Question

I am interested in devoting a good amount of time to improving my debugging ability and am looking for a list of core topics that I need to cover in order to be versed in the principles of commonly used and advanced debugging/testing techniques.

Initially, I figured I would just read through the gdb documentation and glean debugging techniques from its functionality; however, other than jumping into it to get the line number of a segfault and maybe running bt, months later I am still resorting to mass printf‘s as my default strategy. I feel this is because I don’t have any well defined strategies that I could effect through more sophisticated means.

Although my question is in relation to C/C++, and although I operate within a UNIX environment, I would be willing to look at generalized material, or even topics covered in other languages if they will improve my understanding of key concepts.

Answer 1

You have multiple direct strategies which you should consider:

• Mass printfs cry for a logging solution. You have many options here, but logging extensively isn’t particularly a bad strategy, it is in fact vital for any form of client-side debugging.
• Extensively use assertions (and never disable them, even in “release” code). Always write checks for all potential errors and fail as soon as possible (use exceptions in C++ — always throw, never catch).
• Learning to master gdb within emacs is useful. Learning how to step the program, how to set up breakpoints and how to inspect local variables is usually more than enough.
• Unit testing is something to consider too. Especially since small tests are easier to debug, because they are not surrounded by the noise of a fully featured program. Write tests before the code, or better, have someone else write the tests.

More generally, the following points, although not directly related to debugging, will benefit you:

• Learning how a program is executed (learn eg. about stack frames and a small intro to assembly) may prove useful in certain situations where a bug is corrupting memory. More generally, never stop learning stuff about your environment.
• In C++, use good practices: RAII, the standard library, failing as soon as possible, etc. This has a strong tendency to reduce debugging effort, esp. since debuggers can pretty print stuff from the standard library. Also, coding a simply as possible has a positive effect on debugging time.
• Use (distributed) version control. Always. You’ll see the benefits once you’ll get accustomed to it (eg. in combination with unit tests, you have the almighty git bisect available to you).