On 11/2/25 04:09, Jonathan Wakely wrote:
On Sat, 1 Nov 2025, 21:10 François Dumont, <[email protected]> wrote:
Hi
Here is the implementation of the std::__debug::inplace_vector.
It looks like this is going to repeat the assertions in e.g.
operator[], front, back etc because those already have assertions in
the base class.
This is I think unavoidable if you want to cover direct usages of
__gnu_debug::inplace_vector like in
23_containers/inplace_vector/debug/invalidation/*.cc tests.
I eventually had to introduce a dedicated std::erase_if/std::erase
implementation for the __debug version. When directly using
__gnu_debug::inplace_vector the std::erase_if was used downcasting the
If it's converting to a base, it's upcasting.
inplace_vector into the std::inplace_vector base class so breaking
encapsulation. So we really need dedicated implementations and I'll
prepare patches for other containers.
Why is the implicit cast a problem? We know that erase_if doesn't
iterate past the end, and only dereferences valid iterators. That's
one of the benefits of using erase_if: it ensures the container is
accessed safely.
The problem is that the std::__debug::inplace_vector is not aware of the
invalidated iterators.
Is encapsulation broken if a standard library function does that
implicit cast? Is it observable to users?
Yes, some iterators might not be invalidated as they should.
I also added tests for std::swap. Overloading it in std:: namespace
seems the best option to me. If it is defined in std::__debug:: as it
should then calls to std::swap in user code are replaced by the
generic
call to swap in move.h instead of calling inplace_vector<>::swap.
Users should call swap not std::swap. That was the consensus when LWG
discussed https://cplusplus.github.io/LWG/issue4250
Ok, I'll remove the test case with the call to std::swap then.
It
still works to invalidate iterators but is a major performance
issue. I
noticed this running in gdb, is there a way to test for call to the
correct swap ?
I also wonder in
testsuite/23_containers/inplace_vector/debug/invalidation/swap.cc
test02
how gcc does to find the proper swap method on the unqualified call ?
Argument Dependent Lookup ?
That's what it should be but container is in std::__debug:: whereas the
swap definition is in std::.
I'll have some more tests but with your remark above I think I'll just
defined swap as friend in std::__debug::inplace_vector like it's done in
std::inplace_vector.
Add _GLIBCXX_DEBUG std::inplace_vector implementation.
Unlike other _GLIBCXX_DEBUG containers the
std::__debug::inplace_vector is
inheriting privately from both __gnu_debug::_Safe_sequence<> and
std::inplace_vector
classes to preserve encapsulation. Iterators won't be created or
invalidated without
std::__debug::inplace_vector being aware. However
std::__debug::inplace_vector<T, 0>
inherits publicly from std::inplace_vector<T, 0> to benefit from
the same std::
functions overloads.
libstdc++-v3/ChangeLog:
* include/Makefile.am (debug_headers): Add
inplace_vector.
* include/Makefile.in: Regenerate.
* include/debug/inplace_vector: New.
* include/debug/safe_base.h (~_Safe_sequence_base()):
Add
C++11 noexcept
qualification.
(_Safe_sequence_base::operator=(const
_Safe_sequence_base&)): New.
(_Safe_sequence_base::operator=(_Safe_sequence_base&&)): New.
(_Safe_sequence_base::_M_invalidate_all): Add C++20
constexpr qualification.
* include/debug/safe_container.h
(_Safe_container::operator=(const _Safe_container&)):
Implement using same
_Safe_sequence_base operator.
* include/std/inplace_vector
[_GLIBCXX_DEBUG](std::inplace_vector<>): Move
implementation into __cxx1998 namespace.
(erase, erase_if): Limit to non-debug inplace_vector<>,
cleanup code.
[_GLIBCXX_DEBUG]: Add include <debug/inplace_vector>.
* testsuite/23_containers/inplace_vector/cons/1.cc:
Adapt,
skip several
is_trivially_xxx checks when in _GLIBCXX_DEBUG mode.
* testsuite/23_containers/inplace_vector/copy.cc:
Likewise.
* testsuite/23_containers/inplace_vector/move.cc:
Likewise.
*
testsuite/23_containers/inplace_vector/debug/assign1_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/assign2_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/assign3_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/assign4_backtrace_neg.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/assign4_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/construct1_neg.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/construct2_neg.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/construct3_neg.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/construct4_neg.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/debug_functions.cc: New
test case.
* testsuite/23_containers/inplace_vector/debug/erase.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/insert1_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/insert2_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/insert3_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/insert4_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/insert5_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/insert7_neg.cc: New
test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/1.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/2.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/3.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/4.cc:
New test
case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/append_range.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/erase.cc:
New
test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/pop_back.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/push_back.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/swap.cc:
New
test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/try_append_range.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/try_emplace_back.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/try_push_back.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/invalidation/unchecked_emplace_back.cc:
New test case.
*
testsuite/23_containers/inplace_vector/debug/multithreaded_swap.cc:
New
test case.
* testsuite/util/debug/checks.h: Avoid using
_GLIBCXX_DEBUG
containers in test
implementations.
Tested under Linux x86_64.
Ok to commit ?
PR: https://forge.sourceware.org/gcc/gcc-TEST/pulls/119
François
