PR libstdc++/78389 fix backwards size adjustments.

PR libstdc++/78389
* include/bits/list.tcc (merge(list&&)): Fix backwards size adjustments.
(merge(list&&, _StrictWeakOrdering)): Likewise.
* testsuite/23_containers/list/operations/78389.cc: Add
better test for the sizes.

From-SVN: r244490

libstdc++-v3/ChangeLog

+2017-01-16  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	PR libstdc++/78389
+	* include/bits/list.tcc (merge(list&&)): Fix backwards size adjustments.
+	(merge(list&&, _StrictWeakOrdering)): Likewise.
+	* testsuite/23_containers/list/operations/78389.cc: Add
+	better test for the sizes.
+
 2017-01-14  Jonathan Wakely  <jwakely@redhat.com>
 
 	* testsuite/23_containers/array/specialized_algorithms/swap_cxx17.cc:

libstdc++-v3/include/bits/list.tcc

@@ -406,8 +406,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	  __catch(...)
 	    {
 	      size_t __dist = std::distance(__first2, __last2);
-	      this->_M_inc_size(__dist);
-	      __x._M_set_size(__orig_size - __dist);
+	      this->_M_inc_size(__orig_size - __dist);
+	      __x._M_set_size(__dist);
 	      __throw_exception_again;
 	    }
 	}
@@ -454,8 +454,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	    __catch(...)
 	      {
 		size_t __dist = std::distance(__first2, __last2);
-		this->_M_inc_size(__dist);
-		__x._M_set_size(__orig_size - __dist);
+		this->_M_inc_size(__orig_size - __dist);
+		__x._M_set_size(__dist);
 		__throw_exception_again;
 	      }
 	  }

libstdc++-v3/testsuite/23_containers/list/operations/78389.cc

@@ -57,18 +57,20 @@ int main()
   std::list<int> a{1, 2, 3, 4};
   std::list<int> b{5, 6, 7, 8, 9, 10, 11, 12};
   try {
-    a.merge(b, ThrowingComparator{5});
+    a.merge(b, ThrowingComparator{4});
   } catch (...) {
   }
-  VERIFY(a.size() == 8 && b.size() == 4);
+  VERIFY(a.size() == std::distance(a.begin(), a.end()) &&
+	 b.size() == std::distance(b.begin(), b.end()));
   std::list<X> ax{1, 2, 3, 4};
   std::list<X> bx{5, 6, 7, 8, 9, 10, 11, 12};
-  throw_after_X = 5;
+  throw_after_X = 4;
   try {
     ax.merge(bx);
   } catch (...) {
   }
-  VERIFY(ax.size() == 8 && bx.size() == 4);
+  VERIFY(ax.size() == std::distance(ax.begin(), ax.end()) &&
+	 bx.size() == std::distance(bx.begin(), bx.end()));
   std::list<int> ay{5, 6, 7, 8, 9, 10, 11, 12};
   try {
     ay.sort(ThrowingComparator{5});