[google] Work around PR52796 by replacing empty packs with explicit overloads.

[Jeffrey Yasskin (google), 2012-03-31 01:55:24]

Work around http://gcc.gnu.org/PR52796 in gcc-4.6 by adding an
overload of each function that passes a parameter pack directly as the
only arguments of an object's constructor, which explicitly takes no
arguments in place of the pack.

Tested with check-c++ and by trying to provoke the bug in valgrind for
each changed location.  Some of the insert_aux locations appear
inaccessible because of missing emplace() functions.

I plan to only apply this to the google/gcc-4_6 branch, since gcc-4.7
already makes these cases work properly.

2012-03-30   Jeffrey Yasskin  <jyasskin@google.com>

	* libstdc++-v3/include/ext/pool_allocator.h: Add 1-argument construct() method.
	* libstdc++-v3/include/ext/bitmap_allocator.h: Likewise.
	* libstdc++-v3/include/ext/new_allocator.h: Likewise.
	* libstdc++-v3/include/ext/malloc_allocator.h: Likewise.
	* libstdc++-v3/include/ext/array_allocator.h: Likewise.
	* libstdc++-v3/include/ext/mt_allocator.h: Likewise.
	* libstdc++-v3/include/ext/extptr_allocator.h: Likewise.
	* libstdc++-v3/include/bits/stl_construct.h:Add 1-argument _Construct function.
	* libstdc++-v3/include/bits/stl_list.h: Add default _List_node constructor.
	* libstdc++-v3/include/bits/hashtable_policy.h: Add default _Hash_node
constructor.
	* libstdc++-v3/include/bits/forward_list.h:Add default _Fwd_list_node
constructor.
	* libstdc++-v3/include/bits/stl_tree.h:Add default _Rb_tree_node constructor.
	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/assign_neg.cc:
Update line numbers.
	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/insert_neg.cc:
Likewise.
	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_1_neg.cc:
Likewise.
	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_2_neg.cc:
Likewise.
	* libstdc++-v3/testsuite/23_containers/list/requirements/dr438/assign_neg.cc:
Likewise.
	* libstdc++-v3/testsuite/23_containers/list/requirements/dr438/insert_neg.cc:
Likewise.
	*
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_1_neg.cc:
Likewise.
	*
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_2_neg.cc:
Likewise.

Index: libstdc++-v3/include/ext/pool_allocator.h
===================================================================
--- libstdc++-v3/include/ext/pool_allocator.h	(revision 186024)
+++ libstdc++-v3/include/ext/pool_allocator.h	(working copy)
@@ -165,6 +165,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { ::new((void *)__p) _Tp(__val); }
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      void
+      construct(pointer __p)
+      { ::new((void *)__p) _Tp(); }
+
       template<typename... _Args>
         void
         construct(pointer __p, _Args&&... __args)
Index: libstdc++-v3/include/ext/bitmap_allocator.h
===================================================================
--- libstdc++-v3/include/ext/bitmap_allocator.h	(revision 186024)
+++ libstdc++-v3/include/ext/bitmap_allocator.h	(working copy)
@@ -1058,6 +1058,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { ::new((void *)__p) value_type(__data); }
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      void
+      construct(pointer __p)
+      { ::new((void *)__p) _Tp(); }
+
       template<typename... _Args>
         void
         construct(pointer __p, _Args&&... __args)
@@ -1109,4 +1115,3 @@ _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace __gnu_cxx
 
