[cfe-dev] Adding comment callback for documentation tools

Daniel Dunbar daniel at zuster.org
Thu Oct 23 23:53:56 PDT 2008

Hi Cédric,

High bit: yes, I think this is a good idea.

While I'm not exactly sure the form the callback should take, this should
not conflict with anything else in the system and if you want to experiment
with using it to build new tools that would be very cool.

I agree that some sort of callback mechanism is the right approach, this is
in line with the current clang design. It probably makes sense for this to
be both a preprocessor callback and a parser (Action) callback. This would
allow the parser to potentially add additional information about the current
parsing state to the callback, or defer the comment Action callback in some
cases (for example, until the end of statement).

Are you planning on writing this concurrently with a consumer of the

Also, I think it might be reasonable to use this to replace the current
-verify mechanism. I believe this would make it more robust and also
somewhat easier to use. Thoughts?

 - Daniel

On Thu, Oct 23, 2008 at 9:56 AM, Cédric Venet <cedric.venet at laposte.net>wrote:

> Hi,
> Adding information in comment is useful for documentation purpose or for
>  adding information/metadata for others tools like formal proof or DSL
> code generator...
> Actually, there isn't (AFAIK) a facility to extract the comment and the
> AST at the same time.
> Since managing comment token in the parser is to complex (they can
> appear everywhere) I propose that the lexer or the preprocessor use
> callback to inform the client that he encoutered a comment.
> For example, for doxygen like tools, the callback would check if the
> comment is a documentation one, and if so, store it for later use. Once
> the AST complete, it would walk the def and associate the corresponding
> comment (or the other way around).
> Does this seems good, any other idea? alternatively, the lexer/PP could
> create a list of comment token.
> The callback could be added to clang::PPCallbacks. It is the best place
> , isn't it?
> This modification would have zero cost for classical use since lexer
> already has a condition keep comment. It would only had a conditionnal
> in the PP when a comment token is consumed.
> If this is ok, I will prepare a patch.
> regards,
> Cédric
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> cfe-dev at cs.uiuc.edu
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