Tested x86_64-linux. Pushed to trunk. I think we should backport this too, after some soak time on trunk.
-- >8 -- With -fno-elide-constructors the debug iterator post-increment and post-decrement operators are susceptible to deadlock. They take a mutex lock and then return a temporary, which also attempts to take a lock to attach itself to the sequence. If the return value and *this happen to collide and use the same mutex from the pool, then you get a deadlock trying to lock a mutex that is already held by the current thread. The solution is to construct the return value before taking the lock. The copy constructor and pre-inc/pre-dec operators already manage locks correctly, without deadlock, so just implement post-inc/post-dec in the conventional way, taking a copy then modifying *this, then returning the copy. libstdc++-v3/ChangeLog: PR libstdc++/108288 * include/debug/safe_iterator.h (_Safe_iterator::operator++(int)) (_Safe_iterator::operator--(int)): Do not hold lock around construction of return value. --- libstdc++-v3/include/debug/safe_iterator.h | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h index 117dc93de60..f9068eaf8d6 100644 --- a/libstdc++-v3/include/debug/safe_iterator.h +++ b/libstdc++-v3/include/debug/safe_iterator.h @@ -761,12 +761,9 @@ namespace __gnu_debug _Safe_iterator operator++(int) _GLIBCXX_NOEXCEPT { - _GLIBCXX_DEBUG_VERIFY(this->_M_incrementable(), - _M_message(__msg_bad_inc) - ._M_iterator(*this, "this")); - __gnu_cxx::__scoped_lock __l(this->_M_get_mutex()); - return _Safe_iterator(this->base()++, this->_M_sequence, - _Attach_single()); + _Safe_iterator __ret = *this; + ++*this; + return __ret; } // ------ Bidirectional iterator requirements ------ @@ -788,12 +785,9 @@ namespace __gnu_debug _Safe_iterator operator--(int) _GLIBCXX_NOEXCEPT { - _GLIBCXX_DEBUG_VERIFY(this->_M_decrementable(), - _M_message(__msg_bad_dec) - ._M_iterator(*this, "this")); - __gnu_cxx::__scoped_lock __l(this->_M_get_mutex()); - return _Safe_iterator(this->base()--, this->_M_sequence, - _Attach_single()); + _Safe_iterator __ret = *this; + --*this; + return __ret; } // ------ Random access iterator requirements ------ -- 2.39.0