Add reprocessing flag to struct attribute

Some forms require "reprocessing" -- a second pass to update their
value appropriately.  In this case, we'll set the unsigned value on
the attribute, and then later set it to the correct value.

To handle this, we introduce a reprocessing flag to attribute.  Then,
we manage this flag to ensure that setting and unsetting is done
properly.

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

	* dwarf2/read.c (read_cutu_die_from_dwo): Use OBSTACK_ZALLOC.
	(read_attribute_reprocess, read_attribute_value): Update.
	(read_attribute): Clear requires_reprocessing.
	* dwarf2/attribute.h (struct attribute) <as_unsigned_reprocess,
	form_requires_reprocessing>: New methods.
	<string_init>: Clear requires_reprocessing.
	<set_unsigned_reprocess>: New method.
	<name>: Shrink by one bit.
	<requires_reprocessing>: New member.
	* dwarf2/attribute.c (attribute::form_requires_reprocessing): New
	method.

4 files changed, 71 insertions, 6 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ea0a4ae..d02fd7d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,19 @@
 2020-09-29  Tom Tromey  <tom@tromey.com>
 
+	* dwarf2/read.c (read_cutu_die_from_dwo): Use OBSTACK_ZALLOC.
+	(read_attribute_reprocess, read_attribute_value): Update.
+	(read_attribute): Clear requires_reprocessing.
+	* dwarf2/attribute.h (struct attribute) <as_unsigned_reprocess,
+	form_requires_reprocessing>: New methods.
+	<string_init>: Clear requires_reprocessing.
+	<set_unsigned_reprocess>: New method.
+	<name>: Shrink by one bit.
+	<requires_reprocessing>: New member.
+	* dwarf2/attribute.c (attribute::form_requires_reprocessing): New
+	method.
+
+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.
diff --git a/gdb/dwarf2/attribute.c b/gdb/dwarf2/attribute.c
index 69c59cc..5d9c559 100644
--- a/gdb/dwarf2/attribute.c
+++ b/gdb/dwarf2/attribute.c
@@ -182,3 +182,17 @@ attribute::form_is_unsigned () const
 	  || form == DW_FORM_ref8
 	  || form == DW_FORM_ref_udata);
 }
+
+/* See attribute.h.  */
+
+bool
+attribute::form_requires_reprocessing () const
+{
+  return (form == DW_FORM_strx1
+	  || form == DW_FORM_strx2
+	  || form == DW_FORM_strx3
+	  || form == DW_FORM_strx4
+	  || form == DW_FORM_GNU_str_index
+	  || form == DW_FORM_addrx
+	  || form == DW_FORM_GNU_addr_index);
+}
diff --git a/gdb/dwarf2/attribute.h b/gdb/dwarf2/attribute.h
index 3067e2a..b2c824f 100644
--- a/gdb/dwarf2/attribute.h
+++ b/gdb/dwarf2/attribute.h
@@ -73,6 +73,15 @@ struct attribute
     return u.snd;
   }
 
+  /* Return the unsigned value, but only for attributes requiring
+     reprocessing.  */
+  ULONGEST as_unsigned_reprocess () const
+  {
+    gdb_assert (form_requires_reprocessing ());
+    gdb_assert (requires_reprocessing);
+    return u.unsnd;
+  }
+
   /* Return non-zero if ATTR's value is a section offset --- classes
      lineptr, loclistptr, macptr or rangelistptr --- or zero, otherwise.
      You may use DW_UNSND (attr) to retrieve such offsets.
@@ -127,6 +136,10 @@ struct attribute
   /* Check if the attribute's form is an unsigned integer form.  */
   bool form_is_unsigned () const;
 
+  /* Check if the attribute's form is a form that requires
+     "reprocessing".  */
+  bool form_requires_reprocessing () const;
+
   /* Return DIE offset of this attribute.  Return 0 with complaint if
      the attribute is not of the required kind.  */
 
@@ -162,6 +175,7 @@ struct attribute
     gdb_assert (form_is_string ());
     u.str = str;
     string_is_canonical = 0;
+    requires_reprocessing = 0;
   }
 
