Iterator invalidation is a common memory safety issue where you have two references being simultaneously used -- one mutable, one immutable. With multiple mutable references worse errors can happen.
-Manish Goregaokar On Fri, Sep 19, 2014 at 1:09 PM, silvio <silvio.fris...@gmail.com> wrote: > Hi Rust, > > I've recently tried to investigate rust's claim of being fast and had a > look at debian shootout. > > A particular program I took a looked at is the n-body problem in which > you have to loop over pairs of bodies to calculate their gravitational > attraction. What struck me as strange was the number of indexing > operations. > > bodies[i] > bodies[j] > bodies[i] > bodies[j] > ... > > Now I don't know if the compiler is smart enough to optimize this away. > However, it seems generally impossible to make references. > > let mut body_i = bodies.someMethod(i) > let mut body_j = bodies.someMethod(j) > > So how is this usually done? > > Why are multiple mutable references to the same object not allowed. To > achieve safe memory you only need to guarantee that different threads > don't write/read from/to the same memory location at the same time and > that is handled via ownership. (borrowed) references & don't have > ownership. Additionally, you need to ensure that all references not only > mut are not usable anymore until you can transfer ownership. So, I don't > understand why mut and not mut are treated differently. > > An other small thing. I read that you should always return a type directly. > > fn foo(args) -> big_struct > > Does this mean that all return values are secretly pointers passed to > the function except for things that fit into registers? > > > regards > > silvio > _______________________________________________ > Rust-dev mailing list > Rust-dev@mozilla.org > https://mail.mozilla.org/listinfo/rust-dev >
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