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[PATCH 2/3] libdw: Update acceptable forms and attributes for dwarf_getlocation.

dwarf_getlocation has to know which attributes can contain a DWARF
expression or location list because the form alone might be ambiguous.

Since DWARF4 there is DW_FORM_exprloc so always accept that. But for older
DWARF or location lists we cannot just check for DW_FORM_sec_offset since
that could be a reference to diffent kinds of sections (based on attribute).

Update the attribute list based on the latest DWARF5 encodings table.
Note that DW_AT_call_origin wasn't added because that seems to be a
typo in the DWARF5 spec.

Signed-off-by: Mark Wielaard <>
 libdw/ChangeLog           |  5 +++++
 libdw/dwarf_getlocation.c | 26 +++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 7085649..bb9e849 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,5 +1,10 @@
 2017-11-03  Mark Wielaard  <>
+	* dwarf_getlocation.c (attr_ok): Always accept DW_FORM_exprloc.
+	Update list of acceptable attribute codes based on DWARF5.
+2017-11-03  Mark Wielaard  <>
 	* dwarf.h: Add DW_OP_GNU_variable_value.
 2017-10-03  Mark Wielaard  <>
diff --git a/libdw/dwarf_getlocation.c b/libdw/dwarf_getlocation.c
index a4a2761..c59546e 100644
--- a/libdw/dwarf_getlocation.c
+++ b/libdw/dwarf_getlocation.c
@@ -45,10 +45,34 @@ attr_ok (Dwarf_Attribute *attr)
   if (attr == NULL)
     return false;
-  /* Must be one of the attributes listed below.  */
+  /* If it is an exprloc, it is obviously OK.  */
+  if (dwarf_whatform (attr) == DW_FORM_exprloc)
+    return true;
+  /* Otherwise must be one of the attributes listed below.  Older
+     DWARF versions might have encoded the exprloc as block, and we
+     cannot easily distinquish attributes in the loclist class because
+     the same forms are used for different classes.  */
   switch (attr->code)
     case DW_AT_location:
+    case DW_AT_byte_size:
+    case DW_AT_bit_offset:
+    case DW_AT_bit_size:
+    case DW_AT_lower_bound:
+    case DW_AT_bit_stride:
+    case DW_AT_upper_bound:
+    case DW_AT_count:
+    case DW_AT_allocated:
+    case DW_AT_associated:
+    case DW_AT_data_location:
+    case DW_AT_byte_stride:
+    case DW_AT_rank:
+    case DW_AT_call_value:
+    case DW_AT_call_target:
+    case DW_AT_call_target_clobbered:
+    case DW_AT_call_data_location:
+    case DW_AT_call_data_value:
     case DW_AT_data_member_location:
     case DW_AT_vtable_elem_location:
     case DW_AT_string_length:

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