Re: boost::errinfo_stacktrace?

From: Gavin Lambert (boost_at_[hidden])
Date: 2019-11-21 02:59:26

On 21/11/2019 09:58, Mathias Gaunard wrote:
> In any case catching and rethrowing exceptions at every layer to add
> context information as it bubbles up is not really an idiom I would
> recommend.
> Not only is quite ugly and complexifies control flow, it's also
> inefficient and leads to a poor experience when debugging.

I think it works reasonably well, without too much ugliness.

It's a bit better in the .NET languages, since they adopted the idea of 
nested exceptions from the start -- at each catch site, you can choose 
whether to add additional details to the existing exception and rethrow 
it (although this is rarely done since it typically isn't visible in the 
string output), to throw another exception with the original nested 
within (most common), or to throw another exception without the original 
(rarer, but occasionally appropriate).

While C++ now has the ability to do nested exceptions as well, the 
plumbing required to actually deal with them (and to extract and log 
information) is still pretty terrible.  And most existing code will 
neither nest exceptions nor unpack them.

Granted, it can be a little annoying to debug if you have it set to 
break on all exceptions (rather than just uncaught ones), but even so, 
exceptions should be rare and following it up the call chain can be 
useful in itself, so it's not all that poor an experience.

Usually the only time exceptions cause a poor debugging experience is 
when code is using them incorrectly (as control flow, not for 
exceptional cases; which often leads to try-catch-ignore anti-patterns).

> It is a better idea to use normal control flow for this.

How would you use normal control flow for that example?  (Failure to 
parse at a low level that doesn't know the filename, and the higher 
level does know the filename.)