Re: debugging custom array types

[Jan Kratochvil <jan.kratochvil@redhat.com>]

On Wed, 13 Feb 2013 11:50:34 +0100, Michael Haupt wrote:
> Is there documentation somewhere that explicates which pieces of DWARF gdb
> supports out of the box?

No, read the source.


>  <1><5320>: Abbrev Number: 16 (DW_TAG_structure_type)
>     <5321>   DW_AT_name        : (indirect string, offset: 0x177): char_array   
>     <5325>   DW_AT_byte_size   : 10 byte block: 97 23 8 94 4 8 2 1e 23 c        
>     <5330>   DW_AT_sibling     : <0x5359>       
>  <2><5334>: Abbrev Number: 10 (DW_TAG_member)
>     <5335>   DW_AT_name        : (indirect string, offset: 0xdc): __hub_reference__     
>     <5339>   DW_AT_type        : <0x5c6f>       
>     <533d>   DW_AT_data_member_location: 2 byte block: 23 0     (DW_OP_plus_uconst: 0)
>  <2><5340>: Abbrev Number: 10 (DW_TAG_member)
>     <5341>   DW_AT_name        : (indirect string, offset: 0x185): __length__   
>     <5345>   DW_AT_type        : <0x2d> 
>     <5349>   DW_AT_data_member_location: 2 byte block: 23 8     (DW_OP_plus_uconst: 8)
>  <2><534c>: Abbrev Number: 10 (DW_TAG_member)
>     <534d>   DW_AT_name        : (indirect string, offset: 0x195): __array__    
>     <5351>   DW_AT_type        : <0x5a6c>       
>     <5355>   DW_AT_data_member_location: 2 byte block: 23 c     (DW_OP_plus_uconst: 12)
> ...
>  <1><5a6c>: Abbrev Number: 11 (DW_TAG_array_type)
>     <5a6d>   DW_AT_type        : <0x4f11>       
>     <5a71>   DW_AT_byte_size   : 8 byte block: 97 23 8 94 4 8 2 1e      
>     <5a7a>   DW_AT_data_location: 3 byte block: 97 23 c         (DW_OP_push_object_address; DW_OP_plus_uconst: 12)
>     <5a7e>   DW_AT_sibling     : <0x5a91>       
>  <2><5a82>: Abbrev Number: 14 (DW_TAG_subrange_type)
>     <5a83>   DW_AT_type        : <0x2d> 
>     <5a87>   DW_AT_upper_bound : 8 byte block: 97 23 8 94 4 8 1 1c      (DW_OP_push_object_address; DW_OP_plus_uconst: 8; DW_OP_deref_size: 4; DW_OP_const1u: 1; DW_OP_minus)

Even archer-jankratochvil-vla branch does not support dynamic structures:
dwarf2read.c:
read_structure_type:
  attr = dwarf2_attr (die, DW_AT_byte_size, cu);
  if (attr)
    {
      TYPE_LENGTH (type) = DW_UNSND (attr);
    }

That DW_TAG_array_type/DW_TAG_subrange_type with dynamic DW_AT_upper_bound
should be supported but not as a directly embedded part of struct.

BTW archer-jankratochvil-vla is generally wrong, its reimplementation was
discussed in:
	plan: VLA (Variable Length Arrays) and Fortran dynamic types
	http://sourceware.org/ml/gdb/2012-11/msg00094.html


Regards,
Jan