Software Design by Example 10: Build Manager

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Make was the first programming support tool I ever learned how to use, and forty-one years later, I still reach for it whenever I need to automate a workflow. I know there are dozens of others, many of which are objectively better in various ways, but I suppose you never forget your first love.

But that’s not why Software Design by Example includes this chapter on how build managers work—at least, it’s not the main reason. A build manager’s primary responsibility is to manage a directed (hopefully acyclic) graph, so showing people how to implement one is a natural way to introduce fundamental graph algorithms like cycle detection and topological sorting.

As I was revising the book I realized that I should have implemented a second build manager that used observer/observable rather than explicitly constructing and traversing a graph. Comparing the central control of the graph-based implementation with the decentralized execution of the one I didn’t build would have been even more interesting than the discussion of either option, but by the time that was clear I had run out of steam. It’s on the list for the Python version; I’ll let you know in a few months whether my energy levels picked up or not.

Template Method pattern
Figure 10.3: The Template Method pattern in action.

Terms defined: automatic variable, build manager, build recipe, build rule, build target, compiled language, cycle (in a graph), dependency, directed acyclic graph, driver, interpreted language, link (a program), pattern rule, runnable documentation, stale (in build), Template Method pattern, topological order.