Are there any risks or disadvantages to building software from source, compared to installing a package? Can it mess with my system in any way?
I usually avoid it because I’ve found it to be a faff and often doesn’t work anyway but in a couple of cases it has been necessary.
The best would be to ask a Gentoo user. :D
Disadvantage (besides the update procedure mentioned by the other answers here) is, it might take lot of time, download lot of dependencies and files and need additional space on your drive to compile. It can be a hassle to install and setup the required tools and libraries too. This highly depends on the project itself if its worth it. In example nobody in their right mind wants to compile their web browser (Firefox, Chromium, whatever) themselves (sorry if I offended someone with that. :D). But a simple and short C program is as simple as running
makecommand in example (given the dependencies are installed, which are most likely for simple programs after a few programs have been compiled).Most of the time you don’t need to compile software. Especially if you trust the source or its in the official repositories of your distribution.
Depends on what you mean by that.