Rust Systems Programming - Low-Level Programming & Performance

Systems programming is where Rust truly shines. This section teaches you to write low-level, high-performance code while maintaining Rust's safety guarantees wherever possible. You'll learn when and how to use unsafe code, integrate with C libraries, and optimize for maximum performance.

What You'll Learn

This section covers advanced systems programming topics:

Low-Level Programming

Unsafe Rust - When and how to use unsafe code responsibly
FFI & C Interop - Interface with C libraries and system APIs
Performance Optimization - Techniques for maximum speed and efficiency
Memory Layout - Understanding how Rust manages memory at the hardware level

Why Rust for Systems Programming

Rust provides unique advantages for systems development:

Memory Safety - Prevent segfaults and memory corruption in safe code
Zero-Cost Abstractions - High-level features with no runtime overhead
Predictable Performance - No garbage collector or hidden allocations
C Compatibility - Easy integration with existing C codebases
Modern Tooling - Excellent debugging, profiling, and package management

Learning Path

Progress through systems programming concepts:

Unsafe Rust - Understand when safety guarantees are lifted
FFI & C Interop - Interface with C libraries and system calls
Performance Optimization - Write the fastest possible Rust code
Memory Layout - Deep understanding of memory management

Key Concepts

By the end of this section, you'll master:

The five unsafe superpowers and when to use them
Creating safe abstractions over unsafe code
Calling C functions and using C libraries from Rust
Building C-compatible libraries in Rust
Performance profiling and optimization techniques
Memory layout, alignment, and optimization
Working with raw pointers and manual memory management

Systems Programming Patterns

Learn essential patterns for systems code:

use std::ffi::{CStr, CString};
use std::os::raw::{c_char, c_int};

// 1. Unsafe operations
unsafe fn manual_memory_management() {
    let layout = std::alloc::Layout::new::<i32>();
    let ptr = std::alloc::alloc(layout) as *mut i32;
    
    if !ptr.is_null() {
        *ptr = 42;
        println!("Value: {}", *ptr);
        std::alloc::dealloc(ptr as *mut u8, layout);
    }
}

// 2. FFI declarations
extern "C" {
    fn strlen(s: *const c_char) -> usize;
    fn malloc(size: usize) -> *mut std::ffi::c_void;
    fn free(ptr: *mut std::ffi::c_void);
}

// 3. C-compatible function
#[no_mangle]
pub extern "C" fn rust_function(x: c_int) -> c_int {
    x * 2
}

// 4. Safe wrapper around unsafe C function
fn safe_strlen(s: &str) -> usize {
    let c_string = CString::new(s).unwrap();
    unsafe { strlen(c_string.as_ptr()) }
}

// 5. High-performance data structure
#[repr(C)]
struct OptimizedStruct {
    field1: u8,    // 1 byte
    field2: u32,   // 4 bytes, will be aligned
    field3: u16,   // 2 bytes
}

// 6. SIMD operations for performance
#[cfg(target_arch = "x86_64")]
fn simd_sum(data: &[f32]) -> f32 {
    #[cfg(target_feature = "avx2")]
    unsafe {
        // SIMD implementation for maximum performance
        // This is a simplified example
        data.iter().sum()
    }
    
    #[cfg(not(target_feature = "avx2"))]
    data.iter().sum()
}

Prerequisites

Before diving into systems programming, you should understand:

Ownership and borrowing - Critical for understanding when unsafe is needed
Memory management - How Rust manages memory in safe code
Error handling - Systems code needs robust error management
Basic C programming - Helpful for FFI and understanding system interfaces

Review these sections if needed:

Ownership & Borrowing - Essential foundation
Advanced Features - Smart pointers and error handling

Common Use Cases

Systems programming in Rust is ideal for:

Operating system kernels - Low-level system software
Device drivers - Hardware interface code
Embedded systems - Resource-constrained environments
Game engines - Performance-critical graphics and physics
Databases - Storage engines and query processors
Network software - High-performance servers and protocols
Cryptographic libraries - Security-critical implementations

Performance Optimization Techniques

You'll learn to optimize:

Algorithm complexity - Choose the right algorithms and data structures
Memory access patterns - Cache-friendly code design
Branch prediction - Write predictable conditional code
SIMD operations - Vectorized computation for data parallelism
Memory allocation - Minimize allocations and use custom allocators
Compilation optimization - Leverage compiler optimizations effectively

Safety in Unsafe Code

Learn to write unsafe code responsibly:

Minimize unsafe blocks - Keep unsafe code as small as possible
Document invariants - Clearly state what must be true for safety
Test thoroughly - Unsafe code requires extra verification
Provide safe APIs - Wrap unsafe code in safe abstractions
Use tools - Leverage Miri, AddressSanitizer, and other tools

Real-World Examples

You'll build practical systems:

Custom allocators - Memory management for specific use cases
Lock-free data structures - High-performance concurrent collections
System call wrappers - Safe interfaces to OS functionality
Protocol implementations - Network protocol parsers and generators
Embedded applications - Code for microcontrollers and IoT devices

Development Workflow

Systems programming requires special tooling:

Cross-compilation - Target different architectures
Profiling tools - perf, Instruments, and custom profilers
Debugging - GDB, LLDB, and Rust-specific tools
Static analysis - Clippy, Miri, and third-party analyzers
Benchmarking - Criterion and custom performance tests

What Comes Next

After mastering systems programming, you can:

Contribute to Rust itself - Work on the compiler or standard library
Build operating systems - Create new OS kernels or components
Optimize existing software - Improve performance of critical systems
Create embedded applications - Program microcontrollers and IoT devices
Develop game engines - Build high-performance graphics systems

The Challenge and Reward

Systems programming in Rust offers:

Learning opportunity - Deep understanding of how computers work
Performance - Code that runs as fast as C or C++
Safety - Memory safety even in low-level code
Modern experience - Great tooling and ecosystem
Career value - High-demand skills in the industry

Common Pitfalls

Avoid these systems programming mistakes:

Unnecessary unsafe - Using unsafe when safe code would work
Poor FFI hygiene - Not handling C errors or null pointers properly
Premature optimization - Optimizing before measuring
Ignoring platform differences - Not testing on target platforms
Insufficient testing - Systems code needs extensive validation

Ready to push Rust to its limits? Start with Unsafe Rust!