Re: [Boost-users] [Wave] advanced preprocessing hooks

From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2006-06-16 21:12:05

Andreas Sæbjørnsen wrote:

> A change I have done to Wave which I have not told you about 
> earlier is to
> change the behaviour of on_warning(...) in 
> 'tboost/wave/util/cpp_iterator.hpp' to 
> continue if a #warning directive is found, and not treat it 
> like an error. I do not know
> if the CVS-version still behaves in this way. I also added a 
> preprocessing hook 
> on_warning(..) for the warning directive as I need to extract 
> it. What do you think of this
> change? (Code Below for on_warning. Changed 
> 'preprocessing_hooks.hpp' attached).

Hmmm. The 'warning_directive' preprocess_exception is recoverable. That
means you may simply continue to iterate after catching this type of
exception (see the wave driver how this may be achieved). That's the reason
why I made the warning to throw an exception (same as #error). I'm not sure
if we really should change this behaviour (even more as the driver currently
depends on that).

OTOH I like your idea to add a on_warning() pp hook function (same should be
added for #error as well). What do you think, what if we use the return
value of the on_warning() pp hook to decide, whether to throw the exception?
This way we could keep the default behaviour (throwing) but you could
enforce the non-throwing behaviour simply by returning false.

Regards Hartmut

> 
> Thanks
> Andreas
> 
> 
> #if BOOST_WAVE_SUPPORT_WARNING_DIRECTIVE != 0
> //////////////////////////////////////////////////////////////
> /////////////////
> //
> //  on_warning(): handle #warning directives
> //
> //////////////////////////////////////////////////////////////
> /////////////////
> template <typename ContextT>
> inline void
> pp_iterator_functor<ContextT>::on_warning(
>     typename parse_tree_type::const_iterator const &begin,
>     typename parse_tree_type::const_iterator const &end)
> {
>     BOOST_ASSERT(ctx.get_if_block_status());
>                                                               
>                                                               
>                                   
> // preprocess the given sequence into the provided list
> token_sequence_type expanded;
> get_token_value<result_type, parse_node_type> get_value;
>                                                               
>                                                               
>                                   
> typename ref_transform_iterator_generator<
>         get_token_value<result_type, parse_node_type>,
>         typename parse_tree_type::const_iterator
>     >::type first = make_ref_transform_iterator(begin, get_value);
>                                                               
>                                                               
>                                   
> #if BOOST_WAVE_PREPROCESS_ERROR_MESSAGE_BODY != 0
> // preprocess the body of this #warning message
> token_sequence_type toexpand;
>                                                               
>                                                               
>                                   
>     std::copy(first, make_ref_transform_iterator(end, get_value),
>         std::inserter(toexpand, toexpand.end()));
>                                                               
>                                                               
>                                   
>     typename token_sequence_type::iterator begin2 = toexpand.begin();
>     ctx.expand_whole_tokensequence(begin2, toexpand.end(), expanded,
>         false);
> #else
> // simply copy the body of this #warning message to the 
> issued diagnostic
> // message
>     std::copy(first, make_ref_transform_iterator(end, get_value),
>        std::inserter(expanded, expanded.end()));
> #endif
>     //AS(051706) Added an extra hook to send the warning directive
>     std::cout << "The warning is: " << 
> boost::wave::util::impl::as_string(expanded).c_str()
>               << std::endl;
>     ctx.get_hooks().on_warning(toexpand);
>                                                               
>                                                               
>                                   
> //AS(051606) Do not treat warning directives as errors
> #if 0
> // report the corresponding error
>     BOOST_WAVE_THROW(preprocess_exception, warning_directive,
>         boost::wave::util::impl::as_string(expanded).c_str(), 
> act_pos);
> #endif
>                                                               
>                                                               
>                                   
> }
> #endif // BOOST_WAVE_SUPPORT_WARNING_DIRECTIVE != 0
> 
> 
> 
> 
> 
>  
> 
> 
> 	Regards Hartmut
> 	
> 	
> 	_______________________________________________
> 	Boost-users mailing list 
> 	Boost-users_at_[hidden]
> 	http://lists.boost.org/mailman/listinfo.cgi/boost-users
> 	
> 
> 
>