xeus-cling
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jupyter-xeus
Feature request: traceback on segfaults or exceptions (dreaming aloud)
Currently, a segmentation fault in the code results in the kernel dying. While this is a fair enough behavior (after all, this is a segfault of the whole kernel process, and there is not much to do to recover from it), some clue for the reader would be helpful. A minimum would be something like "Segmentation fault" or "the code run by the kernel triggered a segmentation fault". In case of an exception, a printout of the exception itself. Really nice would be a stack trace. Full dream would be a (optional?, post-mortem) debugger prompt.
Of course this is much lower-level, and thus presumably harder than in IPython. In particular there is the question of whether to systematicaclly interpret with debugging symbols on. And once again, this might really be a cling issue rather than xeus-cling.
Context: our students where learning 2D vectors this week, and got a lot of such segfaults. They had no clue on what to do when the kernel crashed. A stacktrace would be a super useful information for them to analyse their code and fix the bug.
It is not as crazy as it sounds. I have been looking into how to do that, which should be doable in the case of exceptions, less so for segfaults.
On linux, the segmentation fault triggers a sigsegv signal which should result in a core dump containing all the info you need. Some reasons may prevent this core dump to be generated (option disabled in the kernel, redirection to a directory that is not writable); if that cannot be fixed, a solution is to set our own signal handler to generate some information, but there are limitations on what can be done inside such a signal handler.
The core dump is actually printed out by the kernel, but I am not sure how we could generate a traceback from it.
ROOT's interpreter (meaning the actual C++ prompt) does it. I think they trap SIGSEV and execute backtrace and print the result before exiting, as explained here
Could https://github.com/bombela/backward-cpp be used? How can I view crash message for now?
