Debugging

Debugging sucks. But there's also nothing quite that "oh fuck, that's why it doesn't work" moment, which happens after you have examined and placed everything that is relevant to the problem into your brain. You just can't see it coming. It just happens. You just learn what you generally have to look at so it happens faster.

keep debug notes

Ciro's call hierarchy notation

This is a simple hierarchical plaintext notation Ciro Santilli created to explain programs to himself.

It is usuall created by doing searches in an IDE, and then manually selecting the information of interest.

It attempts to capture intuitive information not only of the call graph itself, including callbacks, but of when things get called or not, by the addition of some context code.

For example, consider the following pseudocode:

f1() {
}

f2(i) {
  if (i > 5) {
    f1()
  }
}

f3() {
  f1()
  f2_2()
}

f2_2() {
  for (i = 0; i < 10; i++) {

    f2(i)
  }
}

main() {
  f2_2()
  f3()
}

Supose that we are interested in determining what calls f1.

Then a reasonable call hierarchy for f1 would be:

f2(i)
  if (i > 5) {
    f1()

  f2_2()
    for (i = 0; i < 10; i++) {
      f2(i)

    main
    f3
f3()
  main()

Some general principles:

start with a regular call tree
to include context:
- remove any blank lines from the snippet of interest
- add it indented below the function
- and then follow it up with a blank line
- and then finally add any callers at the same indentation level

Bisection (software engineering)

One of the Holiest age old debugging techniques!

Git has some helpers to help you achieve bisection Nirvana: stackoverflow.com/questions/4713088/how-to-use-git-bisect/22592593#22592593

Obviously not restricted to software engineering alone, and used in all areas of engineering, e.g. Video "Air-tight vs. Vacuum-tight by AlphaPhoenix (2020)" uses it in vacuum engineering.

The cool thing about bisection is that it is a brainless process: unlike when using a debugger, you don't have to understand anything about the system, and it incredibly narrows down the problem cause for you. Not having to think is great!