Change SIGPIPE ui from #[unix_sigpipe = "..."] to -Zon-broken-pipe=...

In the stabilization attempt of `#[unix_sigpipe = "sig_dfl"]`, a concern
was raised related to using a language attribute for the feature: Long
term, we want `fn lang_start()` to be definable by any crate, not just
libstd. Having a special language attribute in that case becomes
awkward.

So as a first step towards stabilization, this PR changes the
`#[unix_sigpipe = "..."]` attribute to a compiler flag
`-Zon-broken-pipe=...`, to remove that concern, since now the language
is not "contaminated" by this feature.

Author: Enselic

compiler/rustc/src/main.rs

@@ -1,5 +1,3 @@
-#![feature(unix_sigpipe)]
-
 // A note about jemalloc: rustc uses jemalloc when built for CI and
 // distribution. The obvious way to do this is with the `#[global_allocator]`
 // mechanism. However, for complicated reasons (see
@@ -34,7 +32,6 @@
 // https://github.com/rust-lang/rust/commit/b90cfc887c31c3e7a9e6d462e2464db1fe506175#diff-43914724af6e464c1da2171e4a9b6c7e607d5bc1203fa95c0ab85be4122605ef
 // for an example of how to do so.
 
-#[unix_sigpipe = "sig_dfl"]
 fn main() {
     // See the comment at the top of this file for an explanation of this.
     #[cfg(feature = "jemalloc-sys")]

compiler/rustc_feature/src/builtin_attrs.rs

@@ -396,10 +396,6 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ),
 
     // Entry point:
-    gated!(
-        unix_sigpipe, Normal, template!(NameValueStr: "inherit|sig_ign|sig_dfl"), ErrorFollowing,
-        EncodeCrossCrate::Yes, experimental!(unix_sigpipe)
-    ),
     ungated!(start, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
     ungated!(no_start, CrateLevel, template!(Word), WarnFollowing, EncodeCrossCrate::No),
     ungated!(no_main, CrateLevel, template!(Word), WarnFollowing, EncodeCrossCrate::No),

compiler/rustc_feature/src/unstable.rs

@@ -619,8 +619,6 @@ declare_features! (
     /// Allows creation of instances of a struct by moving fields that have
     /// not changed from prior instances of the same struct (RFC #2528)
     (unstable, type_changing_struct_update, "1.58.0", Some(86555)),
-    /// Enables rustc to generate code that instructs libstd to NOT ignore SIGPIPE.
-    (unstable, unix_sigpipe, "1.65.0", Some(97889)),
     /// Allows unnamed fields of struct and union type
     (incomplete, unnamed_fields, "1.74.0", Some(49804)),
     /// Allows unsized fn parameters.

compiler/rustc_interface/src/tests.rs

@@ -20,7 +20,7 @@ use rustc_span::source_map::{RealFileLoader, SourceMapInputs};
 use rustc_span::symbol::sym;
 use rustc_span::{FileName, SourceFileHashAlgorithm};
 use rustc_target::spec::{
-    CodeModel, LinkerFlavorCli, MergeFunctions, PanicStrategy, RelocModel, WasmCAbi,
+    CodeModel, LinkerFlavorCli, MergeFunctions, OnBrokenPipe, PanicStrategy, RelocModel, WasmCAbi,
 };
 use rustc_target::spec::{RelroLevel, SanitizerSet, SplitDebuginfo, StackProtector, TlsModel};
 use std::collections::{BTreeMap, BTreeSet};
@@ -809,6 +809,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(no_profiler_runtime, true);
     tracked!(no_trait_vptr, true);
     tracked!(no_unique_section_names, true);
+    tracked!(on_broken_pipe, OnBrokenPipe::Default);
     tracked!(oom, OomStrategy::Panic);
     tracked!(osx_rpath_install_name, true);
     tracked!(packed_bundled_libs, true);

compiler/rustc_passes/messages.ftl

@@ -695,9 +695,6 @@ passes_transparent_incompatible =
 passes_undefined_naked_function_abi =
     Rust ABI is unsupported in naked functions
 
