From f886518c3a2daa3e1239b76bbc0f7a92792d5465 Mon Sep 17 00:00:00 2001 From: Alex Crichton Date: Thu, 29 Mar 2018 14:59:13 -0700 Subject: [PATCH] std: Minimize size of panicking on wasm 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` 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. --- src/ci/docker/wasm32-unknown/Dockerfile | 6 ++ src/libcore/panic.rs | 10 +++ src/libpanic_abort/lib.rs | 2 +- src/libpanic_unwind/lib.rs | 12 +-- src/libstd/lib.rs | 1 + src/libstd/panicking.rs | 88 ++++++++++++++++----- src/libstd/sys/cloudabi/stdio.rs | 4 + src/libstd/sys/redox/stdio.rs | 4 + src/libstd/sys/unix/stdio.rs | 4 + src/libstd/sys/wasm/rwlock.rs | 4 +- src/libstd/sys/wasm/stdio.rs | 4 + src/libstd/sys/windows/stdio.rs | 4 + src/libstd/sys_common/backtrace.rs | 13 ++- src/libstd/sys_common/mod.rs | 14 +++- src/libstd/sys_common/thread_local.rs | 4 +- src/libstd/sys_common/util.rs | 5 +- src/libstd/thread/local.rs | 41 +++++++++- src/libstd/thread/mod.rs | 3 + src/test/run-make/wasm-panic-small/Makefile | 11 +++ src/test/run-make/wasm-panic-small/foo.rs | 16 ++++ 20 files changed, 205 insertions(+), 45 deletions(-) create mode 100644 src/test/run-make/wasm-panic-small/Makefile create mode 100644 src/test/run-make/wasm-panic-small/foo.rs diff --git a/src/ci/docker/wasm32-unknown/Dockerfile b/src/ci/docker/wasm32-unknown/Dockerfile index 6c0ec1ad9d4e1..28d11064c6bba 100644 --- a/src/ci/docker/wasm32-unknown/Dockerfile +++ b/src/ci/docker/wasm32-unknown/Dockerfile @@ -25,6 +25,12 @@ ENV RUST_CONFIGURE_ARGS \ --set build.nodejs=/node-v9.2.0-linux-x64/bin/node \ --set rust.lld +# Some run-make tests have assertions about code size, and enabling debug +# assertions in libstd causes the binary to be much bigger than it would +# otherwise normally be. We already test libstd with debug assertions in lots of +# other contexts as well +ENV NO_DEBUG_ASSERTIONS=1 + ENV SCRIPT python2.7 /checkout/x.py test --target $TARGETS \ src/test/run-make \ src/test/ui \ diff --git a/src/libcore/panic.rs b/src/libcore/panic.rs index 4e72eaa57c73e..212139f1f7a41 100644 --- a/src/libcore/panic.rs +++ b/src/libcore/panic.rs @@ -249,3 +249,13 @@ impl<'a> fmt::Display for Location<'a> { write!(formatter, "{}:{}:{}", self.file, self.line, self.col) } } + +/// An internal trait used by libstd to pass data from libstd to `panic_unwind` +/// and other panic runtimes. Not intended to be stabilized any time soon, do +/// not use. +#[unstable(feature = "std_internals", issue = "0")] +#[doc(hidden)] +pub unsafe trait BoxMeUp { + fn box_me_up(&mut self) -> *mut (Any + Send); + fn get(&self) -> &(Any + Send); +} diff --git a/src/libpanic_abort/lib.rs b/src/libpanic_abort/lib.rs index 5f768ef4399e8..a1c4555d0b0e9 100644 --- a/src/libpanic_abort/lib.rs +++ b/src/libpanic_abort/lib.rs @@ -53,7 +53,7 @@ pub unsafe extern fn __rust_maybe_catch_panic(f: fn(*mut u8), // now hopefully. #[no_mangle] #[rustc_std_internal_symbol] -pub unsafe extern fn __rust_start_panic(_data: usize, _vtable: usize) -> u32 { +pub unsafe extern fn __rust_start_panic(_payload: usize) -> u32 { abort(); #[cfg(any(unix, target_os = "cloudabi"))] diff --git a/src/libpanic_unwind/lib.rs b/src/libpanic_unwind/lib.rs index a5cebc3e4d04b..cd7a643140239 100644 --- a/src/libpanic_unwind/lib.rs +++ b/src/libpanic_unwind/lib.rs @@ -30,6 +30,7 @@ issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")] #![deny(warnings)] +#![feature(allocator_api)] #![feature(alloc)] #![feature(core_intrinsics)] #![feature(lang_items)] @@ -37,6 +38,7 @@ #![feature(panic_unwind)] #![feature(raw)] #![feature(staged_api)] +#![feature(std_internals)] #![feature(unwind_attributes)] #![cfg_attr(target_env = "msvc", feature(raw))] @@ -48,9 +50,11 @@ extern crate libc; #[cfg(not(any(target_env = "msvc", all(windows, target_arch = "x86_64", target_env = "gnu"))))] extern crate unwind; +use alloc::boxed::Box; use core::intrinsics; use core::mem; use core::raw; +use core::panic::BoxMeUp; // Rust runtime's startup objects depend on these symbols, so make them public. #[cfg(all(target_os="windows", target_arch = "x86", target_env="gnu"))] @@ -114,9 +118,7 @@ pub unsafe extern "C" fn __rust_maybe_catch_panic(f: fn(*mut u8), #[no_mangle] #[cfg_attr(stage0, unwind)] #[cfg_attr(not(stage0), unwind(allowed))] -pub unsafe extern "C" fn __rust_start_panic(data: usize, vtable: usize) -> u32 { - imp::panic(mem::transmute(raw::TraitObject { - data: data as *mut (), - vtable: vtable as *mut (), - })) +pub unsafe extern "C" fn __rust_start_panic(payload: usize) -> u32 { + let payload = payload as *mut &mut BoxMeUp; + imp::panic(Box::from_raw((*payload).box_me_up())) } diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index 68d3b946d9ef5..d2b32b0f037e0 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -297,6 +297,7 @@ #![feature(rand)] #![feature(raw)] #![feature(rustc_attrs)] +#![feature(std_internals)] #![feature(stdsimd)] #![feature(shrink_to)] #![feature(slice_bytes)] diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs index 454ac64735c67..e5d30e81a8d76 100644 --- a/src/libstd/panicking.rs +++ b/src/libstd/panicking.rs @@ -17,6 +17,8 @@ //! * Executing a panic up to doing the actual implementation //! * Shims around "try" +use core::panic::BoxMeUp; + use io::prelude::*; use any::Any; @@ -27,7 +29,7 @@ use intrinsics; use mem; use ptr; use raw; -use sys::stdio::Stderr; +use sys::stdio::{Stderr, stderr_prints_nothing}; use sys_common::rwlock::RWLock; use sys_common::thread_info; use sys_common::util; @@ -57,7 +59,7 @@ extern { vtable_ptr: *mut usize) -> u32; #[cfg_attr(stage0, unwind)] #[cfg_attr(not(stage0), unwind(allowed))] - fn __rust_start_panic(data: usize, vtable: usize) -> u32; + fn __rust_start_panic(payload: usize) -> u32; } #[derive(Copy, Clone)] @@ -164,6 +166,12 @@ fn default_hook(info: &PanicInfo) { #[cfg(feature = "backtrace")] use sys_common::backtrace; + // Some platforms know that printing to stderr won't ever actually print + // anything, and if that's the case we can skip everything below. + if stderr_prints_nothing() { + return + } + // If this is a double panic, make sure that we print a backtrace // for this panic. Otherwise only print it if logging is enabled. #[cfg(feature = "backtrace")] @@ -213,15 +221,15 @@ fn default_hook(info: &PanicInfo) { let prev = LOCAL_STDERR.with(|s| s.borrow_mut().take()); match (prev, err.as_mut()) { - (Some(mut stderr), _) => { - write(&mut *stderr); - let mut s = Some(stderr); - LOCAL_STDERR.with(|slot| { - *slot.borrow_mut() = s.take(); - }); - } - (None, Some(ref mut err)) => { write(err) } - _ => {} + (Some(mut stderr), _) => { + write(&mut *stderr); + let mut s = Some(stderr); + LOCAL_STDERR.with(|slot| { + *slot.borrow_mut() = s.take(); + }); + } + (None, Some(ref mut err)) => { write(err) } + _ => {} } } @@ -346,7 +354,7 @@ pub fn begin_panic_fmt(msg: &fmt::Arguments, let mut s = String::new(); let _ = s.write_fmt(*msg); - rust_panic_with_hook(Box::new(s), Some(msg), file_line_col) + rust_panic_with_hook(&mut PanicPayload::new(s), Some(msg), file_line_col) } /// This is the entry point of panicking for panic!() and assert!(). @@ -362,7 +370,34 @@ pub fn begin_panic(msg: M, file_line_col: &(&'static str, u32, u3 // be performed in the parent of this thread instead of the thread that's // panicking. - rust_panic_with_hook(Box::new(msg), None, file_line_col) + rust_panic_with_hook(&mut PanicPayload::new(msg), None, file_line_col) +} + +struct PanicPayload { + inner: Option, +} + +impl PanicPayload { + fn new(inner: A) -> PanicPayload { + PanicPayload { inner: Some(inner) } + } +} + +unsafe impl BoxMeUp for PanicPayload { + fn box_me_up(&mut self) -> *mut (Any + Send) { + let data = match self.inner.take() { + Some(a) => Box::new(a) as Box, + None => Box::new(()), + }; + Box::into_raw(data) + } + + fn get(&self) -> &(Any + Send) { + match self.inner { + Some(ref a) => a, + None => &(), + } + } } /// Executes the primary logic for a panic, including checking for recursive @@ -371,9 +406,7 @@ pub fn begin_panic(msg: M, file_line_col: &(&'static str, u32, u3 /// This is the entry point or panics from libcore, formatted panics, and /// `Box` panics. Here we'll verify that we're not panicking recursively, /// run panic hooks, and then delegate to the actual implementation of panics. -#[inline(never)] -#[cold] -fn rust_panic_with_hook(payload: Box, +fn rust_panic_with_hook(payload: &mut BoxMeUp, message: Option<&fmt::Arguments>, file_line_col: &(&'static str, u32, u32)) -> ! { let (file, line, col) = *file_line_col; @@ -393,7 +426,7 @@ fn rust_panic_with_hook(payload: Box, unsafe { let info = PanicInfo::internal_constructor( - &*payload, + payload.get(), message, Location::internal_constructor(file, line, col), ); @@ -421,16 +454,29 @@ fn rust_panic_with_hook(payload: Box, /// Shim around rust_panic. Called by resume_unwind. pub fn update_count_then_panic(msg: Box) -> ! { update_panic_count(1); - rust_panic(msg) + + struct RewrapBox(Box); + + unsafe impl BoxMeUp for RewrapBox { + fn box_me_up(&mut self) -> *mut (Any + Send) { + Box::into_raw(mem::replace(&mut self.0, Box::new(()))) + } + + fn get(&self) -> &(Any + Send) { + &*self.0 + } + } + + rust_panic(&mut