The University of Pennsylvania offers a free series of books called Software Foundations with the following description:
The Software Foundations series is a broad introduction to the mathematical underpinnings of reliable software.
The principal novelty of the series is that every detail is one hundred percent formalized and machine-checked: the entire text of each volume, including the exercises, is literally a “proof script” for the Coq proof assistant.
The series includes Verifiable C, which seems very appealing as a way to avoid some of C’s infamous “footguns.” I haven’t read the series myself, but I might in the future because I like math, logic & programs that do what they’re supposed to do.
Are there any materials that would be good as alternatives or complements to this series?
Edit: Adding the Vercors Wiki to the resources in this thread
You can transform any recursive algorithm into iterative pretty easily though; just create a manual stack.
The rule definitely makes sense in the context of C code running in space. Unbounded recursion always risks stack overflow, and they probably don’t have any tooling to prove stack depth bounds (you totally can do that, but presumably these standards were written in the 1500s).