[PATCH] Support for DW_FORM_strx tag

[Andrew Burgess]

* Ali Tamur via gdb-patches <gdb-patches@sourceware.org> [2019-04-22 19:07:49 -0700]:

> DW_FORM_strx is the new name of DW_FORM_GNU_str_index in the Dwarf 5
> standard.
> This is a small step towards supporting Dwarf 5 in gdb.

This looks good, with a few minor nits below...

> 
> gdb/ChangeLog
> 2019-04-27  Ali Tamur  <tamur@google.com>
> 
>         * dwarf2read.c (skip_one_die): Add DW_FORM_strx
>         (read_attribute_value): Likewise
>         (dwarf2_read_addr_index): Update comment
>         (read_str_index): Add DW_FORM_strx
>         (dwarf2_string_attr): Likewise
>         (dwarf2_const_value_attr): Likewise
>         (dump_die_shallow): Likewise
>         (dwarf2_fetch_constant_bytes): Likewise
>         (skip_form_bytes): Likewise

These should all have '.' at the end.

> ---
>  gdb/dwarf2read.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
> index 829b07f01a..09ecd4fbd4 100644
> --- a/gdb/dwarf2read.c
> +++ b/gdb/dwarf2read.c
> @@ -9369,6 +9369,7 @@ skip_one_die (const struct die_reader_specs *reader,
> const gdb_byte *info_ptr,
>           info_ptr += 4 + read_4_bytes (abfd, info_ptr);
>           break;
>         case DW_FORM_addrx:
> +       case DW_FORM_strx:
>         case DW_FORM_sdata:
>         case DW_FORM_udata:
>         case DW_FORM_ref_udata:
> @@ -19295,6 +19296,7 @@ read_attribute_value (const struct die_reader_specs
> *reader,
>        DW_ADDR (attr) = read_addr_index_from_leb128 (cu, info_ptr,
> &bytes_read);
>        info_ptr += bytes_read;
>        break;
> +    case DW_FORM_strx:
>      case DW_FORM_GNU_str_index:
>        if (reader->dwo_file == NULL)
>         {
> @@ -19890,7 +19892,7 @@ dwarf2_read_addr_index (struct dwarf2_per_cu_data
> *per_cu,
>                             addr_size);
>  }
> 
> -/* Given a DW_FORM_GNU_str_index, fetch the string.
> +/* Given a DW_FORM_GNU_str_index or DW_FORM_strx, fetch the string.
>     This is only used by the Fission support.  */
> 
>  static const char *
> @@ -19907,7 +19909,7 @@ read_str_index (const struct die_reader_specs
> *reader, ULONGEST str_index)
>      &reader->dwo_file->sections.str_offsets;
>    const gdb_byte *info_ptr;
>    ULONGEST str_offset;
> -  static const char form_name[] = "DW_FORM_GNU_str_index";
> +  static const char form_name[] = "DW_FORM_GNU_str_index or DW_FORM_strx";
> 
>    dwarf2_read_section (objfile, str_section);
>    dwarf2_read_section (objfile, str_offsets_section);
> @@ -20073,6 +20075,7 @@ dwarf2_string_attr (struct die_info *die, unsigned
> int name, struct dwarf2_cu *c
>      {
>        if (attr->form == DW_FORM_strp || attr->form == DW_FORM_line_strp
>           || attr->form == DW_FORM_string
> +         || attr->form == DW_FORM_strx

Your mail client seems to have corrupted the patch slightly so I
couldn't check you had the correct tabs/spaces here.  Please double
check before you commit.

>           || attr->form == DW_FORM_GNU_str_index
>           || attr->form == DW_FORM_GNU_strp_alt)
>         str = DW_STRING (attr);
> @@ -21896,6 +21899,7 @@ dwarf2_const_value_attr (const struct attribute
> *attr, struct type *type,
>        break;
>      case DW_FORM_string:
>      case DW_FORM_strp:
> +    case DW_FORM_strx:
>      case DW_FORM_GNU_str_index:
>      case DW_FORM_GNU_strp_alt:
>        /* DW_STRING is already allocated on the objfile obstack, point
> @@ -22900,6 +22904,7 @@ dump_die_shallow (struct ui_file *f, int indent,
> struct die_info *die)
>         case DW_FORM_string:
>         case DW_FORM_strp:
>         case DW_FORM_line_strp:
> +       case DW_FORM_strx:

Same white space check here please.

>         case DW_FORM_GNU_str_index:
>         case DW_FORM_GNU_strp_alt:
>           fprintf_unfiltered (f, "string: \"%s\" (%s canonicalized)",
> @@ -23328,6 +23333,7 @@ dwarf2_fetch_constant_bytes (sect_offset sect_off,
>        break;
>      case DW_FORM_string:
>      case DW_FORM_strp:
> +    case DW_FORM_strx:
>      case DW_FORM_GNU_str_index:
>      case DW_FORM_GNU_strp_alt:
>        /* DW_STRING is already allocated on the objfile obstack, point
> @@ -24293,6 +24299,7 @@ skip_form_bytes (bfd *abfd, const gdb_byte *bytes,
> const gdb_byte *buffer_end,
> 
>      case DW_FORM_addrx:
>      case DW_FORM_sdata:
> +    case DW_FORM_strx:
>      case DW_FORM_udata:
>      case DW_FORM_GNU_addr_index:
>      case DW_FORM_GNU_str_index:

Additionally could you look at expanding 'proc _handle_DW_FORM' in
gdb/testsuite/lib/dwarf.exp to also handle DW_FORM_strx, this should
just require adding a line like this 'DW_FORM_strx -' at the correct
place.

Thanks,
Andrew