diff -urN libstdc++-v3-orig/include/bits/stl_deque.h libstdc++-v3/include/bits/stl_deque.h
--- libstdc++-v3-orig/include/bits/stl_deque.h	2002-06-13 00:07:51.000000000 +0200
+++ libstdc++-v3/include/bits/stl_deque.h	2002-07-05 23:41:40.000000000 +0200
@@ -132,11 +132,6 @@
   reference operator*() const { return *_M_cur; }
   pointer operator->() const { return _M_cur; }
 
-  difference_type operator-(const _Self& __x) const {
-    return difference_type(_S_buffer_size()) * (_M_node - __x._M_node - 1) +
-      (_M_cur - _M_first) + (__x._M_last - __x._M_cur);
-  }
-
   _Self& operator++() {
     ++_M_cur;
     if (_M_cur == _M_last) {
@@ -318,6 +313,22 @@
   return !(__x < __y);
 }
 
+// _GLIBCPP_RESOLVE_LIB_DEFECTS
+// According to the resolution of DR179 not only the various comparison
+// operators but also operator- must accept mixed iterator/const_iterator
+// parameters.
+template <typename _Tp, typename _RefL, typename _PtrL,
+                        typename _RefR, typename _PtrR>
+inline typename _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
+operator-(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x,
+	  const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
+{
+  return _Deque_iterator<_Tp, _RefL, _PtrL>::difference_type
+    (_Deque_iterator<_Tp, _RefL, _PtrL>::_S_buffer_size()) *
+    (__x._M_node - __y._M_node - 1) + (__x._M_cur - __x._M_first) +
+    (__y._M_last - __y._M_cur);
+}
+
 template <typename _Tp, typename _Ref, typename _Ptr>
 inline _Deque_iterator<_Tp, _Ref, _Ptr>
 operator+(ptrdiff_t __n, const _Deque_iterator<_Tp, _Ref, _Ptr>& __x)
diff -urN libstdc++-v3-orig/testsuite/23_containers/deque_operators.cc libstdc++-v3/testsuite/23_containers/deque_operators.cc
--- libstdc++-v3-orig/testsuite/23_containers/deque_operators.cc	2002-05-19 11:16:21.000000000 +0200
+++ libstdc++-v3/testsuite/23_containers/deque_operators.cc	2002-07-06 00:11:50.000000000 +0200
@@ -56,8 +56,30 @@
   VERIFY( constend <= end );
 }
 
+// libstdc++/7186
+void test02()
+{
+  bool test = true;
+
+  std::deque<int> d(2);       
+  typedef std::deque<int>::iterator iter;         
+  typedef std::deque<int>::const_iterator constiter;
+
+  iter beg = d.begin();
+  iter end = d.end();
+  constiter constbeg = d.begin();
+  constiter constend = d.end();
+
+  VERIFY( !(beg - constbeg) );
+  VERIFY( !(constend - end) );
+
+  VERIFY( end - constbeg );
+  VERIFY( constend - beg );
+}
+
 int main()
 {
   test01();
+  test02();
   return 0;
 }