Hi,
I'm trying to use libclang through ruby-ffi.
But calling clang_getLocation causes segfault.
Sample code and result are below.
I ran similar c code and it worked fine.
clang_getLocation specification is here.
http://clang.llvm.org/doxygen/group__CINDEX__LOCATIONS.html#ga86d822034407d60d9e1f36e07cbc0f67

require 'ffi'

module Lib
  extend FFI::Library

  libs = ["clang"]

  ffi_lib libs

 
attach_function :create_index,                       :clang_createIndex,
[:int,      :int],     :pointer

  TranslationUnitFlags     = enum
[:none, :detailed_preprocessing_record, :incomplete, :precompiled_preamble, :cache_completion_results]

 
attach_function :parse_translation_unit,             :clang_parseTranslationUnit,
[:pointer,  :string,   :pointer, :int, :pointer, :uint, :uint], :pointer

  attach_function :get_file, :clang_getFile,
[:pointer, :string], :pointer

  attach_function :get_cursor, :clang_getCursor,
[:pointer, :pointer], :pointer

  class CXSourceLocation < FFI::Struct
    layout :ptr_data, :pointer,
           :int_data, :uint
  end

  attach_function :get_location, :clang_getLocation,
[:pointer, :pointer, :uint, :uint], CXSourceLocation.by_value

  def self.bitmask_from(enum, opts)
    bitmask = 0

    opts.each do |key, val|
      next unless val

      if int = enum[key]
        bitmask |= int
      else
        raise Error, "unknown option: #{key.inspect}, expected one of
#{enum.symbols}"
      end
    end

    bitmask
  end
end

def args_pointer_from(command_line_args)
  args_pointer = FFI::MemoryPointer.new(:pointer)

  strings = command_line_args.map do |arg|
    FFI::MemoryPointer.from_string(arg.to_s)
  end

  args_pointer.put_array_of_pointer(0, strings) unless strings.empty?
  args_pointer
end

def options_bitmask_from(opts)
  Lib.bitmask_from Lib::TranslationUnitFlags, opts
end

filename = "/Users/shinichi/programming/ffi-clang/spec/fixtures/a.c"
index = Lib.create_index(1, 1)
tu = Lib.parse_translation_unit(index, filename,
args_pointer_from([]), 0, nil, 0, options_bitmask_from({}))
file = Lib.get_file(tu, filename)
loc = Lib.get_location(tu, file, 3, 16) # causes segfault
# cursor = Lib.get_cursor(tu, loc)

### Result ###

spec/get_location_test.rb:64: [BUG] Segmentation fault
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.8.0]

-- control frame ----------
c:0004 p:---- s:0018 b:0018 l:000017 d:000017 CFUNC  :get_location
c:0003 p:0181 s:0011 b:0011 l:0014e8 d:000b70 EVAL   spec/
get_location_test.rb:64
c:0002 p:---- s:0004 b:0004 l:000003 d:000003 FINISH
c:0001 p:0000 s:0002 b:0002 l:0014e8 d:0014e8 TOP
---------------------------
-- Ruby level backtrace information
----------------------------------------
spec/get_location_test.rb:64:in `<main>'
spec/get_location_test.rb:64:in `get_location'

-- C level backtrace information
-------------------------------------------

[NOTE]
You may have encountered a bug in the Ruby interpreter or extension
libraries.
Bug reports are welcome.
For details: http://www.ruby-lang.org/bugreport.html