What Building a Debugger Teaches You About Computers

You don’t have to build a debugger to learn from one. What can breakpoints, stack unwinding, and stepping through code reveal about how your programs—and the computers running them—actually work?

In this episode of The Curious Developer, KDAB’s Jesper Pedersen talks with Sy Brand, author of Building a Debugger, about the deeper lessons behind familiar debugging tools. They explore how stack unwinding connects to C++ exceptions, what breakpoints reveal about operating systems, and why debuggers sometimes create an illusion to present code the way developers expect to see it.

The conversation also covers time-travel debugging, the challenges of coroutines and asynchronous code, the complexity behind std::optional and std::expected, and Sy’s work on WebAssembly tooling at Fastly.

Along the way, Sy shares their approach to making complex technical topics approachable, reflects on filmmaking and other creative pursuits, and closes the interview with a reading of their poetry.

Chapters:

01:15 Sy Brand is…

03:39 Why did Sy do the YouTube videos?

05:11 Why are std::optional/std::expected so complicated?

08:25 How does WebAssembly fit into system programming?

10:35 Building a Debugger (book)

13:48 What will the reader get out of the book?

14:50 Breakpoints

15:40 Learning C++ along the way

18:33 How fast are debuggers evolving?

20:37 Co-rutines

25:54 Why do all the debuggers look the same?

28:09 Time travel debugging

31:10 What will the future of debuggers look like?

32:19 How can the same debugger debug Rust and C++?

34:17 Debugging in WebAssembly

35:44 What will Sy be doing next?

37:55 Poetry

Links:

• Sy Brand's YouTube
• Sy Brand on github
• Sy Brand’s homepage
• How Debuggers work

About the guest:

Sy Brand is the author of Building a Debugger and a Staff Software Engineer at Fastly, working on WebAssembly tooling. Their background spans compilers, debuggers, profilers, language runtimes, and standard libraries, with contributions to the C++, DWARF, and HSA standards. Outside software, they write poetry and make experimental films.