SimplifyC++

Article by Ayman Alheraki on January 11 2026 10:38 AM

#20 Modern C++ and Rust Programming – A Comparative Educational Guide from Concepts to Applications

&, *, Box, Rc, RefCell

& — References
- In C++, & denotes a reference type, which acts as an alias for an existing object. A reference must be initialized upon creation and cannot be reseated or be null ([GeeksforGeeks, July 2025]) boardor.com GeeksforGeeks.
- References provide safer syntax for aliasing and avoid pointer-related null or dangling pointer bugs, but rely on programmer discipline for correctness ([StackOverflow, 2023]) Wikipedia.

* — Pointers
- The * operator is used to declare pointers and to dereference them.
  Pointers allow indirect memory access and support operations like pointer arithmetic, nullability, and dynamic memory management ([GeeksforGeeks, July 2025])
  GeeksforGeeks Wikipedia.
- Pointers are flexible but less safe, as they can point to invalid memory or be reassigned, unlike references ([GeeksforGeeks, 2025]) GeeksforGeeks.

C++ provides smart pointers: std::unique_ptr, std::shared_ptr, and std::weak_ptr (since C++11/14) to automate dynamic memory management and prevent leaks ([Wikipedia Smart Pointer, updated recently]) Wikipedia.

unique_ptr provides exclusive ownership; shared_ptr enables reference counting shared ownership; weak_ptr breaks ownership cycles. Recommended to use std::make_unique and std::make_shared for safety and performance ([Wikipedia Smart Pointer]) Wikipedia.

Rust uses its ownership and borrowing rules together with specific pointer types to manage heap data safely and eﬀiciently.

Box
- Allocates data on the heap with single ownership, automatically deallocating when the Box goes out of scope ([DEV Community post May 2025]) DEV Community.
- Ideal for heap allocation, recursive data structures (e.g. linked lists), and dynamic sizing where stack allocation is insuﬀicient DEV Community LinkedIn.

Rc
- A reference-counted smart pointer for enabling shared ownership in single-threaded contexts. Maintains a runtime count of owners and deallocates when count reaches zero ([DEV Community May 2025]) DEV Community boardor.com.
- Allows immutable sharing of data among multiple owners, but does not permit interior mutation on its own ([StackOverflow summary, Oct 2024]) StackOverflow.

RefCell
- Enables interior mutability, allowing mutation of data even when only immutable references exist. Unlike typical borrowing, checks occur at runtime: violations cause panics ([Rust Book ch.15, runtime borrow checks]) web.mit.edu.
- Useful in scenarios where the borrow checker’s compile-time constraints are too restrictive, but safety is still desired.

Combining Rc and RefCell
- To achieve shared ownership with interior mutability, Rust commonly uses Rc<RefCell>. Here, Rc shares ownership and RefCell handles mutable access at runtime ([StackOverflow, 2022]) The Rust Programming Language Forum.
- This combination enables multiple parts of code to mutate a shared data structure behind an owned container, while still preserving safety (barring cyclic reference leaks, which must be managed separately) ([Rust Book ch15, reference cycles]) Rust Documentation.

Concept	C++	Rust
Immutable alias/reference	T& reference	&T reference
Mutable alias/reference	T* via pointer or T&modifiable	&mut T borrow
Single ownership heap type	std::unique_ptr	Box
Shared ownership	std::shared_ptr	Rc (single-thread safe)
Interior mutability	Not standard; const_castunsafe	RefCell with runtime checks
Shared mutable ownership	std::shared_ptr with locking	Rc<RefCell>

Use Box in Rust for recursive data structures, or when heap allocation is required but exclusive ownership suﬀices.
Use Rc when multiple parts of your program need read-only access to shared data.
Use RefCell to sidestep immutable borrow restrictions when necessary, with awareness of its potential runtime panic.
Avoid cyclic references with Rc by using Weak or design without cycles.