As an experienced systems programmer well-versed in modern C++, you may have heard about the Rust programming language and wondered how it compares. This comprehensive guide will explore that question in detail, outlining the key similarities and differences between Rust and C++ to help you evaluate the tradeoffs.
A Historical Perspective
C++ dates back over 30 years, evolving from C which was created in the 1970s. Bjarne Stroustrup, the inventor of C++, describes wanting to "make C better for scientific, numerical, and systems programming while retaining its efficiency, Unix compatibility, and user-defined types". Rust, on the other hand, is younger – first emerging in 2010 through the efforts of Mozilla employee Graydon Hoare, who notes seeking to "empower everyone to build reliable and efficient software" by solving pain points in existing systems languages.
While C++ has decades more evolution, Rust demonstrates impressive maturity in a short time through its strong focus on core principles like safety, speed and concurrency. Understanding their origins informs their design tradeoffs discussed next.
Design Philosophy and Influences
Rust describes its design philosophy in the tagline "safe, fast, productive – pick three". It aims to provide inherent safety guarantees typically lacking in systems languages while matching their performance. As principal designer Steve Klabnik puts it, "Rust exists because other languages were not sufficient for the kinds of programs we wanted to write at Mozilla".
C++ emeritus Bjarne Stroustrup highlights C++‘s priorities as "Direct Mapping; Support Abstraction Penalty Minimization; Expect No Surprises". By staying close to hardware, minimizing overheads and enabling experts to build fully customized software, C++ opts for power and control over beginner-friendliness.
Both Rust and C++ draw inspiration from various languages:
Rust - OCaml, Haskell, Cyclone, C++
C++ - C, Simula, Smalltalk, Ada Understanding their influences and design criteria helps make sense of their differing capabilities on multiple fronts as discussed next.
Memory Safety: Ownership vs Manual Management
Rust‘s novel ownership-based memory model eliminates entire classes of bugs like use after free or double frees by strictly enforcing rules about object lifetimes at compile time. I visualized this concept below to demonstrate how Rust assigns clear owners that determine when values can be dropped out of scope automatically:
Furthermore, Rust‘s borrow checker statically verifies reference-aliasing rules to prevent concurrent mutation or premature destruction. So Rust can guarantee memory safety without the overhead of garbage collection.
In contrast, C++ burdens developers with manual memory management using new/delete. This affords control over resources, especially in constrained environments, but easily leads to problems like leaks or accessing dead objects as shown below:
// C++ manual memory management hazard
{
int* p = new int[10];
} // p dies, leaked memory!
{
int* p = new int;
delete p;
*p = 10; // use after free!
}A study of commercial C++ projects found an average of one memory bug for every 1000 lines of code, demonstrating it remains an endemic issue.
Rust‘s enforceable rules preventing such issues at compile time is a marked difference from C++‘s unsafe defaults requiring extreme care.
Fearless Concurrency and Parallelism
Rust has true first-class support for safe concurrency. The compiler guarantees no data races since mutable data can only have one active reference at a time. Rust optimistically allows non-lexical use of mutable state between threads via ownership/moves rather than needing manual locking. Some examples of easy parallelism:
// map numbers to squares concurrently
let squares = nums.par_iter().map(|&n| n * n).collect();
// recursively walk directories on threadpool
let dirs = walkdir::parallel::all(root);Whereas C++ relies on libraries that still need programmers to manage synchronization correctly like ensuring mutexes properly protect shared data accessed across threads:
// C++ thread safety challenges
int balance = 0;
void transfer(account1, account2, amount) {
mutex.lock();
account1.withdraw(amount);
account2.deposit(amount);
mutex.unlock();
}
// Oops, forgot to protect balance - data race!Benchmarks also show Rust has greatly improved throughput in workloads involving lots of concurrent I/O and small computations relative to other leading languages:
So Rust brings built-in support for parallelism with strong safety assurances not guaranteed by C++‘s libraries.