 #endif 
-
Index: libstdc++-v3/include/ext/new_allocator.h
===================================================================
--- libstdc++-v3/include/ext/new_allocator.h	(revision 186024)
+++ libstdc++-v3/include/ext/new_allocator.h	(working copy)
@@ -115,6 +115,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { ::new((void *)__p) _Tp(__val); }
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      void
+      construct(pointer __p)
+      { ::new((void *)__p) _Tp(); }
+
       template<typename... _Args>
         void
         construct(pointer __p, _Args&&... __args)
Index: libstdc++-v3/include/ext/malloc_allocator.h
===================================================================
--- libstdc++-v3/include/ext/malloc_allocator.h	(revision 186024)
+++ libstdc++-v3/include/ext/malloc_allocator.h	(working copy)
@@ -111,6 +111,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { ::new((void *)__p) value_type(__val); }
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      void
+      construct(pointer __p)
+      { ::new((void *)__p) _Tp(); }
+
       template<typename... _Args>
         void
         construct(pointer __p, _Args&&... __args) 
Index: libstdc++-v3/include/ext/array_allocator.h
===================================================================
--- libstdc++-v3/include/ext/array_allocator.h	(revision 186024)
+++ libstdc++-v3/include/ext/array_allocator.h	(working copy)
@@ -79,6 +79,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { ::new((void *)__p) value_type(__val); }
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      void
+      construct(pointer __p)
+      { ::new((void *)__p) _Tp(); }
+
       template<typename... _Args>
         void
         construct(pointer __p, _Args&&... __args)
Index: libstdc++-v3/include/ext/mt_allocator.h
===================================================================
--- libstdc++-v3/include/ext/mt_allocator.h	(revision 186024)
+++ libstdc++-v3/include/ext/mt_allocator.h	(working copy)
@@ -595,6 +595,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { ::new((void *)__p) _Tp(__val); }
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      void
+      construct(pointer __p)
+      { ::new((void *)__p) _Tp(); }
+
       template<typename... _Args>
         void
         construct(pointer __p, _Args&&... __args)
Index: libstdc++-v3/include/ext/extptr_allocator.h
===================================================================
--- libstdc++-v3/include/ext/extptr_allocator.h	(revision 186024)
+++ libstdc++-v3/include/ext/extptr_allocator.h	(working copy)
@@ -104,6 +104,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { ::new(__p.get()) _Tp(__val); }
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      void
+      construct(pointer __p)
+      { ::new(__p.get()) _Tp(); }
+
       template<typename... _Args>
         void
         construct(pointer __p, _Args&&... __args)
Index: libstdc++-v3/include/bits/stl_list.h
===================================================================
--- libstdc++-v3/include/bits/stl_list.h	(revision 186024)
+++ libstdc++-v3/include/bits/stl_list.h	(working copy)
@@ -108,6 +108,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       _Tp _M_data;
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      _List_node()
+      : __detail::_List_node_base(), _M_data()
+      { }
+
       template<typename... _Args>
         _List_node(_Args&&... __args)
 	: __detail::_List_node_base(), _M_data(std::forward<_Args>(__args)...) 
Index: libstdc++-v3/include/bits/hashtable_policy.h
===================================================================
--- libstdc++-v3/include/bits/hashtable_policy.h	(revision 186024)
+++ libstdc++-v3/include/bits/hashtable_policy.h	(working copy)
@@ -76,6 +76,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       std::size_t  _M_hash_code;
       _Hash_node*  _M_next;
 
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      _Hash_node()
+      : _M_v(),
+        _M_hash_code(), _M_next() { }
+
       template<typename... _Args>
 	_Hash_node(_Args&&... __args)
 	: _M_v(std::forward<_Args>(__args)...),
@@ -88,6 +94,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _Value       _M_v;
       _Hash_node*  _M_next;
 
