How to extract comments and match to declaration with RecursiveASTVisitor in libclang c++?

Question

I am writing a utility which is supposed to parse C++ (and C) header files, extract the structs, enums, fields etc. and generate code in other languages based on the extracted information. I decided to use libclang for this.

I'm using a RecursiveASTVisitor and it seems I'm able to extract all the information I need, except for comments.

I want to have the comment which appears right above every declaration (field, struct, class, enum) read, and add its text when I generate the code in other languages.

The problem is that all the samples I saw which use comments use CxCursor and the C interface for clang, and I have no idea how to get the CxCursor in my context.

So - how can I extract comments while still using RecursiveASTVisitor?

Answer 1

With some more digging up, I found this:

For any relevant visited Decl (VisitXXXDecl), I can do this:

virtual bool VisitDecl(Decl* d)
{
    ASTContext& ctx = d->getASTContext();
    SourceManager& sm = ctx.getSourceManager();

    const RawComment* rc = d->getASTContext().getRawCommentForDeclNoCache(d);
    if (rc)
    {
        //Found comment!
        SourceRange range = rc->getSourceRange();

        PresumedLoc startPos = sm.getPresumedLoc(range.getBegin());
        PresumedLoc endPos = sm.getPresumedLoc(range.getEnd());

        std::string raw = rc->getRawText(sm);
        std::string brief = rc->getBriefText(ctx);

        // ... Do something with positions or comments
    }

    // ...
}

Note that this identifies (as far as I could see...) comments which are in the line(s) above (and adjacent!) to the current declaration in the code, and which are in one of the following formats:

• /// Comment
• /** Comment */
• //! Comment

For example, in the following case:

/// A field with a long long comment
/// A two-liner
long long LongLongData;

raw will be:

/// A field with a long long comment
    /// A two-liner

And brief will be:

A field with a long long comment A two-liner

Either way, it's good enough for my needs.

Answer 2

The above answer is perfect. But to make the API getRawCommentForDeclNoCache return normal comments like // or /* you need to provide option "-fparse-all-comments" while invoking clang. Because by default clang parses only Doxygen style comments.