-passes_unix_sigpipe_values =
-    valid values for `#[unix_sigpipe = "..."]` are `inherit`, `sig_ign`, or `sig_dfl`
-
 passes_unknown_external_lang_item =
     unknown external lang item: `{$lang_item}`
 

compiler/rustc_passes/src/check_attr.rs

@@ -2522,7 +2522,6 @@ fn check_invalid_crate_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
         sym::automatically_derived,
         sym::start,
         sym::rustc_main,
-        sym::unix_sigpipe,
         sym::derive,
         sym::test,
         sym::test_case,

compiler/rustc_passes/src/entry.rs

@@ -12,8 +12,7 @@ use rustc_span::symbol::sym;
 use rustc_span::{Span, Symbol};
 
 use crate::errors::{
-    AttrOnlyInFunctions, AttrOnlyOnMain, AttrOnlyOnRootMain, ExternMain, MultipleRustcMain,
-    MultipleStartFunctions, NoMainErr, UnixSigpipeValues,
+    AttrOnlyInFunctions, ExternMain, MultipleRustcMain, MultipleStartFunctions, NoMainErr,
 };
 
 struct EntryContext<'tcx> {
@@ -67,11 +66,6 @@ fn find_item(id: ItemId, ctxt: &mut EntryContext<'_>) {
         ctxt.tcx.opt_item_name(id.owner_id.to_def_id()),
     );
     match entry_point_type {
-        EntryPointType::None => {
-            if let Some(span) = attr_span_by_symbol(ctxt, id, sym::unix_sigpipe) {
-                ctxt.tcx.dcx().emit_err(AttrOnlyOnMain { span, attr: sym::unix_sigpipe });
-            }
-        }
         _ if !matches!(ctxt.tcx.def_kind(id.owner_id), DefKind::Fn) => {
             for attr in [sym::start, sym::rustc_main] {
                 if let Some(span) = attr_span_by_symbol(ctxt, id, attr) {
@@ -81,9 +75,6 @@ fn find_item(id: ItemId, ctxt: &mut EntryContext<'_>) {
         }
         EntryPointType::MainNamed => (),
         EntryPointType::OtherMain => {
-            if let Some(span) = attr_span_by_symbol(ctxt, id, sym::unix_sigpipe) {
-                ctxt.tcx.dcx().emit_err(AttrOnlyOnRootMain { span, attr: sym::unix_sigpipe });
-            }
             ctxt.non_main_fns.push(ctxt.tcx.def_span(id.owner_id));
         }
         EntryPointType::RustcMainAttr => {
@@ -98,9 +89,6 @@ fn find_item(id: ItemId, ctxt: &mut EntryContext<'_>) {
             }
         }
         EntryPointType::Start => {
-            if let Some(span) = attr_span_by_symbol(ctxt, id, sym::unix_sigpipe) {
-                ctxt.tcx.dcx().emit_err(AttrOnlyOnMain { span, attr: sym::unix_sigpipe });
-            }
             if ctxt.start_fn.is_none() {
                 ctxt.start_fn = Some((id.owner_id.def_id, ctxt.tcx.def_span(id.owner_id)));
             } else {
@@ -111,6 +99,7 @@ fn find_item(id: ItemId, ctxt: &mut EntryContext<'_>) {
                 });
             }
         }
+        _ => (),
     }
 }
 
@@ -120,7 +109,7 @@ fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) -> Option<(DefId,
         Some((def_id.to_def_id(), EntryFnType::Start))
     } else if let Some((local_def_id, _)) = visitor.attr_main_fn {
         let def_id = local_def_id.to_def_id();
-        Some((def_id, EntryFnType::Main { sigpipe: sigpipe(tcx, def_id) }))
+        Some((def_id, EntryFnType::Main { sigpipe: sigpipe(tcx) }))
     } else {
         if let Some(main_def) = tcx.resolutions(()).main_def
             && let Some(def_id) = main_def.opt_fn_def_id()
@@ -133,31 +122,19 @@ fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) -> Option<(DefId,
                 return None;
             }
 
