Re: [boost] [inspect] exceptions (FW: [Boost-users] no exceptions)

Subject: Re: [boost] [inspect] exceptions (FW: [Boost-users] no exceptions)
From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2011-03-23 14:46:01

On Wed, Mar 23, 2011 at 1:05 AM, Vladimir Prus
<vladimir_at_[hidden]> wrote:
> Emil Dotchevski wrote:
>
>> On Tue, Mar 22, 2011 at 1:38 AM, Vladimir Prus
>> <vladimir_at_[hidden]> wrote:
>>> Emil Dotchevski wrote:
>>>
>>>> On Mon, Mar 21, 2011 at 6:39 PM, Robert Kawulak
>>>> <robert.kawulak_at_[hidden]> wrote:
>>>>> >From Boost Users ML:
>>>>>
>>>>>> From: Hochhaus, Andrew
>>>>>> I would like to use boost with BOOST_NO_EXCEPTIONS [1] and the g++
>>>>>> -fno-exceptions flag. However, it appears that some spots in boost
>>>>>> library code:
>>>>>>
>>>>>> a) throw exceptions with the "raw" throw keyword [instead of
>>>>>> BOOST_THROW_EXCEPTION or boost::throw_exception]
>>>>>> b) use try ... catch blocks without "#ifnef BOOST_NO_EXCEPTIONS" guards
>>>>>
>>>>> Wouldn't it be a good idea to add checks for these to the inspect tool? Also, non-empty
>>>>> exception specifications are discouraged by Boost guidelines - should appropriate checks be
>>>>> added too?
>>>>
>>>> +1
>>>
>>> I don't think that Boost libraries are required to support non-conforming compilers or
>>> operation modes of compilers, therefore adding inspect check for a workaround for such
>>> non-comforming behaviour would be wrong, I think.
>>
>> Why use BOOST_THROW_EXCEPTION to throw?
>>
>> - Typically, there is no need to do anything else to support
>> BOOST_NO_EXCEPTIONS builds;
>>
>> - Enables boost::exception_ptr, so the exceptions you throw can be
>> transported between threads;
>>
>> - Enables boost::error_info, so users can attach stuff to exceptions.
>>
>> - Enables better messages from boost::diagnostic_information.
>
> I fail to see how the above refutes my statement. We don't have a requirement
> that Boost libraries work with non-conforming environment.
> Nor is it required that any Boost library uses Boost.Exception.

The semantics of BOOST_THROW_EXCEPTION are such that typically, if a
library uses it to throw, the library also supports BOOST_NO_EXCEPTION
builds. My point was that there is no reason for a Boost library not
to use BOOST_THROW_EXCEPTION to throw.

> Therefore, adding no-exceptions to inspect checks -- whose primary
> purpose is to beat authors whose libraries fail those checks -- would
> be wrong.

AFAIK, the only builds authors are required to support are the ones in
the release test, I'm not proposing to change that requirement. This
is an issue of uniformity and usability. We don't require that
libraries use BOOST_ASSERT to assert but using it makes Boost
libraries more usable. It is the same with BOOST_THROW_EXCEPTION.

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode