I eventually prefer to propose this version.
Compared to the previous one I have the _M_can_advance calling the
former one with correct number of elements to check for advance. And
the former _M_can_advance is also properly making use of the
__dp_sign_max_size precision.
Here is the revisited git log:
libstdc++: [_GLIBCXX_DEBUG] Fix management of __dp_sign_max_size
[PR 99402]
__dp_sign precision indicates that we found out what iterator
comes first or
last in the range. __dp_sign_max_size is the same plus it gives
the information
of the max size of the range that is to say the max_size value
such that
distance(lhs, rhs) < max_size.
Thanks to this additional information we are able to tell when a
copy of n elements
to that range will fail even if we do not know exactly how large
it is.
This patch makes sure that we are properly using this information.
libstdc++-v3/ChangeLog:
PR libstdc++/99402
* include/debug/helper_functions.h
(__can_advance(_InputIterator,
const std::pair<_Diff, _Distance_precision>&, int)): New.
(__can_advance(const _Safe_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
* include/debug/macros.h
(__glibcxx_check_can_increment_dist): New,
use latter.
(__glibcxx_check_can_increment_range): Adapt to use latter.
(__glibcxx_check_can_decrement_range): Likewise.
* include/debug/safe_iterator.h
(_Safe_iterator<>::_M_can_advance(const std::pair<_Diff,
_Distance_precision>&,
int)): New.
(__can_advance(const _Safe_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
* include/debug/safe_iterator.tcc
(_Safe_iterator<>::_M_can_advance(const std::pair<_Diff,
_Distance_precision>&,
int)): New.
(_Safe_iterator<>::_M_valid_range(const _Safe_iterator<>&,
std::pair<difference_type, _Distance_precision>&, bool)):
Adapt for
__dp_sign_max_size.
(__copy_move_a): Adapt to use
__glibcxx_check_can_increment_dist.
(__copy_move_backward_a): Likewise.
(__equal_aux): Likewise.
* include/debug/stl_iterator.h (__can_advance(const
std::reverse_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
(__can_advance(const std::move_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
* testsuite/25_algorithms/copy/debug/99402.cc: New test.
Ok to commit if tests are all PASS ?
François
On 07/03/21 10:30 pm, François Dumont wrote:
Here is the patch to correctly deal with the new __dp_sign_max_size.
I prefer to introduce new __can_advance overloads for this to
correctly deal with the _Distance_precision in it. _M_valid_range
was also ignoring __dp_sign_max_size.
libstdc++: [_GLIBCXX_DEBUG] Fix management of __dp_sign_max_size
[PR 99402]
libstdc++-v3/ChangeLog:
PR libstdc++/99402
* include/debug/helper_functions.h
(__can_advance(_InputIterator,
const std::pair<_Diff, _Distance_precision>&, int)): New.
(__can_advance(const _Safe_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
* include/debug/macros.h
(__glibcxx_check_can_increment_dist): New,
use latter.
(__glibcxx_check_can_increment_range): Adapt to use latter.
(__glibcxx_check_can_decrement_range): Likewise.
* include/debug/safe_iterator.h
(_Safe_iterator<>::_M_can_advance(const std::pair<_Diff,
_Distance_precision>&,
int)): New.
(__can_advance(const _Safe_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
* include/debug/safe_iterator.tcc
(_Safe_iterator<>::_M_can_advance(const std::pair<_Diff,
_Distance_precision>&,
int)): New.
(_Safe_iterator<>::_M_valid_range(const _Safe_iterator<>&,
std::pair<difference_type, _Distance_precision>&,
bool)): Adapt for
__dp_sign_max_size.
(__copy_move_a): Adapt to use
__glibcxx_check_can_increment_dist.
(__copy_move_backward_a): Likewise.
(__equal_aux): Likewise.
* include/debug/stl_iterator.h (__can_advance(const
std::reverse_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
(__can_advance(const std::move_iterator<>&,
const std::pair<_Diff, _Distance_precision>&, int)): New.
* testsuite/25_algorithms/copy/debug/99402.cc: New test.
Tested under Linux x86_64.
Ok to commit ?