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      _Hash_node()
+      : _M_v(),
+        _M_next() { }
+
       template<typename... _Args>
 	_Hash_node(_Args&&... __args)
 	: _M_v(std::forward<_Args>(__args)...),
Index: libstdc++-v3/include/bits/forward_list.h
===================================================================
--- libstdc++-v3/include/bits/forward_list.h	(revision 186024)
+++ libstdc++-v3/include/bits/forward_list.h	(working copy)
@@ -100,6 +100,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
     struct _Fwd_list_node
     : public _Fwd_list_node_base
     {
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      _Fwd_list_node()
+      : _Fwd_list_node_base(),
+        _M_value() { }
+
       template<typename... _Args>
         _Fwd_list_node(_Args&&... __args)
         : _Fwd_list_node_base(), 
Index: libstdc++-v3/include/bits/stl_construct.h
===================================================================
--- libstdc++-v3/include/bits/stl_construct.h	(revision 186024)
+++ libstdc++-v3/include/bits/stl_construct.h	(working copy)
@@ -70,6 +70,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    * object's constructor with an initializer.
    */
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+  // Work around PR52796 by avoiding 0-length parameter packs
+  // passed to constructors.
+  template<typename _T1>
+    inline void
+    _Construct(_T1* __p)
+    { ::new(static_cast<void*>(__p)) _T1(); }
+
   template<typename _T1, typename... _Args>
     inline void
     _Construct(_T1* __p, _Args&&... __args)
@@ -157,4 +164,3 @@ _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 
 #endif /* _STL_CONSTRUCT_H */
-
Index: libstdc++-v3/include/bits/stl_tree.h
===================================================================
--- libstdc++-v3/include/bits/stl_tree.h	(revision 186024)
+++ libstdc++-v3/include/bits/stl_tree.h	(working copy)
@@ -133,6 +133,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _Val _M_value_field;
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
+      // Work around PR52796 by avoiding 0-length parameter packs
+      // passed to constructors.
+      _Rb_tree_node()
+      : _Rb_tree_node_base(),
+        _M_value_field() { }
+
       template<typename... _Args>
         _Rb_tree_node(_Args&&... __args)
 	: _Rb_tree_node_base(),
Index:
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/assign_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/assign_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/assign_neg.cc	(working
copy)
@@ -1,6 +1,6 @@
 // { dg-do compile }
 // { dg-options "-std=gnu++0x" }
-// { dg-error "no matching" "" { target *-*-* } 1206 }
+// { dg-error "no matching" "" { target *-*-* } 1212 }
 // { dg-excess-errors "" }
 
 // Copyright (C) 2009, 2010 Free Software Foundation
Index:
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/insert_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/insert_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/insert_neg.cc	(working
copy)
@@ -1,6 +1,6 @@
 // { dg-do compile }
 // { dg-options "-std=gnu++0x" }
-// { dg-error "no matching" "" { target *-*-* } 1206 }
+// { dg-error "no matching" "" { target *-*-* } 1212 }
 // { dg-excess-errors "" }
 
 // Copyright (C) 2009, 2010, 2011 Free Software Foundation
Index:
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_1_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_1_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_1_neg.cc	(working
copy)
@@ -1,6 +1,6 @@
 // { dg-do compile }
 // { dg-options "-std=gnu++0x" }
-// { dg-error "no matching" "" { target *-*-* } 1206 }
+// { dg-error "no matching" "" { target *-*-* } 1212 }
 // { dg-excess-errors "" }
 
 // Copyright (C) 2009, 2010, 2011 Free Software Foundation
Index:
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_2_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_2_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_2_neg.cc	(working
copy)
@@ -1,6 +1,6 @@
 // { dg-do compile }
 // { dg-options "-std=gnu++0x" }
-// { dg-error "no matching" "" { target *-*-* } 1206 }
+// { dg-error "no matching" "" { target *-*-* } 1212 }
 // { dg-excess-errors "" }
 
 // Copyright (C) 2009, 2010, 2011 Free Software Foundation
Index:
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/assign_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/assign_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/assign_neg.cc	(working
copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1491 }
+// { dg-error "no matching" "" { target *-*-* } 1497 }
 // { dg-excess-errors "" }
 
 #include <list>
Index:
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/insert_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/insert_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/insert_neg.cc	(working
copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1447 }
+// { dg-error "no matching" "" { target *-*-* } 1453 }
 // { dg-excess-errors "" }
 
 #include <list>
Index:
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_1_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_1_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_1_neg.cc	(working
copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1447 }
+// { dg-error "no matching" "" { target *-*-* } 1453 }
 // { dg-excess-errors "" }
 
