From 92eb0adc14a5f84acce7e5bc780b81b1544b24aa Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Thu, 15 Dec 2022 09:52:48 +0000 Subject: [PATCH] libstdc++: Fix self-move for std::weak_ptr [PR108118] I think an alternative fix would be something like: _M_ptr = std::exchange(rhs._M_ptr, nullptr); _M_refcount = std::move(rhs._M_refcount); The standard's move-and-swap implementation generates smaller code at all levels except -O0 and -Og, so it seems simplest to just do what the standard says. libstdc++-v3/ChangeLog: PR libstdc++/108118 * include/bits/shared_ptr_base.h (weak_ptr::operator=): Implement as move-and-swap exactly as specified in the standard. * testsuite/20_util/weak_ptr/cons/self_move.cc: New test. --- libstdc++-v3/include/bits/shared_ptr_base.h | 4 +--- .../testsuite/20_util/weak_ptr/cons/self_move.cc | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+), 3 deletions(-) create mode 100644 libstdc++-v3/testsuite/20_util/weak_ptr/cons/self_move.cc diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h index d9230b7..c22b397 100644 --- a/libstdc++-v3/include/bits/shared_ptr_base.h +++ b/libstdc++-v3/include/bits/shared_ptr_base.h @@ -2049,9 +2049,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __weak_ptr& operator=(__weak_ptr&& __r) noexcept { - _M_ptr = __r._M_ptr; - _M_refcount = std::move(__r._M_refcount); - __r._M_ptr = nullptr; + __weak_ptr(std::move(__r)).swap(*this); return *this; } diff --git a/libstdc++-v3/testsuite/20_util/weak_ptr/cons/self_move.cc b/libstdc++-v3/testsuite/20_util/weak_ptr/cons/self_move.cc new file mode 100644 index 0000000..c890d2b --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/weak_ptr/cons/self_move.cc @@ -0,0 +1,19 @@ +// { dg-do run { target c++11 } } + +#include +#include + +void +test_self_move() +{ + std::shared_ptr sp(new int(66)); + std::weak_ptr wp(sp); + wp = std::move(wp); // PR libstdc++/108118 + std::shared_ptr sp2(wp); + VERIFY(sp2 == sp); +} + +int main() +{ + test_self_move(); +} -- 2.7.4