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Learning and Maintaining a Large Inherited Codebase?
An anonymous reader writes "A couple of times in my career, I've inherited a fairly large (30-40 thousand lines) collection of code. The original authors knew it because they wrote it; I didn't, and I don't. I spend a huge amount of time finding the right place to make a change, far more than I do changing anything. How would you learn such a big hunk of code? And how discouraged should I be that I can't seem to 'get' this code as well as the original developers?"
If you don't have access to the original developers and they didn't document it you're going to just have to spend a lot of time reading the code. =\
"Ubuntu" -- an African word, meaning "Slackware is too hard for me". - stolen from Dan C alt.os.linux.slackware
Try to single-step it in debugger from the beginning up to main loop.
Coding etudes
I inherited a code base of 1.5 million lines of code at the last job I was at. Thankfully I wasn't the only one responsible for it. My advice to the original poster is to add lots of logging information. Log statements should document what the code is doing at any point in time and tell you where it is doing it. If it's java you can get the stack trace from anywhere--this is very handy for logging.
Are you Microsofties really so stupid and ignorant that you're not aware of the ports of GNU utilities to Windows or Cygwin or even your own company's Interix and Services for UNIX products?
No, but to explain this, I need to give you some background.
When I joined Microsoft, I hadn't used any version of Windows at all for any reason other than playing games. After joining Microsoft, I never used Windows at home for any purpose other than logging into the VPN to work from home... and since I did not even have an x86 machine, this required using Virtual PC on my Mac OSX box.
Now, I know of all of these tools, and I even could install GVim on the machine as well. However, I was working in a Build Group. This required me to occasionally log into 100 different machines at once in order to start the build process for WinXP/Server 2003. Most of these machines require no more input than logging in and starting up a single app... thus no reason to install special software on them.
Then, something would break, and I would have to read logs, and/or code on the actual box that had the exact problem. Spending an hour installing apps to do my job would be an unacceptable use of my time, and delay the build unnecessarily.
I learned to use the tools that were available with the environment that I was in. Thus, I did almost all of my programming at Microsoft in notepad.exe, and I'm not kidding you.
Were I in a different group? The results could have been different... but having 100 different machines, most of which I didn't have admin rights to, meant that even just installing Notepad++ or something like that would have been a waste of time.
WARNING! This girl exceeds the MAXIMUM SAFE standards established by the FDA for BRATTINESS
What the hell? Are you serious?
So Microsoft themselves hired you to work on Windows, although you were a Mac user and had absolutely no real experience with Windows?
Not only that, but you had to manually log in to hundreds of systems just to run a script? They didn't push for this to be automated, and you tossed back on the street where you belong? What the hell?
Don't get me wrong, I don't doubt that your story is true. It's the sort of shit that we should expect from any large company, especially Microsoft. Please tell me you're an H1B, though. At least then it'd make some sense why they'd hire you. H1Bs typically aren't worth more than a batch file.
Yeah, it took me about a month before I understood that my entire group would be replaced by a few scripts in the Open Source world.
The primary problem was that because the source code was not a "product", the build code was so full of holes and edge-cases and hacks, that it broke almost constantly, and required someone to babysit it for the whole 14-some hours that it takes to compile.
Actually, in my orientation class, we went over patents, copyright, and trademark, and I knew it all, and the teacher asked me how I knew so much, and I told her that I owned a registered copyright on some GPL code, and she was like, "and your managers hired you knowing that?" And I was like, know about it? It's the only reason I got hired by Microsoft... be damn sure I didn't submit a resumé.
WARNING! This girl exceeds the MAXIMUM SAFE standards established by the FDA for BRATTINESS
Really. A guy asks a question for help and all of these people keep telling him 30-40,000 lines of code isn't much.
That's a lot of code to get your arms around if you didn't write it. It's not the end of the world, but it is a sizeable task, and is the type of topic that few professional journals or books will ever be written about.
Having been in similar situations, I my advice would be:
1) Try to get an understanding of the history of the code. Who wrote it? Why? How many developers? How long has it been around? Do people love it or hate it? Is there a version control system in place you can use for information?
2) Look at it from a technical viewpoint. Is is complete? Does it compile and run? How many languages are used? Are there interfaces with other systems you need to know about? What dependancies are there? How easy is it to setup a test server? What parts are well coded? What parts stink up the joint?
3) Dig for functional documentation. What does it do? For whom does it do it? What business needs does it support? How mission critical is it?
4) Meet with the business owners. Seriously. This helps you do two things: #1-- Define the real business need (which may be different than what was understood by the previous developers), and #2-- Set appropriate expectations about maintenance. You'll work hard to maintain and keep it working, but you are working from a disadvantaged position. It is important they know this and support you in your efforts, rather than complain loudly when something doesn't work.
5) Plan to remove the dead weight. There's always a lot of dead weight in these near-abandonded projects. Get an idea how to simplify things and plan your work in phases.
6) Setup real test and development servers. Yeah, you know that wasn't already done.
7) Use version control. But you know this. It's 2010, and no developer worth his/her salt would code a paying project without version control. Right?
8) All fixes will take much longer than if you wrote the code, so be careful with estimating time.