Re: [PATCH] PR67085 move comparison functions in heap operations

[Jonathan Wakely <jwakely at redhat dot com>]

On 19/01/17 18:50 +0000, Jonathan Wakely wrote:
> On 19/01/17 18:28 +0000, Jonathan Wakely wrote:
> > @@ -397,7 +401,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >      while (__last - __first > 1)
> > 	{
> > 	  --__last;
> > -	  std::__pop_heap(__first, __last, __last, __comp);
> > +	  std::__pop_heap(__first, __last, __last, _GLIBCXX_MOVE(__comp));
>
> Oops, we can't move from the functor in a loop, it might be invalid
> after the first move. Fix coming asap.

Unfortunately this adds some more copies to my testcase. I have
another idea how to avoid that though.

This also adds an extra (safe) move in __is_heap.

Tested powerpc64le-linux, committed to trunk.

commit 41125d036d08d1fdc47c8c0d2ef280a0f8db4f89
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jan 19 19:03:35 2017 +0000

    Fix unsafe moves inside loops
    
    	PR libstdc++/67085
    	* include/bits/stl_heap.h (__is_heap): Use _GLIBCXX_MOVE.
    	(__make_heap, __sort_heap): Don't use _GLIBCXX_MOVE inside loops.
    	* testsuite/23_containers/priority_queue/67085.cc: Adjust expected
    	number of copies.
    	* testsuite/25_algorithms/make_heap/movable.cc: New test.

diff --git a/libstdc++-v3/include/bits/stl_heap.h b/libstdc++-v3/include/bits/stl_heap.h
index c82ce77..b19c9f4 100644
--- a/libstdc++-v3/include/bits/stl_heap.h
+++ b/libstdc++-v3/include/bits/stl_heap.h
@@ -113,7 +113,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     __is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
 	      _Compare __comp)
-    { return std::__is_heap(__first, __comp, std::distance(__first, __last)); }
+    {
+      return std::__is_heap(__first, _GLIBCXX_MOVE(__comp),
+			    std::distance(__first, __last));
+    }
 
   // Heap-manipulation functions: push_heap, pop_heap, make_heap, sort_heap,
   // + is_heap and is_heap_until in C++0x.
@@ -336,7 +339,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{
 	  _ValueType __value = _GLIBCXX_MOVE(*(__first + __parent));
 	  std::__adjust_heap(__first, __parent, __len, _GLIBCXX_MOVE(__value),
-			     _GLIBCXX_MOVE(__comp));
+			     __comp);
 	  if (__parent == 0)
 	    return;
 	  __parent--;
@@ -401,7 +404,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       while (__last - __first > 1)
 	{
 	  --__last;
-	  std::__pop_heap(__first, __last, __last, _GLIBCXX_MOVE(__comp));
+	  std::__pop_heap(__first, __last, __last, __comp);
 	}
     }
 
diff --git a/libstdc++-v3/testsuite/23_containers/priority_queue/67085.cc b/libstdc++-v3/testsuite/23_containers/priority_queue/67085.cc
index 5a3ca32..4ccea30 100644
--- a/libstdc++-v3/testsuite/23_containers/priority_queue/67085.cc
+++ b/libstdc++-v3/testsuite/23_containers/priority_queue/67085.cc
@@ -34,9 +34,9 @@ test01()
 {
   int v[] = {1, 2, 3, 4};
   std::priority_queue<int, std::vector<int>, CopyCounter> q{v, v+4};
-  VERIFY(count == 2);
+  VERIFY(count == 4);
   q.push(1);
-  VERIFY(count == 3);
+  VERIFY(count == 5);
 }
 
 int
diff --git a/libstdc++-v3/testsuite/25_algorithms/make_heap/movable.cc b/libstdc++-v3/testsuite/25_algorithms/make_heap/movable.cc
new file mode 100644
index 0000000..f6738f1
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/make_heap/movable.cc
@@ -0,0 +1,38 @@
+// 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/>.
+
+// { dg-do run { target c++11 } }
+
+#include <functional>
+#include <algorithm>
+#include <iterator>
+
+void
+test01()
+{
+  int i[] = { 1, 2, 3, 4 };
+  std::function<bool(int, int)> f = std::less<>{};
+  // If this uses a moved-from std::function we'll get an exception:
+  std::make_heap(std::begin(i), std::end(i), f);
+  std::sort_heap(std::begin(i), std::end(i), f);
+}
+
+int
+main()
+{
+  test01();
+}