Re: [boost] [config] Request for BOOST_SYMBOL_IMPORT_VISIBLE ?

Subject: Re: [boost] [config] Request for BOOST_SYMBOL_IMPORT_VISIBLE ?
From: Mostafa (mostafa_working_away_at_[hidden])
Date: 2011-02-07 03:35:32

On Mon, 07 Feb 2011 00:10:26 -0800, Mostafa  
<mostafa_working_away_at_[hidden]> wrote:

> On Mon, 31 Jan 2011 07:00:50 -0800, Alexander Arhipenko
> <arhipjan_at_[hidden]> wrote:
>
>> On Sat, Jan 29, 2011 at 2:37 AM, Mostafa  
>> <mostafa_working_away_at_[hidden]> wrote:
>>> Hi,
>>>
>>> I propose the introduction of BOOST_SYMBOL_IMPORT_VISIBLE to  
>>> Boost.Config
>>> that behaves like BOOST_SYMBOL_IMPORT in all cases except gcc (and like
>>> compilers?) where it expands to  
>>> "__attribute__((visibility("default")))".
>> [snip]...
>>
>
> [snip]
>
>> The more elegant solution would be to have (as you are proposing)  
>> special
>> macroses in boost.config. BOOST_SYMBOL_VISIBLE is okay but it does
>> nothing on msvc.
>
> That's the problem I ran into.  On msvc, it's ok if all you want to do is
> catch the exception outside of the defining dll, but if you want to  
> export
> the said exception and throw outside of the dll, then you need to
> export/import from the dll.  It seems to me, from having gone back and
> read the discussion threads on this topic, that BOOST_SYMBOL_VISIBLE was
> sort of a gcc specific addition to enable re-exporting exceptions from  
> gcc
> dso's.  In the least, I believe that your proposal below should  
> completely
> replace BOOST_SYMBOL_VISIBLE, as it takes into account both gcc and msvc.
>
>> So, I propose to have 2 new macroses:
>> BOOST_SYMBOL_VISIBLE_EXPORT//export "always" visible symbol from the  
>> library
>> BOOST_SYMBOL_VISIBLE_IMPORT//import "always" visible symbol to the  
>> library
>
> Mostafa

Though I suggest the names:

BOOST_SYMBOL_EXCEPTION_EXPORT
BOOST_SYMBOL_EXCEPTION_IMPORT

to emphasize that this macros should be only used with exceptions.  Having  
BOOST_SYMBOL_EXPORT and BOOST_SYMBOL_VISIBLE_EXPORT is kind of confusing,  
whereas the names BOOST_SYMBOL_EXPORT and BOOST_SYMBOL_EXCEPTION_EXPORT  
are self-explanatory, I don't need the look up reference manual to figure  
out what they do when I'm scanning code.

Any thoughts?

Regards,

Mostafa