error[E0658]: `#[start]` functions are experimental and their signature may change over time
  --> $DIR/feature-gate-start.rs:2:1
   |
LL | fn foo(_: isize, _: *const *const u8) -> isize { 0 }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #29633 <https://github.com/rust-lang/rust/issues/29633> for more information
   = help: add `#![feature(start)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0658`.