XNFstrdup(const char *s)
{
    char *ret;

    if (s == NULL)
	return NULL;

    ret = strdup(s);
    if (!ret)
	FatalError("XNFstrdup: 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.