Copyright thenewstack
If you’ve ever written low-level code, there’s a good chance you’ve crossed paths with C++. For over four decades, it has been the go-to language for building everything from game engines and operating systems to financial trading systems and embedded devices. Its power comes from giving developers near-complete control over memory, performance and hardware, but that power comes at a cost. One wrong pointer, and your entire program can crash or, worse, open the door to security vulnerabilities. Enter Rust, the new kid on the systems programming block. Backed by Mozilla and designed with modern needs in mind, Rust promises the speed and flexibility of C++ without the memory safety pitfalls. Instead of relying on runtime garbage collection, Rust enforces safety rules at compile time through its unique ownership and borrowing model. The result? A language that aims to make crashes, data races and undefined behavior things of the past while still producing blazing-fast binaries. But does Rust live up to the hype, and can it truly replace a giant like C++? Or is it simply another niche tool in an already crowded landscape of programming languages? In this article, we’ll put Rust and C++ side by side, not to crown a universal winner, but to explore where each shines, where each stumbles and how modern developers can choose the right tool for the job. From memory management and concurrency to tooling, performance and real-world adoption, let’s take a closer look at these two titans of systems programming. Memory Management Manual Memory Management in C++ C++ hands developers the keys to the kingdom when it comes to memory. You can allocate memory exactly where and when you want it, either on the stack or on the heap. This level of control is one of C++’s greatest strengths, but also one of its biggest risks. In classic C++, you often manage heap memory manually using new and delete. This works, but it’s easy to forget to free memory or accidentally free it twice, which can lead to memory leaks, dangling pointers or even security vulnerabilities. To reduce the risk, modern C++ encourages RAII (resource acquisition is initialization) with smart pointers like std::unique_ptr and std::shared_ptr that automatically free memory when they go out of scope. While smart pointers help, they still rely on the developer to choose the correct type and use it consistently. A mistake in ownership design can still cause subtle bugs. Ownership and Borrowing in Rust Rust approaches memory management with a radically different philosophy: Make unsafe memory operations impossible at compile time. The core of Rust’s system is the ownership model: Every piece of data has a single owner. When the owner goes out of scope, the data is automatically freed — no delete or garbage collector required. You can borrow references to data, but the compiler enforces strict rules to prevent data races and dangling references. Borrowing lets you temporarily use data without taking ownership, with the compiler checking that the references stay valid: For mutable borrows, Rust enforces that only one mutable reference can exist at a time, preventing data races even in multithreaded programs: Key Difference In C++, you have total freedom over memory, but that means you’re also responsible for preventing leaks, dangling pointers and other pitfalls. In Rust, the compiler is your safety net. It enforces memory safety rules at compile time without adding runtime overhead, eliminating entire classes of bugs before your program even runs. Safety Guarantees Undefined Behavior in C++ In C++, undefined behavior (UB) refers to any program state where the C++ standard makes no guarantees about what will happen. Once UB occurs, anything can happen — your program might crash, produce incorrect results or appear to work fine until it fails in production. The danger is that UB often goes unnoticed during development but can cause catastrophic failures later. Following are some of the common causes of UB: Dereferencing Null Pointers This might crash on one machine but silently corrupt memory on another. Buffer Overflows C++ doesn’t check array bounds at runtime, so out-of-range access can overwrite unrelated memory, leading to hard-to-find bugs or security exploits. Use-after-Free In multi-threaded C++ programs, accessing shared data from multiple threads without proper synchronization is UB. Rust’s Compile-Time Guarantees Rust was designed to eliminate these categories of undefined behavior before your code even compiles. Its borrow checker and type system enforce strict safety rules without needing a garbage collector. No Null Pointers In Rust, a variable cannot be null. If something may be absent, it’s explicitly represented using Option. Bounds Checking Rust performs bounds checking at runtime for arrays, preventing buffer overflows. No Use-after-Free Rust’s ownership model ensures memory is freed exactly once, and no references to freed memory exist. Data Race Prevention The compiler enforces that either: Multiple immutable references exist, or One mutable reference exists — never both. For multithreading, you must use safe concurrency primitives like Mutex or Arc. Key Difference In C++, safety is in the developer’s hands, and mistakes can easily slip through. In Rust, the compiler enforces safety rules so entire categories of bugs simply can’t happen in safe code — without adding runtime performance penalties. Concurrency Concurrency is one of the trickiest areas in systems programming because it