Re: [boost] Noexcept

On Wed, Jun 28, 2017 at 11:34 PM, Andrzej Krzemienski via Boost < boost@lists.boost.org> wrote:

2017-06-29 8:14 GMT+02:00 Emil Dotchevski via Boost

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On Wed, Jun 21, 2017 at 12:43 AM, Andrzej Krzemienski via Boost < boost@lists.boost.org> wrote:

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In error-neutral contexts, you simply return throw_() to propagate any error from lower level functions.

But does this not compromise exception neutrality? That you have to specify in each function that you want to just pass the exception up?

Compared to what? Is there a better option when you can't throw?

My observation is, if you cannot throw then exception neutrality is not achievable.

In functions that propagate errors in the return value (very common both in C and in -fno-exceptions C++), each caller has to take the returned error code, examine it, then possibly return a copy of it -- but it is also common to return another error, which is known as error translation (which is a bad idea). Instead, functions which can't handle the error should just propagate it to the caller. That is what it means to be neutral: "I don't know what this is, someone else please deal with it". In Noexcept neutrality can be expressed explicitly: you simply return throw_(), which doesn't touch the error object at all.

Here, by "exception neutrality" I mean what function std::qsort is doing.

I would not bet that qsort is exception-safe on all platforms. Emil