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Auto merge of #97802 - Enselic:add-no_ignore_sigkill-feature, r=joshtriplett

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Support `#[unix_sigpipe = "inherit|sig_dfl"]` on `fn main()` to prevent ignoring `SIGPIPE`

When enabled, programs don't have to explicitly handle `ErrorKind::BrokenPipe` any longer. Currently, the program

```rust
fn main() { loop { println!("hello world"); } }
```

will print an error if used with a short-lived pipe, e.g.

    % ./main | head -n 1
    hello world
    thread 'main' panicked at 'failed printing to stdout: Broken pipe (os error 32)', library/std/src/io/stdio.rs:1016:9
    note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

by enabling `#[unix_sigpipe = "sig_dfl"]` like this

```rust
#![feature(unix_sigpipe)]
#[unix_sigpipe = "sig_dfl"]
fn main() { loop { println!("hello world"); } }
```

there is no error, because `SIGPIPE` will not be ignored and thus the program will be killed appropriately:

    % ./main | head -n 1
    hello world

The current libstd behaviour of ignoring `SIGPIPE` before `fn main()` can be explicitly requested by using `#[unix_sigpipe = "sig_ign"]`.

With `#[unix_sigpipe = "inherit"]`, no change at all is made to `SIGPIPE`, which typically means the behaviour will be the same as `#[unix_sigpipe = "sig_dfl"]`.

See https://github.com/rust-lang/rust/issues/62569 and referenced issues for discussions regarding the `SIGPIPE` problem itself

See the [this](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Proposal.3A.20First.20step.20towards.20solving.20the.20SIGPIPE.20problem) Zulip topic for more discussions, including about this PR.

Tracking issue: https://github.com/rust-lang/rust/issues/97889
This commit is contained in:
bors 2022-09-02 21:08:08 +00:00
commit b8169a6da0
1 changed files with 9 additions and 6 deletions
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15
src/main_shim.rs
View File

@ -1,7 +1,7 @@
use rustc_hir::LangItem;
use rustc_middle::ty::subst::GenericArg;
use rustc_middle::ty::AssocKind;
use rustc_session::config::EntryFnType;
use rustc_session::config::{sigpipe, EntryFnType};
use rustc_span::symbol::Ident;
use crate::prelude::*;
@ -15,12 +15,12 @@ pub(crate) fn maybe_create_entry_wrapper(
is_jit: bool,
is_primary_cgu: bool,
) {
let (main_def_id, is_main_fn) = match tcx.entry_fn(()) {
let (main_def_id, (is_main_fn, sigpipe)) = match tcx.entry_fn(()) {
Some((def_id, entry_ty)) => (
def_id,
match entry_ty {
EntryFnType::Main => true,
EntryFnType::Start => false,
EntryFnType::Main { sigpipe } => (true, sigpipe),
EntryFnType::Start => (false, sigpipe::DEFAULT),
},
),
None => return,
@ -35,7 +35,7 @@ pub(crate) fn maybe_create_entry_wrapper(
return;
}
create_entry_fn(tcx, module, unwind_context, main_def_id, is_jit, is_main_fn);
create_entry_fn(tcx, module, unwind_context, main_def_id, is_jit, is_main_fn, sigpipe);
fn create_entry_fn(
tcx: TyCtxt<'_>,
@ -44,6 +44,7 @@ pub(crate) fn maybe_create_entry_wrapper(
rust_main_def_id: DefId,
ignore_lang_start_wrapper: bool,
is_main_fn: bool,
sigpipe: u8,
) {
let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
// Given that `main()` has no arguments,
@ -83,6 +84,7 @@ pub(crate) fn maybe_create_entry_wrapper(
bcx.switch_to_block(block);
let arg_argc = bcx.append_block_param(block, m.target_config().pointer_type());
let arg_argv = bcx.append_block_param(block, m.target_config().pointer_type());
let arg_sigpipe = bcx.ins().iconst(types::I8, sigpipe as i64);
let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
@ -143,7 +145,8 @@ pub(crate) fn maybe_create_entry_wrapper(
let main_val = bcx.ins().func_addr(m.target_config().pointer_type(), main_func_ref);
let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
let call_inst = bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv]);
let call_inst =
bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv, arg_sigpipe]);
bcx.inst_results(call_inst)[0]
} else {
// using user-defined start fn