Re: circular reference chains with DW_AT_containing_type

[Mark Wielaard <mjw at redhat dot com>]

On Mon, 2011-02-21 at 15:23 +0100, Mark Wielaard wrote:
> Unfortunately there are circular reference chains for some larger c++
> programs. That was unexpected. Here is an example running dwarfcmp-test
> on itself:
> 
> $ src/dwarfcmp-test -T src/dwarfcmp-test src/dwarfcmp-test
> Reference chain cycle detected
> offset=[0x2898c8] already on the reference chain stack
> offset=[0x2889cb] subprogram
> offset=[0x2959bd] reference_type
> offset=[0x289b7c] structure_type
> offset=[0x2898c8] structure_type
> Aborted (core dumped)
> 
> And offset=[0x2898c8] is:
> 
>   <structure_type offset=[0x2898c8]
>                   specification=[0x28889b]
>                   byte_size=0x8
>                   decl_file="...libdw/c++/dwarf_data" decl_line=761
>                   containing_type=[0x2898c8]>
>   
> Is this valid dwarf? Can a structure_type have a containing_type? A
> strict reading of the dwarf4 spec seems to imply only a
> DW_TAG_ptr_to_member_type may have a DW_AT_containing_type.

For reference, this is the top of reference chain leading to this
self-referential containing_type:

   <subprogram offset=[0x2889cb]
    external=1
    name="variant<elfutils::dwarf_data::value<elfutils::dwarf_edit,
          true>::value_flag>"
    decl_file="/home/mark/src/elfutils/libdw/c++/dwarf_data"
    decl_line=779
    MIPS_linkage_name="<...some_giant_string...>"
    type=[0x2959bd]
    declaration=1>

  <reference_type offset=[0x2959bd]
   byte_size=0x8
   type=[0x289b7c]/>

  <structure_type offset=[0x289b7c]
   specification=[0x2888bf]
   byte_size=0x10
   decl_file="/home/mark/src/elfutils/libdw/c++/dwarf_data"
   decl_line=882
   containing_type=[0x2898c8]>