PR libstdc++/87872 Avoids iterator transfer on self splice

[François Dumont]

Here is the patch submitted by John and now fully tested.

    PR libstdc++/87872
    * include/debug/safe_sequence.tcc
    (_Safe_sequence<>::_M_transfer_from_if): Skip transfer to self.

Is it fine to commit it now ?

François


diff --git a/libstdc++-v3/include/debug/safe_sequence.tcc b/libstdc++-v3/include/debug/safe_sequence.tcc
index 12de48cf322..ce9a807e79f 100644
--- a/libstdc++-v3/include/debug/safe_sequence.tcc
+++ b/libstdc++-v3/include/debug/safe_sequence.tcc
@@ -68,6 +68,9 @@ namespace __gnu_debug
       _Safe_sequence<_Sequence>::
       _M_transfer_from_if(_Safe_sequence& __from, _Predicate __pred)
       {
+	if (this == std::__addressof(__from))
+	  return;
+
 	typedef typename _Sequence::iterator iterator;
 	typedef typename _Sequence::const_iterator const_iterator;