Re: [Boost-users] [Wave] extracting preprocessing grammar andcommentsfrom sourcefile

From: Andreas Sæbjørnsen (andreas.saebjoernsen_at_[hidden])
Date: 2005-11-01 21:03:25

The hooks you are proposing satisfies my needs very well and appreciate that
you add these hooks to Wave as it makes and will make my life a lot easier.
I agree to your point on the comments and can build the rest I need on top
of Wave. When and how should I expect to be able to test a new Wave version
with these hooks?

Thanks,
Andreas

On 11/1/05, Hartmut Kaiser <hartmut.kaiser_at_[hidden]> wrote:
>
> extracting the C/C++ statement or expression
> > > that the unexpanded macro (and expanded) is
> > > a part of.
> I was thinking about to add new hooks to the preprocessing hooks template
> from the very beginning. Sorry for not beeing consise enough.
>
> For consistency reasons I'ld suggest to add a hook:
>
> template <typename TokenT>
> void
> found_directive(TokenT const& directive);
>
> Where directive refers to the token containing the found pp directive.
>
> >
> > yes, so that I can extract the unexpanded preprocessor
> > conditional expression and when this expression is
> > (macro-)expanded if the result is positive or negative.
> > For instance in the example
> > #define BAR
> > #ifdef BAR
> > int x;
> > #ifdef FOO
> > int y;
> > #endif
> > #endif
> > I would be interested in extracting '#ifdef BAR' and also
> > that it is evaluated as true. I would also be interested in
> > extracting '#ifdef FOO' and that it is evaluated as false.
>
> What about:
>
> template <typename ContainerT>
> void
> evaluated_conditional_expression(ContainerT const& expression,
> bool expression_value);
>
> Where:
> - expression contains the (not expanded) expression tokensequence and
> - expression_value is the result of the evaluation of this expression.
>
> > > *after evaluating the preprocessor conditional,
> > > extract the portion which was evaluated as false as a string
> > >
> > > #define positive
> > > #ifdef int positive
> > > #endif /*Extract this false part as string*/ int x; #endif
>
> template <typename ContainerT>
> void
> skipped_token(TokenT const& token);
>
> Where token is the skipped token. This hook will be called for each token
> which gets skipped due to a false preproccessing condition.
>
> > I am only interested in defined macros. To be more specific I
> > am interested in when the preprocessor recognises a macro.
> > For each macro it is interesting to extract the value and
> > position in the file. The macro can be found in two forms;
> > the one before macro-expansion and the one after. Both forms
> > are interesting. But this is from what I have seen already
> > handled in struct default_preprocessing_hooks.
> > 1: #define FOO int x;
> > 2: FOO
> > On line 2 in this example code the macro FOO is found. This
> > macro can be expanded to 'int x', which to the preprocessor
> > is equivalent to the unexpanded macro FOO found on line 1.
>
> Yeah, I was already wondering how you might want to decide whether a
> identifier actually is a 'undefined' macro :-P
> This information already should be avalable through the existing
> preproceesing hooks.
>
> > > *extracting the C/C++ statement or expression
> > > that the unexpanded macro (and expanded) is
> > > a part of.
> >
> > This conceptually isn't possible at the preprocessor
> > level because it has no
> > notion of a C++ statement/expression.
>
> I would not like to put any functionality into the library which does not
> belong to its purpose: preprocessing C++. I'm pretty sure, that you'll be
> able to build this on top of Wave.
>
> > > *extract the value and position of all C and
> > > C++ comments
> >
> > This one is easy. Just enable the preserve comments
> > mode and all the comment
> > tokens will be part of the generated output token sequence.
> >
> > Great. :) What about making a hook for this within stuct
> > default_preprocessing_hooks also?
>
> Why? The preprocessing hooks are there to allow to access information not
> available from the generated token stream itself, i.e. information about
> the
> actual work inside the preprocessor. But the comments are available in the
> generated token stream already. If I would add such a hook, somebody else
> would like to have a special hook for line endings etc.
>
> > It would be very interesting to do some work on this, and it
> > would be useful to hear what you think about adding the
> > additional hooks we have been talking about. Maybe these
> > hooks should be better specified.
>
> Do these new hooks satisfy your needs?
>
> Regards Hartmut
>
>
>
>
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