Use setter for attribute's unsigned value

This adds form_is_unsigned and an unsigned setter method to struct
attribute, and updates the remaining code.  Now DW_UNSND is no longer
used as an lvalue.

gdb/ChangeLog
2020-09-29  Tom Tromey  <tom@tromey.com>

	* dwarf2/read.c (read_attribute_value): Update.
	* dwarf2/attribute.h (struct attribute) <form_is_unsigned,
	set_unsigned>: New methods.
	* dwarf2/attribute.c (attribute::form_is_unsigned): New method.

3 files changed, 59 insertions, 26 deletions

diff --git a/gdb/dwarf2/attribute.c b/gdb/dwarf2/attribute.c
index c8e556f..69c59cc 100644
--- a/gdb/dwarf2/attribute.c
+++ b/gdb/dwarf2/attribute.c
@@ -159,3 +159,26 @@ attribute::constant_value (int default_value) const
       return default_value;
     }
 }
+
+/* See attribute.h.  */
+
+bool
+attribute::form_is_unsigned () const
+{
+  return (form == DW_FORM_ref_addr
+	  || form == DW_FORM_GNU_ref_alt
+	  || form == DW_FORM_data2
+	  || form == DW_FORM_data4
+	  || form == DW_FORM_data8
+	  || form == DW_FORM_sec_offset
+	  || form == DW_FORM_data1
+	  || form == DW_FORM_flag
+	  || form == DW_FORM_flag_present
+	  || form == DW_FORM_udata
+	  || form == DW_FORM_rnglistx
+	  || form == DW_FORM_ref1
+	  || form == DW_FORM_ref2
+	  || form == DW_FORM_ref4
+	  || form == DW_FORM_ref8
+	  || form == DW_FORM_ref_udata);
+}
diff --git a/gdb/dwarf2/attribute.h b/gdb/dwarf2/attribute.h
index 9178276..3067e2a 100644
--- a/gdb/dwarf2/attribute.h
+++ b/gdb/dwarf2/attribute.h
@@ -124,6 +124,9 @@ struct attribute
   /* Check if the attribute's form is a string form.  */
   bool form_is_string () const;
 
+  /* Check if the attribute's form is an unsigned integer form.  */
+  bool form_is_unsigned () const;
+
   /* Return DIE offset of this attribute.  Return 0 with complaint if
      the attribute is not of the required kind.  */
 
@@ -190,6 +193,13 @@ struct attribute
     u.snd = snd;
   }
 
+  /* Set this attribute to an unsigned integer.  */
+  void set_unsigned (ULONGEST unsnd)
+  {
+    gdb_assert (form_is_unsigned ());
+    u.unsnd = unsnd;
+  }
+
 