RewrapBox(msg)) } /// A private no-mangle function on which to slap yer breakpoints. #[no_mangle] #[allow(private_no_mangle_fns)] // yes we get it, but we like breakpoints -pub fn rust_panic(msg: Box) -> ! { +pub fn rust_panic(mut msg: &mut BoxMeUp) -> ! { let code = unsafe { - let obj = mem::transmute::<_, raw::TraitObject>(msg); - __rust_start_panic(obj.data as usize, obj.vtable as usize) + let obj = &mut msg as *mut &mut BoxMeUp; + __rust_start_panic(obj as usize) }; rtabort!("failed to initiate panic, error {}", code) } diff --git a/src/libstd/sys/cloudabi/stdio.rs b/src/libstd/sys/cloudabi/stdio.rs index 9519a92647108..1d7344f921c9d 100644 --- a/src/libstd/sys/cloudabi/stdio.rs +++ b/src/libstd/sys/cloudabi/stdio.rs @@ -77,3 +77,7 @@ pub fn is_ebadf(err: &io::Error) -> bool { } pub const STDIN_BUF_SIZE: usize = ::sys_common::io::DEFAULT_BUF_SIZE; + +pub fn stderr_prints_nothing() -> bool { + false +} diff --git a/src/libstd/sys/redox/stdio.rs b/src/libstd/sys/redox/stdio.rs index 3abb094ac34e3..7a4d11b0ecb9a 100644 --- a/src/libstd/sys/redox/stdio.rs +++ b/src/libstd/sys/redox/stdio.rs @@ -75,3 +75,7 @@ pub fn is_ebadf(err: &io::Error) -> bool { } pub const STDIN_BUF_SIZE: usize = ::sys_common::io::DEFAULT_BUF_SIZE; + +pub fn stderr_prints_nothing() -> bool { + false +} diff --git a/src/libstd/sys/unix/stdio.rs b/src/libstd/sys/unix/stdio.rs index e9b3d4affc7dd..87ba2aef4f1d3 100644 --- a/src/libstd/sys/unix/stdio.rs +++ b/src/libstd/sys/unix/stdio.rs @@ -75,3 +75,7 @@ pub fn is_ebadf(err: &io::Error) -> bool { } pub const STDIN_BUF_SIZE: usize = ::sys_common::io::DEFAULT_BUF_SIZE; + +pub fn stderr_prints_nothing() -> bool { + false +} diff --git a/src/libstd/sys/wasm/rwlock.rs b/src/libstd/sys/wasm/rwlock.rs index 8b06f54167487..6516010af4759 100644 --- a/src/libstd/sys/wasm/rwlock.rs +++ b/src/libstd/sys/wasm/rwlock.rs @@ -30,7 +30,7 @@ impl RWLock { if *mode >= 0 { *mode += 1; } else { - panic!("rwlock locked for writing"); + rtabort!("rwlock locked for writing"); } } @@ -51,7 +51,7 @@ impl RWLock { if *mode == 0 { *mode = -1; } else { - panic!("rwlock locked for reading") + rtabort!("rwlock locked for reading") } } diff --git a/src/libstd/sys/wasm/stdio.rs b/src/libstd/sys/wasm/stdio.rs index beb19c0ed2c1f..023f29576a27d 100644 --- a/src/libstd/sys/wasm/stdio.rs +++ b/src/libstd/sys/wasm/stdio.rs @@ -69,3 +69,7 @@ pub const STDIN_BUF_SIZE: usize = 0; pub fn is_ebadf(_err: &io::Error) -> bool { true } + +pub fn stderr_prints_nothing() -> bool { + !cfg!(feature = "wasm_syscall") +} diff --git a/src/libstd/sys/windows/stdio.rs b/src/libstd/sys/windows/stdio.rs index b43df20bddd08..81b89da21d3c6 100644 --- a/src/libstd/sys/windows/stdio.rs +++ b/src/libstd/sys/windows/stdio.rs @@ -227,3 +227,7 @@ pub fn is_ebadf(err: &io::Error) -> bool { // idea is that on windows we use a slightly smaller buffer that's // been seen to be acceptable. pub const STDIN_BUF_SIZE: usize = 8 * 1024; + +pub fn stderr_prints_nothing() -> bool { + false +} diff --git a/src/libstd/sys_common/backtrace.rs b/src/libstd/sys_common/backtrace.rs