Actually, there has been some research into building exceptions on the "basically, passing std::exception* into every function and checking what's inside it on every return" idea, and it was about as fast as the traditional table-based unwinding, took way less space in the executable, and re-throwing exceptions was actually faster [0][1]

[0] https://news.ycombinator.com/item?id=22483028

[1] https://www.research.ed.ac.uk/portal/files/78829292/low_cost...

Yeah, it comes down to modeling assumptions on how many different types of exceptions can be thrown, how many actually are thrown, and the shape of the control flow graph of a program at runtime.

You can find one style outperforms the other based on the circumstances of the program, and programmers worried about optimization may someday be able to choose between approaches to meet their performance goals instead of pretending that tables are inherently slow and return codes that they won't even fully implement are inherently fast.

My point was simply that you can't just say "oh but exceptions are not zero-cost" without actually comparing to the alternative of laboriously carting return codes all through the call graph, as done in the research you show here and as also done by Khalil Estell elsewhere for ARM embedded.