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Implements RFC 1937: ? in main

This is the first part of the RFC 1937 that supports new
`Termination` trait in the rust `main` function.
This commit is contained in:
Bastian Köcher 2017-12-03 22:16:24 +01:00
parent 8cdde6db71
commit d7918fb2e8
13 changed files with 304 additions and 52 deletions

View file

@ -338,6 +338,8 @@ language_item_table! {
U128ShloFnLangItem, "u128_shlo", u128_shlo_fn;
I128ShroFnLangItem, "i128_shro", i128_shro_fn;
U128ShroFnLangItem, "u128_shro", u128_shro_fn;
TerminationTraitLangItem, "termination", termination;
}
impl<'a, 'tcx, 'gcx> TyCtxt<'a, 'tcx, 'gcx> {

View file

@ -194,11 +194,13 @@ use rustc::hir::itemlikevisit::ItemLikeVisitor;
use rustc::hir::map as hir_map;
use rustc::hir::def_id::DefId;
use rustc::middle::const_val::ConstVal;
use rustc::middle::lang_items::{ExchangeMallocFnLangItem};
use rustc::middle::lang_items::{ExchangeMallocFnLangItem,StartFnLangItem};
use rustc::middle::trans::TransItem;
use rustc::traits;
use rustc::ty::subst::Substs;
use rustc::ty::subst::{Substs, Kind};
use rustc::ty::{self, TypeFoldable, Ty, TyCtxt};
use rustc::ty::adjustment::CustomCoerceUnsized;
use rustc::session::config;
use rustc::mir::{self, Location};
use rustc::mir::visit::Visitor as MirVisitor;
use rustc::mir::mono::MonoItem;
@ -212,6 +214,8 @@ use rustc_data_structures::bitvec::BitVector;
use syntax::attr;
use std::iter;
#[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
pub enum MonoItemCollectionMode {
Eager,
@ -329,6 +333,8 @@ fn collect_roots<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
tcx.hir.local_def_id(node_id)
});
debug!("collect_roots: entry_fn = {:?}", entry_fn);
let mut visitor = RootCollector {
tcx,
mode,
@ -951,16 +957,8 @@ impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
// actually used somewhere. Just declaring them is insufficient.
}
hir::ItemFn(..) => {
let tcx = self.tcx;
let def_id = tcx.hir.local_def_id(item.id);
if self.is_root(def_id) {
debug!("RootCollector: ItemFn({})",
def_id_to_string(tcx, def_id));
let instance = Instance::mono(tcx, def_id);
self.output.push(MonoItem::Fn(instance));
}
let def_id = self.tcx.hir.local_def_id(item.id);
self.push_if_root(def_id);
}
}
}
@ -973,16 +971,8 @@ impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
match ii.node {
hir::ImplItemKind::Method(hir::MethodSig { .. }, _) => {
let tcx = self.tcx;
let def_id = tcx.hir.local_def_id(ii.id);
if self.is_root(def_id) {
debug!("RootCollector: MethodImplItem({})",
def_id_to_string(tcx, def_id));
let instance = Instance::mono(tcx, def_id);
self.output.push(MonoItem::Fn(instance));
}
let def_id = self.tcx.hir.local_def_id(ii.id);
self.push_if_root(def_id);
}
_ => { /* Nothing to do here */ }
}
@ -1003,6 +993,56 @@ impl<'b, 'a, 'v> RootCollector<'b, 'a, 'v> {
}
}
}
/// If `def_id` represents a root, then push it onto the list of
/// outputs. (Note that all roots must be monomorphic.)
fn push_if_root(&mut self, def_id: DefId) {
if self.is_root(def_id) {
debug!("RootCollector::push_if_root: found root def_id={:?}", def_id);
let instance = Instance::mono(self.tcx, def_id);
self.output.push(create_fn_trans_item(instance));
self.push_extra_entry_roots(def_id);
}
}
/// As a special case, when/if we encounter the
/// `main()` function, we also have to generate a
/// monomorphized copy of the start lang item based on
/// the return type of `main`. This is not needed when
/// the user writes their own `start` manually.
fn push_extra_entry_roots(&mut self, def_id: DefId) {
if self.entry_fn != Some(def_id) {
return;
}
if self.tcx.sess.entry_type.get() != Some(config::EntryMain) {
return;
}
let start_def_id = match self.tcx.lang_items().require(StartFnLangItem) {
Ok(s) => s,
Err(err) => self.tcx.sess.fatal(&err),
};
let main_ret_ty = self.tcx.fn_sig(def_id).output();
// Given that `main()` has no arguments,
// then its return type cannot have
// late-bound regions, since late-bound
// regions must appear in the argument
// listing.
let main_ret_ty = self.tcx.no_late_bound_regions(&main_ret_ty).unwrap();
let start_instance = Instance::resolve(
self.tcx,
ty::ParamEnv::empty(traits::Reveal::All),
start_def_id,
self.tcx.mk_substs(iter::once(Kind::from(main_ret_ty)))
).unwrap();
self.output.push(create_fn_trans_item(start_instance));
}
}
fn item_has_type_parameters<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> bool {

