How does std::move enable resource transfer without copying, and what must a move constructor guarantee about the moved-from object?

A strong answer

A strong candidate frames How does std::move enable resource transfer without copying, and what must a move constructor guarantee about the moved-from object? around the exact memory layout, compiler semantics, and hardware execution model covered in Lvalues, Rvalues and Stealing Resources With Move. Explains the mechanics of rvalue references, the role of std::move as a cast, and the moved-from object contract.

Your 0_Language/implementation/string.cpp already contains the right move (kept here from the second, modern class in that file, after splitting the duplicated class definition):

Three pointer writes replace a full allocation plus copy. Your MyVector move does the same for its block, size and capacity.

In a production interview, always connect the specification rule to its concrete runtime consequence: state what lives on the stack versus the heap or static storage segment, how the compiler or operating system validates alignments, lifetimes, and error codes, and what happens under adversarial or boundary inputs (such as zero-length buffers, integer overflow, concurrent mutation, or partial I/O). Backing your explanation with a small trace of register/memory state transitions immediately separates senior systems engineers from candidates who only memorized syntax.

What the interviewer is listening for

• Mastery of core invariant: Distinguish lvalues from rvalues and explain what std::move does.
• Mastery of core invariant: Write a move constructor and move assignment that steal and null the source.
• Mastery of core invariant: Explain why moved-from objects must stay destructible.
• Hardware and ABI awareness: Explaining how sizes, alignments, calling conventions, or kernel boundaries behave on real 64-bit targets rather than relying on implementation-defined assumptions.
• Defensive engineering: Naming the exact compiler flags (-Wall -Wextra -Werror), static analyzers, or runtime sanitizers (-fsanitize=address,undefined,thread) that verify correctness in CI.

Common mistakes

• Explaining only surface syntax without tracing the underlying memory addresses, ownership lifetime, or kernel/user-space state transitions.
• Assuming undefined behavior (such as signed overflow, uninitialized reads, strict-aliasing violations, or dangling pointers) will "just work" because it passed an unoptimized -O0 debug build.
• Ignoring return codes, partial reads/writes, alignment padding, or cleanup paths when an allocation or syscall fails midway through a function.