Strange offsets in FIELD_DECL's...

[Chris Lattner <sabre at nondot dot org>]

I'm trying to figure out how to calculate the offset of a field in a
RECORD_DECL.  Things seem to be working, except in some simple cases:

struct Virt {
  Virt();
  virtual ~Virt();
  int X, Y;
};

Here the structure logically has three elements in it: a VTable at offset
0, 'X' at offset 4, and 'Y' at offset 8.  The problem that I'm seeing is
that both DECL_FIELD_BIT_OFFSET and DECL_FIELD_OFFSET return an
(INTEGER_CST) offset of zero for the FIELD_DECL corresponding to the X
element.  The FIELD_DECL corresponding to the Y element claims that it is
at an offset of 8 bytes from the start of the structure.  Thus, for the
three logical members, I'm currently getting offsets of [0, 0, 4], and
would like to get [0, 4, 8] in this case.

Are these the right macros to be getting this information with?  (The
tree->rtl expansion function get_inner_reference seems to be using these
macros...). BTW, the documentation on FIELD_DECL seems to be out of date,
referring to a non-existant DECL_FIELD_BITPOS macro.

Thanks for any help!

-Chris

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