I knew SSO conceptually but writing it out under pressure is different.
Start by clarifying the requirements: what is the maximum small string size, alignment considerations, and exception safety guarantees. Then design the class layout using a union or conditional storage, and implement the constructor to branch on length, copying to inline buffer or allocating heap memory, always null-terminating. Finally, handle allocation failure by throwing std::bad_alloc and ensuring no resource leaks.
Pro tip: Mention that you would use a union to avoid wasting space and that you'd consider alignment and strict aliasing rules; also note that throwing std::bad_alloc is standard, but you might offer a non-throwing overload for embedded contexts.
Ask about the maximum inline capacity, whether the string must be null-terminated, and what exception guarantees are expected. Confirm that allocation failure should throw std::bad_alloc.
Decide on a union-based storage: a fixed-size char array for small strings and a pointer+size+capacity for large strings. Include a flag or use the capacity field to distinguish modes.
In the constructor, check if the input length fits in the inline buffer. If so, copy characters and null-terminate. Otherwise, allocate heap memory, copy, and null-terminate; throw std::bad_alloc on failure.
Use RAII to manage heap memory; if allocation fails, ensure no leaks. Verify null-termination in both paths and consider self-assignment and move semantics if relevant.
Explain the performance benefits of small-string optimization (avoiding heap allocation for short strings) and the memory overhead. Mention alignment and potential padding issues.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.