View file

@ -106,7 +106,8 @@ use monomorphize::collector::InliningMap;
use rustc::dep_graph::WorkProductId;
use rustc::hir::def_id::DefId;
use rustc::hir::map::DefPathData;
use rustc::mir::mono::{Linkage, Visibility};
use rustc::middle::lang_items::StartFnLangItem;
use rustc::middle::trans::{Linkage, Visibility};
use rustc::ty::{self, TyCtxt, InstanceDef};
use rustc::ty::item_path::characteristic_def_id_of_type;
use rustc::util::nodemap::{FxHashMap, FxHashSet};
@ -312,7 +313,13 @@ fn place_root_translation_items<'a, 'tcx, I>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
MonoItem::Fn(ref instance) => {
let visibility = match instance.def {
InstanceDef::Item(def_id) => {
if def_id.is_local() {
let start_def_id = tcx.lang_items().require(StartFnLangItem);
// If we encounter the lang start item, we set the visibility to
// default.
if start_def_id == Ok(def_id) {
Visibility::Default
} else if def_id.is_local() {
if tcx.is_exported_symbol(def_id) {
Visibility::Default
} else {

View file

@ -44,6 +44,7 @@ use rustc::ty::{self, Ty, TyCtxt};
use rustc::ty::layout::{self, Align, TyLayout, LayoutOf};
use rustc::ty::maps::Providers;
use rustc::dep_graph::{DepNode, DepConstructor};
use rustc::ty::subst::Kind;
use rustc::middle::cstore::{self, LinkMeta, LinkagePreference};
use rustc::util::common::{time, print_time_passes_entry};
use rustc::session::config::{self, NoDebugInfo};
@ -79,6 +80,7 @@ use std::str;
use std::sync::Arc;
use std::time::{Instant, Duration};
use std::i32;
use std::iter;
use std::sync::mpsc;
use syntax_pos::Span;
use syntax_pos::symbol::InternedString;
@ -540,17 +542,28 @@ fn maybe_create_entry_wrapper(ccx: &CrateContext) {
let et = ccx.sess().entry_type.get().unwrap();
match et {
config::EntryMain => create_entry_fn(ccx, span, main_llfn, true),
config::EntryStart => create_entry_fn(ccx, span, main_llfn, false),
config::EntryMain => create_entry_fn(ccx, span, main_llfn, main_def_id, true),
config::EntryStart => create_entry_fn(ccx, span, main_llfn, main_def_id, false),
config::EntryNone => {} // Do nothing.
}
fn create_entry_fn(ccx: &CrateContext,
fn create_entry_fn<'ccx>(ccx: &'ccx CrateContext,
sp: Span,
rust_main: ValueRef,
rust_main_def_id: DefId,
use_start_lang_item: bool) {
// Signature of native main(), corresponding to C's `int main(int, char **)`
let llfty = Type::func(&[Type::c_int(ccx), Type::i8p(ccx).ptr_to()], &Type::c_int(ccx));
// The libstd lang_start function does not return anything, while user defined lang start
// returns a isize
let start_output_ty = if use_start_lang_item { Type::void(ccx) } else { Type::c_int(ccx) };
let llfty = Type::func(&[Type::c_int(ccx), Type::i8p(ccx).ptr_to()], &start_output_ty);
let main_ret_ty = ccx.tcx().fn_sig(rust_main_def_id).output();
// Given that `main()` has no arguments,
// then its return type cannot have
// late-bound regions, since late-bound
// regions must appear in the argument
// listing.
let main_ret_ty = ccx.tcx().no_late_bound_regions(&main_ret_ty).unwrap();
if declare::get_defined_value(ccx, "main").is_some() {
// FIXME: We should be smart and show a better diagnostic here.
@ -577,8 +590,8 @@ fn maybe_create_entry_wrapper(ccx: &CrateContext) {
let (start_fn, args) = if use_start_lang_item {
let start_def_id = ccx.tcx().require_lang_item(StartFnLangItem);
let start_instance = Instance::mono(ccx.tcx(), start_def_id);
let start_fn = callee::get_fn(ccx, start_instance);
let start_fn = callee::resolve_and_get_fn(ccx, start_def_id, ccx.tcx().mk_substs(
iter::once(Kind::from(main_ret_ty))));
(start_fn, vec![bld.pointercast(rust_main, Type::i8p(ccx).ptr_to()),
arg_argc, arg_argv])
} else {
@ -588,8 +601,11 @@ fn maybe_create_entry_wrapper(ccx: &CrateContext) {
let result = bld.call(start_fn, &args, None);
// Return rust start function's result from native main()
bld.ret(bld.intcast(result, Type::c_int(ccx), true));
if use_start_lang_item {
bld.ret_void();
} else {
bld.ret(bld.intcast(result, Type::c_int(ccx), true));
}
}
}

