c3a5d6b130
This commit applies a few code size optimizations for the wasm target to the standard library, namely around panics. We notably know that in most configurations it's impossible for us to print anything in wasm32-unknown-unknown so we can skip larger portions of panicking that are otherwise simply informative. This allows us to get quite a nice size reduction. Finally we can also tweak where the allocation happens for the `Box<Any>` that we panic with. By only allocating once unwinding starts we can reduce the size of a panicking wasm module from 44k to 350 bytes.
142 lines
4.3 KiB
Rust
142 lines
4.3 KiB
Rust
// Copyright 2014 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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//! Platform-independent platform abstraction
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//!
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//! This is the platform-independent portion of the standard library's
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//! platform abstraction layer, whereas `std::sys` is the
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//! platform-specific portion.
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//!
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//! The relationship between `std::sys_common`, `std::sys` and the
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//! rest of `std` is complex, with dependencies going in all
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//! directions: `std` depending on `sys_common`, `sys_common`
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//! depending on `sys`, and `sys` depending on `sys_common` and `std`.
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//! Ideally `sys_common` would be split into two and the dependencies
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//! between them all would form a dag, facilitating the extraction of
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//! `std::sys` from the standard library.
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#![allow(missing_docs)]
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#![allow(missing_debug_implementations)]
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use sync::Once;
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use sys;
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macro_rules! rtabort {
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($($t:tt)*) => (::sys_common::util::abort(format_args!($($t)*)))
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}
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macro_rules! rtassert {
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($e:expr) => (if !$e {
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rtabort!(concat!("assertion failed: ", stringify!($e)));
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})
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}
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pub mod at_exit_imp;
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#[cfg(feature = "backtrace")]
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pub mod backtrace;
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pub mod condvar;
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pub mod io;
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pub mod mutex;
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pub mod poison;
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pub mod remutex;
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pub mod rwlock;
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pub mod thread;
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pub mod thread_info;
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pub mod thread_local;
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pub mod util;
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pub mod wtf8;
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pub mod bytestring;
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pub mod process;
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cfg_if! {
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if #[cfg(any(target_os = "cloudabi", target_os = "l4re", target_os = "redox"))] {
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pub use sys::net;
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} else if #[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))] {
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pub use sys::net;
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} else {
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pub mod net;
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}
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}
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#[cfg(feature = "backtrace")]
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#[cfg(any(all(unix, not(target_os = "emscripten")),
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all(windows, target_env = "gnu"),
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target_os = "redox"))]
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pub mod gnu;
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// common error constructors
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/// A trait for viewing representations from std types
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#[doc(hidden)]
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pub trait AsInner<Inner: ?Sized> {
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fn as_inner(&self) -> &Inner;
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}
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/// A trait for viewing representations from std types
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#[doc(hidden)]
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pub trait AsInnerMut<Inner: ?Sized> {
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fn as_inner_mut(&mut self) -> &mut Inner;
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}
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/// A trait for extracting representations from std types
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#[doc(hidden)]
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pub trait IntoInner<Inner> {
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fn into_inner(self) -> Inner;
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}
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/// A trait for creating std types from internal representations
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#[doc(hidden)]
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pub trait FromInner<Inner> {
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fn from_inner(inner: Inner) -> Self;
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}
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/// Enqueues a procedure to run when the main thread exits.
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///
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/// Currently these closures are only run once the main *Rust* thread exits.
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/// Once the `at_exit` handlers begin running, more may be enqueued, but not
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/// infinitely so. Eventually a handler registration will be forced to fail.
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///
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/// Returns `Ok` if the handler was successfully registered, meaning that the
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/// closure will be run once the main thread exits. Returns `Err` to indicate
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/// that the closure could not be registered, meaning that it is not scheduled
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/// to be run.
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pub fn at_exit<F: FnOnce() + Send + 'static>(f: F) -> Result<(), ()> {
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if at_exit_imp::push(Box::new(f)) {Ok(())} else {Err(())}
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}
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/// One-time runtime cleanup.
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pub fn cleanup() {
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static CLEANUP: Once = Once::new();
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CLEANUP.call_once(|| unsafe {
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sys::args::cleanup();
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sys::stack_overflow::cleanup();
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at_exit_imp::cleanup();
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});
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}
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// Computes (value*numer)/denom without overflow, as long as both
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// (numer*denom) and the overall result fit into i64 (which is the case
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// for our time conversions).
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#[allow(dead_code)] // not used on all platforms
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pub fn mul_div_u64(value: u64, numer: u64, denom: u64) -> u64 {
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let q = value / denom;
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let r = value % denom;
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// Decompose value as (value/denom*denom + value%denom),
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// substitute into (value*numer)/denom and simplify.
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// r < denom, so (denom*numer) is the upper bound of (r*numer)
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q * numer + r * numer / denom
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}
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#[test]
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fn test_muldiv() {
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assert_eq!(mul_div_u64( 1_000_000_000_001, 1_000_000_000, 1_000_000),
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1_000_000_000_001_000);
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}
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