Rust: low-level programming without the segfaults

Presented at OSCON 2013.

Transcript

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4. The price of performance shouldn’t have to be
   crashes and exploits.
   

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5. • Safe unions and pointers
   • Explicit memory layout & stack allocation
   • Optional garbage collection
   • Mutability control & race-free concurrency
   Rust: perf + safety
   

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6. ALGEBRAIC
   DATA TYPES
   

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7. enum Color {
   Red,
   Green,
   Blue
   }
   

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8. enum Tree {
   Empty,
   Leaf(int),
   Node(~Tree, ~Tree)
   }
   

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9. tag tag
   int
   tag
   ~Tree
   ~Tree
   Empty Leaf(int)
   Node(~Tree,
   ~Tree)
   

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10. struct Tree {
    enum TreeTag tag;
    union {
    int leaf;
    Pair node;
    } data;
    };
    enum TreeTag { Empty, Leaf, Node };
    struct Pair { Tree *left, *right; };
    

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11. PATTERN
    MATCHING
    

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12. match tree {
    Empty => 0,
    Leaf(_) => 1,
    Node(~ref left, ~ref right) =>
    f(left) + f(right)
    }
    

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13. enum Option {
    None,
    Some(T)
    }
    

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15. fn double(p: ~int) -> int {
    *p * 2
    }
    

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16. fn double(p: Option<~int>) -> int {
    match p {
    None => 0,
    Some(~n) => n * 2
    }
    }
    

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17. OWNERSHIP
    

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18. void *realloc(void *, ...);
    void free(void *);
    Owned pointers
    

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19. void *realloc(void *, ...);
    void free(void *);
    template
    class Hashtable {
    vector> buckets;
    ...
    };
    Owned pointers
    

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20. memcpy(void *dest,
    const void *src,
    uintptr_t count);
    Temporary pointers
    

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21. memcpy(void *dest,
    const void *src,
    uintptr_t count);
    template
    class Hashtable {
    ...
    V& find(K& key);
    };
    Temporary pointers
    

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22. the right to free memory
    What is ownership?
    

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23. struct Hashtable {
    buckets: ~[Option>]
    }
    struct Bucket {
    key: K,
    value: V
    }
    

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24. {
    let b = ~[];
    let table = Hashtable {
    buckets: b
    };
    ...
    }
    

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25. {
    let b = ~[];
    let table = Hashtable {
    buckets: b
    };
    ...
    }
    heap
    allocate
    

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26. {
    let b = ~[];
    let table = Hashtable {
    buckets: b
    };
    ...
    }
    heap
    allocate
    stack
    allocate
    

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27. {
    let b = ~[];
    let table = Hashtable {
    buckets: b
    };
    ...
    }
    heap
    allocate
    stack
    allocate
    move
    

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28. fn move_from() {
    let x: ~int = ~22;
    move_to(x);
    }
    fn move_to(p: ~int) {
    printfln!(“%d”, *p);
    }
    

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29. fn move_from() {
    let x: ~int = ~22;
    move_to(x);
    }
    fn move_to(p: ~int) {
    printfln!(“%d”, *p);
    }
    heap
    allocate
    

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30. fn move_from() {
    let x: ~int = ~22;
    move_to(x);
    }
    fn move_to(p: ~int) {
    printfln!(“%d”, *p);
    }
    heap
    allocate
    move
    

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31. fn move_from() {
    let x: ~int = ~22;
    move_to(x);
    }
    fn move_to(p: ~int) {
    printfln!(“%d”, *p);
    }
    heap
    allocate
    free p
    move
    

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32. fn move_from() {
    let x: ~int = ~22;
    move_to(x);
    }
    fn move_to(p: ~int) {
    printfln!(“%d”, *p);
    }
    heap
    allocate
    free p
    move
    printfln!(“%d”, *x); // error
    

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33. BORROWING
    

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34. fn f() {
    let x: ~int = ~22;
    borrow(x);
    printfln!(“%d”, *x);
    }
    fn borrow(x: &int) {
    printfln!(“borrowing: %d”, *x);
    }
    

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35. fn f() {
    let x: int = 22;
    borrow(&x);
    printfln!(“%d”, *x);
    }
    fn borrow(x: &int) {
    printfln!(“borrowing: %d”, *x);
    }
    

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36. let w = ~22;
    {
    let x = &w;
    let y = &*x;
    }
    ‘a
    ‘b
    ‘c
    ‘d
    Lifetimes
    

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37. fn find<‘a,K,V>(tbl: &’a Hashtable,
    key: &K)
    -> Option<&’a V>
    {
    ...
    }
    

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38. fn find<‘a,K,V>(tbl: &’a Hashtable,
    key: &K)
    -> Option<&’a V>
    {
    ...
    }
    pointer with
    lifetime ‘a to table
    

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39. fn find<‘a,K,V>(tbl: &’a Hashtable,
    key: &K)
    -> Option<&’a V>
    {
    ...
    }
    pointer with
    lifetime ‘a to table
    pointer with lifetime ‘a
    to value
    

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40. template
    class Hashtable
    V& Hashtable::find(K& key);
    unsafe!
    

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41. CONCURRENCY
    

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42. Heap
    

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43. Heap
    

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44. let (port, chan) = stream();
    do spawn {
    let p = ~Point { x: 1.0, y: 2.0 };
    chan.send(p);
    }
    let p = port.recv();
    printfln!(p.to_str());
    

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45. • Pluggable I/O
    • Optional scheduler
    • Data race-free shared data structures
    • Potential for race-free fork-join parallelism
    • Working on SIMD and GPU libs
    There’s more
    

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46. UNSAFE
    

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47. unsafe {
    transmute::<&str,&[u8]>(“L”)
    == &[76, 0]
    }
    unsafe fn f(...) { ... }
    

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48. unsafe {
    transmute::<&str,&[u8]>(“L”)
    == &[76, 0]
    }
    unsafe fn f(...) { ... }
    ☢
    

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49. 1. Don’t use unsafe code.
    2. If you absolutely must break Rule 1,
    • get out of unsafe code ASAP, and
    • always provide a safe interface at the
    boundaries.
    The rules
    

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50. Low-level programming… without the segfaults.
    

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51. Thank you.
    

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52. Image credits
    Sean Martell
    http://blog.seanmartell.com
    Ben Clinch
    http://www.flickr.com/photos/benclinch/3048906022/
    juicyrai
    http://www.flickr.com/photos/wink/180979062/
    Rama, Wikimedia Commons
    http://en.wikipedia.org/wiki/File:Sir_Tony_Hoare_IMG_5125.jpg
    Jared Zimmerman
    http://www.flickr.com/photos/spoinknet/7932382540/
    CCAC North Library
    http://www.flickr.com/photos/ccacnorthlib/3553821699/
    Mike Hayes
    http://www.flickr.com/photos/rotties/449650275/
    

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