pointer being freed was not allocated

[omartijn]

#942 was closed, and I cannot re-open it (because I do not have permissions), but it's still broken:

#include <algorithm>
#include <chrono>
#include <functional>
#include <iostream>
#include <thread>
#include <vector>

int main() {
    std::vector<std::unique_ptr<std::size_t>> numbers(1024 * 1024 * 100);
    std::vector<std::thread> threads(1);

    std::atomic<std::size_t> index{};

    auto start = std::chrono::system_clock::now();

    for (auto& thread : threads) {
        thread = std::thread{[&index, &numbers]() {
            while (true) {
                auto i = index.fetch_add(1, std::memory_order_relaxed);
                if (i >= numbers.size()) return;

                numbers[i] = std::make_unique<std::size_t>(i);
            }
        }};
    }

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

    auto end = std::chrono::system_clock::now();

    auto duration =
        std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
    std::cout << "Running on " << threads.size() << " threads took " << duration
              << std::endl;
}

Compiling this on macOS, like this:

c++ -std=c++20 -g -Wall -Wextra -L/Users/martijn/test -lmimalloc -o allocate allocate.cpp

leads to the following output when run:

allocate(16926,0x16d067000) malloc: *** error for object 0x3ff8c010020: pointer being freed was not allocated
allocate(16926,0x16d067000) malloc: *** set a breakpoint in malloc_error_break to debug