gdb/dwarf: few fixes for handling DW_FORM_{rng,loc}listx

We hit an assertion when loading the binary from PR 26813.  When fixing
it, execution goes a up bit further but then hits another assert, and
another, and another.  With these fours fixes, I am able to load the
binary and get to the prompt.  An error is shown (index pointing outside
of the section), because the DW_FORM_rnglistx attribute is not read
correctly, but that one is taken care of by the next patch.

The four fixes are:

- attribute::form_requires_reprocessing needs to handle forms
  DW_FORM_rnglistx and DW_FORM_loclistx, because set_unsigned_reprocess
  is called for them in read_attribute_value.

- read_attribute_reprocess must call set_unsigned for them, not
  set_address.  The parameter of set_address is a CORE_ADDR, meaning
  it's for program addresses.  Post-reprocess, DW_FORM_rnglistx and
  DW_FORM_loclistx are offsets into their respective sections
  (.debug_rnglists and .debug_loclists).  set_unsigned is the current
  attribute value setter that fits the best.  But perhaps we should have
  a setter that takes a sect_offset?

- read_attribute_process must call as_unsigned_reprocess instead of
  as_unsigned to get the pre-reprocess value, otherwise we hit the
  assert inside as_unsigned that makes sure the attribute doesn't need
  reprocessing.

- attribute::set_unsigned needs to clear the requires_reprocessing flag,
  otherwise it stays set when reprocessing DW_FORM_rnglistx and
  DW_FORM_loclistx attributes.

There's another assert that we hit once the next patch is applied, but
since it's in the same vein as the changes in this patch, I included it
in this patch:

- attribute::form_is_unsigned must handle form DW_FORM_loclistx,
  otherwise we hit the assert when trying to call set_unsigned for an
  attribute of this form.  DW_FORM_rnglistx is already handled.

gdb/ChangeLog:

	PR gdb/26813
	* dwarf2/attribute.h (struct attribute) <set_unsigned>: Clear
	requires_reprocessing flag.
	* dwarf2/attribute.c (attribute::form_is_unsigned): Handle
	DW_FORM_loclistx.
	(attribute::form_requires_reprocessing): Handle DW_FORM_rnglistx
	and DW_FORM_loclistx.
	* dwarf2/read.c (read_attribute_reprocess): Use set_unsigned
	instead of set_address for DW_FORM_loclistx and
	DW_FORM_rnglistx.

Change-Id: I06c156fa3913ca98e4e39085f4ef171645b4bc1e

4 files changed, 31 insertions, 4 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b420a94..4f9944a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,18 @@
 2021-02-02  Simon Marchi  <simon.marchi@efficios.com>
 
+	PR gdb/26813
+	* dwarf2/attribute.h (struct attribute) <set_unsigned>: Clear
+	requires_reprocessing flag.
+	* dwarf2/attribute.c (attribute::form_is_unsigned): Handle
+	DW_FORM_loclistx.
+	(attribute::form_requires_reprocessing): Handle DW_FORM_rnglistx
+	and DW_FORM_loclistx.
+	* dwarf2/read.c (read_attribute_reprocess): Use set_unsigned
+	instead of set_address for DW_FORM_loclistx and
+	DW_FORM_rnglistx.
+
+2021-02-02  Simon Marchi  <simon.marchi@efficios.com>
+
 	* dwarf2/read.c (read_loclist_index): Remove bound check for
 	start of offset.
 	(read_rnglist_index): Likewise.
diff --git a/gdb/dwarf2/attribute.c b/gdb/dwarf2/attribute.c
index 4792610..b4f188a 100644
--- a/gdb/dwarf2/attribute.c
+++ b/gdb/dwarf2/attribute.c
@@ -179,6 +179,7 @@ attribute::form_is_unsigned () const
 	  || form == DW_FORM_flag_present
 	  || form == DW_FORM_udata
 	  || form == DW_FORM_rnglistx
+	  || form == DW_FORM_loclistx
 	  || form == DW_FORM_ref1
 	  || form == DW_FORM_ref2
 	  || form == DW_FORM_ref4
@@ -197,7 +198,9 @@ attribute::form_requires_reprocessing () const
 	  || form == DW_FORM_strx4
 	  || form == DW_FORM_GNU_str_index
 	  || form == DW_FORM_addrx
-	  || form == DW_FORM_GNU_addr_index);
+	  || form == DW_FORM_GNU_addr_index
+	  || form == DW_FORM_rnglistx
+	  || form == DW_FORM_loclistx);
 }
 
 /* See attribute.h.  */
diff --git a/gdb/dwarf2/attribute.h b/gdb/dwarf2/attribute.h
index a3ff9b0..56776d6 100644
--- a/gdb/dwarf2/attribute.h
+++ b/gdb/dwarf2/attribute.h
@@ -223,6 +223,7 @@ struct attribute
   {
     gdb_assert (form_is_unsigned ());
     u.unsnd = unsnd;
+    requires_reprocessing = 0;
   }
 
   /* Temporarily set this attribute to an unsigned integer.  This is
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index ee0f8be..4fe4f94 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -20315,10 +20315,20 @@ read_attribute_reprocess (const struct die_reader_specs *reader,
 					    attr->as_unsigned_reprocess ()));
 	break;
       case DW_FORM_loclistx:
-	attr->set_address (read_loclist_index (cu, attr->as_unsigned ()));
-	 break;
+	{
+	  CORE_ADDR loclists_sect_off
+	    = read_loclist_index (cu, attr->as_unsigned_reprocess ());
+
+	  attr->set_unsigned (loclists_sect_off);
+	}
+	break;
       case DW_FORM_rnglistx:
-	attr->set_address (read_rnglist_index (cu, attr->as_unsigned (), tag));
+	{
+	  CORE_ADDR rnglists_sect_off
+	    = read_rnglist_index (cu, attr->as_unsigned_reprocess (), tag);
+
+	  attr->set_unsigned (rnglists_sect_off);
+	}
 	break;
       case DW_FORM_strx:
       case DW_FORM_strx1: