[patchv2+8.0] DWARF-5 Fix DW_FORM_implicit_const

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Thu, 24 Aug 2017 01:08:01 +0200, Pedro Alves wrote:
> Wouldn't that be more direct and to the point?  If I'm imagining
> that version of the patch correctly, that'd seem like a
> more obvious choice to me.  The proposed version looks like is
> frobbing the form so that DW_FORM_sdata so that those two other
> functions end up doing the right thing as side effect.  Right?
> Is there some advantage to doing it the sdata way?  It kind of feels
> like a hack, but maybe I'm missing something.

Is this patch OK?

Regression tested on fedora-rawhide {x86_64,x86_64-m32,i686}.


Thanks,
Jan

gdb/ChangeLog
2017-08-24  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* dwarf2read.c (dwarf2_const_value_attr, dump_die_shallow)
	(dwarf2_get_attr_constant_value, dwarf2_fetch_constant_bytes)
	(skip_form_bytes, attr_form_is_constant): Handle DW_FORM_implicit_const.

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 38228500ab..d4dd01b8b3 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -19499,6 +19499,7 @@ dwarf2_const_value_attr (const struct attribute *attr, struct type *type,
       break;
 
     case DW_FORM_sdata:
+    case DW_FORM_implicit_const:
       *value = DW_SND (attr);
       break;
 
@@ -20492,6 +20493,10 @@ dump_die_shallow (struct ui_file *f, int indent, struct die_info *die)
 	  fprintf_unfiltered (f, 
 			      "unexpected attribute form: DW_FORM_indirect");
 	  break;
+	case DW_FORM_implicit_const:
+	  fprintf_unfiltered (f, "constant: %s",
+			      plongest (DW_SND (&die->attrs[i])));
+	  break;
 	default:
 	  fprintf_unfiltered (f, "unsupported attribute form: %d.",
 		   die->attrs[i].form);
@@ -20583,7 +20588,7 @@ dwarf2_get_ref_die_offset (const struct attribute *attr)
 static LONGEST
 dwarf2_get_attr_constant_value (const struct attribute *attr, int default_value)
 {
-  if (attr->form == DW_FORM_sdata)
+  if (attr->form == DW_FORM_sdata || attr->form == DW_FORM_implicit_const)
     return DW_SND (attr);
   else if (attr->form == DW_FORM_udata
            || attr->form == DW_FORM_data1
@@ -20918,6 +20923,7 @@ dwarf2_fetch_constant_bytes (sect_offset sect_off,
       break;
 
     case DW_FORM_sdata:
+    case DW_FORM_implicit_const:
       type = die_type (die, cu);
       result = write_constant_as_bytes (obstack, byte_order,
 					type, DW_SND (attr), len);
@@ -21854,6 +21860,9 @@ skip_form_bytes (bfd *abfd, const gdb_byte *bytes, const gdb_byte *buffer_end,
 	}
       break;
 
+    case DW_FORM_implicit_const:
+      break;
+
     default:
       {
       complain:
@@ -22495,6 +22504,7 @@ attr_form_is_constant (const struct attribute *attr)
     case DW_FORM_data2:
     case DW_FORM_data4:
     case DW_FORM_data8:
+    case DW_FORM_implicit_const:
       return 1;
     default:
       return 0;