Re: [PATCH 2/3] GDB: Add support for 24 bit addresses

[Simon Marchi <simon.marchi@polymtl.ca>]

(CCing gcc-patches because of the change in include/dwarf2.h)

On 2018-08-23 13:35, John Darrington wrote:
> * include/dwarf2.h (enum dwarf_unit_type)[DW_EH_PE_udata3]: New member.
> * gdb/dwarf2-frame.c (encoding_for_size): Deal with case 3.
> 	    (read_encoded_value): Deal with case DW_EH_PE_udata3
> ---
>  gdb/dwarf2-frame.c | 7 ++++++-
>  include/dwarf2.h   | 5 ++++-
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
> index f7dc820f4d..b329e34997 100644
> --- a/gdb/dwarf2-frame.c
> +++ b/gdb/dwarf2-frame.c
> @@ -1527,12 +1527,14 @@ encoding_for_size (unsigned int size)
>      {
>      case 2:
>        return DW_EH_PE_udata2;
> +    case 3:
> +      return DW_EH_PE_udata3;
>      case 4:
>        return DW_EH_PE_udata4;
>      case 8:
>        return DW_EH_PE_udata8;
>      default:
> -      internal_error (__FILE__, __LINE__, _("Unsupported address 
> size"));
> +      internal_error (__FILE__, __LINE__, _("Unsupported address size
> %d"), size);
>      }
>  }
> 
> @@ -1605,6 +1607,9 @@ read_encoded_value (struct comp_unit *unit,
> gdb_byte encoding,
>      case DW_EH_PE_udata2:
>        *bytes_read_ptr += 2;
>        return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
> +    case DW_EH_PE_udata3:
> +      *bytes_read_ptr += 3;
> +      return (base + bfd_get_24 (unit->abfd, (bfd_byte *) buf));
>      case DW_EH_PE_udata4:
>        *bytes_read_ptr += 4;
>        return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
> diff --git a/include/dwarf2.h b/include/dwarf2.h
> index cf0039a92a..05c328057b 100644
> --- a/include/dwarf2.h
> +++ b/include/dwarf2.h
> @@ -474,11 +474,14 @@ enum dwarf_unit_type
>  #define DW_EH_PE_udata2		0x02
>  #define DW_EH_PE_udata4		0x03
>  #define DW_EH_PE_udata8		0x04
> +
> +#define DW_EH_PE_udata3		0x05
> +
> +#define DW_EH_PE_signed		0x08
>  #define DW_EH_PE_sleb128	0x09
>  #define DW_EH_PE_sdata2		0x0A
>  #define DW_EH_PE_sdata4		0x0B
>  #define DW_EH_PE_sdata8		0x0C
> -#define DW_EH_PE_signed		0x08
> 
>  #define DW_EH_PE_pcrel		0x10
>  #define DW_EH_PE_textrel	0x20

This file is owned by GCC (see the MAINTAINERS file at the top of 
binutils-gdb).  To get a modification in it, you would need to provide a 
patch to gcc, then we can import the change in binutils-gdb.

I am not too sure who is responsible for allocating these values, as 
they are not from the DWARF standard.  At the very least, there should 
be a comment to say what architecture uses this non-standard value.  Is 
there also a gcc port you are planning to upstream, that would use this 
value?

Simon