The friend function defined in enable_shared_from_this did not match
the declaration at namespace scope, so instead of defining the
previously declared function it added a new overload, which was always
a better match than the declared (but never defined) one.
That worked fine for a single base class, the friend function got
found by ADL, but with two enable_shared_from_this base classes the
two friend overloads were ambiguous.
This changes the friend to match the declaration, so that it can only
be called when an unambiguous enable_shared_from_this base can be
deduced, and so fails silently (as it is supposed to) when there is
not an unambiguous base class.
Tested powerpc64le-linux, committed to trunk.
This fix is simple enough that I'm going to backport it after 5.3 is
released.
commit 1fa7fd2d7699c41f147b42ae96f70bf7b9e8e2d6
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Dec 2 14:43:34 2015 +0000
Fix ambiguity with multiple enable_shared_from_this bases
PR libstdc++/56383
* testsuite/20_util/enable_shared_from_this/56383.cc: New.
* include/bits/shared_ptr_base.h (__enable_shared_from_this): Make
friend declaration match previous declaration of
__enable_shared_from_this_helper.
* include/bits/shared_ptr.h (enable_shared_from_this): Likewise.
diff --git a/libstdc++-v3/include/bits/shared_ptr.h b/libstdc++-v3/include/bits/shared_ptr.h
index 2413b1b..26a0ad3 100644
--- a/libstdc++-v3/include/bits/shared_ptr.h
+++ b/libstdc++-v3/include/bits/shared_ptr.h
@@ -582,19 +582,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
{ _M_weak_this._M_assign(__p, __n); }
- template<typename _Tp1>
+ template<typename _Tp1, typename _Tp2>
friend void
- __enable_shared_from_this_helper(const __shared_count<>& __pn,
- const enable_shared_from_this* __pe,
- const _Tp1* __px) noexcept
- {
- if (__pe != nullptr)
- __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
- }
+ __enable_shared_from_this_helper(const __shared_count<>&,
+ const enable_shared_from_this<_Tp1>*,
+ const _Tp2*) noexcept;
mutable weak_ptr<_Tp> _M_weak_this;
};
+ template<typename _Tp1, typename _Tp2>
+ inline void
+ __enable_shared_from_this_helper(const __shared_count<>& __pn,
+ const enable_shared_from_this<_Tp1>*
+ __pe, const _Tp2* __px) noexcept
+ {
+ if (__pe != nullptr)
+ __pe->_M_weak_assign(const_cast<_Tp2*>(__px), __pn);
+ }
+
/**
* @brief Create an object that is owned by a shared_ptr.
* @param __a An allocator.
diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h
index 1a96b4c..f4f98e6 100644
--- a/libstdc++-v3/include/bits/shared_ptr_base.h
+++ b/libstdc++-v3/include/bits/shared_ptr_base.h
@@ -1546,19 +1546,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
{ _M_weak_this._M_assign(__p, __n); }
- template<typename _Tp1>
+ template<_Lock_policy _Lp1, typename _Tp1, typename _Tp2>
friend void
- __enable_shared_from_this_helper(const __shared_count<_Lp>& __pn,
- const __enable_shared_from_this* __pe,
- const _Tp1* __px) noexcept
- {
- if (__pe != nullptr)
- __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
- }
+ __enable_shared_from_this_helper(const __shared_count<_Lp1>&,
+ const __enable_shared_from_this<_Tp1,
+ _Lp1>*, const _Tp2*) noexcept;
mutable __weak_ptr<_Tp, _Lp> _M_weak_this;
};
+ template<_Lock_policy _Lp1, typename _Tp1, typename _Tp2>
+ inline void
+ __enable_shared_from_this_helper(const __shared_count<_Lp1>& __pn,
+ const __enable_shared_from_this<_Tp1,
+ _Lp1>* __pe,
+ const _Tp2* __px) noexcept
+ {
+ if (__pe != nullptr)
+ __pe->_M_weak_assign(const_cast<_Tp2*>(__px), __pn);
+ }
template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args>
inline __shared_ptr<_Tp, _Lp>
diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/56383.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/56383.cc
new file mode 100644
index 0000000..ea0f28d
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/56383.cc
@@ -0,0 +1,56 @@
+// Copyright (C) 2015 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-options "-std=gnu++11" }
+
+#include <memory>
+#include <testsuite_hooks.h>
+
+struct A : std::enable_shared_from_this<A>
+{
+ void* a() { return shared_from_this().get(); }
+};
+
+struct B : std::enable_shared_from_this<B>
+{
+};
+
+struct D : A, B
+{
+};
+
+void test01()
+{
+ bool test = false;
+
+ auto d = std::make_shared<D>();
+ try
+ {
+ d->a();
+ }
+ catch (const std::bad_weak_ptr&)
+ {
+ test = true;
+ }
+ VERIFY(test);
+}
+
+int
+main()
+{
+ test01();
+}
