Considering this code, VC9 doesn't detect aliasing :

```
typedef struct { int x, y; } vec_t;

void rotate_cw(vec_t const *from,
               vec_t       *to)
{
        /* Notice x depends on y and vice versa */
        to->x = from->y;
        to->y = -from->x;
}

/* ... */
vec_t a, b;
rotate_cw(&a, &b); /* OK, no aliasing */
rotate_cw(&a, &a); /* FAIL, aliasing is not detected */

```

The obvious fix is to use a temporary :

```
void rotate_cw(vec_t const *from,
               vec_t       *to)
{
        int temp = from->x;
        to->x = from->y;
        to->y = -temp;
}

```

Is this standard behavior ? I was expecting that the compiler, unless told so, would assume **both** pointers to be possibly aliased.