 #include <list>
Index:
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_2_neg.cc
===================================================================
---
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_2_neg.cc	(revision
186024)
+++
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_2_neg.cc	(working
copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1447 }
+// { dg-error "no matching" "" { target *-*-* } 1453 }
 // { dg-excess-errors "" }
 
 #include <list>

--
This patch is available for review at http://codereview.appspot.com/5971053

[Diego Novillo, 2012-04-01 16:38:40]

On 3/30/12 9:55 PM, Jeffrey Yasskin wrote:
> Work around http://gcc.gnu.org/PR52796 in gcc-4.6 by adding an
> overload of each function that passes a parameter pack directly as the
> only arguments of an object's constructor, which explicitly takes no
> arguments in place of the pack.
>
> Tested with check-c++ and by trying to provoke the bug in valgrind for
> each changed location.  Some of the insert_aux locations appear
> inaccessible because of missing emplace() functions.
>
> I plan to only apply this to the google/gcc-4_6 branch, since gcc-4.7
> already makes these cases work properly.
>
> 2012-03-30   Jeffrey Yasskin<jyasskin@google.com>
>
> 	* libstdc++-v3/include/ext/pool_allocator.h: Add 1-argument construct()
method.
> 	* libstdc++-v3/include/ext/bitmap_allocator.h: Likewise.
> 	* libstdc++-v3/include/ext/new_allocator.h: Likewise.
> 	* libstdc++-v3/include/ext/malloc_allocator.h: Likewise.
> 	* libstdc++-v3/include/ext/array_allocator.h: Likewise.
> 	* libstdc++-v3/include/ext/mt_allocator.h: Likewise.
> 	* libstdc++-v3/include/ext/extptr_allocator.h: Likewise.
> 	* libstdc++-v3/include/bits/stl_construct.h:Add 1-argument _Construct
function.
> 	* libstdc++-v3/include/bits/stl_list.h: Add default _List_node constructor.
> 	* libstdc++-v3/include/bits/hashtable_policy.h: Add default _Hash_node
constructor.
> 	* libstdc++-v3/include/bits/forward_list.h:Add default _Fwd_list_node
constructor.
> 	* libstdc++-v3/include/bits/stl_tree.h:Add default _Rb_tree_node constructor.
> 	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/assign_neg.cc:
Update line numbers.
> 	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/insert_neg.cc:
Likewise.
> 	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_1_neg.cc:
Likewise.
> 	*
libstdc++-v3/testsuite/23_containers/forward_list/requirements/dr438/constructor_2_neg.cc:
Likewise.
> 	* libstdc++-v3/testsuite/23_containers/list/requirements/dr438/assign_neg.cc:
Likewise.
> 	* libstdc++-v3/testsuite/23_containers/list/requirements/dr438/insert_neg.cc:
Likewise.
> 	*
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_1_neg.cc:
Likewise.
> 	*
libstdc++-v3/testsuite/23_containers/list/requirements/dr438/constructor_2_neg.cc:
Likewise.

This is OK for google/gcc-4_6.

I'm not sure it makes sense to propose it for gcc-4_6-branch. 
Jason/Ben, any opinions on PR 52796 and what should we do for 
gcc-4_6-branch?


Thanks.  Diego.

[jason_redhat.com, 2012-04-04 01:38:56]

On 04/01/2012 12:38 PM, Diego Novillo wrote:
> I'm not sure it makes sense to propose it for gcc-4_6-branch. Jason/Ben,
> any opinions on PR 52796 and what should we do for gcc-4_6-branch?

Fixed.  :)

Jason

[pcarlini_gmail.com, 2012-04-04 04:19:18]

> On 04/01/2012 12:38 PM, Diego Novillo wrote:
>> I'm not sure it makes sense to propose it for gcc-4_6-branch. Jason/Ben,
>> any opinions on PR 52796 and what should we do for gcc-4_6-branch?
> 
> Fixed.  :)

I'm so relieved, seriously.

Thanks,
Paolo