   ENUM_BITFIELD(dwarf_attribute) name : 16;
   ENUM_BITFIELD(dwarf_form) form : 15;
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 190d38e..c572ed4 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -19692,15 +19692,16 @@ read_attribute_value (const struct die_reader_specs *reader,
     {
     case DW_FORM_ref_addr:
       if (cu->header.version == 2)
-	DW_UNSND (attr) = cu->header.read_address (abfd, info_ptr,
-						   &bytes_read);
+	attr->set_unsigned (cu->header.read_address (abfd, info_ptr,
+						     &bytes_read));
       else
-	DW_UNSND (attr) = cu->header.read_offset (abfd, info_ptr,
-						  &bytes_read);
+	attr->set_unsigned (cu->header.read_offset (abfd, info_ptr,
+						    &bytes_read));
       info_ptr += bytes_read;
       break;
     case DW_FORM_GNU_ref_alt:
-      DW_UNSND (attr) = cu->header.read_offset (abfd, info_ptr, &bytes_read);
+      attr->set_unsigned (cu->header.read_offset (abfd, info_ptr,
+						  &bytes_read));
       info_ptr += bytes_read;
       break;
     case DW_FORM_addr:
@@ -19728,15 +19729,15 @@ read_attribute_value (const struct die_reader_specs *reader,
       attr->set_block (blk);
       break;
     case DW_FORM_data2:
-      DW_UNSND (attr) = read_2_bytes (abfd, info_ptr);
+      attr->set_unsigned (read_2_bytes (abfd, info_ptr));
       info_ptr += 2;
       break;
     case DW_FORM_data4:
-      DW_UNSND (attr) = read_4_bytes (abfd, info_ptr);
+      attr->set_unsigned (read_4_bytes (abfd, info_ptr));
       info_ptr += 4;
       break;
     case DW_FORM_data8:
-      DW_UNSND (attr) = read_8_bytes (abfd, info_ptr);
+      attr->set_unsigned (read_8_bytes (abfd, info_ptr));
       info_ptr += 8;
       break;
     case DW_FORM_data16:
@@ -19747,7 +19748,8 @@ read_attribute_value (const struct die_reader_specs *reader,
       attr->set_block (blk);
       break;
     case DW_FORM_sec_offset:
-      DW_UNSND (attr) = cu->header.read_offset (abfd, info_ptr, &bytes_read);
+      attr->set_unsigned (cu->header.read_offset (abfd, info_ptr,
+						  &bytes_read));
       info_ptr += bytes_read;
       break;
     case DW_FORM_loclistx:
@@ -19812,15 +19814,12 @@ read_attribute_value (const struct die_reader_specs *reader,
       attr->set_block (blk);
       break;
     case DW_FORM_data1:
-      DW_UNSND (attr) = read_1_byte (abfd, info_ptr);
-      info_ptr += 1;
-      break;
     case DW_FORM_flag:
-      DW_UNSND (attr) = read_1_byte (abfd, info_ptr);
+      attr->set_unsigned (read_1_byte (abfd, info_ptr));
       info_ptr += 1;
       break;
     case DW_FORM_flag_present:
-      DW_UNSND (attr) = 1;
+      attr->set_unsigned (1);
       break;
     case DW_FORM_sdata:
       attr->set_signed (read_signed_leb128 (abfd, info_ptr, &bytes_read));
@@ -19830,27 +19829,27 @@ read_attribute_value (const struct die_reader_specs *reader,
       *need_reprocess = true;
       /* FALLTHROUGH */
     case DW_FORM_udata:
-      DW_UNSND (attr) = read_unsigned_leb128 (abfd, info_ptr, &bytes_read);
+      attr->set_unsigned (read_unsigned_leb128 (abfd, info_ptr, &bytes_read));
       info_ptr += bytes_read;
       break;
     case DW_FORM_ref1:
-      DW_UNSND (attr) = (to_underlying (cu->header.sect_off)
-			 + read_1_byte (abfd, info_ptr));
+      attr->set_unsigned ((to_underlying (cu->header.sect_off)
+			   + read_1_byte (abfd, info_ptr)));
       info_ptr += 1;
       break;
     case DW_FORM_ref2:
-      DW_UNSND (attr) = (to_underlying (cu->header.sect_off)
-			 + read_2_bytes (abfd, info_ptr));
+      attr->set_unsigned ((to_underlying (cu->header.sect_off)
+			   + read_2_bytes (abfd, info_ptr)));
       info_ptr += 2;
       break;
     case DW_FORM_ref4:
-      DW_UNSND (attr) = (to_underlying (cu->header.sect_off)
-			 + read_4_bytes (abfd, info_ptr));
+      attr->set_unsigned ((to_underlying (cu->header.sect_off)
+			   + read_4_bytes (abfd, info_ptr)));
       info_ptr += 4;
       break;
     case DW_FORM_ref8:
-      DW_UNSND (attr) = (to_underlying (cu->header.sect_off)
-			 + read_8_bytes (abfd, info_ptr));
+      attr->set_unsigned ((to_underlying (cu->header.sect_off)
+			   + read_8_bytes (abfd, info_ptr)));
       info_ptr += 8;
       break;
     case DW_FORM_ref_sig8:
@@ -19858,8 +19857,9 @@ read_attribute_value (const struct die_reader_specs *reader,
       info_ptr += 8;
       break;
     case DW_FORM_ref_udata:
-      DW_UNSND (attr) = (to_underlying (cu->header.sect_off)
-			 + read_unsigned_leb128 (abfd, info_ptr, &bytes_read));
+      attr->set_unsigned ((to_underlying (cu->header.sect_off)
+			   + read_unsigned_leb128 (abfd, info_ptr,
+						   &bytes_read)));
       info_ptr += bytes_read;
       break;
     case DW_FORM_indirect:
@@ -19942,7 +19942,7 @@ read_attribute_value (const struct die_reader_specs *reader,
       complaint
         (_("Suspicious DW_AT_byte_size value treated as zero instead of %s"),
          hex_string (DW_UNSND (attr)));
-      DW_UNSND (attr) = 0;
+      attr->set_unsigned (0);
     }
 
   return info_ptr;