-            return Some((def_id, EntryFnType::Main { sigpipe: sigpipe(tcx, def_id) }));
+            return Some((def_id, EntryFnType::Main { sigpipe: sigpipe(tcx) }));
         }
         no_main_err(tcx, visitor);
         None
     }
 }
 
-fn sigpipe(tcx: TyCtxt<'_>, def_id: DefId) -> u8 {
-    if let Some(attr) = tcx.get_attr(def_id, sym::unix_sigpipe) {
-        match (attr.value_str(), attr.meta_item_list()) {
-            (Some(sym::inherit), None) => sigpipe::INHERIT,
-            (Some(sym::sig_ign), None) => sigpipe::SIG_IGN,
-            (Some(sym::sig_dfl), None) => sigpipe::SIG_DFL,
-            (Some(_), None) => {
-                tcx.dcx().emit_err(UnixSigpipeValues { span: attr.span });
-                sigpipe::DEFAULT
-            }
-            _ => {
-                // Keep going so that `fn emit_malformed_attribute()` can print
-                // an excellent error message
-                sigpipe::DEFAULT
-            }
-        }
-    } else {
-        sigpipe::DEFAULT
+fn sigpipe(tcx: TyCtxt<'_>) -> u8 {
+    match tcx.sess.opts.unstable_opts.on_broken_pipe {
+        rustc_target::spec::OnBrokenPipe::Default => sigpipe::DEFAULT,
+        rustc_target::spec::OnBrokenPipe::Kill => sigpipe::SIG_DFL,
+        rustc_target::spec::OnBrokenPipe::Error => sigpipe::SIG_IGN,
+        rustc_target::spec::OnBrokenPipe::Inherit => sigpipe::INHERIT,
     }
 }
 

compiler/rustc_passes/src/errors.rs

@@ -1259,13 +1259,6 @@ pub struct ExternMain {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(passes_unix_sigpipe_values)]
-pub struct UnixSigpipeValues {
-    #[primary_span]
-    pub span: Span,
-}
-
 pub struct NoMainErr {
     pub sp: Span,
     pub crate_name: Symbol,

compiler/rustc_session/src/config.rs

@@ -2891,7 +2891,9 @@ pub(crate) mod dep_tracking {
     use rustc_feature::UnstableFeatures;
     use rustc_span::edition::Edition;
     use rustc_span::RealFileName;
-    use rustc_target::spec::{CodeModel, MergeFunctions, PanicStrategy, RelocModel, WasmCAbi};
+    use rustc_target::spec::{
+        CodeModel, MergeFunctions, OnBrokenPipe, PanicStrategy, RelocModel, WasmCAbi,
+    };
     use rustc_target::spec::{
         RelroLevel, SanitizerSet, SplitDebuginfo, StackProtector, TargetTriple, TlsModel,
     };
@@ -2955,6 +2957,7 @@ pub(crate) mod dep_tracking {
         InstrumentXRay,
         CrateType,
         MergeFunctions,
+        OnBrokenPipe,
         PanicStrategy,
         RelroLevel,
         OptLevel,

compiler/rustc_session/src/config/sigpipe.rs

@@ -1,6 +1,6 @@
 //! NOTE: Keep these constants in sync with `library/std/src/sys/pal/unix/mod.rs`!
 
-/// The default value if `#[unix_sigpipe]` is not specified. This resolves
+/// The default value if `-Zon-broken-pipe=...` is not specified. This resolves
 /// to `SIG_IGN` in `library/std/src/sys/pal/unix/mod.rs`.
 ///
 /// Note that `SIG_IGN` has been the Rust default since 2014. See