Why must a move constructor be noexcept?
A performance question disguised as a keyword question. It connects directly to M3, and the honest answer explains a decision the standard library makes on your behalf.
Exam
Answer these to pass this module.
Start here rather than at the reading. Whatever you miss tells you which part of Learn you actually need — and anything you get right is a part you can skip.
Your type's move constructor is not marked noexcept. A std::vector of it reallocates. What happens?
Why can't vector use a move that might throw?
What does the missing noexcept do to correctness?
Explain mode
Why must a move constructor be noexcept?
Explain what vector does during growth, step by step, and where the choice between move and copy is made.
Your own words, two or three sentences, nothing looked up. The rubric unlocks once you submit.
Graded against a set rubric. Three a day on a free account. Need more? Ask on our Facebook page — it's free.
Learn
std::move_if_noexcept, the strong exception guarantee, what vector reallocation has to do to keep it, and how a missing noexcept silently turns your moves into copies.
Ask an AI to teach you this
I'm preparing for a quant developer interview on "Why must a move constructor be noexcept?" Concepts I need to own: std::move_if_noexcept, the strong exception guarantee, what vector reallocation has to do to keep it, and how a missing noexcept silently turns your moves into copies. Run this as interview practice, not a lecture. One concept at a time. Wait for my answer before moving on. Per concept: 1. Teach it. Lead with the one-line core claim, then a few short paragraphs. Assume I write C++ but have never had this explained properly. No jargon without defining it. 2. "The 60-second version" — what a strong candidate would SAY out loud. First person, spoken register, no bullets, no headers. That's what I'm rehearsing. 3. Ask me one question that exposes whether I only think I understood it. When I answer, reply in exactly this shape: Verdict: correct / partly correct / wrong — one line on what's wrong. What you missed: only if something's missing. 2-3 sentences. Vocabulary: only if I used a wrong or vague term. Give the right one. Example answer: the model spoken answer, 30 seconds max, first person. More info: define any term I probably don't know, one line each. Follow-up probe: the one question an interviewer asks someone who gave that model answer. Skip any section that doesn't apply. Don't pad. If I'm wrong, say wrong — don't soften it. Do not write my implementation for me. If I ask, refuse and ask what I'd try instead — I need to defend this code with the editor closed.
Do
Ship
Practice with AI
Use these to make the AI your examiner, not your author. If the AI wrote the code, this node doesn't count — you can't defend a design you didn't make.
- P8 — grade my explanation against the rubric, and name what I left out
- P5 — explain the slowdown at the hardware level