Program logic bugs vs input/environmental errors

[Iain Buclaw via Digitalmars-d]

On 9 October 2014 17:33, Johannes Pfau via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> Am Thu, 09 Oct 2014 13:10:34 +0000
> schrieb "Dicebot" <public at dicebot.lv>:
>
>> On Wednesday, 8 October 2014 at 03:20:21 UTC, Walter Bright wrote:
>> >> Can we at least agree that Dicebot's request for having the
>> >> behaviour of
>> >> inadvisable constructs defined such that an implementation
>> >> cannot randomly
>> >> change behaviour and then have the developers close down the
>> >> corresponding
>> >> bugzilla issue because it was the user's fault anyway is not
>> >> unreasonable by
>> >> definition because the system will not reach a perfect state
>> >> anyway, and then
>> >> retire this discussion?
>> >
>> > I've been working with Dicebot behind the scenes to help
>> > resolve the particular issues with the code he's responsible
>> > for.
>> >
>> > As for D, D cannot offer any guarantees about behavior after a
>> > program crash. Nor can any other language.
>>
>> Just wanted to point out that resulting solution (== manually
>> switching many of contracts to exceptions from asserts) to me is
>> an unhappy workaround to deal with overly opinionated language
>> and not actually a solution. I still consider this a problem.
>
> A point which hasn't been discussed yet:
>
> Errors and therefore assert can be used in nothrow functions. This is a
> pita for compilers because it now can't do certain optimizations. When
> porting GDC to ARM we started to see problems because of that (can't
> unwind from nothrow functions on ARM, program just aborts). And now we
> therefore have to worsen the codegen for nothrow functions because of
> this.
>
> I think Walter sometimes suggested that it would be valid for a
> compiler to not unwind Errors at all (in release mode), but simply kill
> the program and dump a error message. This would finally allow us to
> optimize nothrow functions.
>

This behaviour was agreed at the bar at DConf.  We'd have to put it in
the spec to give it the official stamp of approval though.

Iain.