Title: Class 9: Pointers in Rust Date: 2014-02-18 Category: Classes Tags: operating systems, Rust, Morris worm, memory management, NX bit Author: David Evans

**[Problem Set 3](|filename|../../pages/ps/ps3/ps3.md)** is due on Monday, 3 March. Everyone should have a team formed for PS3 now and be making progress on it soon! **Thursday's class will be a project work day.** Take advantage of this opportunity to coordinate with your team and make progress on PS3. (Dave is [out of town](http://research.microsoft.com/en-us/events/mpcworkshop/) Wednesday-Friday. Several of the TAs will come to class Thursday and be available to help with PS3.)

What the &~#@<!? (Pointers in Rust)

# Unmanaged vs. Managed Memory Management What does it mean for a programming language to have unmanaged memory?

What are different ways to provide management memory?

# Type Safety and Garbage Collection Why is it hard to provide automatic memory management in a language that is not type-safe?

Garbage collection for C: Hans-J. Boehm, [_Simple Garbage-Collector-Safety_](|filename|./pldi96-gc.pdf), PLDI 1996. Latest version: [https://github.com/ivmai/bdwgc/](https://github.com/ivmai/bdwgc/). What are the advantages and disadvantages of reference counting compare to mark-and-sweep garbage collection?

## Systematic Memory Management Paper on willy-nilly memory management: [_Static Detection of Dynamic Memory Errors_](http://www.cs.virginia.edu/~evans/pldi96-abstract.html) (PLDI 1996). The Splint tool is available from [http://www.splint.org](http://www.split.org). # Pointers in Rust What does it mean to _borrow_ an object?

What restrictions should there be on what code can do with borrowed objects and why?

What is wrong with this code? ````Rust fn main() { let ref stolen : ~str; { let mine: ~str = ~"Mine, all mine!"; stolen = &mine; } println!("Whose is it? {:s}", *stolen); } ```` How does this code establish the lifetime of the result? ````Rust fn bigger<'a>(s1: &'a str, s2: &'a str) -> &'a str { if s1.len() > s2.len() { s1 } else { s2 } } ````

# Problem Set 3 You should have your team formed for PS3 now. If you are having trouble forming a team, make sure I know about it by the end of today. > Les noms zepto et zetta évoquent le chiffre sept (septième puissance de 10³) et la lettre « z » remplace la lettre « s » pour éviter le double emploi de la lettre « s » comme symbole. Les noms yocto et yotta sont dérivés de octo, qui évoque le chiffre huit (huitième puissance de 10³) ; la lettre « y » est ajoutée pour éviter l'emploi de la lettre « o » comme symbole à cause de la confusion possible avec le chiffre zéro. > [_Résolution 4 de la 19^e réunion de la CGPM_ (1991)](http://www.bipm.org/fr/CGPM/db/19/4/) ([Unofficial English version](http://www.bipm.org/en/CGPM/db/19/4/)). (Note that I am leaving room for one of you to produce a Yohtta server.)