Re: [boost] Hello?

From: Robert Ramey (ramey_at_[hidden])
Date: 2005-09-14 16:35:25

David Abrahams wrote:

>  The best thing you could do, IMO, is write a recommendation that
>  works on conforming compilers, e.g.
>
>    Overload serialize in the namespace of your class.
>

Oh, that's news to me.  I thought that would work only in compilers that 
implemented ADL.  I understood from previous postings that this would entail 
building a set a macros which addressed  the varying aspect of conformity. 
In 1.32 I had #if ... in order to place stl serializations in either the stl 
namespace or the boost::serialization namespace depending on whether the 
compiler supported ADL and two-phase lookup or neither of these things. 
That was the only way I could get everything to compile on all platforms. 
Then generated the requirement to address the issue in the documentation 
with a table on what the user should use.  That's what I call ugly.

FWIW - I'm not sure if the example you site would ever come up in practice - 
it certainly hasn't yet.  If I understand this correctly, the problem would 
occur if someone writes somethng like:

my_class.hpp

class my_class ...

template<class Archive, my_class>
void serialize(Archive &ar, my_class & t, cont unsigned int version); // 
declaration only

my_app.cpp

main(...
{
    my_class mc;
    ...
    ar & mc;
}

template<class Archive, my_class>
void serialize(Archive &ar, my_class & t, cont unsigned int version); // 
definition only

I'm not absolutly sure that this is the only scenario which would create 
problem and that's why I wanted more time to consider it.

If this is the only way the two-phase problem could manifest itself, I would 
guess that in practice it would never be an issue.  I don't see users doing 
this.  This was what I was getting at when I asked why the problem hasn't 
appeared upto now.  Of course I don't really know whether this is because so 
many compilers fail to implement two-phase lookup.

>> b) I'm going to remove the class declaration and function
>> implementation from the Archive Concept part of the document.

> Are you planning to replace it with anything?  It would be pretty
> silly to have a section called Archive Concept with no concept
> description.

I meant to leave in the text below the "class" schema.  Before I started I 
reviewed again the SGI documents and concluded that that text could be fit 
into the SGI form for concepts. I'm using 
http://www.sgi.com/tech/stl/Container.html as a "typical example".  This 
isn't hard - its basically a question of reformatting.  I hope that will be 
satisfactory.

>> The above I will check into RC_1_33_0
>>
>> Other issues that I intend to defer for the next version

>> d) investicate the two-phase lookup issue.  There is no way any such
>> change could be made for RC_1_33_0 and the next boost release won't
>> be for another 10? months, so I feel that I can take some time with
>> this.
>
> That seems extreme to me.  Surely for RC_1_33_0 a documentation fix
> that provides instructions that are both correct for conforming
> compilers and consistent with the current library implementation is
> possible?  Not much more than a small tweak in emphasis would be
> required.

see above.

Robert Ramey