what about opening a ticket / doing a pull request with a better trivial example that does not "teach" bad habits?
(There isn't a way in C/C++ to request an exception or fault on integer overflow, which is what you'd want here, since you're running inside Python. A better conceptual fix is just doing the addition in Python, which is a more robust language than C/C++ for signed integer addition, but that kind of defeats the point of the example.)
This is incorrect.
See compiler options: -ftrapv, -fsanitize=undefined. See compiler builtins: __builtin_add_overflow and friends.
I'm not sure that pybind11 wants to have its docs using a nonstandard variant of C, though, for lots of reasons, including that I expect the major use case of pybind11 is binding to existing C or C++ projects which are generally written in standard C or C++. (But not always! Postgres, for instance, is written in a variant of C with -fwrapv - not even -ftrapv, but a definition of signed overflow - instead of standard C.)
To my knowledge that's solely because historically there's been signed integer overflow checks that relied on signed overflow semantics, not because there's otherwise use of overflows. At some point we didn't have a nice, portable and fast way to do overflow checks and so -fwrapv was added... I'd like to revisit that.