Code change:
<ins> // Copyright 2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. struct StateMachineIter<'a> { statefn: &'a fn(&mut StateMachineIter<'a>) -> Option<&'static str> } impl<'a> Iterator<&'static str> for StateMachineIter<'a> { fn next(&mut self) -> Option<&'static str> { return  (*self.statefn)(self); } } fn state1(self_: &mut StateMachineIter) -> Option<&'static str> { self_.statefn = &state2; //~^ ERROR borrowed value does not live long enough return Some("state1"); } fn state2(self_: &mut StateMachineIter) -> Option<(&'static str)> { self_.statefn = &state3; //~^ ERROR borrowed value does not live long enough return Some("state2"); } fn state3(self_: &mut StateMachineIter) -> Option<(&'static str)> { self_.statefn = &finished; //~^ ERROR borrowed value does not live long enough return Some("state3"); } fn finished(_: &mut StateMachineIter) -> Option<(&'static str)> { return None; } fn state_iter() -> StateMachineIter<'static> { StateMachineIter { statefn: &state1 //~ ERROR borrowed value does not live long enough } } fn main() { let mut it = state_iter(); println!("{}",it.next()); println!("{}",it.next()); println!("{}",it.next()); println!("{}",it.next()); println!("{}",it.next()); } </ins>

Related discussion:
text: Hello! The following dumps core when run on my machine (Ubuntu 12.04 LTS, rust-nightly downloaded today (18th Apr)). Ziad Hatahet confirmed the same on a slightly older version of rust.
There's an extra layer of indirection in that struct definition. A is a pointer to a pointer to a function. A statement like expands to . That's obviously creating a dangling pointer onto the stack which is why it ends up crashing. Adjusting the struct definition to should make things work as you want. There's also a bug in rustc for even letting that program compile. I'm not sure if it's already been run into and filed.
cc
This fixes it: But I didn't quite understand why.
it probably happens to reset that part of the stack to the right value.
p.s. This is still crashing in . Thanks
Nominating, something fishy is going on here.
Here's the simplest possible reduction I could make:
Is the compiler mixing up the function pointer with the actual function code? That is, is like So writing is like , i.e. a non- reference to the function pointer.
It's just creating an alloca, storing the function pointer into it, borrowing that, and returning the borrowed pointer. For example, on the program I get this LLVM IR: Basically, the borrow checker doesn't seem to be in on the joke that is referring to a local alloca.
That is the behaviour I would expect if my statement were true. (The double in the LLVM signature indicates what I was talking about: a function value is already the pointer, and so the name doesn't have lifetime.)
0 backcompat-lang
This is probably a mismatch between trans/mem-categorization. I expect mem-categorization is saying that the "reference to the fn" is a static item, but trans is translating it into an rvalue (and hence on the stack).