[RFC 2/7] [gdb/symtab] Check effect in parent_map::set_parent

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

Set_parent uses m_die_range_map.set_empty to set the parent of a range.

If part of the range is already set, it remains the same.

If the entire range is already set, the set_empty has no effect, silently.

Fix this by verifying that calling set_empty has the desired effect on the
start and end points of the range.

Tested on x86_64-linux.
---
 gdb/dwarf2/cooked-index.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gdb/dwarf2/cooked-index.h b/gdb/dwarf2/cooked-index.h
index 39809b488ca..a921f25ecf2 100644
--- a/gdb/dwarf2/cooked-index.h
+++ b/gdb/dwarf2/cooked-index.h
@@ -254,6 +254,13 @@ class parent_map
 		   const cooked_index_entry *parent_entry)
   {
     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
+       has no effect.  */
+    gdb_assert (m_parent_map.find (start) == parent_entry);
+    if (end != start)
+      gdb_assert (m_parent_map.find (end) == parent_entry);
   }
 
 private:
-- 
2.35.3