Use more lifetimes

[Manishearth]

Currently this crate has FFI functions which have no lifetimes in the arguments but a lifetime in the return type.

This currently compiles, but is a bug -- you can't do the same for non-FFI functions, for example.

Nor does it make sense, such a function will return an unbounded lifetime.

On the latest nightly this causes ICEs, and one of the possible fixes is to turn this into a hard error as we do for non FFI functions.

I added some lifetimes so that it will elide correctly. It would be possible to implement Deref for StructPtr and Base, however currently they have public pointer fields so it is not possible to dereference these safely. Instead I added an unsafe borrow() method that cleanly gives you the contents as a pointer with the right lifetimes. I can clean this up further if you'd like.

[SimonSapin]

@Manishearth This PR only includes changes to src/base.rs. Did you also make changes to .gitignore’d files generated by a Python script?

[Manishearth]

yeah, I did :|

[SimonSapin]

This is https://github.com/rtbo/rust-xcb/issues/40

[Manishearth]

Updated; works now.

It uses lifetimes in a few more situations than necessary but that's just easier for autogenerated code. Still safe.

[Manishearth]

I'm getting a lot of unrelated test failures locally

Here's a patch that fixes one of the examples:

diff --git a/examples/must_fail_borrow_check__setup.rs b/examples/must_fail_borrow_check__setup.rs
index 719b2ad..9f2266a 100644
--- a/examples/must_fail_borrow_check__setup.rs
+++ b/examples/must_fail_borrow_check__setup.rs
@@ -4,10 +4,12 @@ use std::iter::{Iterator};
 
 fn main() {
 
+    let conn;
     let setup;
     let screen_num;
     {
-        let (conn, sn) = xcb::Connection::connect(None).unwrap();
+        let (conn_, sn) = xcb::Connection::connect(None).unwrap();
+        conn = conn_;
         setup = conn.get_setup();
         screen_num = sn;
     }

[Manishearth]

Oh, wait, no, that example is supposed to fail.

[Manishearth]

So there's this other xkb crate with similar issues.

I'm not really familiar with this bindings generation setup and I'm unsure why my changes didn't work for the xkb stuff so I'm going to leave it as is.

[SimonSapin]

@rtbo, would you agree to backport this change to a 0.7.x version? Otherwise to get this fix in Servo we’d need to make changes through the dependency chain of clipboard and x11-clipboard.

[SimonSapin]

Ah, it turns out this PR needs some more changes. As it is, compiling on Nightly still fails like in #40. Travis is green because the build with Rust Nightly is an "allowed failure".

[rtbo]

@SimonSapin Yes, fixing both 0.7.x and 0.8.x is no problem.

[SimonSapin]

@rtbo Manish and I didn’t manage to make the code generation script generate appropriate code to make this build on Nightly. Can you have a look?

[rtbo]

@Manishearth @SimonSapin I pushed a37d1fa that does the necessary lifetime assignments. (still need confirmation by you servo guys).
Also it's branched from 0.7.x.

[rtbo]

Addressed by rtbo@a37d1fa.
Closing