[llvm-dev] Examples of exception-free code

[David Blaikie via llvm-dev]

Hi there,

You're right that some of the differences are based on different
conditions/needs, and some are based on different styles (some which are
historic - some which might vary by individual developer preferences, or
common idioms within one part of the codebase that might be different in
other parts)

Probably one of the more generically/full-functioned examples of
non-exception error handling would be llvm::Error (& llvm::Expected), like
google's util::Status (& util::StatusOr).

But if there's nothing interesting to say about the failure, a boolean
return (or Optional<T> - where T is the success value, and non-present for
failure).

A long time ago some parts of Clang got in the habit of returning 'true' on
failure, instead of false - this was in part motivated by the C idiom of
non-zero-on-failure/errorcode style failures - but it's gotten all a bit
muddled up and I think the general sense is that false on failure is the
direction to go moving forward for those sort of situations (where boolean
failure is sufficient - no descriptive error message).

- Dave

On Sat, Nov 3, 2018 at 2:08 AM A. Ilchinger via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hello,
>
> as I understand, the LLVM project prohibits the use of exceptions. I
> don't want to start a discussion about this decision, but I'd love to
> see what alternative error handling is used.
>
> Could you please point me to some good code examples in the LLVM tree
> where one can see how exceptions are avoided? Skimming through the code
> I found different approaches (private ctor and create() method with
> error return code; using only the ctor and ignoring possible allocation
> errors; ...)
> Surely, the use of the right error handling strategy is highly
> situational, but LLVM also improved over time and without deeper
> knowledge of the code base it is impossible for me to see which parts
> are "good" and which parts are older and might need refactoring.
>
> Kind regards
> Andreas
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