remove_if bug (vs find_if)

remove_if_vs_find_if.cpp

// Run this code here: https://coliru.stacked-crooked.com/a/1a9ad442077cd0f6

#include <vector>
#include <algorithm>
#include <iostream>
#include <memory>
 
int main()
{
    std::vector<std::unique_ptr<int>> vec;
    vec.push_back(std::make_unique<int>(3));
    vec.push_back(std::make_unique<int>(5));
    vec.push_back(std::make_unique<int>(7));
    std::cout << "Original vector\n";
    for (auto const& elem : vec) {
        std::cout << "  [" << elem.get() << "] " << *elem << std::endl;
    }
    constexpr bool brokenCode = false;
    constexpr int searchValue{5};
    auto const rem = [&]{
        // If you remove_if(), the unique_ptr will be moved from, thus nullified,
        // so we'll get undefined behaviour when trying to dereference it later.
        // Better to find_if()! The vec.erase() still works fine when the iterator
        // is not at the end of the vector.
        if (brokenCode)
            return std::remove_if(vec.begin(), vec.end(), [&](auto const& elem) { return *elem == searchValue; });
        else
            return std::find_if(vec.begin(), vec.end(), [&](auto const& elem) { return *elem == searchValue; });
    }();
    std::cout << "Found unique_ptr: [" << rem->get() << "] with value: " << **rem << std::endl;
    vec.erase(rem);
    std::cout << "\nFinal vector\n";
    for (auto const& elem : vec) {
        std::cout << "  [" << elem.get() << "] " << *elem << std::endl;
    }
}

// Possible output when brokenCode is false:
// ==========
// Original vector
//   [0x2293c20] 3
//   [0x2293c60] 5
//   [0x2293c40] 7
// Found unique_ptr: [0x2293c60] with value: 5
// 
// Final vector
//   [0x2293c20] 3
//   [0x2293c40] 7

// Possible output when brokenCode is true:
// ==========
// Original vector
//   [0x1349c20] 3
//   [0x1349c60] 5
//   [0x1349c40] 7
// bash: line 7: 14344 Segmentation fault      (core dumped) ./a.out