[PATCH] Handle DW_FORM_implicit_const for DW_AT_decl_line

[Tom de Vries <tdevries@suse.de>]

Hi,

When running the test-suite like this:
...
$ make clean; make; make check CC="gcc -gdwarf-5" CXX="g++ -gdwarf-5"
...
we run into:
...
FAIL: dwz/testsuite/dwz.tests/odr-struct.sh
...

The reason for the FAIL is that this DIE:
...
 <1><115>: Abbrev Number: 2 (DW_TAG_structure_type)
    <116>   DW_AT_name        : aaa
    <11a>   DW_AT_byte_size   : 16
    <11b>   DW_AT_decl_file   : 2
    <11c>   DW_AT_decl_line   : 4
    <11d>   DW_AT_sibling     : <0x13a>
...
with abbrev:
...
   2      DW_TAG_structure_type    [has children]
    DW_AT_name         DW_FORM_string
    DW_AT_byte_size    DW_FORM_data1
    DW_AT_decl_file    DW_FORM_data1
    DW_AT_decl_line    DW_FORM_data1
    DW_AT_sibling      DW_FORM_ref4
    DW_AT value: 0     DW_FORM value: 0
...
is not recognized as a duplicate of DIE:
...
 <1><1b9>: Abbrev Number: 2 (DW_TAG_structure_type)
    <1ba>   DW_AT_name        : aaa
    <1be>   DW_AT_byte_size   : 16
    <1bf>   DW_AT_decl_file   : 2
    <1c0>   DW_AT_decl_line   : 4
    <1c0>   DW_AT_sibling     : <0x1dd>
...
with abbrev:
...
   2      DW_TAG_structure_type    [has children]
    DW_AT_name         DW_FORM_string
    DW_AT_byte_size    DW_FORM_data1
    DW_AT_decl_file    DW_FORM_data1
    DW_AT_decl_line    DW_FORM_implicit_const: 4
    DW_AT_sibling      DW_FORM_ref4
    DW_AT value: 0     DW_FORM value: 0
...
due to the DW_AT_decl_line attribute having different forms, DW_FORM_data1 and
DW_FORM_implicit_const.

Fix this in checksum_die and die_eq_1 by adding dedicated handling for
DW_AT_decl_line, similar to how that's done for DW_AT_decl_file.

Any comments?

Thanks,
- Tom

Handle DW_FORM_implicit_const for DW_AT_decl_line

2021-02-14  Tom de Vries  <tdevries@suse.de>

	PR dwz/27400
	* dwz.c (checksum_die, die_eq_1): Handle DW_FORM_implicit_const for
	DW_AT_decl_line.

---
 dwz.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/dwz.c b/dwz.c
index 992da77..971c402 100644
--- a/dwz.c
+++ b/dwz.c
@@ -3510,7 +3510,35 @@ checksum_die (DSO *dso, dw_cu_ref cu, dw_die_ref top_die, dw_die_ref die)
 	case DW_AT_call_line:
 	case DW_AT_call_column:
 	  if (ignore_locus)
-	    handled = true;
+	    {
+	      handled = true;
+	      break;
+	    }
+	  switch (form)
+	    {
+	    case DW_FORM_data1: value = read_8 (ptr); handled = true; break;
+	    case DW_FORM_data2: value = read_16 (ptr); handled = true; break;
+	    case DW_FORM_data4: value = read_32 (ptr); handled = true; break;
+	    case DW_FORM_data8: value = read_64 (ptr); handled = true; break;
+	    case DW_FORM_udata:
+	      value = read_uleb128 (ptr); handled = true; break;
+	    case DW_FORM_implicit_const:
+	      value = t->values[i]; handled = true; break;
+	    default:
+	      error (0, 0, "%s: Unhandled %s for %s",
+		     dso->filename, get_DW_FORM_str (form),
+		     get_DW_AT_str (t->attr[i].attr));
+	      return 1;
+	    }
+	  if (handled)
+	    {
+	      ptr = old_ptr;
+	      s = t->attr[i].attr;
+	      die->u.p1.die_hash
+		= iterative_hash_object (s, die->u.p1.die_hash);
+	      die->u.p1.die_hash
+		= iterative_hash_object (value, die->u.p1.die_hash);
+	    }
 	  break;
 	default:
 	  break;
@@ -4797,8 +4825,35 @@ die_eq_1 (dw_cu_ref cu1, dw_cu_ref cu2,
 	case DW_AT_call_line:
 	case DW_AT_call_column:
 	  if (ignore_locus)
-	    old_ptr1 = NULL;
-	  break;
+	    {
+	      old_ptr1 = NULL;
+	      break;
+	    }
+	  switch (form1)
+	    {
+	    case DW_FORM_data1: value1 = read_8 (ptr1); break;
+	    case DW_FORM_data2: value1 = read_16 (ptr1); break;
+	    case DW_FORM_data4: value1 = read_32 (ptr1); break;
+	    case DW_FORM_data8: value1 = read_64 (ptr1); break;
+	    case DW_FORM_udata: value1 = read_uleb128 (ptr1); break;
+	    case DW_FORM_implicit_const: value1 = t1->values[i]; break;
+	    default: abort ();
+	    }
+	  switch (form2)
+	    {
+	    case DW_FORM_data1: value2 = read_8 (ptr2); break;
+	    case DW_FORM_data2: value2 = read_16 (ptr2); break;
+	    case DW_FORM_data4: value2 = read_32 (ptr2); break;
+	    case DW_FORM_data8: value2 = read_64 (ptr2); break;
+	    case DW_FORM_udata: value2 = read_uleb128 (ptr2); break;
+	    case DW_FORM_implicit_const: value2 = t2->values[j]; break;
+	    default: abort ();
+	    }
+	  if (value1 != value2)
+	    FAIL;
+	  i++;
+	  j++;
+	  continue;
 	default:
 	  break;
 	}