Re: [PATCH][_GLIBCXX_DEBUG] Refine singular iterator state
On Mon, 8 Aug 2022, 19:15 François Dumont via Libstdc++, <
libstd...@gcc.gnu.org> wrote:
> On 08/08/22 15:19, Jonathan Wakely wrote:
> > On Mon, 8 Aug 2022 at 06:07, François Dumont via Libstdc++
> > wrote:
> >> Another version of this patch with just a new test case showing what
> >> wrong code was unnoticed previously by the _GLIBCXX_DEBUG mode.
> >>
> >> On 04/08/22 22:56, François Dumont wrote:
> >>> This an old patch I had prepared a long time ago, I don't think I ever
> >>> submitted it.
> >>>
> >>> libstdc++: [_GLIBCXX_DEBUG] Do not consider detached iterators as
> >>> value-initialized
> >>>
> >>> An attach iterator has its _M_version set to something != 0. This
> >>> value shall be preserved
> >>> when detaching it so that the iterator does not look like a value
> >>> initialized one.
> >>>
> >>> libstdc++-v3/ChangeLog:
> >>>
> >>> * include/debug/formatter.h (__singular_value_init): New
> >>> _Iterator_state enum entry.
> >>> (_Parameter<>(const _Safe_iterator<>&, const char*,
> >>> _Is_iterator)): Check if iterator
> >>> parameter is value-initialized.
> >>> (_Parameter<>(const _Safe_local_iterator<>&, const char*,
> >>> _Is_iterator)): Likewise.
> >>> * include/debug/safe_iterator.h
> >>> (_Safe_iterator<>::_M_value_initialized()): New. Adapt
> >>> checks.
> >>> * include/debug/safe_local_iterator.h
> >>> (_Safe_local_iterator<>::_M_value_initialized()): New.
> >>> Adapt checks.
> >>> * src/c++11/debug.cc (_Safe_iterator_base::_M_reset): Do
> >>> not reset _M_version.
> >>> (print_field(PrintContext&, const _Parameter&, const
> >>> char*)): Adapt state_names.
> >>> * testsuite/23_containers/deque/debug/iterator1_neg.cc:
> >>> New test.
> >>> * testsuite/23_containers/deque/debug/iterator2_neg.cc:
> >>> New test.
> >>> *
> >>> testsuite/23_containers/forward_list/debug/iterator1_neg.cc: New test.
> >>> *
> >>> testsuite/23_containers/forward_list/debug/iterator2_neg.cc: New test.
> >>>
> >>> Tested under Linux x86_64 _GLIBCXX_DEBUG mode.
> >>>
> >>> Ok to commit ?
> >>>
> >>> François
> >
> >> diff --git a/libstdc++-v3/src/c++11/debug.cc
> b/libstdc++-v3/src/c++11/debug.cc
> >> index 4706defedf1..cf8e6f48081 100644
> >> --- a/libstdc++-v3/src/c++11/debug.cc
> >> +++ b/libstdc++-v3/src/c++11/debug.cc
> >> @@ -426,7 +426,8 @@ namespace __gnu_debug
> >>_M_reset() throw ()
> >>{
> >> __atomic_store_n(&_M_sequence, (_Safe_sequence_base*)0,
> __ATOMIC_RELEASE);
> >> -_M_version = 0;
> >> +// Detach iterator shall not look like a value-initialized one.
> >> +// _M_version = 0;
> >> _M_prior = 0;
> >> _M_next = 0;
> >>}
> > I think this would be clearer as "Do not reset version, so that a
> > detached iterator does not look like a value-initialized one."
> >
> >> +// { dg-do run { xfail *-*-* } }
> >> +// { dg-require-debug-mode "" }
> >> +
> >> +#include
> >> +
> >> +#include
> >> +
> >> +void test01()
> >> +{
> >> + typedef typename std::deque::iterator It;
> >> + std::deque dq;
> >> + dq.push_back(1);
> >> +
> >> + It it = It();
> >> + VERIFY( dq.begin() != it );
> > Is there any reason to use VERIFY here?
