std::deque Iterator Invalidation guide When Modifying Elements in C++20
I'm running into an scenario with modifying elements in a `std::deque` while iterating over it using an iterator. The question arises when I try to update the value of an element in the `deque`, which seems to invalidate the iterator, leading to undefined behavior. I'm using C++20, and here's a simplified version of what I'm doing: ```cpp #include <iostream> #include <deque> void updateDeque(std::deque<int>& d) { for (auto it = d.begin(); it != d.end(); ++it) { if (*it % 2 == 0) { *it += 10; // Modify the element } } } int main() { std::deque<int> myDeque = {1, 2, 3, 4, 5}; updateDeque(myDeque); for (const auto& val : myDeque) { std::cout << val << ' '; } return 0; } ``` When I run this code, I get an output of `1 12 3 14 5`, which is what I expected, but I also get several instances of the following warning during compilation: ``` warnings: dereferencing past end of iterator ``` This warning leads me to believe that there might be an iterator invalidation happening. I read somewhere that modifying the structure of the `deque` in certain ways can invalidate iterators, but in this case, I'm only modifying the values, not adding or removing elements. Is there something I'm missing here? Should I be using a different method to reliably update the elements without causing iterator issues? Any insights would be greatly appreciated! This is part of a larger web app I'm building. Any help would be greatly appreciated!