François
diff --git a/libstdc++-v3/include/debug/helper_functions.h
b/libstdc++-v3/include/debug/helper_functions.h
index 513e5460eba..c0144ced979 100644
--- a/libstdc++-v3/include/debug/helper_functions.h
+++ b/libstdc++-v3/include/debug/helper_functions.h
@@ -291,6 +291,18 @@ namespace __gnu_debug
__can_advance(const _Safe_iterator<_Iterator, _Sequence,
_Category>&,
_Size);
+ template<typename _InputIterator, typename _Diff>
+ _GLIBCXX_CONSTEXPR
+ inline bool
+ __can_advance(_InputIterator, const std::pair<_Diff,
_Distance_precision>&, int)
+ { return true; }
+
+ template<typename _Iterator, typename _Sequence, typename _Category,
+ typename _Diff>
+ bool
+ __can_advance(const _Safe_iterator<_Iterator, _Sequence,
_Category>&,
+ const std::pair<_Diff, _Distance_precision>&, int);
+
/** Helper function to extract base iterator of random access safe
iterator
* in order to reduce performance impact of debug mode. Limited to
random
* access iterator because it is the only category for which it is
possible
diff --git a/libstdc++-v3/include/debug/macros.h
b/libstdc++-v3/include/debug/macros.h
index 0988437046f..9ac52ebd09d 100644
--- a/libstdc++-v3/include/debug/macros.h
+++ b/libstdc++-v3/include/debug/macros.h
@@ -94,6 +94,12 @@
_GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size), \
._M_iterator(_First, #_First) \
._M_integer(_Size, #_Size))
+#define __glibcxx_check_can_increment_dist(_First,_Dist,_Way) \
+ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Dist,
_Way), \
+ _M_message(__gnu_debug::__msg_iter_subscript_oob) \
+ ._M_iterator(_First, #_First) \
+ ._M_integer(_Way * _Dist.first, #_Dist))
+
#define __glibcxx_check_can_increment_range(_First1,_Last1,_First2) \
do \
{ \
@@ -105,7 +111,7 @@
_GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size), \
._M_iterator(_Last1, #_Last1), \
__FILE__,__LINE__,__PRETTY_FUNCTION__); \
_GLIBCXX_DEBUG_VERIFY_AT_F( \
- __gnu_debug::__can_advance(_First2, __dist.first),\
+ __gnu_debug::__can_advance(_First2, __dist, 1), \
_M_message(__gnu_debug::__msg_iter_subscript_oob)\
._M_iterator(_First2, #_First2) \
._M_integer(__dist.first), \
@@ -123,7 +129,7 @@
_GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size), \
._M_iterator(_Last1, #_Last1), \
__FILE__,__LINE__,__PRETTY_FUNCTION__); \
_GLIBCXX_DEBUG_VERIFY_AT_F( \
- __gnu_debug::__can_advance(_First2, -__dist.first),\
+ __gnu_debug::__can_advance(_First2, __dist, -1), \
_M_message(__gnu_debug::__msg_iter_subscript_oob)\
._M_iterator(_First2, #_First2) \
._M_integer(-__dist.first), \
diff --git a/libstdc++-v3/include/debug/safe_iterator.h
b/libstdc++-v3/include/debug/safe_iterator.h
index a10df190969..8e138fd32e5 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -407,6 +407,12 @@ namespace __gnu_debug
bool
_M_can_advance(difference_type __n, bool __strict = false) const;
+ // Can we advance the iterator using @p __dist in @p __way
direction.
+ template<typename _Diff>
+ bool
+ _M_can_advance(const std::pair<_Diff, _Distance_precision>& __dist,
+ int __way) const;
+
// Is the iterator range [*this, __rhs) valid?
bool
_M_valid_range(const _Safe_iterator& __rhs,
@@ -958,6 +964,14 @@ namespace __gnu_debug
_Size __n)
{ return __it._M_can_advance(__n); }
+ template<typename _Iterator, typename _Sequence, typename _Category,
+ typename _Diff>
+ inline bool
+ __can_advance(const _Safe_iterator<_Iterator, _Sequence,
_Category>& __it,
+ const std::pair<_Diff, _Distance_precision>& __dist,
+ int __way)
+ { return __it._M_can_advance(__dist, __way); }
+
template<typename _Iterator, typename _Sequence>
_Iterator
__base(const _Safe_iterator<_Iterator, _Sequence,
diff --git a/libstdc++-v3/include/debug/safe_iterator.tcc
b/libstdc++-v3/include/debug/safe_iterator.tcc
index 81deb10125b..6f14c40bf41 100644
--- a/libstdc++-v3/include/debug/safe_iterator.tcc
+++ b/libstdc++-v3/include/debug/safe_iterator.tcc
@@ -92,22 +92,30 @@ namespace __gnu_debug
if (__n == 0)
return true;
+ std::pair<difference_type, _Distance_precision> __dist = __n < 0
+ ? _M_get_distance_from_begin()
+ : _M_get_distance_to_end();
+
if (__n < 0)
- {
- std::pair<difference_type, _Distance_precision> __dist =
- _M_get_distance_from_begin();
- return __dist.second == __dp_exact
- ? __dist.first >= -__n
+ __n = -__n;
+
+ return __dist.second > __dp_sign
+ ? __dist.first >= __n
: !__strict && __dist.first > 0;
}
- else
+
+ template<typename _Iterator, typename _Sequence, typename _Category>
+ template<typename _Diff>
+ bool
+ _Safe_iterator<_Iterator, _Sequence, _Category>::
+ _M_can_advance(const std::pair<_Diff, _Distance_precision>&
__dist,
+ int __way) const
{
- std::pair<difference_type, _Distance_precision> __dist =
- _M_get_distance_to_end();
return __dist.second == __dp_exact
- ? __dist.first >= __n
- : !__strict && __dist.first > 0;
- }
+ ? _M_can_advance(__way * __dist.first)
+ : _M_can_advance(__way * (__dist.first == 0
+ ? 0
+ : __dist.first < 0 ? -1 : 1));
}
template<typename _Iterator, typename _Sequence, typename _Category>
@@ -194,20 +202,15 @@ namespace __gnu_debug
switch (__dist.second)
{
case __dp_equality:
- if (__dist.first == 0)
+ // Assume that this is a valid range; we can't check anything
else.
return true;
- break;
- case __dp_sign:
- case __dp_exact:
+ default:
// If range is not empty first iterator must be dereferenceable.
- if (__dist.first > 0)
- return !__check_dereferenceable || _M_dereferenceable();
- return __dist.first == 0;
+ return __dist.first == 0
+ || (__dist.first > 0
+ && (!__check_dereferenceable || _M_dereferenceable()));
}
