Fast and Small C++: When Efficiency Matters

• 0:00:10 Introduction: The talk focuses on achieving both speed and small size in C++, particularly in resource-constrained environments like embedded systems.
• 0:01:31 Personal Introduction: The speaker introduces himself as Andreas Fertig, a C++ trainer, consultant, author of books on C++, and developer of the C++ Insights tool.
• 0:04:07 Unique Pointer Optimization: Discusses how std::unique_ptr can be customized with deleters to manage resources other than dynamically allocated memory, such as file handles.
• 0:07:52 Empty Base Class Optimization (EBCO): Explains how EBCO is used within std::unique_ptr to avoid storing an extra pointer when a custom deleter is stateless, thus saving space.
• 0:14:23 No Unique Address Attribute: Introduces the C++20 [[no_unique_address]] attribute as a way to achieve similar space savings to EBCO without inheritance, simplifying the implementation of compressed pairs.
• 0:15:35 Compressed Pair in std::unique_ptr: Shows how std::unique_ptr utilizes a compressed pair to store both the managed pointer and the deleter efficiently.
• 0:18:49 Small String Optimization (SSO): Explores how std::string implementations often employ SSO to avoid dynamic allocation for short strings by storing them within the string object itself.
• 0:24:16 SSO Implementations: Compares SSO strategies in different standard library implementations (libstdc++, libc++, MSVC STL), highlighting their trade-offs in terms of payload size and branch overhead.
• 0:37:25 Facebook's fbstring: Presents Facebook's fbstring as an example of a highly optimized string implementation that achieves a larger SSO capacity (23 bytes) by cleverly encoding mode and length information.
• 0:40:17 constxpr and RAM Savings: Demonstrates how using constexpr with a custom FixString class can significantly reduce RAM usage by allowing string literals to reside solely in ROM, avoiding runtime copying to the stack.
• 0:47:51 std::initializer_list and Defect Report: Discusses a defect report that allows compilers to optimize std::initializer_list backing arrays as if they were static in certain cases, leading to further code size reductions.
• 0:55:49 Conclusion: Emphasizes the importance of understanding these optimization techniques for writing efficient C++ code, especially in memory-constrained environments.
• 0:56:21 Q&A: The speaker answers several questions about the topics presented, including the application of these techniques to other data structures like std::vector and the use of bit fields and unions in standard library implementations.