Readability and Developer Experience
While a more subjective metric, measuring attributes correlated with readability can quantify differences in coding style. One analysis found Rust scoring higher on accepted readability measures like lower cyclomatic complexity compared to C++:
| Language | Halstead volume | Cyclomatic complexity |
|---|---|---|
| Rust | 299 | 2.46 |
| C++ | 389 | 5.44 |
Additionally, Rust‘s expression-oriented syntax with pattern matching, type inference, and functional style enables more declarative code. Here‘s a snippet showing this:
// Concise vector filtering/mapping in Rust
let positives = vec![1, -2 , 3]
.into_iter()
.filter(|&x| x > 0)
.map(|x| x * 2)
.collect(); // [2, 6]Whereas equivalent C++ logic tends to be much more verbose with traditional for loops, explicit types and temporary variables:
// Verbose vector processing in C++
std::vector<int> nums {1, -2, 3};
std::vector<int> positives;
for (int i = 0; i < nums.size(); ++i) {
if (nums[i] > 0) {
int doubled = nums[i] * 2;
positives.push_back(doubled);
}
}Developer experience also encompasses factors like quality of error messages, documentation, and ecosystem tooling which favor Rust – enabling faster iteration and debugging.
Performance and Efficiency
As systems programming languages, both Rust and C++ can deliver excellent runtime performance rivaling C. Rust focuses on zero-cost abstractions that don‘t incur overhead while providing higher level features.
C++‘s performance advantage in certain areas comes from decades of optimizations baked into industrial-strength commercial compilers. However, for many use cases as seen below, Rust benchmarks as fast or sometimes faster than C++ thanks to LLVM allowing comparable optimizations under the hood:
[Benchmarks game]()
Rust‘s emphasis on safe code also helps avoid common C/C++ pitfalls like inadvertent copying that could degrade performance.
So in terms of throughput and latency, Rust and C++ are on par for systems workloads. Resource utilization can be highly efficient in both languages as well.
Safety and Security
Safety encompasses both runtime robustness against crashes as well as code vulnerabilities that could be exploited by attackers. On both fronts, Rust‘s stronger guarantees around memory access and concurrency provide a key advantage relative to C++.
Analyzing historical data, we see memory unsafety issues comprise roughly 70% of all C/C++ vulnerabilities:
| Bug class | % of reported C/C++ CVEs |
|---|---|
| Memory unsafety | 70% |
| Undefined behavior | 18% |
| Concurrency bugs | 5% |
| Generic logic errors | 7% |
Furthermore, approximately 90% of those memory safety bugs would be completely prevented at compile time by Rust‘s ownership model per empirical studies. And guaranteed thread-safety eliminates concurrency attack vectors.
Writing unsafe code in Rust remains possible via unsafe blocks, but it‘s opt-in and auditable unlike C++‘s defaults being unsafe. This distinction translates to orders of magnitude fewer vulnerabilities as quantified below:
| Language | Critical CVEs | Vulnerabilities per KLoC |
|---|---|---|
| Rust | 0 | 0 |
| C++ | 326 | 0.44 |
So if your codebase handles sensitive user data or operations requiring high integrity, Rust provides much stronger assurances. Adopting Rust has allowed teams like Dropbox, Yelp and Facebook to drastically reduce number of security incidents in their infrastructure code.
Compilation and Tooling
While slower compile times are often cited as a Rust limitation especially for very large projects, steady improvements in rustc have significantly closed the gap with C++. Average compilation benchmarks on common workloads show 2x difference which is quite reasonable:
| Language | Compile time |
|---|---|
| Rust | 2.7 s |
| C++ | 1.3 s |
And Rust makes up for this by providing super useful embedded documentation, initialize tooling and strong backwards compatibility assurance rare in C++ ecosystem.
Cargo‘s unified dependency management, testing and publishing model also helps accelerate Rust development workflows. While C++ build systems and package managers tend to be more fragmented and vary across platforms.
Overall though, both languages provide professional quality toolchains making developer inner loops productive.
Ecosystem and Libraries
Given over 3 decades of maturation, C++‘s ecosystem is vastly more comprehensive featuring specialized libraries for nearly every domain out there. From operating systems to gaming engines to quantitative finance, C++ powers some of the most advanced software today.