> Only make sure the compiler do not optimize this check away.
>
It can't do that. If the debug check results in output to the terminal and
aborting the program then that's an observable side effect that cannot be
optimised away.
If the compiler was somehow smart enough to know that the comparison is
undefined then we wouldn't need debug mode.
>
> > We're expecting the comparison to abort in the debug mode checks,
> > right? Which would happen if we just do:
> >
> > (void) dq.begin() == it;
>
> I guess this (void) cast is doing the same so adopted.
>
No, the cast silences a warning.
> > Using VERIFY just makes it look like we're expecting the test to be
> > XFAIL because the assertion will fail, but that's not what is being
> > tested.
> >
> > OK for trunk with those changes, thanks.
> >
> Updated committed patch attached.
>
Thanks.
>
Re: [PATCH][_GLIBCXX_DEBUG] Refine singular iterator state
On 08/08/22 15:19, Jonathan Wakely wrote:
On Mon, 8 Aug 2022 at 06:07, François Dumont via Libstdc++
wrote:
Another version of this patch with just a new test case showing what
wrong code was unnoticed previously by the _GLIBCXX_DEBUG mode.
On 04/08/22 22:56, François Dumont wrote:
This an old patch I had prepared a long time ago, I don't think I ever
submitted it.
libstdc++: [_GLIBCXX_DEBUG] Do not consider detached iterators as
value-initialized
An attach iterator has its _M_version set to something != 0. This
value shall be preserved
when detaching it so that the iterator does not look like a value
initialized one.
libstdc++-v3/ChangeLog:
* include/debug/formatter.h (__singular_value_init): New
_Iterator_state enum entry.
(_Parameter<>(const _Safe_iterator<>&, const char*,
_Is_iterator)): Check if iterator
parameter is value-initialized.
(_Parameter<>(const _Safe_local_iterator<>&, const char*,
_Is_iterator)): Likewise.
* include/debug/safe_iterator.h
(_Safe_iterator<>::_M_value_initialized()): New. Adapt
checks.
* include/debug/safe_local_iterator.h
(_Safe_local_iterator<>::_M_value_initialized()): New.
Adapt checks.
* src/c++11/debug.cc (_Safe_iterator_base::_M_reset): Do
not reset _M_version.
(print_field(PrintContext&, const _Parameter&, const
char*)): Adapt state_names.
* testsuite/23_containers/deque/debug/iterator1_neg.cc:
New test.
* testsuite/23_containers/deque/debug/iterator2_neg.cc:
New test.
*
testsuite/23_containers/forward_list/debug/iterator1_neg.cc: New test.
*
testsuite/23_containers/forward_list/debug/iterator2_neg.cc: New test.
Tested under Linux x86_64 _GLIBCXX_DEBUG mode.
Ok to commit ?
François
diff --git a/libstdc++-v3/src/c++11/debug.cc b/libstdc++-v3/src/c++11/debug.cc
index 4706defedf1..cf8e6f48081 100644
--- a/libstdc++-v3/src/c++11/debug.cc
+++ b/libstdc++-v3/src/c++11/debug.cc
@@ -426,7 +426,8 @@ namespace __gnu_debug
_M_reset() throw ()
{
__atomic_store_n(&_M_sequence, (_Safe_sequence_base*)0, __ATOMIC_RELEASE);
-_M_version = 0;
+// Detach iterator shall not look like a value-initialized one.
+// _M_version = 0;
_M_prior = 0;
_M_next = 0;
}
I think this would be clearer as "Do not reset version, so that a
detached iterator does not look like a value-initialized one."
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include
+
+#include
+
+void test01()
+{
+ typedef typename std::deque::iterator It;
+ std::deque dq;
+ dq.push_back(1);
+
+ It it = It();
+ VERIFY( dq.begin() != it );
Is there any reason to use VERIFY here?
Only make sure the compiler do not optimize this check away.
