Re: [boost] [system] Would it be possible to trial a breaking change to Boost.System and see what happens?

Subject: Re: [boost] [system] Would it be possible to trial a breaking change to Boost.System and see what happens?
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2018-01-14 23:54:49

>> `f` should not need to know what errors are being returned by
>> `do_f1`, `do_f2`, `do_f3`, in order to check whether the calls
>> succeeded; the whole point of using error_code is that errors from
>> different domains can be handled in a generic manner.
> 
> No, this is just one approach to error handling, and defining the
> error handling approach is beyond error_code's scope. The
> responsibility of error_code is simply to encapsulate the error
> values that originate from different domains.

I think that *was* the case in the past, and by individuals such as
yourself Chris in the code that you personally have written.

But Peter's right: the typical use case patterns for error_code have
evolved into something different, more complex, more generic. And that's
a good thing, even if currently there is lots of subtly broken code out
there right now.

>> There must exist a generic way to test for failure.
> 
> Why must this exist? (With the emphasis placed on "generic".)

So templated code which composites unknown code can be useful. Right now
it must assume "if(ec)" means "if error" due to no generic alternative.

> You can achieve this within certain domains and error handling
> designs, sure. However, testing for failure using only the error code
> is not possible for all use cases where error codes are applicable
> or, indeed, already used.

Currently, yes. But a retrofitted error_code ought to work nicely.

Niall

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