizes for the arrays.

Answer 2

Your code has undefined behaviour. In this line:
int a[s_o_1],b[s_o_2];
It declares arrays with zero size. When later get values for s_o_1 and s_o_2 the array size won't change. So all your reads & writes lead to undefined behaviour.
C standard requires array should be of non-zero length.

Answer 3

The way you reserve memory is not correct int a[s_o_1],b[s_o_2];
You must use int *a, *b; and later after scanf("%d",&s_o_1); you need to do something like a = (int*)malloc(sizeof(int)*s_o_1);
The same goes to allocating memory for b.
Also bubble sort alghorithm should be something like bellow
for(j=0;j<size - 1;j++)
{
for(i=j + 1;i<size;i++)
{
if(arr[i]>arr[j])
{
temp=arr[i];
arr[i]=arr[j];
arr[j]=temp;
}
}
}