Re: [boost] [wave] ifndef/ifdef callbacks

From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2006-05-11 19:54:54

Felipe Magno de Almeida wrote:

> I see that there are some hooks for appending callbacks for 
> certain situations in the preprocessing. I think this is 
> great. But, I would like to know if it is possible for the 
> user to know when the preprocessor is evaluating an 
> preprocessor conditional, and to know what the condition is. 

There is the evaluated_conditional_expression() preprocessing hook getting
called whenever a #if/#elif/#ifdef/#ifndef directive was encountered. This
hook gets 2 parameters: the (non-expanded) evaluated expression and the
outcome of this evaluation (true/false).

Is that what you need?

> And to fork the preprocessing to when the condition is met 
> and when not.

Could you please elaborate on this? I'm not sure what you've meant here.

Regards Hartmut