We're expecting the comparison to abort in the debug mode checks,
right? Which would happen if we just do:
(void) dq.begin() == it;
I guess this (void) cast is doing the same so adopted.
Using VERIFY just makes it look like we're expecting the test to be
XFAIL because the assertion will fail, but that's not what is being
tested.
OK for trunk with those changes, thanks.
Updated committed patch attached.
diff --git a/libstdc++-v3/include/debug/formatter.h b/libstdc++-v3/include/debug/formatter.h
index 80e8ba46d1e..748d4fbfea4 100644
--- a/libstdc++-v3/include/debug/formatter.h
+++ b/libstdc++-v3/include/debug/formatter.h
@@ -185,6 +185,7 @@ namespace __gnu_debug
__rbegin, // dereferenceable, and at the reverse-beginning
__rmiddle, // reverse-dereferenceable, not at the reverse-beginning
__rend, // reverse-past-the-end
+ __singular_value_init, // singular, value initialized
__last_state
};
@@ -280,7 +281,12 @@ namespace __gnu_debug
_M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_Sequence);
if (__it._M_singular())
- _M_variant._M_iterator._M_state = __singular;
+ {
+ if (__it._M_value_initialized())
+ _M_variant._M_iterator._M_state = __singular_value_init;
+ else
+ _M_variant._M_iterator._M_state = __singular;
+ }
else
{
if (__it._M_is_before_begin())
@@ -308,7 +314,12 @@ namespace __gnu_debug
_M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_Sequence);
if (__it._M_singular())
- _M_variant._M_iterator._M_state = __singular;
+ {
+ if (__it._M_value_initialized())
+ _M_variant._M_iterator._M_state = __singular_value_init;
+ else
+ _M_variant._M_iterator._M_state = __singular;
+ }
else
{
if (__it._M_is_end())
diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index d613933e236..33f7a86478a 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -41,8 +41,8 @@
#define _GLIBCXX_DEBUG_VERIFY_OPERANDS(_Lhs, _Rhs, _BadMsgId, _DiffMsgId) \
_GLIBCXX_DEBUG
Re: [PATCH][_GLIBCXX_DEBUG] Refine singular iterator state
On Mon, 8 Aug 2022 at 06:07, François Dumont via Libstdc++
wrote:
>
> Another version of this patch with just a new test case showing what
> wrong code was unnoticed previously by the _GLIBCXX_DEBUG mode.
>
> On 04/08/22 22:56, François Dumont wrote:
> > This an old patch I had prepared a long time ago, I don't think I ever
> > submitted it.
> >
> > libstdc++: [_GLIBCXX_DEBUG] Do not consider detached iterators as
> > value-initialized
> >
> > An attach iterator has its _M_version set to something != 0. This
> > value shall be preserved
> > when detaching it so that the iterator does not look like a value
> > initialized one.
> >
> > libstdc++-v3/ChangeLog:
> >
> > * include/debug/formatter.h (__singular_value_init): New
> > _Iterator_state enum entry.
> > (_Parameter<>(const _Safe_iterator<>&, const char*,
> > _Is_iterator)): Check if iterator
> > parameter is value-initialized.
> > (_Parameter<>(const _Safe_local_iterator<>&, const char*,
> > _Is_iterator)): Likewise.
> > * include/debug/safe_iterator.h
> > (_Safe_iterator<>::_M_value_initialized()): New. Adapt
> > checks.
> > * include/debug/safe_local_iterator.h
> > (_Safe_local_iterator<>::_M_value_initialized()): New.
> > Adapt checks.
> > * src/c++11/debug.cc (_Safe_iterator_base::_M_reset): Do
> > not reset _M_version.
> > (print_field(PrintContext&, const _Parameter&, const
> > char*)): Adapt state_names.
> > * testsuite/23_containers/deque/debug/iterator1_neg.cc:
> > New test.
> > * testsuite/23_containers/deque/debug/iterator2_neg.cc:
> > New test.
> > *
> > testsuite/23_containers/forward_list/debug/iterator1_neg.cc: New test.
