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* [gcc r13-7625] libstdc++: Avoid bogus overflow warnings in std::vector<bool> [PR110807]
@ 2023-07-28 17:32 Jonathan Wakely
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From: Jonathan Wakely @ 2023-07-28 17:32 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:962cd3e2c475e8197fd0cfa7330a8f352b4ff5b2
commit r13-7625-g962cd3e2c475e8197fd0cfa7330a8f352b4ff5b2
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Wed Jul 26 14:09:24 2023 +0100
libstdc++: Avoid bogus overflow warnings in std::vector<bool> [PR110807]
GCC thinks the allocation can alter the object being copied if it's
globally reachable, so doesn't realize that [x.begin(), x.end()) after
the allocation is the same as x.size() before it.
This causes a testsuite failure when testing with -D_GLIBCXX_DEBUG:
FAIL: 23_containers/vector/bool/swap.cc (test for excess errors)
A fix is to move the calls to x.begin() and x.end() to before the
allocation.
A similar problem exists in vector<bool>::_M_insert_range where *this is
globally reachable, as reported in PR libstdc++/110807. That can also be
fixed by moving calls to begin() and end() before the allocation.
libstdc++-v3/ChangeLog:
PR libstdc++/110807
* include/bits/stl_bvector.h (vector(const vector&)): Access
iterators before allocating.
* include/bits/vector.tcc (vector<bool>::_M_insert_range):
Likewise.
* testsuite/23_containers/vector/bool/110807.cc: New test.
(cherry picked from commit 7931a1de9ec87b996d51d3d60786f5c81f63919f)
Diff:
---
libstdc++-v3/include/bits/stl_bvector.h | 3 ++-
libstdc++-v3/include/bits/vector.tcc | 5 +++--
libstdc++-v3/testsuite/23_containers/vector/bool/110807.cc | 14 ++++++++++++++
3 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h
index ad462c5933c..8d18bcaffd4 100644
--- a/libstdc++-v3/include/bits/stl_bvector.h
+++ b/libstdc++-v3/include/bits/stl_bvector.h
@@ -773,8 +773,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
vector(const vector& __x)
: _Base(_Bit_alloc_traits::_S_select_on_copy(__x._M_get_Bit_allocator()))
{
+ const_iterator __xbegin = __x.begin(), __xend = __x.end();
_M_initialize(__x.size());
- _M_copy_aligned(__x.begin(), __x.end(), begin());
+ _M_copy_aligned(__xbegin, __xend, begin());
}
#if __cplusplus >= 201103L
diff --git a/libstdc++-v3/include/bits/vector.tcc b/libstdc++-v3/include/bits/vector.tcc
index d6fdea2dd01..c762dbf798f 100644
--- a/libstdc++-v3/include/bits/vector.tcc
+++ b/libstdc++-v3/include/bits/vector.tcc
@@ -910,11 +910,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{
const size_type __len =
_M_check_len(__n, "vector<bool>::_M_insert_range");
+ const iterator __begin = begin(), __end = end();
_Bit_pointer __q = this->_M_allocate(__len);
iterator __start(std::__addressof(*__q), 0);
- iterator __i = _M_copy_aligned(begin(), __position, __start);
+ iterator __i = _M_copy_aligned(__begin, __position, __start);
__i = std::copy(__first, __last, __i);
- iterator __finish = std::copy(__position, end(), __i);
+ iterator __finish = std::copy(__position, __end, __i);
this->_M_deallocate();
this->_M_impl._M_end_of_storage = __q + _S_nword(__len);
this->_M_impl._M_start = __start;
diff --git a/libstdc++-v3/testsuite/23_containers/vector/bool/110807.cc b/libstdc++-v3/testsuite/23_containers/vector/bool/110807.cc
new file mode 100644
index 00000000000..2e9d4019edb
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/bool/110807.cc
@@ -0,0 +1,14 @@
+// { dg-options "-O2" }
+// { dg-do compile { target c++11 } }
+
+// Bug 110807
+// Copy list initialisation of a vector<bool> raises a warning with -O2
+
+#include <vector>
+
+std::vector<bool> byCallSpread;
+
+void f()
+{
+ byCallSpread = {true};
+}
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