introduces timing-dependent bugs that are often hard to reproduce. Both C++ and Rust give you tools for multithreading, but they take very different approaches to safety. Threads and Race Conditions in C++ C++ provides a standard threading library (std::thread, std::mutex, std::lock_guard, etc.) that allows you to spawn threads and synchronize access to shared data. However, C++ does not enforce thread safety at compile time. It’s the programmer’s responsibility to ensure shared resources are properly protected. If you forget to synchronize access, you can easily create data races that cause unpredictable results. The above code illustrates a data race in C++. On some runs, you might get 200,000 (correct), but more often you’ll get a smaller number due to race conditions. We can however fix this with mutex. While std::mutex works, it’s easy to forget to lock it, and nothing in C++ warns you at compile time if you do. Fearless Concurrency in Rust Rust’s ownership model and type system extend to concurrency. This means: You can’t share mutable data across threads without explicit synchronization. The compiler prevents data races at compile time. Unsafe access to shared mutable state simply won’t compile. The previous code illustrates compile-time prevention. Here, Rust refuses to compile because counter is being accessed mutably from multiple threads without synchronization. Safe Concurrency with Arc and Mutex To share mutable data between threads in Rust, you must use thread-safe wrappers like Arc (atomic reference counted pointer) and Mutex. Arc allows multiple threads to own the same data. Mutex ensures only one thread accesses the data at a time. If you try to use the data without Arc/Mutex, the compiler will reject it. Key Difference C++ gives you powerful threading tools but leaves all safety checks to you. Data races are a runtime bug that can go unnoticed until it’s too late. Rust forces you to handle concurrency safely at compile time. Unsafe patterns simply won’t compile unless you explicitly mark them as unsafe. Performance When comparing Rust and C++, raw performance is a key battleground. Both languages compile to native machine code, both can optimize aggressively, and both give developers low-level control over memory and CPU usage. In many cases, Rust matches C++ performance — and sometimes even surpasses it — thanks to its zero-cost abstractions and safety checks that happen at compile time rather than at runtime. Compilation Speed and Binary Size Often faster to compile for small projects. Large projects suffer from long build times due to header file inclusion and template instantiation. Binary size can be smaller because developers have more direct control over what’s compiled in. Slower compile times due to heavy analysis by the borrow checker and optimizations. No header files — the module system and Cargo dependency management avoid C++-style compile cascades. Binary size is generally competitive, but sometimes larger because debug info and monomorphization (generics) increase output size. Runtime Benchmarks Example 1: Sorting Large Arrays Result: On optimized builds (-O3 for C++, –release for Rust), both complete in roughly the same time (~100–120ms on modern CPUs). Example 2: Parallel Computation (Sum of Squares) C++ with OpenMP: Rust with Rayon: Result: Both complete in ~20–30ms on a four-core machine. Rust’s Rayon crate provides ergonomic, safe parallelism without explicit locks or directives. Why Rust Can Match C++ Performance Zero-cost abstractions: High-level Rust features (iterators, closures, traits) compile down to tight loops without extra overhead. Aggressive compiler optimizations: LLVM backend optimizes similarly for both. Safety without runtime penalty: Bounds checking can often be eliminated by the compiler when proven unnecessary. Where C++ Still Has an Edge Compile time for small iterative builds. Extremely size-constrained environments (embedded systems with <64KB flash). More control over avoiding bounds checks (though Rust can do this in unsafe). Tooling and Ecosystem A language’s syntax and performance matter, but the tooling and ecosystem often determine how productive you’ll be day to day. Here, Rust and C++ take very different approaches: One is a patchwork of decades-old tools and standards, the other is a unified, batteries-included experience. Build Systems No official build system. Most projects use CMake, Make or Ninja. Powerful and flexible but comes with a steep learning curve. Build files can get verbose, and cross-platform compatibility often requires custom scripts. Example minimal CMakeLists.txt: Uses Cargo, the official build system and package manager. Handles compiling, testing, benchmarking and documentation with a single tool. Cross-platform by default. Cargo automatically creates a project structure, builds it and runs it without any external configuration. Dependency Management No standard package manager; developers rely on tools like Conan or vcpkg. Often requires manually downloading and compiling third-party libraries. Dependency versioning and compatibility can be a headache in large projects. Cargo integrates with crates.io, Rust’s official package registry. Adding a dependency is as simple as editing Cargo.toml: Cargo automatically fetches, builds and links dependencies with proper version resolution. Testing and Documentation No built-in testing framework; developers use libraries like GoogleTest or Catch2. Documentation often handled via Doxygen or manual READMEs. Built-in test framework: