Ask HN: What are the ways you go about getting comfortable with a new codebase?

I use "go to definition"/"find references" to go all around the code base and at the same time try to figure out how each files interact with each others.

Projects, especially messy ones, often behave like lava flows where there is an active and ever expanding edge where changes are currently being made. Beneath this are layer upon layer of nearly impenetrable and often implicitly deprecated code from former developers.

This practice came from a time when I was brought in midway through a rewrite to get rid of unmaintainable code from some offshore contractors. I saw a repository where half the code lacked any organizing principles and had massive security issues. The second half was textbook (pedantic even) OOP, the kind taught in Java textbooks. It was beautifully executed except for using a few outdated tricks to do OOP in early versions of PHP (no longer needed in the version used for this project).

Because I didn't look at the dates, I assumed the neat OOP code was the result of the rewrite. I was wrong.

Sort of unrelated, but I've got a story about a project I was looking through that confused the hell out of me. It was a C# library that would allow you to render an element from a shockwave flash file (it was either .swf or .fla).

I spent ages digging through the code. The example worked really well, but I couldn't get it to work with one of my files.

Eventually I contacted the author and he told me the library used reflection to get the name of your variable and would look for that variable name in the flash document.