cppcourse/.agents/skills/cpp-code-review/references/memory-ub.md

Memory Safety & Undefined Behavior

Docs: cppreference "Undefined behavior", "Object lifetime", "Smart pointers" (see cppreference.md).

Ownership & lifetime

• No owning raw pointers; use std::unique_ptr / std::shared_ptr, containers, or RAII wrappers.
• No new/delete in application code; use std::make_unique / std::make_shared.
• No references, pointers, string_view, or span that outlive what they point to (returning views of locals or temporaries, lambdas capturing locals by & that escape).
• Iterators/pointers/references into containers aren't used after an operation that may invalidate them (push_back, insert, erase, rehash).
• No use after std::move except to reassign or destroy.
• Rule of 0/3/5: if a class defines a destructor, copy, or move, it handles all of them correctly (or = deletes them).
• Base classes used polymorphically have a virtual (or protected) destructor.

Bounds & buffers

• Indexing is bounds-checked or provably in range; prefer .at() at trust boundaries, std::span, range-for.
• No strcpy, sprintf, gets, unchecked memcpy; sizes come from the destination.
• Off-by-one in loop bounds and null terminators.

Undefined behavior

• Signed integer overflow; shifts by negative or >= bit width.
• Uninitialized variables (especially scalars and POD members).
• Strict aliasing violations; use std::memcpy or std::bit_cast (C++20) for type punning.
• reinterpret_cast / C-style casts that change object type; misaligned access.
• Null dereference, including .get() on empty smart pointers.
• Unsequenced modifications (i = i++-style).

C interop

• extern "C" boundaries: no exceptions propagate into C code.
• Memory allocated by C (malloc) freed with free, not delete (and vice versa).
• C strings: buffer size and termination checked.