libbacktrace: gather address ranges from skeleton units

	* dwarf.c (find_address_ranges): Handle skeleton units.
	(read_function_entry): Likewise.

Author: ianlancetaylor

dwarf.c

@@ -49,6 +49,7 @@ enum dwarf_tag {
   DW_TAG_compile_unit = 0x11,
   DW_TAG_inlined_subroutine = 0x1d,
   DW_TAG_subprogram = 0x2e,
+  DW_TAG_skeleton_unit = 0x4a,
 };
 
 enum dwarf_form {
@@ -2322,42 +2323,48 @@ find_address_ranges (struct backtrace_state *state, uintptr_t base_address,
 	      break;
 
 	    case DW_AT_stmt_list:
-	      if (abbrev->tag == DW_TAG_compile_unit
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
 		  && (val.encoding == ATTR_VAL_UINT
 		      || val.encoding == ATTR_VAL_REF_SECTION))
 		u->lineoff = val.u.uint;
 	      break;
 
 	    case DW_AT_name:
-	      if (abbrev->tag == DW_TAG_compile_unit)
+	      if (abbrev->tag == DW_TAG_compile_unit
+		  || abbrev->tag == DW_TAG_skeleton_unit)
 		{
 		  name_val = val;
 		  have_name_val = 1;
 		}
 	      break;
 
 	    case DW_AT_comp_dir:
-	      if (abbrev->tag == DW_TAG_compile_unit)
+	      if (abbrev->tag == DW_TAG_compile_unit
+		  || abbrev->tag == DW_TAG_skeleton_unit)
 		{
 		  comp_dir_val = val;
 		  have_comp_dir_val = 1;
 		}
 	      break;
 
 	    case DW_AT_str_offsets_base:
-	      if (abbrev->tag == DW_TAG_compile_unit
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
 		  && val.encoding == ATTR_VAL_REF_SECTION)
 		u->str_offsets_base = val.u.uint;
 	      break;
 
 	    case DW_AT_addr_base:
-	      if (abbrev->tag == DW_TAG_compile_unit
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
 		  && val.encoding == ATTR_VAL_REF_SECTION)
 		u->addr_base = val.u.uint;
 	      break;
 
 	    case DW_AT_rnglists_base:
-	      if (abbrev->tag == DW_TAG_compile_unit
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
 		  && val.encoding == ATTR_VAL_REF_SECTION)
 		u->rnglists_base = val.u.uint;
 	      break;
@@ -2385,17 +2392,19 @@ find_address_ranges (struct backtrace_state *state, uintptr_t base_address,
 	}
 
       if (abbrev->tag == DW_TAG_compile_unit
-	  || abbrev->tag == DW_TAG_subprogram)
+	  || abbrev->tag == DW_TAG_subprogram
+	  || abbrev->tag == DW_TAG_skeleton_unit)
 	{
 	  if (!add_ranges (state, dwarf_sections, base_address,
 			   is_bigendian, u, pcrange.lowpc, &pcrange,
 			   add_unit_addr, (void *) u, error_callback, data,
 			   (void *) addrs))
 	    return 0;
 
-	  /* If we found the PC range in the DW_TAG_compile_unit, we
-	     can stop now.  */
-	  if (abbrev->tag == DW_TAG_compile_unit
+	  /* If we found the PC range in the DW_TAG_compile_unit or
+	     DW_TAG_skeleton_unit, we can stop now.  */
+	  if ((abbrev->tag == DW_TAG_compile_unit
+	       || abbrev->tag == DW_TAG_skeleton_unit)
 	      && (pcrange.have_ranges
 		  || (pcrange.have_lowpc && pcrange.have_highpc)))
 	    return 1;
@@ -3607,7 +3616,8 @@ read_function_entry (struct backtrace_state *state, struct dwarf_data *ddata,
 
 	  /* The compile unit sets the base address for any address
 	     ranges in the function entries.  */
-	  if (abbrev->tag == DW_TAG_compile_unit
+	  if ((abbrev->tag == DW_TAG_compile_unit
+	       || abbrev->tag == DW_TAG_skeleton_unit)
 	      && abbrev->attrs[i].name == DW_AT_low_pc)
 	    {
 	      if (val.encoding == ATTR_VAL_ADDRESS)