[cfe-dev] Regarding clang-c and comments...

[Doug]

Right, well thanks for the help.

Looks like for the time being it's going to be a case of handling it
manually.

Once the whole project is working I may come back and dig this thread
backup again for a bit of help with the PreprocessedEntity as you've
describe.

Personally I think it'd be very valuable to support comments as some kind
of entity in the AST; its pretty much a fundamental requirement for
building an visual studio style editor with contextual tooltips (something
I notice the eclipse CDT is particularly poor at, probably for this reason).

Cheers,
Doug.

On Wed, Nov 2, 2011 at 2:28 AM, Douglas Gregor <dgregor at apple.com> wrote:

> On Oct 26, 2011, at 8:59 PM, Doug wrote:
>
> > Hi there,
> >
> > I'm writing a very simple c parser (dumps formatted symbols, something
> similar to ctags but actually working) using clang-c, which is working
> well, but I'm hoping to add some support for source comments in the code.
> >
> > At the moment I'm using the clang-c subset for this, but there doesn't
> seem to be any api for accessing comments; specifically CXCursorKind
> doesn't seem to have a type for 'comment', and I've ended up doing
> something similar to:
> >
> > for each cursor
> >   get cursor info
> >   save info (specifically, offset, filename, display name)
> >
> > for each saved symbol:
> >   find the closest previous symbol
> >   walk backwards through the file from position of symbol -> position of
> previous symbol looking for closest comment
> >
> > This is quite annoying to do, and has a few problems (example: symbols
> with no filename, unsaved files, large projects means loading every symbol
> into memory).
> >
> > Is there a to get comments as elements through to the visitor function?
> > If no in clang-c, then perhaps in the full clang api?
>
> As Eli noted, Clang's ASTs don't keep track of comments at all. I took a
> stab at this a few years ago, here
>
>        http://llvm.org/viewvc/llvm-project?view=rev&revision=74704
>
> but then reverted all of the code because it never actually got used.
>
> For Clang's C API, there's another (fairly simple) approach: one could
> extend the PreprocessingRecord to include comments as a new kind of
> "PreprocessedEntity", and then provide cursors for those comment entities.
> It would then be fairly easy to provide an API function in the C API to
> retrieve the comment text.
>
> > Finally, as a slightly better alternative, is there a way to query a
> cursor to get the previous lexical cursor? At the very least this would
> save me having to save the entire set of data in memory first..
>
> No, there is no way to get the previous lexical cursor. This information
> is not stored in the AST (we don't want to pay a pointer per node for
> something that's rarely needed).
>
>        - Doug
>
>
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