The start function should always be recognized as reachable, even with --crate-type=dylib

[zwarich]

Running rustc --crate-type=dylib test.rs on

#[start]
fn start(_argc: int, _argv: **u8) -> int { 0 }

gives the warning

test.rs:2:1: 2:47 warning: code is never used: `start`, #[warn(dead_code)] on by default
test.rs:2 fn start(_argc: int, _argv: **u8) -> int { 0 }
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

despite the start function being generated and exported. Servo hits this warning in src/components/main/servo.rs.

[alexcrichton]

If you're building a library, the compiler doesn't use #[start] at all, so this seems like it's an accurate warning?

[zwarich]

I was just confused by Servo's workaround for #13905, which involves building the same .rs file with two different crate types, and thought that the dylib also contained the start function.