I want to add to this. People might think they lack opportunities for this exercise because they don't have special requirements out of the open source packages they use. But realize that
breaking a piece of code in a
controlled manner also needs roughly the same level of understanding as adding a feature.
It could be as simple as a `sleep` in the right circumstances. Maybe your resulting patch is a boring handful like:
bool cond1 = ...;
bool cond2 = ...;
if (cond1 || cond2) {
sleep(1000);
}
but you need to read and develop understanding of the code to define the conditions in terms of the program's state. And you also need the same understanding to know where exactly in the code to introduce this snippet. Not to mention compiling it; even with Makefiles, lower-level languages could still be tricky to build.
How this can be useful: Long time ago, we were observing odd behavior from Redis under extremely high load. Of course it did not replicate consistently and when it did, it lasted too short for us to properly observe and make hypotheses. So I had the brilliant idea of installing a custom Redis binary in our test environment that tweaked the odds so that the behavior happened almost consistently, no need to thrash the server. I had to read through Redis source code to make it happen (and added a hell lot of logs too). Plus in the end, it's not quite compiling Linux but, boy, I did compile Redis from scratch!