The following code which implements a simple insertion sort,
yields, when built with Pelles C for Windows V10.00.6,
a) in debug mode: correct results
b) in release mode without any optimization: correct results
c) in release mode with any speed optimization: *INcorrect* results
d) in release mode with any size optimization: correct results
int main(void)
{
int a_arr[] = {5, 2, 1};
int i;
int j;
int n;
int temp;
n = sizeof(a_arr) / sizeof(a_arr[0]);
puts("Before sorting");
for (i = 0; i < n; ++i)
printf("%i ", a_arr[i]);
putchar('\n');
/*
insertion sort
compare each element to the right (i) with all elements to the left (j)
*/
for (i = 1; i < n; ++i) // start outer loop with second array element to sort
for (j = 0; j < i; ++j) // inner loop always starts with the first of the already sorted array elements
{
if (a_arr[j] > a_arr[i]) // if already sorted element to the left is greater than the element to sort, ...
{
temp = a_arr[i]; // ... save element to sort, ...
memmove(&a_arr[j + 1], &a_arr[j], (i - j) * sizeof(int)); // ... shift all already sorted greater elements 1 postion to the right, ...
a_arr[j] = temp; // ... insert element to sort to the left of the shifted elements, and ...
break; // ... start over with next element to sort
}
}
puts("After sorting");
for (i = 0; i < n; ++i)
printf("%i ", a_arr[i]);
putchar('\n');
}
