A Rust attribute macro to require that the compiler prove a function can't ever panic.
toml
[dependencies]
no-panic = "0.1"
```rust use nopanic::nopanic;
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:
rust
fn main() {
println!("{}", demo("\u{1f980}input string"));
}
``console
Compiling no-panic-demo v0.0.1
error: linking withccfailed: exit code: 1
|
= note: /no-panic-demo/target/release/deps/no_panic_demo-7170785b672ae322.no_p
anic_demo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs.rcgu.o: In function$LT$nopani
cdemo..demo..NoPanic$u20$as$u20$core..ops..drop..Drop$GT$::drop::h72f8f423002
b8d9f':
nopanicdemo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs:(.text.ZN72$LT$no
_panicdemo..demo..NoPanic$u20$as$u20$core..ops..drop..Drop$GT$4drop17h72f8f42
3002b8d9fE+0x2): undefined reference to `
ERROR[no-panic]: detected panic in function `demo`
'
collect2: error: ld returned 1 exit status
```
The error is not stellar but notice the ERROR[no-panic] part at the end that provides the name of the offending function.
Compiler support: requires rustc 1.31+
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].
Panic detection happens at link time across the entire dependency graph, so
any Cargo commands that do not invoke a linker will not trigger panic
detection. This includes cargo build of library crates and cargo check of
binary and library crates.
The attribute is useless in code built with panic = "abort".
If you find that code requires optimization to pass #[no_panic], either make
no-panic an optional dependency that you only enable in release builds, or add a
section like the following to Cargo.toml to enable very basic optimization in
debug builds.
toml
[profile.dev]
opt-level = 1
If the code that you need to prove isn't panicking makes function calls to non-generic non-inline functions from a different crate, you may need thin LTO enabled for the linker to deduce those do not panic.
toml
[profile.release]
lto = "thin"
If you want no_panic to just assume that some function you call doesn't panic,
and get Undefined Behavior if it does at runtime, see [dtolnay/no-panic#16]; try
wrapping that call in an unsafe extern "C" wrapper.
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.
Licensed under either of Apache License, Version 2.0 or MIT license at your option.
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.