Mastering Delphi Programming: A Complete Reference Guide

Simultaneous reading and writing

The next situation which I'm regularly seeing while looking at a badly-written parallel code is simultaneous reading and writing from/to a shared data structure, such as a list.  The SharedList program demonstrates how things can go wrong when you share a data structure between threads. Actually, scrap that, it shows how things will go wrong if you do that.

This program creates a shared list, FList: TList<Integer>. Then it creates one background thread which runs the method ListWriter and multiple background threads, each running the ListReader method. Indeed, you can run the same code in multiple threads. This is a perfectly normal behavior and is sometimes extremely useful.

The ListReader method is incredibly ...