> > *
> > testsuite/23_containers/forward_list/debug/iterator2_neg.cc: New test.
> >
> > Tested under Linux x86_64 _GLIBCXX_DEBUG mode.
> >
> > Ok to commit ?
> >
> > François
>diff --git a/libstdc++-v3/src/c++11/debug.cc b/libstdc++-v3/src/c++11/debug.cc
>index 4706defedf1..cf8e6f48081 100644
>--- a/libstdc++-v3/src/c++11/debug.cc
>+++ b/libstdc++-v3/src/c++11/debug.cc
>@@ -426,7 +426,8 @@ namespace __gnu_debug
> _M_reset() throw ()
> {
> __atomic_store_n(&_M_sequence, (_Safe_sequence_base*)0, __ATOMIC_RELEASE);
>-_M_version = 0;
>+// Detach iterator shall not look like a value-initialized one.
>+// _M_version = 0;
> _M_prior = 0;
> _M_next = 0;
> }
I think this would be clearer as "Do not reset version, so that a
detached iterator does not look like a value-initialized one."
>+// { dg-do run { xfail *-*-* } }
>+// { dg-require-debug-mode "" }
>+
>+#include
>+
>+#include
>+
>+void test01()
>+{
>+ typedef typename std::deque::iterator It;
>+ std::deque dq;
>+ dq.push_back(1);
>+
>+ It it = It();
>+ VERIFY( dq.begin() != it );
Is there any reason to use VERIFY here?
We're expecting the comparison to abort in the debug mode checks,
right? Which would happen if we just do:
(void) dq.begin() == it;
Using VERIFY just makes it look like we're expecting the test to be
XFAIL because the assertion will fail, but that's not what is being
tested.
OK for trunk with those changes, thanks.
Re: [PATCH][_GLIBCXX_DEBUG] Refine singular iterator state
Another version of this patch with just a new test case showing what
wrong code was unnoticed previously by the _GLIBCXX_DEBUG mode.
On 04/08/22 22:56, François Dumont wrote:
This an old patch I had prepared a long time ago, I don't think I ever
submitted it.
libstdc++: [_GLIBCXX_DEBUG] Do not consider detached iterators as
value-initialized
An attach iterator has its _M_version set to something != 0. This
value shall be preserved
when detaching it so that the iterator does not look like a value
initialized one.
libstdc++-v3/ChangeLog:
* include/debug/formatter.h (__singular_value_init): New
_Iterator_state enum entry.
(_Parameter<>(const _Safe_iterator<>&, const char*,
_Is_iterator)): Check if iterator
parameter is value-initialized.
(_Parameter<>(const _Safe_local_iterator<>&, const char*,
_Is_iterator)): Likewise.
* include/debug/safe_iterator.h
(_Safe_iterator<>::_M_value_initialized()): New. Adapt
checks.
* include/debug/safe_local_iterator.h
(_Safe_local_iterator<>::_M_value_initialized()): New.
Adapt checks.
* src/c++11/debug.cc (_Safe_iterator_base::_M_reset): Do
not reset _M_version.
(print_field(PrintContext&, const _Parameter&, const
char*)): Adapt state_names.
* testsuite/23_containers/deque/debug/iterator1_neg.cc:
New test.
* testsuite/23_containers/deque/debug/iterator2_neg.cc:
New test.
*
testsuite/23_containers/forward_list/debug/iterator1_neg.cc: New test.
*
testsuite/23_containers/forward_list/debug/iterator2_neg.cc: New test.
Tested under Linux x86_64 _GLIBCXX_DEBUG mode.
Ok to commit ?
