Thanks for the review, Richard. Here is a new patch that hopefully addresses your feedback.
I'm honestly a bit uncertain about how I'm handling the LHS of an assignment. Evaluating it as an LValue makes sense because, as you pointed out, there may be overflow there. However I don't see anything particularly useful that can be done with the result, particularly since I go on to set LHSOK to false. That said, the code looks awkward enough that it feels like I could be overlooking something here.

Refreshing a _very_ old patch.