[PATCH] libdw: dwarf_get_units should handle existing failure to open Dwarf.

[Mark Wielaard]

The other dwarf unit/cu iterators handle a NULL Dwarf handle as an
existing error and return NULL. Don't crash.

Signed-off-by: Mark Wielaard <m...@klomp.org>
---
 libdw/ChangeLog         | 5 +++++
 libdw/dwarf_get_units.c | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 23e11b9..21cb03c 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,5 +1,10 @@
 2018-06-08  Mark Wielaard  <m...@klomp.org>
 
+       * dwarf_get_units.c (dwarf_get_units): Handle existing error, no
+       dwarf.
+
+2018-06-08  Mark Wielaard  <m...@klomp.org>
+
        * dwarf_getlocation.c (store_implicit_value): Return error when
        seeing bad DWARF or when tsearch runs out of memory.
        (__libdw_intern_expression): Report error when store_implicit_value
diff --git a/libdw/dwarf_get_units.c b/libdw/dwarf_get_units.c
index aece17e..6215bf4 100644
--- a/libdw/dwarf_get_units.c
+++ b/libdw/dwarf_get_units.c
@@ -40,6 +40,10 @@ dwarf_get_units (Dwarf *dwarf, Dwarf_CU *cu, Dwarf_CU 
**next_cu,
                 Dwarf_Half *version, uint8_t *unit_type,
                 Dwarf_Die *cudie, Dwarf_Die *subdie)
 {
+  /* Handle existing error.  */
+  if (dwarf == NULL)
+    return -1;
+
   Dwarf_Off off;
   bool v4type;
   if (cu == NULL)
-- 
1.8.3.1