memory-safety-patterns

name	memory-safety-patterns
description	Implement memory-safe programming with RAII, ownership, smart pointers, and resource management across Rust, C++, and C. Use when writing safe systems code, managing resources, or preventing memory bugs.

Memory Safety Patterns

Cross-language patterns for memory-safe programming including RAII, ownership, smart pointers, and resource management.

When to Use This Skill

• Writing memory-safe systems code
• Managing resources (files, sockets, memory)
• Preventing use-after-free and leaks
• Implementing RAII patterns
• Choosing between languages for safety
• Debugging memory issues

Core Concepts

1. Memory Bug Categories

Bug Type	Description	Prevention
Use-after-free	Access freed memory	Ownership, RAII
Double-free	Free same memory twice	Smart pointers
Memory leak	Never free memory	RAII, GC
Buffer overflow	Write past buffer end	Bounds checking
Dangling pointer	Pointer to freed memory	Lifetime tracking
Data race	Concurrent unsynchronized access	Ownership, Sync

2. Safety Spectrum

Manual (C) → Smart Pointers (C++) → Ownership (Rust) → GC (Go, Java)
Less safe                                              More safe
More control                                           Less control

Patterns by Language

Pattern 1: RAII in C++

// RAII: Resource Acquisition Is Initialization
// Resource lifetime tied to object lifetime

#include <memory>
#include <fstream>
#include <mutex>

// File handle with RAII
class FileHandle {
public:
    explicit FileHandle(const std::string& path)
        : file_(path) {
        if (!file_.is_open()) {
            throw std::runtime_error("Failed to open file");
        }
    }

    // Destructor automatically closes file
    ~FileHandle() = default; // fstream closes in its destructor

    // Delete copy (prevent double-close)
    FileHandle(const FileHandle&) = delete;
    FileHandle& operator=(const FileHandle&) = delete;

    // Allow move
    FileHandle(FileHandle&&) = default;
    FileHandle& operator=(FileHandle&&) = default;

    void write(const std::string& data) {
        file_ << data;
    }

private:
    std::fstream file_;
};

// Lock guard (RAII for mutexes)
class  {
:
    {
        ; 
        data_[key] = value;
    }

    {
        ;
         data_[key];
    }

:
    std::mutex mutex_;
    std::shared_mutex shared_mutex_;
    std::map<std::string, std::string> data_;
};


< T>
  {
:
    }

    ~() {
         (!committed_) {
            target_ = backup_; 
        }
    }

    { committed_ = ; }

    {  target_; }

:
    T& target_;
    T backup_;
     committed_;
};

Pattern 2: Smart Pointers in C++

#include <memory>

// unique_ptr: Single ownership
class Engine {
public:
    void start() { /* ... */ }
};

class Car {
public:
    Car() : engine_(std::make_unique<Engine>()) {}

    void start() {
        engine_->start();
    }

    // Transfer ownership
    std::unique_ptr<Engine> extractEngine() {
        return std::move(engine_);
    }

private:
    std::unique_ptr<Engine> engine_;
};

// shared_ptr: Shared ownership
class Node {
public:
    std::string data;
    std::shared_ptr<Node> next;

    // Use weak_ptr to break cycles
    std::weak_ptr<Node> parent;
};

void sharedPtrExample() {
    auto node1 = std::make_shared<Node>();
    auto node2 = std::make_shared<Node>();

    node1->next = node2;
    node2->parent = node1; // Weak reference prevents cycle

    // Access weak_ptr
    if (auto parent = node2->parent.lock()) {
        // parent is valid shared_ptr
    }
}


  {
:
    {
         (fd && *fd >= ) {
            ::(*fd);
             fd;
        }
    }
};

{
     fd = (AF_INET, SOCK_STREAM, );
     std::<, (&Socket::close)>(
         (fd),
        &Socket::close
    );
}


{
    
     ptr = std::<Widget>();

    
    ;

    
     arr = std::<[]>();
}

Pattern 3: Ownership in Rust

// Move semantics (default)
fn move_example() {
    let s1 = String::from("hello");
    let s2 = s1; // s1 is MOVED, no longer valid

    // println!("{}", s1); // Compile error!
    println!("{}", s2);
}

// Borrowing (references)
fn borrow_example() {
    let s = String::from("hello");

    // Immutable borrow (multiple allowed)
    let len = calculate_length(&s);
    println!("{} has length {}", s, len);

    // Mutable borrow (only one allowed)
    let mut s = String::from("hello");
    change(&mut s);
}

fn calculate_length(s: &String) -> usize {
    s.len()
} // s goes out of scope, but doesn't drop since borrowed

fn change(s: &mut String) {
    s.push_str();
}


 <>(x: & , y: & )  &  {
     x.() > y.() { x }  { y }
}


 <> {
    part: & ,
}

<> ImportantExcerpt<> {
     (&)   {
        
    }

    
     (&, announcement: &)  & {
        (, announcement);
        .part
    }
}


 std::cell::{Cell, RefCell};
 std::rc::Rc;

  {
    count: Cell<>,           
    data: RefCell<<>>, 
}

  {
     (&) {
        .count.(.count.() + );
    }

     (&, item: ) {
        .data.().(item);
    }
}


 () {
      = Rc::([, , ]);
      = Rc::(&data); 

    (, Rc::(&data)); 
}


 std::sync::Arc;
 std::thread;

 () {
      = Arc::([, , ]);

