From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: [committed] libstdc++: Avoid bogus warning in std::vector::insert [PR107852]
Date: Tue, 29 Nov 2022 17:14:46 +0000 [thread overview]
Message-ID: <20221129171446.149751-1-jwakely@redhat.com> (raw)
Tested x86_64-linux. Pushed to trunk.
-- >8 --
GCC assumes that any global variable might be modified by operator new,
and so in the testcase for this PR all data members get reloaded after
allocating new storage. By making local copies of the _M_start and
_M_finish members we avoid that, and then the compiler has enough info
to remove the dead branches that trigger bogus -Warray-bounds warnings.
libstdc++-v3/ChangeLog:
PR libstdc++/107852
PR libstdc++/106199
PR libstdc++/100366
* include/bits/vector.tcc (vector::_M_fill_insert): Copy
_M_start and _M_finish members before allocating.
(vector::_M_default_append): Likewise.
(vector::_M_range_insert): Likewise.
---
libstdc++-v3/include/bits/vector.tcc | 63 ++++++++++++++++------------
1 file changed, 37 insertions(+), 26 deletions(-)
diff --git a/libstdc++-v3/include/bits/vector.tcc b/libstdc++-v3/include/bits/vector.tcc
index 33faabf2eae..27ef1a4ee7f 100644
--- a/libstdc++-v3/include/bits/vector.tcc
+++ b/libstdc++-v3/include/bits/vector.tcc
@@ -539,9 +539,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
if (__elems_after > __n)
{
_GLIBCXX_ASAN_ANNOTATE_GROW(__n);
- std::__uninitialized_move_a(this->_M_impl._M_finish - __n,
- this->_M_impl._M_finish,
- this->_M_impl._M_finish,
+ std::__uninitialized_move_a(__old_finish - __n,
+ __old_finish,
+ __old_finish,
_M_get_Tp_allocator());
this->_M_impl._M_finish += __n;
_GLIBCXX_ASAN_ANNOTATE_GREW(__n);
@@ -554,7 +554,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{
_GLIBCXX_ASAN_ANNOTATE_GROW(__n);
this->_M_impl._M_finish =
- std::__uninitialized_fill_n_a(this->_M_impl._M_finish,
+ std::__uninitialized_fill_n_a(__old_finish,
__n - __elems_after,
__x_copy,
_M_get_Tp_allocator());
@@ -569,9 +569,15 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
}
else
{
+ // Make local copies of these members because the compiler thinks
+ // the allocator can alter them if 'this' is globally reachable.
+ pointer __old_start = this->_M_impl._M_start;
+ pointer __old_finish = this->_M_impl._M_finish;
+ const pointer __pos = __position.base();
+
const size_type __len =
_M_check_len(__n, "vector::_M_fill_insert");
- const size_type __elems_before = __position - begin();
+ const size_type __elems_before = __pos - __old_start;
pointer __new_start(this->_M_allocate(__len));
pointer __new_finish(__new_start);
__try
@@ -584,15 +590,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
__new_finish
= std::__uninitialized_move_if_noexcept_a
- (this->_M_impl._M_start, __position.base(),
- __new_start, _M_get_Tp_allocator());
+ (__old_start, __pos, __new_start, _M_get_Tp_allocator());
__new_finish += __n;
__new_finish
= std::__uninitialized_move_if_noexcept_a
- (__position.base(), this->_M_impl._M_finish,
- __new_finish, _M_get_Tp_allocator());
+ (__pos, __old_finish, __new_finish, _M_get_Tp_allocator());
}
__catch(...)
{
@@ -606,12 +610,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_deallocate(__new_start, __len);
__throw_exception_again;
}
- std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
- _M_get_Tp_allocator());
+ std::_Destroy(__old_start, __old_finish, _M_get_Tp_allocator());
_GLIBCXX_ASAN_ANNOTATE_REINIT;
- _M_deallocate(this->_M_impl._M_start,
- this->_M_impl._M_end_of_storage
- - this->_M_impl._M_start);
+ _M_deallocate(__old_start,
+ this->_M_impl._M_end_of_storage - __old_start);
this->_M_impl._M_start = __new_start;
this->_M_impl._M_finish = __new_finish;
this->_M_impl._M_end_of_storage = __new_start + __len;
@@ -645,6 +647,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
}
else
{
+ // Make local copies of these members because the compiler thinks
+ // the allocator can alter them if 'this' is globally reachable.
