High concurrency causes crashing

[gh-markt]

I wrote the following test program:

void test_concurrent_inserts_and_deletes(RBTree<int, int>& map) {
    std::vector<std::thread> threads;
    int num_threads = 10;
    int operations_per_thread = 1000;

    for (int i = 0; i < num_threads; ++i) {
        threads.emplace_back([&]() {
            for (int j = 0; j < operations_per_thread; ++j) {
                map.Insert(j, 10);
                map.Remove(j);
            }
        });
    }

    for (auto& thread : threads) {
        thread.join();
    }
}

This was the output running with address sanitization:

==17418==ERROR: AddressSanitizer: heap-use-after-free on address 0x602000002050 at pc 0x000000515b79 bp 0x7f3d644fd990 sp 0x7f3d644fd988
READ of size 8 at 0x602000002050 thread T2
    #0 0x515b78 in std::__atomic_base<DataNode<int, int>*>::operator DataNode<int, int>*() const (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x515b78)
    #1 0x510a0d in std::atomic<DataNode<int, int>*>::operator DataNode<int, int>*() const (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x510a0d)
    #2 0x511973 in TreeNode<int, int>::GetData() (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x511973)
    #3 0x51044d in TreeNode<int, int>::swap_window(TreeNode<int, int>*, DataNode<int, int>*) (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x51044d)
    #4 0x50e84c in RBTree<int, int>::Remove(int) (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x50e84c)
    #5 0x50ada9 in operator() /home/markt/CLionProjects/test_rbtree/main.cpp:20
    #6 0x50bee5 in __invoke_impl<void, test_concurrent_inserts_and_deletes(RBTree<int, int>&)::<lambda()> > /usr/include/c++/13.2.0/bits/invoke.h:61
    #7 0x50bea8 in __invoke<test_concurrent_inserts_and_deletes(RBTree<int, int>&)::<lambda()> > /usr/include/c++/13.2.0/bits/invoke.h:96
    #8 0x50be55 in _M_invoke<0> /usr/include/c++/13.2.0/bits/std_thread.h:292
    #9 0x50be29 in operator() /usr/include/c++/13.2.0/bits/std_thread.h:299
    #10 0x50be0d in _M_run /usr/include/c++/13.2.0/bits/std_thread.h:244
    #11 0x7f3d67c2f452  (/usr/lib64/libstdc++.so.6+0xe4452)
    #12 0x7f3d67873d56 in start_thread (/lib64/libc.so.6+0x94d56)
    #13 0x7f3d678f86a7 in __clone3 (/lib64/libc.so.6+0x1196a7)

0x602000002050 is located 0 bytes inside of 8-byte region [0x602000002050,0x602000002058)
freed by thread T2 here:
    #0 0x4bb938 in operator delete(void*, unsigned long) (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x4bb938)
    #1 0x5142b8 in RBTree<int, int>::fix_delete(std::vector<TreeNode<int, int>*, std::allocator<TreeNode<int, int>*> >&) (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x5142b8)
    #2 0x5102c6 in RBTree<int, int>::fix_window_color(std::vector<TreeNode<int, int>*, std::allocator<TreeNode<int, int>*> >&, int) (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x5102c6)
    #3 0x50e834 in RBTree<int, int>::Remove(int) (/home/markt/CLionProjects/test_rbtree/cmake-build-debug/test_rbtree+0x50e834)
    #4 0x50ada9 in operator() /home/markt/CLionProjects/test_rbtree/main.cpp:20
    #5 0x50bee5 in __invoke_impl<void, test_concurrent_inserts_and_deletes(RBTree<int, int>&)::<lambda()> > /usr/include/c++/13.2.0/bits/invoke.h:61
    #6 0x50bea8 in __invoke<test_concurrent_inserts_and_deletes(RBTree<int, int>&)::<lambda()> > /usr/include/c++/13.2.0/bits/invoke.h:96
    #7 0x50be55 in _M_invoke<0> /usr/include/c++/13.2.0/bits/std_thread.h:292
    #8 0x50be29 in operator() /usr/include/c++/13.2.0/bits/std_thread.h:299
    #9 0x50be0d in _M_run /usr/include/c++/13.2.0/bits/std_thread.h:244
    #10 0x7f3d67c2f452  (/usr/lib64/libstdc++.so.6+0xe4452)