use std::intrinsics;
#[deriving(Show)]
struct NewType<‘a, T: ‘a> {
a:int,
b:String,
v: &‘a T
}
fn main() {
let t: NewType<int> = unsafe{ intrinsics::init()};
println!("{}", t); // Error at this line
}
$ rustc mem.rs $ ./mem Illegal instruction: 4
why?
答案：
11:33 < Dragon> hello, I got a runtime error: Illegal instruction: 4, can any one help me out? code
snipet at http://my.oschina.net/zengsai/blog/360320
11:33 * Twisol shuffles over to the corner.
11:33 < Dragon> based on latest rustc
11:34 -!- chingucha [[email protected]] has quit [Ping timeout: 121 seconds]
11:34 < FreeFull> Dragon: That‘s because you‘re creating a null pointer dereference
11:35 < Dragon> FreeFull: how?
11:35 < FreeFull> When it‘s trying to print out the v field, specifically
11:35 < Twisol> Dragon: `unsafe{ intrinsics::init()}`
11:36 -!- nucleartide [[email protected]] has quit [Ping timeout: 121 seconds]
11:36 < FreeFull> References are meant to be never null, but you created a null reference with that
unsafe block, and tried to print it out
11:36 -!- chingucha [[email protected]] has joined #rust
11:36 < FreeFull> Printing a reference prints the data behind it
11:36 < Twisol> Dragon: `intrinsics::init()` creates a value initialized with all zeroes. Your data
has a pointer in it, so that pointer gets set to 0.
11:36 < meh> shouldn‘t it segfault tho?
11:37 < Dragon> ok, i see , thanks FreeFull Twisol