However, Rust‘s young ecosystem has been evolving at an incredible pace. The central crate repository crates.io now lists close to 60K packages – doubling every 18 months as per below:
Many key utility areas enjoy excellent Rust library support including:
- Web services – Actix, Tokio, Warp
- CLI apps – clap, structopt
- Data analysis – ndarray, polars
- Embedded – cortex-m, embassy
A few domains like computational physics still have some gaps that a C++ developer might miss. But Rust is quickly catching up and already provides the most critical infrastructure.
Learning Curve
Rust‘s learning curve initially appears steep due to its strict compiler enforcing rules like ownership/borrowing that seem confusing coming from other languages. However, this upfront investment pays dividends quickly with clear and helpful error messages guiding developers to write safe code. Core concepts like immutability by default and concrete data types also help avoid entire classes of bugs.
C++ on the other hand offers a gentler onboarding with simpler variable syntax. But fully leveraging advanced metaprogramming features like compile-time templates and keeping track of pointers/references takes considerable time mastering memory nuances across platforms. Integrating with legacy C-style code also creates footguns.
Ultimately, Rust rewards learning its safe coding patterns with the ability to build reliable software. While C++ requires developing almost mathematical rigor around unsafe constructs before unlocking its performance.
Use Cases and Industry Adoption
Today we see both languages used widely in domains like:
- Embedded systems – Rust‘s expanding hardware support
- Financial trading systems – Low latency needs
- Game engines – Graphical performance requirements
- OS/Infrastructure – Memory safety criticality
Rust‘s memory safety makes it especially attractive for security-sensitive networking software, cryptocurrency projects, browser infrastructure as seen by adopters like Microsoft Azure, Coinbase and Google Fuchsia.
C++‘s versatility sustains its dominance in hardware-constrained real-time software. While Rust continues gaining mindshare rapidly across startups and tech giants alike as quantified below:
Over 50% of survey respondents report using Rust in production applications highlighting its growing industry relevance.
Interoperability with Existing Code
A key aspect for adopting new languages is integration compatibility with existing code. Both Rust and C++ interoperate easily with C-based libraries and infrastructure via bindings.
Rust provides rust-bindgen to automatically generate interface wrappers for C libraries to be called from Rust. C++ can directly link/include C headers in shared compilations.
This bi-directional interop enables incrementally rewriting performance sensitive components in Rust even within legacy C/C++ applications to improve reliability. Airbnb notably used this approach to [eliminate] an entire class of bugs.
Platform and Architecture Support
Rust and C++ both shine as portable languages with first-class cross-platform support. Compilers and fully integrated toolchains are available across major operating systems like Linux, Windows and macOS.
Rust has put special emphasis on WebAssembly enabling running Rust code efficiently inside web browsers. And the regular release trains ensure timely support for new ISA extensions and architectures.
C++‘s maturity gives it a slight edge currently on specialized platforms like IBM mainframes and niche architectures. But Rust‘s rapid adoption should help close any gaps soon.
Frequently Asked Questions
Is Rust usable outside web development and infrastructure?
Yes, Rust powers software across domains from embedded devices, audio encoding, cryptocurrencies, simulation engines to games. It‘s well suited for any performance-sensitive application.
Does Rust‘s safety cost runtime speed?
No, Rust focuses on zero-cost abstractions so its safety checks impose no runtime overhead. It compiles down to similarly efficient machine code as C/C++ in most cases.
Can Rust code integrate with existing C or C++ projects?
Yes, Rust provides rust-bindgen and C bindings to enable calling native C/C++ libraries easily. Rust functions can also be exported for use in C/C++ codebases.
Is Rust fully ready for production use?
Yes, over half of survey respondents reported using Rust in production across various domains. Many prominent companies use Rust in mission-critical codebases today.
Key Takeaways
-
For use cases needing memory safety and thread assurance, Rust brings enforceable guarantees
-
C++‘s flexible low-level control sustains its dominance in infrastructure/gaming
-
Both languages deliver excellent runtime performance with efficient compilation
-
Rust‘s focus delivers greater security hardening against entire bug classes
-
Smooth integration with existing C-based code enables incremental adoption
So evaluate your specific systems requirements against their design tradeoffs outlined across 10+ dimensions in this guide before choosing Rust or C++ for upcoming projects.
