De-fragmenting C++: Making Exceptions and RTTI More Affordable and Usable
summary
C++ currently pays for exceptions and RTTI even when unused; proposal makes error reporting static by default, dynamic by opt-in via a new throws annotation that lets the compiler implement value-based exceptions with no heap allocation and no RTTI, preserving throw/catch semantics and automatic propagation. Library/allocator tweaks let allocators choose fail-fast vs throw so many functions become noexcept, cutting roughly 90% of exceptions seen today. For casts, a five-instruction downcast range check (CFI-style) gives fast, safe downcasts with ~1–1.5% binary impact in trials.
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chapters (12)
- 0:00Introduction and welcome
- 1:36Context for exceptions and RTTI
- 9:47Exception handling problems
- 20:07Zero overhead exception proposal
- 31:15Static exception handling details
- 44:42Reducing exceptions via contracts
- 50:53Memory allocation failure handling
- 1:09:57RTTI problems and solutions
- 1:17:11Static reflection for RTTI
- 1:25:37Efficient downcast proposal
- 1:27:48Future of C++ simplification
- 1:33:08Q&A
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