I think this is 6.3.2.3.7 in C99 about casting between pointer types:

> If the resulting pointer is not correctly aligned for the pointed-to type, the behavior is undefined.

However, unless I’m missing something, producing such a pointer from an integer is apparently not insta-UB? 6.3.2.2.5:

> An integer may be converted to any pointer type. Except as previously specified, the result is implementation-defined, might not be correctly aligned, might not point to an entity of the referenced type, and might be a trap representation

And later on 6.5.3.2.4:

> If an invalid value has been assigned to the pointer, the behavior of the unary * operator is undefined.

Which implies that the invalid pointer must have been obtained without being already undefined, right?