> I don't see what the undefined behavior. Can you specify exactly the
> item of the Standard, in which it is mentioned?

It's C99 section 6.5, paragraph 7:  "An object shall have its stored value accessed only by an lvalue expression that has one of the following types ...".  It's the dereferencing of the pointer that's the problem: that's accessing a stored value of type 'char' by an lvalue expression that has type 'unsigned long'.

> In any case, I don't think that the original patch introduces some new
> undefined behavior.

Ah;  were the strict aliasing problems already there before the patch?  I didn't check.