libclang: "Spelling" for built-in types?

Clang Frontend
1

Hi,

Using the libclang python bindings, how do I retrieve the name ("spelling") of a built-in type?

I'll clarify with an example. For this source code "type.cpp":

    struct S { };
    S s;
    int i;

I obtain 2 Cursor objects "cs" and "ci" for the above variables "s" and "i":

    import clang.cindex
    index = clang.cindex.Index.create()
    tu = index.parse("type.cpp")
    cursors = tu.cursor.get_children()
    c = cursors.next()
    while c.spelling != "s":
        c = cursors.next()
    cs = c
    ci = cursors.next()

I can get the name of the user-defined type S:

    cs.type.get_declaration().spelling

which returns "S". But how do I get the type of "i"? Trying the same as the above:

    ci.type.get_declaration().spelling

returns None (python's null). The closest I've found is:

    ci.type.kind.spelling

which returns "Int". For other types it will return strings like "UChar", "Char16", "LongLong", or "Pointer". What I want is "int", "char", "int*", etc -- the way the type would be written in the source code.

Is this information available and I just haven't found it?

If not currently exposed by libclang, how hard would it be to add this information? And how would I go about it? (I don't want to reverse-engineer from the TypeKind.spelling†, and in some cases I couldn't if I wanted -- e.g. "Pointer" doesn't give me enough information.)

Thanks very much!
Dave.

† clang_getTypeKindSpelling: clang/CXType.cpp at 25bd27932a5b94c8314bf1b999fdea1c4032f11d · llvm-mirror/clang · GitHub
and its python binding: clang/cindex.py at a63ef1f63f9c2ae847fac25534c9e1a214efabbc · llvm-mirror/clang · GitHub

2

I have a big switch statement, used on type.kind, for the built-in types.

If it's a pointer you can do the same as above but append a star "*". I don't know if there's a better way, I would prefer that "spelling" worked on built-in types as well.

3

Thanks Jacob. I was afraid that would be the case. Is your code publicly
available, and if so, can you share a link to it?

I've found BuiltinType::getName in clang/lib/AST/Type.cpp, which does a
switch statement mapping from the enum values like "UChar" to a string
like "unsigned char".

To anyone else familiar with clang internals, could I please have your
thoughts on the following addition to libclang (I know next to nothing
about the clang & libclang internals, so any guidance is greatly
appreciated):

A new function: CXString clang_getTypeSpelling(CXType)

What it does:
1. For builtin types, returns a string like "unsigned char" (see
   BuiltinType::getName in clang/lib/AST/Type.cpp).
2. For more complex types (pointers, templates) recurses over the type's
   components, constructing a string like "int*" or "map<int, int>".
3. For user-defined types, returns
   clang_getCursorSpelling(clang_getTypeDeclaration(type)).

Justification: Prevent different libclang clients from implementing the
same functionality over and over.
The existing clang_getTypeKindSpelling operates on a CXTypeKind, which
is just an enum and lacks the information for 2 & 3 above.

Thanks,
Dave.

4

Sure:

https://github.com/jacob-carlborg/dstep/blob/master/dstep/translator/Type.d

This code is written in D and a bit specialized for my tool but it should be easy to make it do what you want it to do. Feel free to ask if there's something you don't understand.