     : <_> = (..)
        .(|_| {
              = Arc::(&data);
            thread::( || {
                (, data);
            })
        })
        .();

       handles {
        handle.().();
    }
}

Pattern 4: Safe Resource Management in C

// C doesn't have RAII, but we can use patterns

#include <stdlib.h>
#include <stdio.h>

// Pattern: goto cleanup
int process_file(const char* path) {
    FILE* file = NULL;
    char* buffer = NULL;
    int result = -1;

    file = fopen(path, "r");
    if (!file) {
        goto cleanup;
    }

    buffer = malloc(1024);
    if (!buffer) {
        goto cleanup;
    }

    // Process file...
    result = 0;

cleanup:
    if (buffer) free(buffer);
    if (file) fclose(file);
    return result;
}

// Pattern: Opaque pointer with create/destroy
typedef struct Context Context;

Context* context_create(void);
void context_destroy(Context* ctx);
int context_process(Context* ctx, const char* data);

// Implementation
struct Context {
    * data;
     size;
    FILE* ;
};

Context*  {
    Context* ctx = (, (Context));
     (!ctx)  ;

    ctx->data = ( * ());
     (!ctx->data) {
        (ctx);
         ;
    }

    ctx-> = fopen(, );
     (!ctx->) {
        (ctx->data);
        (ctx);
         ;
    }

     ctx;
}

  {
     (ctx) {
         (ctx->) fclose(ctx->);
         (ctx->data) (ctx->data);
        (ctx);
    }
}




  {
    (*ptr);
}

  {
    AUTO_FREE * buffer = ();
    
}

Pattern 5: Bounds Checking

// C++: Use containers instead of raw arrays
#include <vector>
#include <array>
#include <span>

void safe_array_access() {
    std::vector<int> vec = {1, 2, 3, 4, 5};

    // Safe: throws std::out_of_range
    try {
        int val = vec.at(10);
    } catch (const std::out_of_range& e) {
        // Handle error
    }

    // Unsafe but faster (no bounds check)
    int val = vec[2];

    // Modern C++20: std::span for array views
    std::span<int> view(vec);
    // Iterators are bounds-safe
    for (int& x : view) {
        x *= 2;
    }
}

// Fixed-size arrays
void fixed_array() {
    std::array<int, 5> arr = {1, 2, 3, 4, 5};

    // Compile-time size known
    static_assert(arr.size() == );

    
     val = arr.();
}

// Rust: Bounds checking by default

fn rust_bounds_checking() {
    let vec = vec![1, 2, 3, 4, 5];

    // Runtime bounds check (panics if out of bounds)
    let val = vec[2];

    // Explicit option (no panic)
    match vec.get(10) {
        Some(val) => println!("Got {}", val),
        None => println!("Index out of bounds"),
    }

    // Iterators (no bounds checking needed)
    for val in &vec {
        println!("{}", val);
    }

    // Slices are bounds-checked
    let slice = &vec[1..3]; // [2, 3]
}

Pattern 6: Preventing Data Races

// C++: Thread-safe shared state
#include <mutex>
#include <shared_mutex>
#include <atomic>

class ThreadSafeCounter {
public:
    void increment() {
        // Atomic operations
        count_.fetch_add(1, std::memory_order_relaxed);
    }

    int get() const {
        return count_.load(std::memory_order_relaxed);
    }

private:
    std::atomic<int> count_{0};
};

class ThreadSafeMap {
public:
    void write(const std::string& key, int value) {
        std::unique_lock lock(mutex_);
        data_[key] = value;
    }

    std::optional<int> read(const std::string& key) {
        std::shared_lock lock(mutex_);
        auto it = data_.find(key);
        if (it != data_.end()) {
             it->second;
        }
         std::;
    }

:
     std::shared_mutex mutex_;
    std::map<std::string, > data_;
};

// Rust: Data race prevention at compile time

use std::sync::{Arc, Mutex, RwLock};
use std::sync::atomic::{AtomicI32, Ordering};
use std::thread;

// Atomic for simple types
fn atomic_example() {
    let counter = Arc::new(AtomicI32::new(0));

    let handles: Vec<_> = (0..10)
        .map(|_| {
            let counter = Arc::clone(&counter);
            thread::spawn(move || {
                counter.fetch_add(1, Ordering::SeqCst);
            })
        })
        .collect();

    for handle in handles {
        handle.join().unwrap();
    }

    println!("Counter: {}", counter.load(Ordering::SeqCst));
}

// Mutex for complex types
fn mutex_example() {
    let data = Arc::new(Mutex::new(vec![]));

    let handles: Vec<_> = (0..)
        .(|i| {
              = Arc::(&data);
            thread::( || {
                  = data.().();
                vec.(i);
            })
        })
        .();

       handles {
        handle.().();
    }
}


 () {
      = Arc::(RwLock::(HashMap::()));

    
      = data.().();

    
      = data.().();
}

Best Practices

Do's

• Prefer RAII - Tie resource lifetime to scope
• Use smart pointers - Avoid raw pointers in C++
• Understand ownership - Know who owns what
• Check bounds - Use safe access methods
• Use tools - AddressSanitizer, Valgrind, Miri

Don'ts

• Don't use raw pointers - Unless interfacing with C
• Don't return local references - Dangling pointer
• Don't ignore compiler warnings - They catch bugs
• Don't use unsafe carelessly - In Rust, minimize it
• Don't assume thread safety - Be explicit

Debugging Tools

# AddressSanitizer (Clang/GCC)
clang++ -fsanitize=address -g source.cpp

# Valgrind
valgrind --leak-check=full ./program

# Rust Miri (undefined behavior detector)
cargo +nightly miri run

# ThreadSanitizer
clang++ -fsanitize=thread -g source.cpp

Resources

• C++ Core Guidelines
• Rust Ownership
• AddressSanitizer