[This post is based on data gathered by my student Peng Li. He also wrote the undefined behavior checker.] The other day I posted about undefined integer behaviors in code written by students in a class I used to teach. This post is more of the same, this time from CS 5785, my advanced embedded…

[This post is based on data gathered by Chad Brubaker and Peng Li, respectively an undergrad and grad student in CS at Utah.] Two courses I’ve taught at Utah, CS 4400 and CS 5785, have assignments where students write short integer functions for which we — the instructors — have automatic graders. In 4400 the…

As a followup to last night’s post, here are some saturating signed subtraction functions I’ve received. Hopefully the correct one is obvious.

After getting too tired to work tonight, I realized I had no Netflix and that I’m bored with the books I’m reading. Therefore, I present visualizations of several solutions I’ve received to my saturating arithmetic homework over the years. This is what a correct saturating signed add looks like, where the z-axis is the output:…

Klee isn’t the only tool in its class, nor was it the first, but it’s open source and well-engineered and it works. Klee’s goal is to generate a set of test inputs that collectively induce path coverage in a system under test. One of the scenarios I was curious about is the one where Klee…

[This post is based on material from Chad Brubaker, a really smart CS undergrad at Utah who did all the work getting these data. The integer undefined behavior checker was created by my student Peng Li.] Integer undefined behaviors in C/C++, such as INT_MAX+1 or 1<<-1, create interesting opportunities for compiler optimizations and they also…

One of the painful parts of teaching a lab-based embedded systems course is that over and over I have to watch a team with a relatively simple bug in their code, but who is trying to fix it by repeatedly making random changes. Generally they start with code that’s pretty close to working and break…