C++26: Standard Library Hardening Experiments

This article explores the concept of 'hardening' in the C++ Standard Library as introduced in C++26, discussing its implications for safety and error handling in library implementations.

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“Hardening” seems to be a very popular term in the C++ World in 2026. In this article we’ll explore what this word means and see some core examples. Can a hardened library make C++ fully safe? Let’s find out.

When you learned about std::vector you may remember that you can access an element at the i -th position using at least two expressions:

std :: vector < int > v { 1 , 2 , 3 , 4 }; v [ i ] = 10 ; // for some i v . at ( j ) = 11 ; // for some j The main difference between those two is that [] is unchecked (and can generate undefined behaviour if you try to access an element which is not there), while .at() may throw std::out_of_range (so it’s a well defined behaviour).

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