   /* Set the canonical string value for this attribute.  */
@@ -200,8 +214,29 @@ struct attribute
     u.unsnd = unsnd;
   }
 
+  /* Temporarily set this attribute to an unsigned integer.  This is
+     used only for those forms that require reprocessing.  */
+  void set_unsigned_reprocess (ULONGEST unsnd)
+  {
+    gdb_assert (form_requires_reprocessing ());
+    u.unsnd = unsnd;
+    requires_reprocessing = 1;
+  }
+
+
+  ENUM_BITFIELD(dwarf_attribute) name : 15;
+
+  /* A boolean that is used for forms that require reprocessing.  A
+     form may require data not directly available in the attribute.
+     E.g., DW_FORM_strx requires the corresponding
+     DW_AT_str_offsets_base.  In this case, the processing for the
+     attribute must be done in two passes.  In the first past, this
+     flag is set and the value is an unsigned.  In the second pass,
+     the unsigned value is turned into the correct value for the form,
+     and this flag is cleared.  This flag is unused for other
+     forms.  */
+  unsigned int requires_reprocessing : 1;
 
-  ENUM_BITFIELD(dwarf_attribute) name : 16;
   ENUM_BITFIELD(dwarf_form) form : 15;
 
   /* Has u.str already been updated by dwarf2_canonicalize_name?  This
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index c572ed4..57b667e 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -6869,7 +6869,7 @@ read_cutu_die_from_dwo (dwarf2_cu *cu,
   else if (stub_comp_dir != NULL)
     {
       /* Reconstruct the comp_dir attribute to simplify the code below.  */
-      comp_dir = XOBNEW (&cu->comp_unit_obstack, struct attribute);
+      comp_dir = OBSTACK_ZALLOC (&cu->comp_unit_obstack, struct attribute);
       comp_dir->name = DW_AT_comp_dir;
       comp_dir->form = DW_FORM_string;
       comp_dir->set_string_noncanonical (stub_comp_dir);
@@ -19640,7 +19640,7 @@ read_attribute_reprocess (const struct die_reader_specs *reader,
     {
       case DW_FORM_addrx:
       case DW_FORM_GNU_addr_index:
-        DW_ADDR (attr) = read_addr_index (cu, DW_UNSND (attr));
+        DW_ADDR (attr) = read_addr_index (cu, attr->as_unsigned_reprocess ());
         break;
       case DW_FORM_loclistx:
 	 DW_UNSND (attr) = read_loclist_index (cu, DW_UNSND (attr));
@@ -19655,7 +19655,7 @@ read_attribute_reprocess (const struct die_reader_specs *reader,
       case DW_FORM_strx4:
       case DW_FORM_GNU_str_index:
 	{
-	  unsigned int str_index = DW_UNSND (attr);
+	  unsigned int str_index = attr->as_unsigned_reprocess ();
 	  gdb_assert (!attr->canonical_string_p ());
 	  if (reader->dwo_file != NULL)
 	    attr->set_string_noncanonical (read_dwo_str_index (reader,
@@ -19879,7 +19879,8 @@ read_attribute_value (const struct die_reader_specs *reader,
     case DW_FORM_addrx:
     case DW_FORM_GNU_addr_index:
       *need_reprocess = true;
-      DW_UNSND (attr) = read_unsigned_leb128 (abfd, info_ptr, &bytes_read);
+      attr->set_unsigned_reprocess (read_unsigned_leb128 (abfd, info_ptr,
+							  &bytes_read));
       info_ptr += bytes_read;
       break;
     case DW_FORM_strx:
@@ -19916,7 +19917,7 @@ read_attribute_value (const struct die_reader_specs *reader,
 	    info_ptr += bytes_read;
 	  }
 	*need_reprocess = true;
-	 DW_UNSND (attr) = str_index;
+	attr->set_unsigned_reprocess (str_index);
 	}
       break;
     default:
@@ -19957,6 +19958,7 @@ read_attribute (const struct die_reader_specs *reader,
 {
   attr->name = abbrev->name;
   attr->string_is_canonical = 0;
+  attr->requires_reprocessing = 0;
   return read_attribute_value (reader, attr, abbrev->form,
 			       abbrev->implicit_const, info_ptr,
 			       need_reprocess);