Your second link seems to agree with my original post, i.e. it is not UB. Read on to point 20: <a href="http:&#x2F;&#x2F;port70.net&#x2F;~nsz&#x2F;c&#x2F;c11&#x2F;n1570.html#6.7.2.1p20" rel="nofollow">http:&#x2F;&#x2F;port70.net&#x2F;~nsz&#x2F;c&#x2F;c11&#x2F;n1570.html#6.7.2.1p20</a> and it talks about my example of putting the struct in a malloc&#x27;d area of memory with space after the struct.