[RFC 3/7] [gdb/symtab] Handle nullptr parent in parent_map::set_parent

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

Set_parent uses m_die_range_map.set_empty, which doesn't allow
parent_entry == nullptr.

So it may be necessary to guard calls to set_parent with
"if (parent_entry != nullptr)".

Fix this by handling the parent_entry == nullptr case.

Tested on x86_64-linux.
---
 gdb/dwarf2/cooked-index.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gdb/dwarf2/cooked-index.h b/gdb/dwarf2/cooked-index.h
index a921f25ecf2..23db5918878 100644
--- a/gdb/dwarf2/cooked-index.h
+++ b/gdb/dwarf2/cooked-index.h
@@ -253,7 +253,10 @@ class parent_map
   void set_parent (CORE_ADDR start, CORE_ADDR end,
 		   const cooked_index_entry *parent_entry)
   {
-    m_parent_map.set_empty (start, end, (void *)parent_entry);
+    /* Calling set_empty with nullptr is currently not allowed.  Note that we
+       still check the desired effect.  */
+    if (parent_entry != nullptr)
+      m_parent_map.set_empty (start, end, (void *)parent_entry);
 
     /* Assert that set_parent has the desired effect.  This is not trivial due
        to how set_empty works.  If the range already has been set before, it
-- 
2.35.3