Rust: low-level programming without the segfaults

Presented at OSCON 2013.

Transcript

4. The price of performance shouldn’t have to be crashes and exploits.
5. • Safe unions and pointers • Explicit memory layout & stack allocation • Optional garbage collection • Mutability control & race-free concurrency Rust: perf + safety
6. ALGEBRAIC DATA TYPES
7. enum Color { Red, Green, Blue }
8. enum Tree { Empty, Leaf(int), Node(~Tree, ~Tree) }
9. tag tag int tag ~Tree ~Tree Empty Leaf(int) Node(~Tree, ~Tree)
10. struct Tree { enum TreeTag tag; union { int leaf; Pair node; } data; }; enum TreeTag { Empty, Leaf, Node }; struct Pair { Tree *left, *right; };
11. PATTERN MATCHING
12. match tree { Empty => 0, Leaf(_) => 1, Node(~ref left, ~ref right) => f(left) + f(right) }
13. enum Option<T> { None, Some(T) }
15. fn double(p: ~int) -> int { *p * 2 }
16. fn double(p: Option<~int>) -> int { match p { None => 0, Some(~n) => n * 2 } }
17. OWNERSHIP
18. void *realloc(void *, ...); void free(void *); Owned pointers
19. void *realloc(void *, ...); void free(void *); template<class K, class V> class Hashtable { vector<Bucket<K,V>> buckets; ... }; Owned pointers
20. memcpy(void *dest, const void *src, uintptr_t count); Temporary pointers
21. memcpy(void *dest, const void *src, uintptr_t count); template<class K, class V> class Hashtable { ... V& find(K& key); }; Temporary pointers
22. the right to free memory What is ownership?
23. struct Hashtable<K,V> { buckets: ~[Option<Bucket<K,V>>] } struct Bucket<K,V> { key: K, value: V }
24. { let b = ~[]; let table = Hashtable { buckets: b }; ... }
25. { let b = ~[]; let table = Hashtable { buckets: b }; ... } heap allocate
26. { let b = ~[]; let table = Hashtable { buckets: b }; ... } heap allocate stack allocate
27. { let b = ~[]; let table = Hashtable { buckets: b }; ... } heap allocate stack allocate move
28. fn move_from() { let x: ~int = ~22; move_to(x); } fn move_to(p: ~int) { printfln!(“%d”, *p); }
29. fn move_from() { let x: ~int = ~22; move_to(x); } fn move_to(p: ~int) { printfln!(“%d”, *p); } heap allocate
30. fn move_from() { let x: ~int = ~22; move_to(x); } fn move_to(p: ~int) { printfln!(“%d”, *p); } heap allocate move
31. fn move_from() { let x: ~int = ~22; move_to(x); } fn move_to(p: ~int) { printfln!(“%d”, *p); } heap allocate free p move
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
33. BORROWING
34. fn f() { let x: ~int = ~22; borrow(x); printfln!(“%d”, *x); } fn borrow(x: &int) { printfln!(“borrowing: %d”, *x); }
35. fn f() { let x: int = 22; borrow(&x); printfln!(“%d”, *x); } fn borrow(x: &int) { printfln!(“borrowing: %d”, *x); }
36. let w = ~22; { let x = &w; let y = &*x; } ‘a ‘b ‘c ‘d Lifetimes
37. fn find<‘a,K,V>(tbl: &’a Hashtable<K,V>, key: &K) -> Option<&’a V> { ... }
38. fn find<‘a,K,V>(tbl: &’a Hashtable<K,V>, key: &K) -> Option<&’a V> { ... } pointer with lifetime ‘a to table
39. fn find<‘a,K,V>(tbl: &’a Hashtable<K,V>, key: &K) -> Option<&’a V> { ... } pointer with lifetime ‘a to table pointer with lifetime ‘a to value
40. template<class K, class V> class Hashtable<K,V> V& Hashtable<K,V>::find(K& key); unsafe!
41. CONCURRENCY
42. Heap
43. Heap
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());
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
46. UNSAFE
47. unsafe { transmute::<&str,&[u8]>(“L”) == &[76, 0] } unsafe fn f(...) { ... }
48. unsafe { transmute::<&str,&[u8]>(“L”) == &[76, 0] } unsafe fn f(...) { ... } ☢
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
50. Low-level programming… without the segfaults.
51. Thank you.
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/