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* [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
@ 2011-12-19 18:33 redi at gcc dot gnu.org
2011-12-19 18:41 ` [Bug libstdc++/51626] " paolo.carlini at oracle dot com
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2011-12-19 18:33 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
Bug #: 51626
Summary: [4.6 Regression] [C++0x] can't use C++98 allocators
with -std=c++0x
Classification: Unclassified
Product: gcc
Version: 4.6.2
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: libstdc++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: redi@gcc.gnu.org
#include <memory>
#include <vector>
template <class T>
struct allocator98 : std::allocator<T>
{
template <class U> struct rebind { typedef allocator98<U> other; };
allocator98() { }
template <class U> allocator98(const allocator98<U>&) { };
void construct(T* p, const T& val) { std::allocator<T>::construct(p, val);
}
};
int main()
{
std::vector< int, allocator98<int> > v(1);
}
This fails in c++0x mode because std::__uninitialized_default_n_a() incorrectly
assumes it's OK to call Alloc::construct with a single argument. That is true
for std::allocator in C++0x mode, but not true for most user-defined allocators
written to the C++98 requirements.
This is the cause of https://svn.boost.org/trac/boost/ticket/5538
The bug is fixed in 4.7 because std::allocator_traits provides a default
implementation of construct, ensuring backwards-compatibility with C++98-style
allocators.
A workaround for user-defined allocators is to add:
void construct(pointer p) { return construct(p, value_type()); }
The fix for libstdc++ would be to avoid calling construct with a single
argument, or to backport a minimal version of allocator_traits from 4.7
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/51626] [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
@ 2011-12-19 18:41 ` paolo.carlini at oracle dot com
2011-12-19 19:05 ` redi at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: paolo.carlini at oracle dot com @ 2011-12-19 18:41 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-12-19 18:38:56 UTC ---
Bah, in my opinion it's late to attempt sophisticated things in 4.6, either we
can do something minimal or we should just tell people that in 4.6 a C++0x
container wants a C++0x allocator.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/51626] [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
2011-12-19 18:41 ` [Bug libstdc++/51626] " paolo.carlini at oracle dot com
@ 2011-12-19 19:05 ` redi at gcc dot gnu.org
2011-12-19 19:14 ` redi at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2011-12-19 19:05 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-12-19 18:57:45 UTC ---
I agree with the sentiment, but unfortunately a C++11 allocator isn't required
to provide a construct member at all. 17.6.3.5 p5 shows a minimal C++11
allocator, and that won't work either, so 4.6 doesn't correctly support
user-defined C++98 allocators or user-defined C++11 allocators!
I think the minimal fix is for __uninitialized_default_n_a and
__uninitialized_default_a to default construct an object of the iterator's
value_type and pass that to __alloc.construct(addressof(*cur))
A less-minimal fix would be to change all the containers to use
__uninitialized_fill_a instead of __uninitialized_default_a
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/51626] [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
2011-12-19 18:41 ` [Bug libstdc++/51626] " paolo.carlini at oracle dot com
2011-12-19 19:05 ` redi at gcc dot gnu.org
@ 2011-12-19 19:14 ` redi at gcc dot gnu.org
2011-12-19 19:17 ` redi at gcc dot gnu.org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2011-12-19 19:14 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-12-19 19:04:53 UTC ---
Unfortunately either of those would cause a regression for PR 32618
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/51626] [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
` (2 preceding siblings ...)
2011-12-19 19:14 ` redi at gcc dot gnu.org
@ 2011-12-19 19:17 ` redi at gcc dot gnu.org
2011-12-19 22:42 ` redi at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2011-12-19 19:17 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2011-12-19
AssignedTo|unassigned at gcc dot |redi at gcc dot gnu.org
|gnu.org |
Target Milestone|--- |4.6.3
Ever Confirmed|0 |1
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/51626] [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
` (3 preceding siblings ...)
2011-12-19 19:17 ` redi at gcc dot gnu.org
@ 2011-12-19 22:42 ` redi at gcc dot gnu.org
2011-12-21 18:37 ` redi at gcc dot gnu.org
2011-12-21 19:02 ` redi at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2011-12-19 22:42 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-12-19 22:40:19 UTC ---
suggested patch posted to
http://gcc.gnu.org/ml/gcc-patches/2011-12/msg01421.html
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/51626] [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
` (4 preceding siblings ...)
2011-12-19 22:42 ` redi at gcc dot gnu.org
@ 2011-12-21 18:37 ` redi at gcc dot gnu.org
2011-12-21 19:02 ` redi at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2011-12-21 18:37 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-12-21 18:35:48 UTC ---
Author: redi
Date: Wed Dec 21 18:35:40 2011
New Revision: 182600
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=182600
Log:
PR libstdc++/51626
* include/bits/stl_uninitialized.h (_Construct_default_a_impl): Define
overloaded functions to conditionally use allocator::construct.
(_Construct_default_a): Define to dispatch to appropriate
_Construct_default_a_impl overload.
(__uninitialized_default_a, __uninitialized_default_n_a): Use
_Construct_default_a.
* testsuite/20_util/allocator/51626.cc: New.
Added:
branches/gcc-4_6-branch/libstdc++-v3/testsuite/20_util/allocator/51626.cc
Modified:
branches/gcc-4_6-branch/libstdc++-v3/ChangeLog
branches/gcc-4_6-branch/libstdc++-v3/include/bits/stl_uninitialized.h
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/51626] [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x
2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
` (5 preceding siblings ...)
2011-12-21 18:37 ` redi at gcc dot gnu.org
@ 2011-12-21 19:02 ` redi at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2011-12-21 19:02 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-12-21 18:37:23 UTC ---
fixed for 4.6.3
^ permalink raw reply [flat|nested] 8+ messages in thread
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2011-12-19 18:33 [Bug libstdc++/51626] New: [4.6 Regression] [C++0x] can't use C++98 allocators with -std=c++0x redi at gcc dot gnu.org
2011-12-19 18:41 ` [Bug libstdc++/51626] " paolo.carlini at oracle dot com
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