François
diff --git a/libstdc++-v3/include/debug/formatter.h b/libstdc++-v3/include/debug/formatter.h
index 80e8ba46d1e..748d4fbfea4 100644
--- a/libstdc++-v3/include/debug/formatter.h
+++ b/libstdc++-v3/include/debug/formatter.h
@@ -185,6 +185,7 @@ namespace __gnu_debug
__rbegin, // dereferenceable, and at the reverse-beginning
__rmiddle, // reverse-dereferenceable, not at the reverse-beginning
__rend, // reverse-past-the-end
+ __singular_value_init, // singular, value initialized
__last_state
};
@@ -280,7 +281,12 @@ namespace __gnu_debug
_M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_Sequence);
if (__it._M_singular())
- _M_variant._M_iterator._M_state = __singular;
+ {
+ if (__it._M_value_initialized())
+ _M_variant._M_iterator._M_state = __singular_value_init;
+ else
+ _M_variant._M_iterator._M_state = __singular;
+ }
else
{
if (__it._M_is_before_begin())
@@ -308,7 +314,12 @@ namespace __gnu_debug
_M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_Sequence);
if (__it._M_singular())
- _M_variant._M_iterator._M_state = __singular;
+ {
+ if (__it._M_value_initialized())
+ _M_variant._M_iterator._M_state = __singular_value_init;
+ else
+ _M_variant._M_iterator._M_state = __singular;
+ }
else
{
if (__it._M_is_end())
diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index d613933e236..33f7a86478a 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -41,8 +41,8 @@
#define _GLIBCXX_DEBUG_VERIFY_OPERANDS(_Lhs, _Rhs, _BadMsgId, _DiffMsgId) \
_GLIBCXX_DEBUG_VERIFY(!_Lhs._M_singular() && !_Rhs._M_singular() \
- || (_Lhs.base() == _Iterator() \
- && _Rhs.base() == _Iterator()), \
+ || (_Lhs._M_value_initialized() \
+ && _Rhs._M_value_initialized()), \
_M_message(_BadMsgId)\
._M_iterator(_Lhs, #_Lhs) \
._M_iterator(_Rhs, #_Rhs)); \
@@ -177,7 +177,7 @@ namespace __gnu_debug
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 408. Is vector > forbidden?
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
- || __x.base() == _Iterator(),
+ || __x._M_value_initialized(),
_M_message(__msg_init_copy_singular)
._M_iterator(*this, "this")
._M_iterator(__x, "other"));
@@ -193,7 +193,7 @@ namespace __gnu_debug
: _Iter_base()
{
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
- || __x.base() == _Iterator(),
+ || __x._M_value_initialized(),
_M_message(__msg_init_copy_singular)
._M_iterator(*this, "this")
._M_iterator(__x, "other"));
@@ -220,7 +220,7 @@ namespace __gnu_debug
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 408. Is vector > forbidden?
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
-|| __x.base() == _MutableIterator(),
+|| __x._M_value_initialized(),
_M_message(__msg_init_const_singular)
._M_iterator(*this, "this")
._M_iterator(__x, "other"));
@@ -236,7 +236,7 @@ namespace __gnu_debug
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 408. Is vector > forbidden?
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
[PATCH][_GLIBCXX_DEBUG] Refine singular iterator state
This an old patch I had prepared a long time ago, I don't think I ever
submitted it.
libstdc++: [_GLIBCXX_DEBUG] Do not consider detached iterators as
value-initialized
An attach iterator has its _M_version set to something != 0. This
value shall be preserved
when detaching it so that the iterator does not look like a value
initialized one.
libstdc++-v3/ChangeLog:
* include/debug/formatter.h (__singular_value_init): New
_Iterator_state enum entry.
(_Parameter<>(const _Safe_iterator<>&, const char*,
_Is_iterator)): Check if iterator
parameter is value-initialized.
(_Parameter<>(const _Safe_local_iterator<>&, const char*,
_Is_iterator)): Likewise.
* include/debug/safe_iterator.h
(_Safe_iterator<>::_M_value_initialized()): New. Adapt
checks.
* include/debug/safe_local_iterator.h
(_Safe_local_iterator<>::_M_value_initialized()): New.
Adapt checks.
* src/c++11/debug.cc (_Safe_iterator_base::_M_reset): Do
not reset _M_version.
