[Bug libdw/26321] New: Possible bug in dwarf_getlocation

gprocida+abigail at google dot com sourceware-bugzilla@sourceware.org
Thu Jul 30 14:18:05 GMT 2020


https://sourceware.org/bugzilla/show_bug.cgi?id=26321

            Bug ID: 26321
           Summary: Possible bug in dwarf_getlocation
           Product: elfutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libdw
          Assignee: unassigned at sourceware dot org
          Reporter: gprocida+abigail at google dot com
                CC: elfutils-devel at sourceware dot org
  Target Milestone: ---

At commit 15495182302edbe0142101ec3a09e478901ab994.

The check_constant_offset helper is called from a few places.

In one instance, a return value of 0 from check_constant_offset would result in
dwarf_getlocation also returning 0. In the other instances, this is prevented
by treating the zero case differently from the non-zero one.

Making the obvious "fix" at libdw/dwarf_getlocation.c line 670 breaks one test.

```
FAIL: run-exprlocs.sh
=====================

--- varlocs.out 2020-07-30 14:49:10.840263557 +0100
+++ -   2020-07-30 14:49:10.848279328 +0100
@@ -23,15 +23,13 @@
       decl_file (data1)
       decl_line (data1)
       type (ref4)
-      data_member_location (data1)
-            [0,ffffffffffffffff) {plus_uconst(0)}
+      data_member_location (data1) {plus_uconst(0)}
     [4d] member "small_pad"
       name (strp)
       decl_file (data1)
       decl_line (data1)
       type (ref4)
-      data_member_location (data1)
-            [0,ffffffffffffffff) {plus_uconst(40)}
+      data_member_location (data1) {plus_uconst(40)}
   [5a] string_type
     byte_size (data1)
   [5c] base_type "integer(kind=4)"
FAIL run-exprlocs.sh (exit status: 1)
```

It's very possible the existing code is working as intended, in which case
please just close this report.

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