A stupid C++ bug. The insert() on line 23 has its last two parameters swapped, but "false" is silently converted to 0, so no compiler warnings/errors are raised.

stupid_vector_bug.cpp

#include <iostream>
#include <vector>

void Show(const std::vector<std::vector<bool>> &two_dim_vect) {
    for (const auto &row : two_dim_vect) {
        for (bool b : row) {
            std::cout  << b << " ";
        }
        std::cout << "\n";
    }
}

int main() {
    std::vector<std::vector<bool>> two_dim_vect;
    std::vector<bool> tmp;
    const int size1 = 5;
    const int size2 = 5;

    tmp.reserve(size1);

    // This compiles without errors or warnings
    // The last two parameters are swapped and "false" is treated as integer 0
    tmp.insert(tmp.begin(), false, size1);

    two_dim_vect.reserve(size2);
    two_dim_vect.insert(two_dim_vect.begin(), size2, tmp);

    Show(two_dim_vect);
    two_dim_vect[3][2] = true;
    Show(two_dim_vect);
    return 0;
}