XNFrealloc(void *ptr, unsigned long amount)
{
    void *ret = realloc(ptr, amount);
    if (!ret)
	FatalError("XNFrealloc: Out of memory");
    return ret;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.