[v3 PATCH] PR libstdc++/78389

[Ville Voutilainen]

Tested on Linux-x64.

This patch doesn't try to fix the reported sort() issue, because
a) it would require undoing a throwing move operation, which
is impossible.
b) in order to avoid the throwing move, we would need to add a
level of indirection and the scratch space for the indirect data
would need to be allocated.

2017-01-13  Ville Voutilainen  <ville.voutilainen@gmail.com>

    PR libstdc++/78389
    * include/bits/list.tcc (merge(list&&)):
    Adjust list sizes if the comparator throws.
    (merge(list&&, _StrictWeakOrdering)): Likewise.
    * testsuite/23_containers/list/operations/78389.cc: New.
-------------- next part --------------
diff --git a/libstdc++-v3/include/bits/list.tcc b/libstdc++-v3/include/bits/list.tcc
index c4f397f..fabbe7b 100644
--- a/libstdc++-v3/include/bits/list.tcc
+++ b/libstdc++-v3/include/bits/list.tcc
@@ -386,20 +386,29 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	  iterator __last1 = end();
 	  iterator __first2 = __x.begin();
 	  iterator __last2 = __x.end();
-	  while (__first1 != __last1 && __first2 != __last2)
-	    if (*__first2 < *__first1)
-	      {
-		iterator __next = __first2;
-		_M_transfer(__first1, __first2, ++__next);
-		__first2 = __next;
-	      }
-	    else
-	      ++__first1;
-	  if (__first2 != __last2)
-	    _M_transfer(__last1, __first2, __last2);
+	  size_t __orig_size = __x.size();
+	  __try {
+	    while (__first1 != __last1 && __first2 != __last2)
+	      if (*__first2 < *__first1)
+		{
+		  iterator __next = __first2;
+		  _M_transfer(__first1, __first2, ++__next);
+		  __first2 = __next;
+		}
+	      else
+		++__first1;
+	    if (__first2 != __last2)
+	      _M_transfer(__last1, __first2, __last2);
 
-	  this->_M_inc_size(__x._M_get_size());
-	  __x._M_set_size(0);
+	    this->_M_inc_size(__x._M_get_size());
+	    __x._M_set_size(0);
+	  }
+	  __catch(...)
+	    {
+	      size_t __dist = distance(__first2, __last2);
+	      this->_M_inc_size(__dist);
+	      __x._M_set_size(__orig_size - __dist);
+	    }
 	}
     }
 
@@ -423,20 +432,30 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	    iterator __last1 = end();
 	    iterator __first2 = __x.begin();
 	    iterator __last2 = __x.end();
-	    while (__first1 != __last1 && __first2 != __last2)
-	      if (__comp(*__first2, *__first1))
-		{
-		  iterator __next = __first2;
-		  _M_transfer(__first1, __first2, ++__next);
-		  __first2 = __next;
-		}
-	      else
-		++__first1;
-	    if (__first2 != __last2)
-	      _M_transfer(__last1, __first2, __last2);
-
-	    this->_M_inc_size(__x._M_get_size());
-	    __x._M_set_size(0);
+	    size_t __orig_size = __x.size();
+	    __try
+	      {
+		while (__first1 != __last1 && __first2 != __last2)
+		  if (__comp(*__first2, *__first1))
+		    {
+		      iterator __next = __first2;
+		      _M_transfer(__first1, __first2, ++__next);
+		      __first2 = __next;
+		    }
+		  else
+		    ++__first1;
+		if (__first2 != __last2)
+		  _M_transfer(__last1, __first2, __last2);
+
+		this->_M_inc_size(__x._M_get_size());
+		__x._M_set_size(0);
+	      }
+	    __catch(...)
+	      {
+		size_t __dist = distance(__first2, __last2);
+		this->_M_inc_size(__dist);
+		__x._M_set_size(__orig_size - __dist);
+	      }
 	  }
       }
 
diff --git a/libstdc++-v3/testsuite/23_containers/list/operations/78389.cc b/libstdc++-v3/testsuite/23_containers/list/operations/78389.cc
new file mode 100644
index 0000000..3fa9501
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/list/operations/78389.cc
@@ -0,0 +1,73 @@
+// { dg-do run { target c++11 } }
+
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// 23.2.2.4 list operations [lib.list.ops]
+
+#include <testsuite_hooks.h>
+#include <list>
+
+#include <list>
+
+struct ThrowingComparator
+{
+    unsigned int throw_after = 0;
+    unsigned int count = 0;
+    bool operator()(int, int) {
+        if (++count >= throw_after) {
+            throw 666;
+        }
+        return true;
+    }
+};
+
+struct X
+{
+  X() = default;
+  X(int) {}
+};
+
+unsigned int throw_after_X = 0;
+unsigned int count_X = 0;
+
+bool operator<(const X&, const X&) {
+  if (++count_X >= throw_after_X) {
+    throw 666;
+  }
+  return true;
+}
+
+
+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});
+    } catch (...) {
+    }
+    VERIFY(a.size() == 8 && b.size() == 4);
+    std::list<X> ax{1, 2, 3, 4};
+    std::list<X> bx{5, 6, 7, 8, 9, 10, 11, 12};
+    throw_after_X = 5;
+    try {
+        ax.merge(bx);
+    } catch (...) {
+    }
+    VERIFY(ax.size() == 8 && bx.size() == 4);
+}