Understanding Memory Management, Part 5: Fighting with Rust

Overall reception of the post

• Many readers found the piece exceptionally clear and useful for understanding Rust’s memory model and borrow checker.
• Some non-Rust or non-systems programmers read it as a way to grasp Rust’s design and possibly “borrow” its ideas for C/C++.

Core Rust ownership model

• Key mental model repeated: each value has exactly one owner; multiple ownership requires Rc/Arc; at any time either one writer or many readers, never both; enforced at compile time (and sometimes runtime).
• Once this is understood, the borrow checker’s behavior is seen as enforcing these simple rules rather than being arbitrary.

Traits, name resolution, and pseudo-overloading

• Clarification that Rust doesn’t have traditional function overloading; behavior that looks like overloading is usually trait implementations (e.g., From for different types).
• Some argue that in practice this is overloading, just expressed through traits and type-directed dispatch.
• Discussion of how constructs like for x in y, x?, and x + y desugar into trait calls (IntoIterator, Try, Add, etc.), with “lang items” tying syntax to specific traits.
• Debate over why for uses IntoIterator::into_iter(y) instead of y.into_iter(): to avoid identifier-based magic and keep behavior trait-driven and predictable.

Ergonomics, borrow checker, and the for example

• Several comments focus on the initial for x in vec example: it moves the vector and makes later use illegal, which feels like “wrestling the compiler” for trivial code.
• Defenders say this is not a borrow-checker limitation but a deliberate move-by-default semantic preventing potential use-after-free; adding &vec is a one-character, compiler-suggested fix.
• Critics argue the compiler could infer that a borrow suffices for this loop and see this as needless friction and a sign that Rust rejects some obviously safe programs.
• Counter-argument: making the borrow checker “smart” in many special cases would turn it into “dark magic” that’s hard to reason about; Rust favors simple, explicit rules and local reasoning.

Rust vs other languages and models

• Some see Rust’s complexity as worth it only for systems or performance-critical code; others note that for simple “glue” code, lifetimes are often trivial—until async or more advanced patterns appear.
• Comparisons:
  • C/C++: same conceptual rules, but enforced only in programmers’ heads; examples of dangling pointers with std::vector are used to justify Rust’s stricter semantics.
  • Zig: allocator-passing model and arenas seen as more “pleasant,” with fewer compiler fights but fewer static guarantees.
  • Odin and Zig highlighted as alternatives with simpler loops and memory models; critics say Rust’s ownership view is not the only viable systems design.
  • SPARK and Oberon cited as memory-safe without explicit borrowing syntax; their analyzers infer safety more automatically.
  • GC languages: some argue in 2020s we should rely more on high-quality GC and avoid manual memory reasoning except where absolutely necessary.

Systems programming, unsafe, and scope of safety

• Debate over whether Rust is a good first systems language:
  • One side: yes, because it forces correct thinking about ownership and concurrency.
  • Other side: no, because much real systems work has inherently ambiguous ownership (e.g., hardware holding pointers), requiring unsafe and patterns Rust struggles to express.
• Examples given of kernels and HALs with relatively little unsafe, suggesting Rust can confine unsafety to small, well-audited regions.