Debugging constexpr evaluation

Hosted by BMW (bmw.de)

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Our second MUC++ meeting in 2026 will be on January 29th. We'll have to honor to welcome Artemy Pestretsov to our user group. Artemy started as a C++ developer, taught programming languages at university, and then moved into developer tools at JetBrains. He’s worked on IDEs such as PhpStorm and Fleet, including integrating dataflow analysis with the debugger to help developers understand and predict code behavior. Passionate about developer productivity, he eventually found his way back to C++, leading CLion and later taking responsibility for JetBrains’ C and C++ direction. He is now Head of C and C++ Ecosystems at JetBrains, focusing on improving the day-to-day experience of C and C++ developers through better tools and workflows.

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Abstract
Modern C++ keeps pushing more logic into constexpr/consteval: parsers, tables, DSLs, hashing -- code with branches, state, and failure modes that happen before your program ever runs. When something goes wrong at compile time, you can either try to guess the reason from the compiler’s notes or de‑constexpr it... and hope the runtime reproduction matches what the compiler actually did.
In this talk, we’ll treat compile-time execution as something you can debug rather than guess. Using CLion’s constexpr debugger, we’ll step through constexpr evaluation, inspect values as they evolve, and see which if constexpr branches fired. We’ll also go deeper under the hood: how constant evaluation is represented, what makes debugging possible, and today’s limits.

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Live Stream: No live stream this time.

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Schedule
18:00 -- Welcome with Snacks and Drinks
19:00 -- Welcome by BMW/MUC++
19:05 -- "Embedded template library”
19:20 -- “Debugging constexpr evaluation”
~22:00 -- Official End