Isn't sizeof only standardised in C89? Wouldn't shock me if this form needs to be an rvalue.

The author did try pointer arithmetic:

> I initially attempted a fix using pointer arithmetic, but the 1973 C compiler didn’t like it, while it didn’t refuse the syntax, the code had no effect.

This surprised me too. The snippet I was quoting from was already using sizeof, though.

I missed the blurb about pointer arithmetic. Would be interesting to go into detail about what "had no effect" means.