78 lines
2.4 KiB
Rust
78 lines
2.4 KiB
Rust
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use fmt::Debug;
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#[cfg(target_arch = "wasm32")]
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mod exit {
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pub const SUCCESS: i32 = 0;
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pub const FAILURE: i32 = 1;
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}
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#[cfg(not(target_arch = "wasm32"))]
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mod exit {
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use libc;
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pub const SUCCESS: i32 = libc::EXIT_SUCCESS;
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pub const FAILURE: i32 = libc::EXIT_FAILURE;
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}
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/// A trait for implementing arbitrary return types in the `main` function.
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///
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/// The c-main function only supports to return integers as return type.
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/// So, every type implementing the `Termination` trait has to be converted
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/// to an integer.
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///
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/// The default implementations are returning `libc::EXIT_SUCCESS` to indicate
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/// a successful execution. In case of a failure, `libc::EXIT_FAILURE` is returned.
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#[cfg_attr(not(test), lang = "termination")]
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#[unstable(feature = "termination_trait", issue = "43301")]
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#[rustc_on_unimplemented =
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"`main` can only return types that implement {Termination}, not `{Self}`"]
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pub trait Termination {
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/// Is called to get the representation of the value as status code.
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/// This status code is returned to the operating system.
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fn report(self) -> i32;
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}
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#[unstable(feature = "termination_trait", issue = "43301")]
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impl Termination for () {
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fn report(self) -> i32 { exit::SUCCESS }
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}
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#[unstable(feature = "termination_trait", issue = "43301")]
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impl<T: Termination, E: Debug> Termination for Result<T, E> {
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fn report(self) -> i32 {
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match self {
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Ok(val) => val.report(),
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Err(err) => {
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eprintln!("Error: {:?}", err);
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exit::FAILURE
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}
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}
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}
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}
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#[unstable(feature = "termination_trait", issue = "43301")]
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impl Termination for ! {
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fn report(self) -> i32 { unreachable!(); }
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}
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#[unstable(feature = "termination_trait", issue = "43301")]
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impl Termination for bool {
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fn report(self) -> i32 {
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if self { exit::SUCCESS } else { exit::FAILURE }
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}
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}
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#[unstable(feature = "termination_trait", issue = "43301")]
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impl Termination for i32 {
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fn report(self) -> i32 {
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self
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}
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}
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