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

From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2006-06-16 20:03:04

Andreas Sæbjørnsen wrote:

> I have a question and a suggestion regarding Wave. First I 
> have a problem when preprocessing the following file:
> #if 0                                                         
> #elif 1
> test
> #endif
>                                                               
> #if 1                                                         
> #elif 0
> int x;                                                        
> #endif
> The first '#elif' directive is registered as an 
> 'evaluated_conditional_expression(...)', but the second 
> '#elif' is never evaluated since the previous
> '#if' directive is true, and it is therefore not registered 
> as either a 'skipped_token(...)' or  an 
> 'evaluated_conditional_expression(...)'. The way I 
> expected it to work was to register it as a 
> 'skipped_token(...)'. Do you have a suggestion to how I 
> should otherwise be handling this? 
> If not, could it be possible to add the non-evaluated '#elif' 
> to the skipped token stream? 

This is fixed now (Boost CVS::HEAD and Boost CVS::BOOST_RC_1_34). Thanks for
reporting.

> The suggestion is for preprocessor generated tokens where the 
> 'macro.get_position().get_file().size() == 0'. An example
> of this is in the following code
> 
> #ifdef SOME_MACRO
> //DO SOMETHING
> #endif
> 
> Since 'SOME_MACRO' is not defined the 
> 'expanding_object_like_macro(TokenT const &macro,....)' will 
> be passed a TokentT& const& macro
> with no position object, so asking for the line or column 
> number will give a hard to debug segmentation fault. 

This one is really strange, because if SOME_MACRO is not defined then the
expanding_object_like_macro() pp hook shouldn't be called for this macro.
For this reason I'm not able to reproduce this issue here. 

Nevertheless, I think it's a bug if 'macro.get_position().get_file().size()
== 0' in any case (any token should have some associated file/position it
was encountered at). Could you please try to isolate this problem and send
me a sample?

Regards Hartmut