How do I iterate safely under modification with std::deque in performance-sensitive code?

Iterating over a container while modifying it can lead to undefined behavior in C++. This is a common problem for developers working with performance-sensitive code. Using std::deque in C++, it’s important to ensure safe iteration even when you're adding or removing elements. One reliable way to do this is to maintain a separate list of elements to process, which minimizes issues when adding or removing elements during iteration.

Here's a simple example that demonstrates how to safely iterate over a std::deque while modifying it:


        #include <iostream>
        #include <deque>

        int main() {
            std::deque myDeque = {1, 2, 3, 4, 5};

            // Create a temporary deque for modification
            std::deque toAdd;

            for (auto it = myDeque.begin(); it != myDeque.end(); /* no increment here */) {
                // Example condition to modify container
                if (*it % 2 == 0) {
                    toAdd.push_back(*it * 10); // Add 10x of even elements to the temporary deque
                    it = myDeque.erase(it); // safely erase and move the iterator forward
                } else {
                    ++it; // Increment only if no modification has happened
                }
            }

            // Now add new elements to original deque
            myDeque.insert(myDeque.end(), toAdd.begin(), toAdd.end());

            // Printing the modified deque
            for (const auto& val : myDeque) {
                std::cout << val << " ";
            }
            std::cout << std::endl;

            return 0;
        }

How do I iterate safely under modification with std::deque in performance-sensitive code?

Popular Topics

Recent Languages

How do I iterate safely under modification with std::deque in performance-sensitive code?

Related Questions

Popular Topics

Recent Languages