Retrieving comments using python libclang

Question

In the following header file I'd like to get the corresponding +reflect comment to the class and member variable:

#ifndef __HEADER_FOO
#define __HEADER_FOO

//+reflect
class Foo
{
    public:
    private:
        int m_int; //+reflect
};

#endif

Using the python bindings for libclang and the following script:

import sys
import clang.cindex

def dumpnode(node, indent):
    print ' ' * indent, node.kind, node.spelling
    for i in node.get_children():
        dumpnode(i, indent+2)

def main():
    index = clang.cindex.Index.create()
    tu = index.parse(sys.argv[1], args=['-x', 'c++'])

    dumpnode(tu.cursor, 0)

if __name__ == '__main__':
    main()

Gives me this output:

CursorKind.TRANSLATION_UNIT None
  CursorKind.TYPEDEF_DECL __builtin_va_list
  CursorKind.CLASS_DECL type_info
  CursorKind.CLASS_DECL Foo
    CursorKind.CXX_ACCESS_SPEC_DECL
    CursorKind.CXX_ACCESS_SPEC_DECL
    CursorKind.FIELD_DECL m_int

The problem is that the comments are missing. Are they stripped by the preprocessor? Is there any way to prevent that?

Answer 1

To do this you need to get the tokens, not the cursors. If I run this script on the file above:

import sys
import clang.cindex

def srcrangestr(x):
    return '%s:%d:%d - %s:%d:%d' % (x.start.file, x.start.line, x.start.column, x.end.file, x.end.line, x.end.column)

def main():
    index = clang.cindex.Index.create()
    tu = index.parse(sys.argv[1], args=['-x', 'c++'])

    for x in tu.cursor.get_tokens():
        print x.kind
        print "  " + srcrangestr(x.extent)
        print "  '" + str(x.spelling) + "'"

if __name__ == '__main__':
    main()

I get the following:

TokenKind.PUNCTUATION
  test2.h:1:1 - test2.h:1:2
  '#'
TokenKind.IDENTIFIER
  test2.h:1:2 - test2.h:1:8
  'ifndef'
TokenKind.IDENTIFIER
  test2.h:1:9 - test2.h:1:21
  '__HEADER_FOO'
TokenKind.PUNCTUATION
  test2.h:2:1 - test2.h:2:2
  '#'
TokenKind.IDENTIFIER
  test2.h:2:2 - test2.h:2:8
  'define'
TokenKind.IDENTIFIER
  test2.h:2:9 - test2.h:2:21
  '__HEADER_FOO'
TokenKind.COMMENT
  test2.h:4:1 - test2.h:4:11
  '//+reflect'
TokenKind.KEYWORD
  test2.h:5:1 - test2.h:5:6
  'class'
TokenKind.IDENTIFIER
  test2.h:5:7 - test2.h:5:10
  'Foo'
TokenKind.PUNCTUATION
  test2.h:6:1 - test2.h:6:2
  '{'
TokenKind.KEYWORD
  test2.h:7:5 - test2.h:7:11
  'public'
TokenKind.PUNCTUATION
  test2.h:7:11 - test2.h:7:12
  ':'
TokenKind.KEYWORD
  test2.h:8:5 - test2.h:8:12
  'private'
TokenKind.PUNCTUATION
  test2.h:8:12 - test2.h:8:13
  ':'
TokenKind.KEYWORD
  test2.h:9:9 - test2.h:9:12
  'int'
TokenKind.IDENTIFIER
  test2.h:9:13 - test2.h:9:18
  'm_int'
TokenKind.PUNCTUATION
  test2.h:9:18 - test2.h:9:19
  ';'
TokenKind.COMMENT
  test2.h:9:20 - test2.h:9:30
  '//+reflect'
TokenKind.PUNCTUATION
  test2.h:10:1 - test2.h:10:2
  '}'
TokenKind.PUNCTUATION
  test2.h:10:2 - test2.h:10:3
  ';'
TokenKind.PUNCTUATION
  test2.h:12:1 - test2.h:12:2
  '#'
TokenKind.IDENTIFIER
  test2.h:12:2 - test2.h:12:7
  'endif'

Which should be enough for me to work with.

Answer 2

You need to modify the cindex.py script and expose the following function.

class Cursor(Structure):
   def getRawComment(self):
    return conf.lib.clang_Cursor_getRawCommentText(self)

also add this to the correct spot in cindex.py

("clang_Cursor_getRawCommentText",
 [Cursor],
 _CXString,
 _CXString.from_result),

I had to make my comments using

 /*!
  * +reflect
  */

though

Answer 3

Yes, all comments are removed by the preprocessor. You can see that by doing clang -E mycode.c > mycode.i, which will give you a mycode.i file with all the preprocessing, but no comments.

You may be able to do something using a #pragma or something that isn't stripped and is ignored by the compiler.