+ pointer __old_start = this->_M_impl._M_start;
+ pointer __old_finish = this->_M_impl._M_finish;
+
const size_type __len =
_M_check_len(__n, "vector::_M_default_append");
pointer __new_start(this->_M_allocate(__len));
@@ -660,7 +667,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_deallocate(__new_start, __len);
__throw_exception_again;
}
- _S_relocate(this->_M_impl._M_start, this->_M_impl._M_finish,
+ _S_relocate(__old_start, __old_finish,
__new_start, _M_get_Tp_allocator());
}
else
@@ -672,7 +679,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
__n, _M_get_Tp_allocator());
__destroy_from = __new_start + __size;
std::__uninitialized_move_if_noexcept_a(
- this->_M_impl._M_start, this->_M_impl._M_finish,
+ __old_start, __old_finish,
__new_start, _M_get_Tp_allocator());
}
__catch(...)
@@ -683,13 +690,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_deallocate(__new_start, __len);
__throw_exception_again;
}
- std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
+ std::_Destroy(__old_start, __old_finish,
_M_get_Tp_allocator());
}
_GLIBCXX_ASAN_ANNOTATE_REINIT;
- _M_deallocate(this->_M_impl._M_start,
- this->_M_impl._M_end_of_storage
- - this->_M_impl._M_start);
+ _M_deallocate(__old_start,
+ this->_M_impl._M_end_of_storage - __old_start);
this->_M_impl._M_start = __new_start;
this->_M_impl._M_finish = __new_start + __size + __n;
this->_M_impl._M_end_of_storage = __new_start + __len;
@@ -782,6 +788,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
}
else
{
+ // Make local copies of these members because the compiler
+ // thinks the allocator can alter them if 'this' is globally
+ // reachable.
+ pointer __old_start = this->_M_impl._M_start;
+ pointer __old_finish = this->_M_impl._M_finish;
+
const size_type __len =
_M_check_len(__n, "vector::_M_range_insert");
pointer __new_start(this->_M_allocate(__len));
@@ -790,7 +802,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{
__new_finish
= std::__uninitialized_move_if_noexcept_a
- (this->_M_impl._M_start, __position.base(),
+ (__old_start, __position.base(),
__new_start, _M_get_Tp_allocator());
__new_finish
= std::__uninitialized_copy_a(__first, __last,
@@ -798,7 +810,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_get_Tp_allocator());
__new_finish
= std::__uninitialized_move_if_noexcept_a
- (__position.base(), this->_M_impl._M_finish,
+ (__position.base(), __old_finish,
__new_finish, _M_get_Tp_allocator());
}
__catch(...)
@@ -808,12 +820,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_deallocate(__new_start, __len);
__throw_exception_again;
}
- std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
+ std::_Destroy(__old_start, __old_finish,
_M_get_Tp_allocator());
_GLIBCXX_ASAN_ANNOTATE_REINIT;
- _M_deallocate(this->_M_impl._M_start,
- this->_M_impl._M_end_of_storage
- - this->_M_impl._M_start);
+ _M_deallocate(__old_start,
+ this->_M_impl._M_end_of_storage - __old_start);
this->_M_impl._M_start = __new_start;
this->_M_impl._M_finish = __new_finish;
this->_M_impl._M_end_of_storage = __new_start + __len;
--
2.38.1
reply other threads:[~2022-11-29 17:14 UTC|newest]
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