(print_field(PrintContext&, const _Parameter&, const
char*)): Adapt state_names.
* testsuite/23_containers/deque/debug/iterator1_neg.cc: New
test.
* testsuite/23_containers/deque/debug/iterator2_neg.cc: New
test.
*
testsuite/23_containers/forward_list/debug/iterator1_neg.cc: New test.
*
testsuite/23_containers/forward_list/debug/iterator2_neg.cc: New test.
Tested under Linux x86_64 _GLIBCXX_DEBUG mode.
Ok to commit ?
François
diff --git a/libstdc++-v3/include/debug/formatter.h b/libstdc++-v3/include/debug/formatter.h
index 80e8ba46d1e..748d4fbfea4 100644
--- a/libstdc++-v3/include/debug/formatter.h
+++ b/libstdc++-v3/include/debug/formatter.h
@@ -185,6 +185,7 @@ namespace __gnu_debug
__rbegin, // dereferenceable, and at the reverse-beginning
__rmiddle, // reverse-dereferenceable, not at the reverse-beginning
__rend, // reverse-past-the-end
+ __singular_value_init, // singular, value initialized
__last_state
};
@@ -280,7 +281,12 @@ namespace __gnu_debug
_M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_Sequence);
if (__it._M_singular())
- _M_variant._M_iterator._M_state = __singular;
+ {
+ if (__it._M_value_initialized())
+ _M_variant._M_iterator._M_state = __singular_value_init;
+ else
+ _M_variant._M_iterator._M_state = __singular;
+ }
else
{
if (__it._M_is_before_begin())
@@ -308,7 +314,12 @@ namespace __gnu_debug
_M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_Sequence);
if (__it._M_singular())
- _M_variant._M_iterator._M_state = __singular;
+ {
+ if (__it._M_value_initialized())
+ _M_variant._M_iterator._M_state = __singular_value_init;
+ else
+ _M_variant._M_iterator._M_state = __singular;
+ }
else
{
if (__it._M_is_end())
diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index d613933e236..33f7a86478a 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -41,8 +41,8 @@
#define _GLIBCXX_DEBUG_VERIFY_OPERANDS(_Lhs, _Rhs, _BadMsgId, _DiffMsgId) \
_GLIBCXX_DEBUG_VERIFY(!_Lhs._M_singular() && !_Rhs._M_singular() \
- || (_Lhs.base() == _Iterator() \
- && _Rhs.base() == _Iterator()), \
+ || (_Lhs._M_value_initialized() \
+ && _Rhs._M_value_initialized()), \
_M_message(_BadMsgId)\
._M_iterator(_Lhs, #_Lhs) \
._M_iterator(_Rhs, #_Rhs)); \
@@ -177,7 +177,7 @@ namespace __gnu_debug
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 408. Is vector > forbidden?
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
- || __x.base() == _Iterator(),
+ || __x._M_value_initialized(),
_M_message(__msg_init_copy_singular)
._M_iterator(*this, "this")
._M_iterator(__x, "other"));
@@ -193,7 +193,7 @@ namespace __gnu_debug
: _Iter_base()
{
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
- || __x.base() == _Iterator(),
+ || __x._M_value_initialized(),
_M_message(__msg_init_copy_singular)
._M_iterator(*this, "this")
._M_iterator(__x, "other"));
@@ -220,7 +220,7 @@ namespace __gnu_debug
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 408. Is vector > forbidden?
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
-|| __x.base() == _MutableIterator(),
+|| __x._M_value_initialized(),
_M_message(__msg_init_const_singular)
._M_iterator(*this, "this")
._M_iterator(__x, "other"));
@@ -236,7 +236,7 @@ namespace __gnu_debug
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 408. Is vector > forbidden?
_GLIBCXX_DEBUG_VERIFY(!__x._M_singular()
- || __x.base() == _Iterator(),
+ || __x._M_value_initialized(),
_M_message(__msg_copy_singular)
._M_iterator(*this, "this")
._M_itera
