[TUHS] Unix stories

[Ron Natalie]

> I assume you're imagining it as being equivalent to i = j + i + 1, with a redundant store operation.

It's what the language standard specifies, not imagination.  C and C++ state that modifying twice between sequence points or using the value other than to compute the value for a store is undefined behavior.
The languages put no constraint on what may happen when you do this.