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Subject: Re: [important] C++ Zero-Overhead exception proposal
From: Denis Kotov (redradist_at_[hidden])
Date: 2020-11-04 15:25:55


Are there any other thoughts on this mail list ?

On Tue, 20 Oct 2020 at 11:35, Denis Kotov <redradist_at_[hidden]> wrote:

> Also it would be useful to look how error handling do in Rust with Result
> where Result<> is exactly the same idea that I suggest for C++
> Result<> in Rust is union with additional value that say what is it -
> result or error, and this union returned by value
>
> Nobody enforce users to use dynamic memory at all, instead user can use
> dynamic memory directly to return pointer to data as error. It is provided
> as option
>
> On Mon, 19 Oct 2020 at 23:40, Denis Kotov <redradist_at_[hidden]> wrote:
>
>> >> but returning large structs isn't exactly
>> "zero-overhead" either
>>
>> Why ? Zero-overhead is all about if it is not possible to do better by
>> hand ... And it is not possible to return better by hand !!
>> With `exception_ptr` you enforce all to use dynamic memory management,
>> but to return an object directly is more flexible because the user can
>> return struct, it can return pointer to struct, it can return raw integer
>> ... This solution more flexible for embedded as well as for general
>> programming
>>
>> I just want in C++ Zero-overhead with ability to choose how exactly I
>> want return error (by pointer or by value)
>>
>> On Mon, 19 Oct 2020 at 20:49, Jason McKesson via Std-Discussion <
>> std-discussion_at_[hidden]> wrote:
>>
>>> FYI: You need to reply to the list to keep the discussion on the list.
>>>
>>> On Mon, Oct 19, 2020 at 3:49 AM Denis Kotov <redradist_at_[hidden]> wrote:
>>> >
>>> > >> Being a "raw integer" is what gives us "zero overhead" (also,
>>> > `std::error` is not a "raw integer"; it's two pointers in size)
>>> >
>>> > "Zero-overhead abstraction - don't pay for what you don't use, what
>>> you use is as efficient as you can reasonably write by hand" from side of
>>> Herb Sutter https://youtu.be/ARYP83yNAWk?t=328
>>> > You cannot write more efficiently than that:
>>> > ```cppunion SubscribeResult { Subscription res; SubscriptionError
>>> err;
>>> > };```
>>> >
>>> > Returning raw integer as error code is also "Zero-overhead", but it is
>>> applied for some specific case ...
>>> >
>>> > What if with error you want to return data for this error ?
>>> > It will become very hard to extend such an error system ..
>>>
>>> `std::error` as proposed by P0709 ***is not an integer***. It is a
>>> specialized type that can store integer values, but it can also store
>>> any data structure through an `exception_ptr`. Yes, they must be
>>> dynamically-allocated, but returning large structs isn't exactly
>>> "zero-overhead" either. This is especially true when throwing them.
>>>
>>> The functionality you want can already be done with the existing
>>> P0709, just not in quite as convenient a way.
>>> --
>>> Std-Discussion mailing list
>>> Std-Discussion_at_[hidden]
>>> https://lists.isocpp.org/mailman/listinfo.cgi/std-discussion
>>>
>>
>>
>> --
>>
>> *Best RegardsDenis Kotov*
>>
>
>
> --
>
> *Best RegardsDenis Kotov*
>

-- 
*Best RegardsDenis Kotov*


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