index 1955f3ec9a28f..20109d2d0d5ac 100644 --- a/src/libstd/sys_common/backtrace.rs +++ b/src/libstd/sys_common/backtrace.rs @@ -139,10 +139,10 @@ pub fn __rust_begin_short_backtrace(f: F) -> T /// Controls how the backtrace should be formatted. #[derive(Debug, Copy, Clone, Eq, PartialEq)] pub enum PrintFormat { - /// Show all the frames with absolute path for files. - Full = 2, /// Show only relevant data from the backtrace. - Short = 3, + Short = 2, + /// Show all the frames with absolute path for files. + Full = 3, } // For now logging is turned off by default, and this function checks to see @@ -150,11 +150,10 @@ pub enum PrintFormat { pub fn log_enabled() -> Option { static ENABLED: atomic::AtomicIsize = atomic::AtomicIsize::new(0); match ENABLED.load(Ordering::SeqCst) { - 0 => {}, + 0 => {} 1 => return None, - 2 => return Some(PrintFormat::Full), - 3 => return Some(PrintFormat::Short), - _ => unreachable!(), + 2 => return Some(PrintFormat::Short), + _ => return Some(PrintFormat::Full), } let val = match env::var_os("RUST_BACKTRACE") { diff --git a/src/libstd/sys_common/mod.rs b/src/libstd/sys_common/mod.rs index 27504d374ddbf..d0c4d6a773746 100644 --- a/src/libstd/sys_common/mod.rs +++ b/src/libstd/sys_common/mod.rs @@ -28,6 +28,16 @@ use sync::Once; use sys; +macro_rules! rtabort { + ($($t:tt)*) => (::sys_common::util::abort(format_args!($($t)*))) +} + +macro_rules! rtassert { + ($e:expr) => (if !$e { + rtabort!(concat!("assertion failed: ", stringify!($e))); + }) +} + pub mod at_exit_imp; #[cfg(feature = "backtrace")] pub mod backtrace; @@ -101,10 +111,6 @@ pub fn at_exit(f: F) -> Result<(), ()> { if at_exit_imp::push(Box::new(f)) {Ok(())} else {Err(())} } -macro_rules! rtabort { - ($($t:tt)*) => (::sys_common::util::abort(format_args!($($t)*))) -} - /// One-time runtime cleanup. pub fn cleanup() { static CLEANUP: Once = Once::new(); diff --git a/src/libstd/sys_common/thread_local.rs b/src/libstd/sys_common/thread_local.rs index a4aa3d96d25c0..d0d6224de0a15 100644 --- a/src/libstd/sys_common/thread_local.rs +++ b/src/libstd/sys_common/thread_local.rs @@ -169,7 +169,7 @@ impl StaticKey { self.key.store(key, Ordering::SeqCst); } INIT_LOCK.unlock(); - assert!(key != 0); + rtassert!(key != 0); return key } @@ -190,7 +190,7 @@ impl StaticKey { imp::destroy(key1); key2 }; - assert!(key != 0); + rtassert!(key != 0); match self.key.compare_and_swap(0, key as usize, Ordering::SeqCst) { // The CAS succeeded, so we've created the actual key 0 => key as usize, diff --git a/src/libstd/sys_common/util.rs b/src/libstd/sys_common/util.rs index a391c7cc6ef0c..a373e980b970d 100644 --- a/src/libstd/sys_common/util.rs +++ b/src/libstd/sys_common/util.rs @@ -10,10 +10,13 @@ use fmt; use io::prelude::*; -use sys::stdio::Stderr; +use sys::stdio::{Stderr, stderr_prints_nothing}; use thread; pub fn dumb_print(args: fmt::Arguments) { + if stderr_prints_nothing() { + return + } let _ = Stderr::new().map(|mut stderr| stderr.write_fmt(args)); } diff --git a/src/libstd/thread/local.rs b/src/libstd/thread/local.rs index 99479bc56eff3..40d3280baa687 