Run tests with: Automatic documentation generation from doc comments with: cargo doc --open Ecosystem Maturity Massive ecosystem built over decades. Virtually every domain — gaming, finance, embedded, scientific computing — has deep C++ library support. Mature debugging and profiling tools (GDB, Valgrind, Visual Studio). Rapidly growing ecosystem, especially in systems programming, CLI tools and web backends. Some gaps in very specialized areas (certain graphics or scientific libraries still rely on C++). Strong tooling culture: rustfmt for formatting, clippy for linting. Key Differences C++ tooling is powerful but fragmented — you choose your build system, package manager and testing tools. Rust tooling is unified and consistent, making it easy to get started and maintain projects, even across teams. Use Cases and Adoption Where C++ Still Dominates AAA game engines (such as Unreal Engine, CryEngine). Legacy systems where rewriting is cost-prohibitive. Real-time embedded systems with extremely tight hardware constraints. High-performance scientific computing where existing C++ libraries are deeply optimized. Where Rust is Replacing C++ Web browsers: Rust powers major components of Firefox (Servo engine) for security and stability. Command-line tools: Many modern CLI apps (ripgrep, fd, bat) are written in Rust for speed and safety. Distributed systems and cloud infrastructure: Companies like Dropbox, Cloudflare and Amazon use Rust for network services. Safety-critical code: Microsoft uses Rust for parts of Windows to reduce memory-safety vulnerabilities. Embedded development: Rust is gaining traction in microcontroller projects for predictable performance and safety. Key Differences: Rust is unlikely to completely replace C++ in the near term, but it’s already becoming the default choice for new systems programming projects where safety, maintainability and concurrency correctness are essential. Interoperability One of Rust’s most practical strengths is its ability to integrate with existing C and C++ codebases. This makes it possible for teams to gradually adopt Rust without rewriting millions of lines of legacy code. Example: Calling a C function from Rust This approach allows Rust to wrap existing C++ APIs with a safe Rust interface, preventing unsafe patterns from leaking into the rest of the Rust codebase. Calling C/C++ from Rust Rust can call C and C++ functions using its Foreign Function Interface (FFI) via the extern “C” keyword. You simply declare the external functions in Rust and link against the compiled C++ library. Example: Rust Library Called from C++ Compile to a library: This is ideal for incrementally migrating C++ projects to Rust — critical modules can be rewritten in Rust for safety while the rest of the application remains in C++. Learning Curve and Developer Experience Error Messages and Debugging Powerful but notorious for cryptic compiler errors, especially with templates and metaprogramming. An example: error: no matching function for call to ‘foo(double)’ This may expand into pages of template instantiation messages that are hard to decipher. Compiler errors are clear, detailed, and often suggest fixes. An example: error[E0502]: cannot borrow x as mutable because it is also borrowed as immutable help: consider changing this borrow to be mutable The compiler acts more like a teacher than a gatekeeper. Community and Documentation Exceptionally strong, beginner-friendly community. Official guide (“The Rust Programming Language,” aka “The Rust Book”) is comprehensive and free. Active forums, Discord channels and frequent conference talks. Huge, global developer base and decades of knowledge. Resources are abundant but fragmented — from Stack Overflow posts to academic papers. No single “canonical” beginner resource; learning paths vary widely. In conclusion, when it comes to systems programming, both C++ and Rust are undeniably powerful, but they cater to slightly different philosophies. C++ is the veteran: mature, battle-tested and deeply entrenched in industries like gaming, embedded systems, high-performance computing and finance. Its ecosystem is unmatched in scope, and its integration with existing platforms and toolchains makes it indispensable for maintaining and extending large, established codebases. If you’re working on a legacy system or in a domain where proven, decades-old libraries are critical, C++ still holds the crown. Rust, on the other hand, represents a new era of systems programming, one where safety and performance are not mutually exclusive. Its ownership model eliminates entire classes of bugs before your program even runs, while Cargo and its modern ecosystem make development smooth and predictable. For new projects, especially where memory safety, concurrency correctness and developer productivity are top priorities, Rust offers a compelling, future-facing choice. In reality, many teams don’t have to pick a single winner. A hybrid approach often makes the most sense: keep critical legacy code in C++, but write new components in Rust to benefit from its safety and tooling. With both languages capable of talking to each other through FFI, this interoperability allows you to evolve your codebase gradually without sacrificing stability. In the end, the “right” tool isn’t the one that wins an internet debate, it’s the one that fits your project’s needs, your team’s expertise and your long-term maintenance goals. Rust and C++ are both here to stay; the smartest developers will learn to leverage the strengths of each.
