C++26 define_static_array cleanly materializes constexpr-time data into static storage, but has four structural gaps the older “constexpr two-step” handles fine.
Key Takeaways
define_static_array returns a span<const T> over a rodata array; it cannot produce mutable static storage, unlike the two-step lambda approach.
It requires every element to be a structural NTTP-compatible type, blocking optional<int>, string, string_view, and span outright.
Pointers to string literals fail because they are not valid template arguments, even though const char* itself is a structural type.
Move-only types are blocked: creating a template parameter object requires copying the element, so types without copy constructors cannot be used.
Barry Revzin’s P3380R1 would let programmers mark types as explicitly structural, potentially fixing gaps 1-3, but at the cost of arcane annotations.
Hacker News Comment Review
The single substantive comment frames the limitations as emblematic of C++ complexity accrual: solving self-created problems yields elaborate machinery with conspicuous gaps.
Notable Comments
@oseityphelysiol: “C++ people are great at making problems for themselves and then solving them to no end.”
