[cfe-dev] Parsing C++ template parameters using cindex.py

David Röthlisberger david at rothlis.net
Sun Nov 18 09:47:18 PST 2012

On 15 Nov 2012, at 09:11, Joel de Vahl wrote:
> I am parsing a C++ file using cindex.py and want to get the template
> parameters to a specific node. However, the tree seems to be different
> depending on if the template parameter is a struct/class or a simple
> type such as int or float. In the first case the template type is
> appended as a child to the VAR_DECL node (the TYPE_REF node seen in
> the example below), but this is not the case with for example int. Any
> hint on where the template type is located for int/float/etc?

I don't have the answer (sorry) but have you tried using ipython to
experiment interactively with each member of the Cursor you're
interested in? For example see:

With ipython and your example C++ code I found that
c.type.get_declaration().displayname (where c is the cursor for
test_int) is "Test<int>" -- so it clearly *knows* the information, but I
couldn't find a way of getting at an explicit list of the type
parameters. It wouldn't surprise me if either libclang or its python
bindings is missing this functionality.

After giving up with ipython, the next thing I checked was the libclang
C headers. Index.h[1] is the public API; I searched all functions taking
a "CXCursor" or a "CXType" but didn't see anything that would return
type parameters for a template instantiation.

CXCursor.h[2], which is part of libclang's private implementation, does

    std::pair<TemplateDecl *, SourceLocation>
    getCursorTemplateRef(CXCursor C);

and TemplateDecl "stores the list of template parameters"[3].

So it seems you'd have to expose the information you want in Index.h,
then add the corresponding python bindings[4].

(Or, I could be entirely wrong and have missed something obvious. I'm
far from an expert on clang or libclang.)

[1] https://github.com/llvm-mirror/clang/blob/master/include/clang-c/Index.h
[2] https://github.com/llvm-mirror/clang/blob/bbf66ca1/tools/libclang/CXCursor.h#L102
[3] https://github.com/llvm-mirror/clang/blob/b43d87b0/include/clang/AST/DeclTemplate.h#L213
[4] https://github.com/llvm-mirror/clang/blob/master/bindings/python/clang/cindex.py

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