Why should one use a build system over that which is included as part of an IDE?

Question

I've heard more than one person say that if your build process is clicking the build button, than your build process is broken. Frequently this is accompanied with advice to use things like make, cmake, nmake, MSBuild, etc. What exactly do these tools offer that justifies manually maintaining a separate configuration file?

EDIT: I'm most interested in answers that would apply to a single developer working on a ~20k line C++ project, but I'm interested in the general case as well.

EDIT2: It doesn't look like there's one good answer to this question, so I've gone ahead and made it CW. In response to those talking about Continuous Integration, yes, I understand completely when you have many developers on a project having CI is nice. However, that's an advantage of CI, not of maintaining separate build scripts. They are orthogonal: For example, Team Foundation Build is a CI solution that uses Visual Studio's project files as it's configuration.

Answer 1

If you have a hands-off, continuous integration build process it's going to be driven by an Ant or make-style script. Your CI process will check the code out of version control when changes are detected onto a separate build machine, compile, test, package, deploy, and create a summary report.

Answer 2

Let's say you have 5 people working on the same set of code. Each of of those 5 people are making updates to the same set of files. Now you may click the build button and you know that you're code works, but what about when you integrate it with everyone else. The only you'll know is that if you get everyone else's and try. This is easy every once in a while, but it quickly becomes tiresome to do this over and over again.

With a build server that does it automatically, it checks if the code compiles for everyone all the time. Everyone always knows if the something is wrong with the build, and what the problem is, and no one has to do any work to figure it out. Small things add up, it may take a couple of minutes to pull down the latest code and try and compile it, but doing that 10-20 times a day quickly becomes a waste of time, especially if you have multiple people doing it. Sure you can get by without it, but it is so much easier to let an automated process do the same thing over and over again, then having a real person do it.

Here's another cool thing too. Our process is setup to test all the sql scripts as well. Can't do that with pressing the build button. It reloads snapshots of all the databases it needs to apply patches to and runs them to make sure that they all work, and run in the order they are supposed to. The build server is also smart enough to run all the unit tests/automation tests and return the results. Making sure it can compile is fine, but with an automation server, it can handle many many steps automatically that would take a person maybe an hour to do.

Taking this a step further, if you have an automated deployment process along with the build server, the deployment is automatic. Anyone who can press a button to run the process and deploy can move code to qa or production. This means that a programmer doesn't have to spend time doing it manually, which is error prone. When we didn't have the process, it was always a crap shoot as to whether or not everything would be installed correctly, and generally it was a network admin or a programmer who had to do it, because they had to know how to configure IIS and move the files. Now even our most junior qa person can refresh the server, because all they need to know is what button to push.

Answer 3

Aside from continuous integration needs which everyone else has already addressed, you may also simply want to automate some other aspects of your build process. Maybe it's something as simple as incrementing a version number on a production build, or running your unit tests, or resetting and verifying your test environment, or running FxCop or a custom script that automates a code review for corporate standards compliance. A build script is just a way to automate something in addition to your simple code compile. However, most of these sorts of things can also be accomplished via pre-compile/post-compile actions that nearly every modern IDE allows you to set up.

Truthfully, unless you have lots of developers committing to your source control system, or have lots of systems or applications relying on shared libraries and need to do CI, using a build script is probably overkill compared to simpler alternatives. But if you are in one of those aforementioned situations, a dedicated build server that pulls from source control and does automated builds should be an essential part of your team's arsenal, and the easiest way to set one up is to use make, MSBuild, Ant, etc.

Answer 4

the IDE build systems I've used are all usable from things like Automated Build / CI tools so there is no need to have a separate build script as such.

However on top of that build system you need to automate testing, versioning, source control tagging, and deployment (and anything else you need to release your product).

So you create scripts that extend your IDE build and do the extras.

Answer 5

One practical reason why IDE-managed build descriptions are not always ideal has to do with version control and the need to integrate with changes made by other developers (ie. merge).

If your IDE uses a single flat file, it can be very hard (if not impossible) to merge two project files into one. It may be using a text-based format, like XML, but XML it notoriously hard with standard diff/merge tools. Just the fact that people are using a GUI to make edits makes it more likely that you end up with unnecessary changes in the project files.

With distributed, smaller build scripts (CMake files, Makefiles, etc.), it can be easier to reconcile changes to project structure just like you would merge two source files. Some people prefer IDE project generation (using CMake, for example) for this reason, even if everyone is working with the same tools on the same platform.