undefined | Better HN

0 points_ph_5y ago0 comments

But that is the point I was trying to make. No language can save you from logic errors, but a lot of languages let you recover from errors in functions. The simplest way is exception handling in Java like try { parse(xmlFile) } catch ( ... ) {.... } There is no reason the device should get in an undefined state if parsing that file fails or even completely crash.

0 comments

dspillett5y ago

> There is no reason the device should get in an undefined state

That is impossible to guarantee. It isn't even possible to completely generally[†] test for - what you have there is a variant of the halting problem (https://en.wikipedia.org/wiki/Halting_problem).

[†] added "generically" there as it is possible, using formal methods from the start, to prove that a program is correct so will not error (in an unexpected manner) on any input, but such methods are time-consuming so outside of certain specific fields you'll not find them used

GordonS5y ago

But not having a `try...catch` for such events is a kind of logic error.

The choice of programming language only gets you so far - it's up to the developers to actually handle errors in a meaningful way.

jen205y ago

I'd argue that languages which force handling via the type system (e.g. `Result<T, Error>` in Rust) makes it less likely that bugs like this will go unhandled, since the position if the programmer does not explicitly opt out of error handling (with `unwrap` etc) is a compilation error rather than missing error handling.

tedunangst5y ago

What specifically goes in the catch block? Please be precise.

sjwright5y ago

In the case of an appliance device where the XML file was externally supplied? Continue as though the file never existed (and possibly also delete the XML file).

_ph_OP5y ago

Either proceed with some safe default values or at least go into a maintenance mode, where the file can be replaced or newly downloaded.

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