[PATCH] bfd: Handle DW_FORM_data16 for .debug_line tables containing MD5

[Mark Wielaard]

When building with gas using -gdwarf-5 the .debug_line table will
contain an MD5 checksum which bdf/dwarf2 failed to process. Also
there was an off-by-one in the line table when processing DWARF5
.debug_line. To make the line table standalone it contains as zero
entry to comp dir and line. This is redundant information when
reading the line table as part of a debug_info CU, so those entries
must be skipped.

Both issues caused the binutils objdump -S testcases to fail.

bfd/ChangeLog:

	* dwarf2.c (read_attribute_value): Handle DW_FORM_data16.
	(read_formatted_entries): Likewise. And skip zero entry.
---
 bfd/ChangeLog |  5 +++++
 bfd/dwarf2.c  | 21 +++++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 511cee96337..d68bb36a581 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,8 @@
+2020-08-24  Mark Wielaard  <mark@klomp.org>
+
+	* dwarf2.c (read_attribute_value): Handle DW_FORM_data16.
+	(read_formatted_entries): Likewise. And skip zero entry.
+
 2020-08-21  Mark Wielaard  <mark@klomp.org>
 
 	* dwarf2.c (struct dwarf2_debug_file): Add dwarf_rnglists_buffer
diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index b8daa13c374..b8f0008a10d 100644
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -1337,6 +1337,17 @@ read_attribute_value (struct attribute *  attr,
       attr->form = DW_FORM_sdata;
       attr->u.sval = implicit_const;
       break;
+    case DW_FORM_data16:
+      /* This is really a "constant", but there is no way to store that
+         so pretend it is a 16 byte block instead.  */
+      amt = sizeof (struct dwarf_block);
+      blk = (struct dwarf_block *) bfd_alloc (abfd, amt);
+      if (blk == NULL)
+	return NULL;
+      blk->size = 16;
+      info_ptr = read_n_bytes (info_ptr, info_ptr_end, blk);
+      attr->u.blk = blk;
+      break;
     default:
       _bfd_error_handler (_("DWARF error: invalid or unhandled FORM value: %#x"),
 			  form);
@@ -2077,11 +2088,17 @@ read_formatted_entries (struct comp_unit *unit, bfd_byte **bufp,
 	    case DW_FORM_udata:
 	      *uintp = attr.u.val;
 	      break;
+
+	    case DW_FORM_data16:
+	      /* MD5 data is in the attr.blk, but we are ignoring those.  */
+	      break;
 	    }
 	}
 
-      if (!callback (table, fe.name, fe.dir, fe.time, fe.size))
-	return FALSE;
+      /* Skip the first "zero entry", which is the compilation dir/file.  */
+      if (datai != 0)
+	if (!callback (table, fe.name, fe.dir, fe.time, fe.size))
+	  return FALSE;
     }
 
   *bufp = buf;
-- 
2.18.4