View file

@ -93,17 +93,18 @@ use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
use rustc::infer::anon_types::AnonTypeDecl;
use rustc::infer::type_variable::{TypeVariableOrigin};
use rustc::middle::region;
use rustc::middle::lang_items::TerminationTraitLangItem;
use rustc::ty::subst::{Kind, Subst, Substs};
use rustc::traits::{self, FulfillmentContext, ObligationCause, ObligationCauseCode};
use rustc::ty::{ParamTy, LvaluePreference, NoPreference, PreferMutLvalue};
use rustc::ty::{self, Ty, TyCtxt, Visibility};
use rustc::ty::{self, Ty, TyCtxt, Visibility, ToPredicate};
use rustc::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
use rustc::ty::fold::TypeFoldable;
use rustc::ty::maps::Providers;
use rustc::ty::util::{Representability, IntTypeExt};
use errors::{DiagnosticBuilder, DiagnosticId};
use require_c_abi_if_variadic;
use session::{CompileIncomplete, Session};
use session::{CompileIncomplete, config, Session};
use TypeAndSubsts;
use lint;
use util::common::{ErrorReported, indenter};
@ -115,6 +116,7 @@ use std::collections::hash_map::Entry;
use std::cmp;
use std::fmt::Display;
use std::mem::replace;
use std::iter;
use std::ops::{self, Deref};
use syntax::abi::Abi;
use syntax::ast;
@ -1064,6 +1066,24 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
}
fcx.demand_suptype(span, ret_ty, actual_return_ty);
if let Some((id, _)) = *fcx.tcx.sess.entry_fn.borrow() {
if id == fn_id {
match fcx.sess().entry_type.get() {
Some(config::EntryMain) => {
let term_id = fcx.tcx.require_lang_item(TerminationTraitLangItem);
let substs = fcx.tcx.mk_substs(iter::once(Kind::from(ret_ty)));
let trait_ref = ty::TraitRef::new(term_id, substs);
let cause = traits::ObligationCause::new(span, fn_id,
ObligationCauseCode::MainFunctionType);
inherited.register_predicate(
traits::Obligation::new(cause, param_env, trait_ref.to_predicate()));
},
_ => {},
}
}
}
(fcx, gen_ty)
}

View file

@ -115,7 +115,6 @@ use syntax::ast;
use syntax::abi::Abi;
use syntax_pos::Span;
use std::iter;
// NB: This module needs to be declared first so diagnostics are
// registered before they are used.
mod diagnostics;
@ -200,21 +199,6 @@ fn check_main_fn_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
}
_ => ()
}
let se_ty = tcx.mk_fn_ptr(ty::Binder(
tcx.mk_fn_sig(
iter::empty(),
tcx.mk_nil(),
false,
hir::Unsafety::Normal,
Abi::Rust
)
));
require_same_types(
tcx,
&ObligationCause::new(main_span, main_id, ObligationCauseCode::MainFunctionType),
se_ty,
tcx.mk_fn_ptr(tcx.fn_sig(main_def_id)));
}
_ => {
span_bug!(main_span,

View file

@ -308,6 +308,7 @@
#![feature(str_char)]
#![feature(str_internals)]
#![feature(str_utf16)]
#![feature(termination_trait)]
#![feature(test, rustc_private)]
#![feature(thread_local)]
#![feature(toowned_clone_into)]
@ -499,6 +500,11 @@ mod memchr;
// The runtime entry point and a few unstable public functions used by the
// compiler
pub mod rt;
// The trait to support returning arbitrary types in the main function
mod termination;
#[unstable(feature = "termination_trait", issue = "0")]
pub use self::termination::Termination;
// Include a number of private modules that exist solely to provide
// the rustdoc documentation for primitive types. Using `include!`

