Anything can be a Constexpr if you try hard enough
summary
Shows a working constexpr implementation of std::array<T,0>::data() when T may not be default‑constructible, not just a theory. Starts from aligned char buffer and explains why reinterpret_cast and static_cast fail for constexpr or invoke UB, then uses Richard Smith’s union-with-bool-tag pattern to provide a constexpr constructor without default-constructing T. Fixes aggregate requirements by adding a container-wrapper-to-preserve-aggregate and exposes wrapper.T pointer as data, with code and slides on the CppCon 2019 repo.
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chapters (6)
- 0:00Start
- 0:31THE PROBLEM
- 0:55THE SOLUTION
- 1:54WHY THE BOOL?
- 2:14THE CONSTEXPR SOLUTION
- 2:29THE FINAL PROGRAM
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