Re: [boost] [Review] Type Traits Introspection library by Edward Diener starts tomorrow Friday 1

Subject: Re: [boost] [Review] Type Traits Introspection library by Edward Diener starts tomorrow Friday 1
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2011-07-03 11:17:35

On 07/03/2011 02:21 PM, Edward Diener wrote:

>> This seems a serious deficiency. I feel it would be better to generate
>> these macro metafunctions in a namespace specific to the code that wants
>> to use them, rather than putting them all in boost::tti. That would
>> essentially eliminate the risk of cross-library ODR violations. What
>> is your motivation for putting all the macro metafunctions in the same
>> namespace?
>
> You have made a very good point.
>
> My intention, evidently misguided, was to put the generated
> metafunctions in the boost::tti namespace to avoid polluting the global
> namespace. But I see now that I should not have added a namespace at all
> and the end-user could then use the macros in whatever namespace he
> wants in order to avoid ODR violations, and/or just use the complicated
> macro form to create a unique name for the metafunction. Actually, of
> course, that still could be done, but a full metafuncion name of
> 'anamespace::boost::tti::has_type_mytype' is more gruesome than
> 'anamespace::has_type_mytype'.
>
> Thanks for pointing this out.

How about checking with the preprocessor if the meta-function has 
already been defined, and not defining it in that case?