mozilla/rust — pull request #7828 by alexcrichton (2013-07-16 18:34:28+00:00)
Title: Make all lang_items optional

Whenever a lang_item is required, some relevant message is displayed, often with
a span of what triggered the usage of the lang item.

Now "hello word" is as small as:

```rust
#[no_std];

extern {
fn puts(s: *u8);
}

extern "rust-intrinsic" {
fn transmute(t: T) -> U;
}

#[start]
fn main(_: int, _: **u8, _: *u8) -> int {
unsafe {
let (ptr, _): (*u8, uint) = transmute("Hello!");
puts(ptr);
}
return 0;
}
```