From: Jonathan Wakely <jwakely@redhat.com>
To: "Daniel Krügler" <daniel.kruegler@gmail.com>
Cc: libstdc++ <libstdc++@gcc.gnu.org>,
gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Re: [patch] Fix std::experimental::any for small, non-trivial objects
Date: Sat, 02 May 2015 18:20:00 -0000 [thread overview]
Message-ID: <20150502182029.GF3618@redhat.com> (raw)
In-Reply-To: <CAGNvRgAoybxapDxp-6Ls_mWu3ZFVUA11haAzSjnZAHv=gWPayQ@mail.gmail.com>
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On 02/05/15 19:51 +0200, Daniel Krügler wrote:
>2015-05-02 19:33 GMT+02:00 Jonathan Wakely <jwakely@redhat.com>:
>> Looking at it now, I think the _Internal alias template should also
>> check that alignof(_Tp) <= alignof(void*) so that it can safely be
>> stored in the _Storage.
>>
>> Otherwise a type with sizeof(T) <= sizeof(void*) but
>> alignof(T) > alignof(void*) would not be correctly aligned when stored
>> in the buffer.
>
>Yes, I agree.
Fixed like so, tested powerpc64le-linux and powerpc-aix, committed to
trunk. I'll do something similar on the gcc5 branch too, but not
today.
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commit a29ec813a90122d1c23eb74af379ce6e0c416c8e
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Sat May 2 19:05:51 2015 +0100
* include/experimental/any (any::_Storage): Fix alignment of buffer.
(any::_Internal): Check alignment of type.
* testsuite/experimental/any/cons/aligned.cc: New.
* testsuite/experimental/any/misc/any_cast_neg.cc: Adjust dg-error.
diff --git a/libstdc++-v3/include/experimental/any b/libstdc++-v3/include/experimental/any
index b2d1b9c..7b5e5ec 100644
--- a/libstdc++-v3/include/experimental/any
+++ b/libstdc++-v3/include/experimental/any
@@ -98,11 +98,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Storage& operator=(const _Storage&) = delete;
void* _M_ptr;
- std::aligned_storage<sizeof(_M_ptr), sizeof(_M_ptr)>::type _M_buffer;
+ aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer;
};
template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>,
- bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))>
+ bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))
+ && (alignof(_Tp) <= alignof(_Storage))>
using _Internal = std::integral_constant<bool, _Safe::value && _Fits>;
template<typename _Tp>
diff --git a/libstdc++-v3/testsuite/experimental/any/cons/aligned.cc b/libstdc++-v3/testsuite/experimental/any/cons/aligned.cc
new file mode 100644
index 0000000..3923994
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/any/cons/aligned.cc
@@ -0,0 +1,52 @@
+// 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++14" }
+
+#include <experimental/any>
+#include <cstdint>
+#include <testsuite_hooks.h>
+
+// Alignment requiremnts of this type prevent it being stored in 'any'
+struct alignas(2 * alignof(void*)) X { };
+
+bool
+stored_internally(void* obj, const std::experimental::any& a)
+{
+ std::uintptr_t a_addr = reinterpret_cast<std::uintptr_t>(&a);
+ std::uintptr_t a_end = a_addr + sizeof(a);
+ std::uintptr_t obj_addr = reinterpret_cast<std::uintptr_t>(obj);
+ return (a_addr <= obj_addr) && (obj_addr < a_end);
+}
+
+void
+test01()
+{
+ std::experimental::any a = X{};
+ X& x = std::experimental::any_cast<X&>(a);
+ VERIFY( !stored_internally(&x, a) );
+
+ a = 'X';
+ char& c = std::experimental::any_cast<char&>(a);
+ VERIFY( stored_internally(&c, a) );
+}
+
+int
+main()
+{
+ test01();
+}
diff --git a/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc b/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc
index 5823175..39e3226 100644
--- a/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc
+++ b/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc
@@ -26,5 +26,5 @@ void test01()
using std::experimental::any_cast;
const any y(1);
- any_cast<int&>(y); // { dg-error "qualifiers" "" { target { *-*-* } } 355 }
+ any_cast<int&>(y); // { dg-error "qualifiers" "" { target { *-*-* } } 356 }
}
prev parent reply other threads:[~2015-05-02 18:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-02 12:39 Jonathan Wakely
2015-05-02 13:04 ` Jonathan Wakely
2015-05-02 17:05 ` Daniel Krügler
2015-05-02 17:33 ` Jonathan Wakely
2015-05-02 17:51 ` Daniel Krügler
2015-05-02 18:20 ` Jonathan Wakely [this message]
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