100644 --- a/src/libstd/thread/local.rs +++ b/src/libstd/thread/local.rs @@ -172,12 +172,16 @@ macro_rules! __thread_local_inner { &'static $crate::cell::UnsafeCell< $crate::option::Option<$t>>> { + #[cfg(target_arch = "wasm32")] + static __KEY: $crate::thread::__StaticLocalKeyInner<$t> = + $crate::thread::__StaticLocalKeyInner::new(); + #[thread_local] - #[cfg(target_thread_local)] + #[cfg(all(target_thread_local, not(target_arch = "wasm32")))] static __KEY: $crate::thread::__FastLocalKeyInner<$t> = $crate::thread::__FastLocalKeyInner::new(); - #[cfg(not(target_thread_local))] + #[cfg(all(not(target_thread_local), not(target_arch = "wasm32")))] static __KEY: $crate::thread::__OsLocalKeyInner<$t> = $crate::thread::__OsLocalKeyInner::new(); @@ -295,6 +299,39 @@ impl LocalKey { } } +/// On some platforms like wasm32 there's no threads, so no need to generate +/// thread locals and we can instead just use plain statics! +#[doc(hidden)] +#[cfg(target_arch = "wasm32")] +pub mod statik { + use cell::UnsafeCell; + use fmt; + + pub struct Key { + inner: UnsafeCell>, + } + + unsafe impl ::marker::Sync for Key { } + + impl fmt::Debug for Key { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + f.pad("Key { .. }") + } + } + + impl Key { + pub const fn new() -> Key { + Key { + inner: UnsafeCell::new(None), + } + } + + pub unsafe fn get(&self) -> Option<&'static UnsafeCell>> { + Some(&*(&self.inner as *const _)) + } + } +} + #[doc(hidden)] #[cfg(target_thread_local)] pub mod fast { diff --git a/src/libstd/thread/mod.rs b/src/libstd/thread/mod.rs index 71aee673cfe3e..1b976b79b4c98 100644 --- a/src/libstd/thread/mod.rs +++ b/src/libstd/thread/mod.rs @@ -202,6 +202,9 @@ pub use self::local::{LocalKey, AccessError}; // where fast TLS was not available; end-user code is compiled with fast TLS // where available, but both are needed. +#[unstable(feature = "libstd_thread_internals", issue = "0")] +#[cfg(target_arch = "wasm32")] +#[doc(hidden)] pub use self::local::statik::Key as __StaticLocalKeyInner; #[unstable(feature = "libstd_thread_internals", issue = "0")] #[cfg(target_thread_local)] #[doc(hidden)] pub use self::local::fast::Key as __FastLocalKeyInner; diff --git a/src/test/run-make/wasm-panic-small/Makefile b/src/test/run-make/wasm-panic-small/Makefile new file mode 100644 index 0000000000000..a11fba235957b --- /dev/null +++ b/src/test/run-make/wasm-panic-small/Makefile @@ -0,0 +1,11 @@ +-include ../../run-make-fulldeps/tools.mk + +ifeq ($(TARGET),wasm32-unknown-unknown) +all: + $(RUSTC) foo.rs -C lto -O --target wasm32-unknown-unknown + wc -c < $(TMPDIR)/foo.wasm + [ "`wc -c < $(TMPDIR)/foo.wasm`" -lt "1024" ] +else +all: +endif + diff --git a/src/test/run-make/wasm-panic-small/foo.rs b/src/test/run-make/wasm-panic-small/foo.rs new file mode 100644 index 0000000000000..9654d5f7c0991 --- /dev/null +++ b/src/test/run-make/wasm-panic-small/foo.rs @@ -0,0 +1,16 @@ +// Copyright 2018 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![crate_type = "cdylib"] + +#[no_mangle] +pub fn foo() { + panic!("test"); +}