Stabilize #[unix_sigpipe = "sig_dfl"] on fn main()

The attribute is used like this:

    #[unix_sigpipe = "sig_dfl"]
    fn main() {
        // ...
    }

When used, `SIGPIPE` will be set to `SIG_DFL` before `fn main()` is
invoked, rather than being set to `SIG_IGN` which is the default.

This commit does NOT stabilize `#[unix_sigpipe = "sig_ign"]` or
`#[unix_sigpipe = "inherit"]`.

See the PR for more info.

Author: Enselic

compiler/rustc/src/main.rs

@@ -1,4 +1,4 @@
-#![feature(unix_sigpipe)]
+#![cfg_attr(bootstrap, 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]`

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -200,6 +200,21 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 );
             }
         }
+        // Check unstable flavors of the `#[unix_sigpipe]` attribute.
+        if attr.has_name(sym::unix_sigpipe)
+            && let Some(value) = attr.value_str()
+            && (value == sym::sig_ign || value == sym::inherit)
+        {
+            gate!(
+                self,
+                unix_sigpipe,
+                attr.span,
+                format!(
+                    "the `#[unix_sigpipe = \"{}\"]` attribute is an experimental feature",
+                    value.as_str()
+                )
+            );
+        }
         if !attr.is_doc_comment()
             && let [seg, _] = attr.get_normal_item().path.segments.as_slice()
             && seg.ident.name == sym::diagnostic

compiler/rustc_feature/src/builtin_attrs.rs

@@ -364,7 +364,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ),
 
     // Entry point:
-    gated!(unix_sigpipe, Normal, template!(Word, NameValueStr: "inherit|sig_ign|sig_dfl"), ErrorFollowing, experimental!(unix_sigpipe)),
+    ungated!(unix_sigpipe, Normal, template!(Word, NameValueStr: "inherit|sig_ign|sig_dfl"), ErrorFollowing),
     ungated!(start, Normal, template!(Word), WarnFollowing),
     ungated!(no_start, CrateLevel, template!(Word), WarnFollowing),
     ungated!(no_main, CrateLevel, template!(Word), WarnFollowing),

compiler/rustc_passes/messages.ftl

@@ -692,7 +692,7 @@ 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`
+    the only valid variant of the `unix_sigpipe` attribute is `#[unix_sigpipe = "sig_dfl"]`
 
 passes_unknown_external_lang_item =
     unknown external lang item: `{$lang_item}`

src/tools/rustdoc/main.rs

@@ -1,4 +1,4 @@
-#![feature(unix_sigpipe)]
+#![cfg_attr(bootstrap, feature(unix_sigpipe))]
 
 #[unix_sigpipe = "sig_dfl"]
 fn main() {

tests/ui/attributes/unix_sigpipe/unix_sigpipe-bare.rs

@@ -1,4 +1,6 @@
-#![feature(unix_sigpipe)]
+// revisions: with_feature without_feature
 
-#[unix_sigpipe] //~ error: valid values for `#[unix_sigpipe = "..."]` are `inherit`, `sig_ign`, or `sig_dfl`
+#![cfg_attr(with_feature, feature(unix_sigpipe))]
+
+#[unix_sigpipe] //~ error: the only valid variant of the `unix_sigpipe` attribute is `#[unix_sigpipe = "sig_dfl"]
 fn main() {}

tests/ui/attributes/unix_sigpipe/unix_sigpipe-bare.stderr

@@ -0,0 +1,8 @@
+error: the only valid variant of the `unix_sigpipe` attribute is `#[unix_sigpipe = "sig_dfl"]`
+  --> $DIR/unix_sigpipe-bare.rs:5:1
+   |
+LL | #[unix_sigpipe]
+   | ^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/attributes/unix_sigpipe/unix_sigpipe-bare.with_feature.stderr

@@ -0,0 +1,8 @@
+error: the only valid variant of the `unix_sigpipe` attribute is `#[unix_sigpipe = "sig_dfl"]`
+  --> $DIR/unix_sigpipe-bare.rs:5:1
+   |
+LL | #[unix_sigpipe]
+   | ^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/attributes/unix_sigpipe/unix_sigpipe-bare.without_feature.stderr

@@ -1,4 +1,6 @@
-#![feature(unix_sigpipe)]
+// revisions: with_feature without_feature
+
+#![cfg_attr(with_feature, feature(unix_sigpipe))]
 #![unix_sigpipe = "sig_dfl"] //~ error: `unix_sigpipe` attribute cannot be used at crate level
 
 fn main() {}