no-panic 0.1.6

Attribute macro to require that the compiler prove a function can't ever panic.
Documentation

#[no_panic]

Build Status Latest Version

A Rust attribute macro to require that the compiler prove a function can't ever panic.

[dependencies]
no-panic = "0.1"
extern crate no_panic;
use no_panic::no_panic;

#[no_panic]
fn demo(s: &str) -> &str {
    &s[1..]
}

fn main() {
    println!("{}", demo("input string"));
}

If the function does panic (or the compiler fails to prove that the function cannot panic), the program fails to compile with a linker error that identifies the function name. Let's trigger that by passing a string that cannot be sliced at the first byte:

fn main() {
    println!("{}", demo("\u{1f980}input string"));
}
   Compiling no-panic-demo v0.0.1
error: linking with `cc` failed: exit code: 1
  |
  = note: /no-panic-demo/target/release/deps/no_panic_demo-7170785b672ae322.no_p
anic_demo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs.rcgu.o: In function `_$LT$no_pani
c_demo..demo..__NoPanic$u20$as$u20$core..ops..drop..Drop$GT$::drop::h72f8f423002
b8d9f':
          no_panic_demo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs:(.text._ZN72_$LT$no
_panic_demo..demo..__NoPanic$u20$as$u20$core..ops..drop..Drop$GT$4drop17h72f8f42
3002b8d9fE+0x2): undefined reference to `RUST_PANIC_IN_FUNCTION<demo>'
          collect2: error: ld returned 1 exit status

The error is not stellar but notice the useful part at the end that provides the name of the offending function: undefined reference to `RUST_PANIC_IN_FUNCTION<demo>'

Requires rustc >=1.30.0.

Caveats

  • Functions that require some amount of optimization to prove that they do not panic may no longer compile in debug mode after being marked #[no_panic].

  • The attribute is useless in code built with panic = "abort".

Acknowledgments

The linker error technique is based on @Kixunil's crate dont_panic. Check out that crate for other convenient ways to require absence of panics.

License

Licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.