The C++ Standard Library Has Been Walking Itself Back for Fifteen Years
5 hours ago
- #Software Maintenance
- #Standard Library
- #C++
- The C++ standard library has been incrementally replacing or deprecating its own features for fifteen years, with public documentation of these changes.
- Three tiers of 'walk-backs' exist: formal deprecations/removals (e.g., std::auto_ptr, dynamic exception specifications), unwritten but widely avoided features (e.g., std::regex, std::async), and ABI-locked broken defaults (e.g., std::unordered_map, std::list) that cannot be fixed.
- A benchmark shows C++'s naive use of standard containers (std::unordered_map, std::map, std::list) results in 58x higher P99 latency compared to Rust's defaults, highlighting performance issues from legacy designs.
- The 'Vasa problem' describes the committee adding unnecessary features (e.g., std::simd) that increase complexity without practical benefit, burdening implementers and users.
- Compared to other languages, C++ uniquely retains mistakes due to permanent ABI stability, enforced by linker compatibility, preventing removal or major fixes of flawed features.