View file

@ -26,7 +26,50 @@
// Reexport some of our utilities which are expected by other crates.
pub use panicking::{begin_panic, begin_panic_fmt, update_panic_count};
#[cfg(not(test))]
#[cfg(not(any(test, stage0)))]
#[lang = "start"]
fn lang_start<T: ::termination::Termination + 'static>
(main: fn() -> T, argc: isize, argv: *const *const u8) -> !
{
use panic;
use sys;
use sys_common;
use sys_common::thread_info;
use thread::Thread;
use process;
#[cfg(not(feature = "backtrace"))]
use mem;
sys::init();
process::exit(unsafe {
let main_guard = sys::thread::guard::init();
sys::stack_overflow::init();
// Next, set up the current Thread with the guard information we just
// created. Note that this isn't necessary in general for new threads,
// but we just do this to name the main thread and to give it correct
// info about the stack bounds.
let thread = Thread::new(Some("main".to_owned()));
thread_info::set(main_guard, thread);
// Store our args if necessary in a squirreled away location
sys::args::init(argc, argv);
// Let's run some code!
#[cfg(feature = "backtrace")]
let exit_code = panic::catch_unwind(|| {
::sys_common::backtrace::__rust_begin_short_backtrace(move || main().report())
});
#[cfg(not(feature = "backtrace"))]
let exit_code = panic::catch_unwind(mem::transmute::<_, fn()>(main).report());
sys_common::cleanup();
exit_code.unwrap_or(101)
});
}
#[cfg(all(not(test), stage0))]
#[lang = "start"]
fn lang_start(main: fn(), argc: isize, argv: *const *const u8) -> isize {
use panic;

74
src/libstd/termination.rs Normal file
View file

@ -0,0 +1,74 @@
// Copyright 2017 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 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use error::Error;
use libc;
/// A trait for implementing arbitrary return types in the `main` function.
///
/// The c-main function only supports to return integers as return type.
/// So, every type implementing the `Termination` trait has to be converted
/// to an integer.
///
/// The default implementations are returning `libc::EXIT_SUCCESS` to indicate
/// a successful execution. In case of a failure, `libc::EXIT_FAILURE` is returned.
#[cfg_attr(not(stage0), lang = "termination")]
#[unstable(feature = "termination_trait", issue = "0")]
pub trait Termination {
/// Is called to get the representation of the value as status code.
/// This status code is returned to the operating system.
fn report(self) -> i32;
}
#[unstable(feature = "termination_trait", issue = "0")]
impl Termination for () {
fn report(self) -> i32 { libc::EXIT_SUCCESS }
}
#[unstable(feature = "termination_trait", issue = "0")]
impl<T: Termination, E: Error> Termination for Result<T, E> {
fn report(self) -> i32 {
match self {
Ok(val) => val.report(),
Err(err) => {
print_error(err);
libc::EXIT_FAILURE
}
}
}
}
#[unstable(feature = "termination_trait", issue = "0")]
fn print_error<E: Error>(err: E) {
eprintln!("Error: {}", err.description());
if let Some(ref err) = err.cause() {
eprintln!("Caused by: {}", err.description());
}
}
#[unstable(feature = "termination_trait", issue = "0")]
impl Termination for ! {
fn report(self) -> i32 { unreachable!(); }
}
#[unstable(feature = "termination_trait", issue = "0")]
impl Termination for bool {
fn report(self) -> i32 {
if self { libc::EXIT_SUCCESS } else { libc::EXIT_FAILURE }
}
}
#[unstable(feature = "termination_trait", issue = "0")]
impl Termination for i32 {
fn report(self) -> i32 {
self
}
}

View file

@ -0,0 +1,15 @@
// Copyright 2017 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 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
struct ReturnType {}
fn main() -> ReturnType { //~ ERROR `ReturnType: std::Termination` is not satisfied
ReturnType {}
}

View file

@ -0,0 +1,13 @@
// Copyright 2017 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 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(termination_trait)]
fn main() {}

View file

@ -0,0 +1,15 @@
// Copyright 2017 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 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(termination_trait)]
fn main() -> i32 {
0
}

View file

@ -0,0 +1,17 @@
// Copyright 2017 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 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(termination_trait)]
use std::io::Error;
fn main() -> Result<(), Error> {
Ok(())
}