1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204
//! [![github]](https://github.com/dtolnay/no-panic) [![crates-io]](https://crates.io/crates/no-panic) [![docs-rs]](https://docs.rs/no-panic) //! //! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github //! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust //! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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 //! //! <br> //! //! A Rust attribute macro to require that the compiler prove a function can't //! ever panic. //! //! ```toml //! [dependencies] //! no-panic = "0.1" //! ``` //! //! ``` //! use no_panic::no_panic; //! //! #[no_panic] //! fn demo(s: &str) -> &str { //! &s[1..] //! } //! //! fn main() { //! # fn demo(s: &str) -> &str { //! # &s[1..] //! # } //! # //! 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: //! //! ```should_panic //! # fn demo(s: &str) -> &str { //! # &s[1..] //! # } //! # //! fn main() { //! println!("{}", demo("\u{1f980}input string")); //! } //! ``` //! //! ```console //! 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 ` //! //! 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+* //! //! <br> //! //! ## 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]`. //! //! - 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. //! //! [dtolnay/no-panic#16]: https://github.com/dtolnay/no-panic/issues/16 //! //! <br> //! //! ## 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. //! //! [Kixunil]: https://github.com/Kixunil //! [`dont_panic`]: https://github.com/Kixunil/dont_panic extern crate proc_macro; use proc_macro::TokenStream; use proc_macro2::Span; use quote::quote; use syn::{parse_macro_input, parse_quote, Attribute, FnArg, Ident, ItemFn, PatType, ReturnType}; #[proc_macro_attribute] pub fn no_panic(args: TokenStream, function: TokenStream) -> TokenStream { assert!(args.is_empty()); let mut function = parse_macro_input!(function as ItemFn); let mut move_self = None; let mut arg_pat = Vec::new(); let mut arg_val = Vec::new(); for (i, input) in function.sig.inputs.iter_mut().enumerate() { let numbered = Ident::new(&format!("__arg{}", i), Span::call_site()); match input { FnArg::Typed(PatType { pat, .. }) => { arg_pat.push(quote!(#pat)); arg_val.push(quote!(#numbered)); *pat = parse_quote!(mut #numbered); } FnArg::Receiver(_) => { move_self = Some(quote! { if false { loop {} #[allow(unreachable_code)] { let __self = self; } } }); } } } let has_inline = function .attrs .iter() .flat_map(Attribute::parse_meta) .any(|meta| meta.path().is_ident("inline")); if !has_inline { function.attrs.push(parse_quote!(#[inline])); } let ret = match &function.sig.output { ReturnType::Default => quote!(-> ()), output @ ReturnType::Type(..) => quote!(#output), }; let stmts = function.block.stmts; let message = format!( "\n\nERROR[no-panic]: detected panic in function `{}`\n", function.sig.ident, ); function.block = Box::new(parse_quote!({ struct __NoPanic; extern "C" { #[link_name = #message] fn trigger() -> !; } impl core::ops::Drop for __NoPanic { fn drop(&mut self) { unsafe { trigger(); } } } let __guard = __NoPanic; let __result = (move || #ret { #move_self #( let #arg_pat = #arg_val; )* #(#stmts)* })(); core::mem::forget(__guard); __result })); TokenStream::from(quote!(#function)) }