Unexpected memory allocation behavior with std::vector and move semantics in C++20
I'm encountering an issue with `std::vector` and move semantics in C++20 that is causing unexpected memory allocations... I have a class `Data` that contains a `std::vector<int>`, and I'm trying to move the vector from one instance of the class to another. However, instead of the expected behavior where the new instance takes ownership of the vector's memory, I'm seeing additional allocations happening when I access the vector in the new instance. Here’s a simplified version of my class: ```cpp #include <iostream> #include <vector> class Data { public: std::vector<int> values; Data(std::vector<int> vals) : values(std::move(vals)) {} Data(Data&& other) noexcept : values(std::move(other.values)) {} void print() const { for (const auto& val : values) { std::cout << val << " "; } std::cout << std::endl; } }; ``` When I create an instance of `Data` and then move it to a new instance, I expect `values` in the moved-from instance to be empty, but when I print the values of the new instance, it outputs as if it's not moved at all: ```cpp int main() { Data d1({1, 2, 3, 4, 5}); Data d2(std::move(d1)); d2.print(); // Expected: 1 2 3 4 5 d1.print(); // Expected: (empty) return 0; } ``` Instead, I'm getting the output: ``` 1 2 3 4 5 1 2 3 4 5 ``` I’ve tried checking if the move constructor is being called correctly, and it seems to be, but the original instance `d1` still holds onto its values. I've also ensured that no other copies are made unintentionally. I am compiling with C++20 flag enabled. Am I missing something in my move semantics implementation, or is there a specific detail in `std::vector` that I'm overlooking? Any help would be appreciated! I'm working in a CentOS environment. Thanks for taking the time to read this!