Exceptions in C++ are never zero-overhead. There is a time-space tradeoff for performance of uncaught exceptions, and G++ picks space over time.
Including checking return codes instead of exceptions. It's even possible for exceptions as implemented by g++ in the Itanium ABI to be cheaper than the code that would be used for consistently checking return codes.
[0] https://news.ycombinator.com/item?id=22483028
[1] https://www.research.ed.ac.uk/portal/files/78829292/low_cost...
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.
By definition, that's zero-overhead because Ultrassembler doesn't care about space.