Rollup of 9 pull requests

compiler/rustc_driver/src/lib.rs

@@ -895,7 +895,12 @@ Available lint options:
     let print_lints = |lints: Vec<&Lint>| {
         for lint in lints {
             let name = lint.name_lower().replace("_", "-");
-            println!("    {}  {:7.7}  {}", padded(&name), lint.default_level.as_str(), lint.desc);
+            println!(
+                "    {}  {:7.7}  {}",
+                padded(&name),
+                lint.default_level(sess.edition()).as_str(),
+                lint.desc
+            );
         }
         println!("\n");
     };

compiler/rustc_incremental/src/assert_dep_graph.rs

@@ -57,6 +57,10 @@ pub fn assert_dep_graph(tcx: TyCtxt<'_>) {
             dump_graph(tcx);
         }
 
+        if !tcx.sess.opts.debugging_opts.query_dep_graph {
+            return;
+        }
+
         // if the `rustc_attrs` feature is not enabled, then the
         // attributes we are interested in cannot be present anyway, so
         // skip the walk.

compiler/rustc_incremental/src/persist/dirty_clean.rs

@@ -148,6 +148,10 @@ impl Assertion {
 }
 
 pub fn check_dirty_clean_annotations(tcx: TyCtxt<'_>) {
+    if !tcx.sess.opts.debugging_opts.query_dep_graph {
+        return;
+    }
+
     // can't add `#[rustc_dirty]` etc without opting in to this feature
     if !tcx.features().rustc_attrs {
         return;

compiler/rustc_passes/src/check_attr.rs

@@ -99,6 +99,12 @@ impl CheckAttrVisitor<'tcx> {
                 self.check_naked(hir_id, attr, span, target)
             } else if self.tcx.sess.check_name(attr, sym::rustc_legacy_const_generics) {
                 self.check_rustc_legacy_const_generics(&attr, span, target, item)
+            } else if self.tcx.sess.check_name(attr, sym::rustc_clean)
+                || self.tcx.sess.check_name(attr, sym::rustc_dirty)
+                || self.tcx.sess.check_name(attr, sym::rustc_if_this_changed)
+                || self.tcx.sess.check_name(attr, sym::rustc_then_this_would_need)
+            {
+                self.check_rustc_dirty_clean(&attr)
             } else {
                 // lint-only checks
                 if self.tcx.sess.check_name(attr, sym::cold) {
@@ -1012,6 +1018,20 @@ impl CheckAttrVisitor<'tcx> {
         }
     }
 
+    /// Checks that the dep-graph debugging attributes are only present when the query-dep-graph
+    /// option is passed to the compiler.
+    fn check_rustc_dirty_clean(&self, attr: &Attribute) -> bool {
+        if self.tcx.sess.opts.debugging_opts.query_dep_graph {
+            true
+        } else {
+            self.tcx
+                .sess
+                .struct_span_err(attr.span, "attribute requires -Z query-dep-graph to be enabled")
+                .emit();
+            false
+        }
+    }
+
     /// Checks if `#[link_section]` is applied to a function or static.
     fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
         match target {

compiler/rustc_session/src/session.rs

@@ -863,7 +863,7 @@ impl Session {
         } else if self.target.requires_uwtable {
             true
         } else {
-            self.opts.cg.force_unwind_tables.unwrap_or(false)
+            self.opts.cg.force_unwind_tables.unwrap_or(self.target.default_uwtable)
         }
     }
 

compiler/rustc_target/src/spec/android_base.rs

@@ -12,7 +12,10 @@ pub fn opts() -> TargetOptions {
     base.dwarf_version = Some(2);
     base.position_independent_executables = true;
     base.has_elf_tls = false;
-    base.requires_uwtable = true;
+    // This is for backward compatibility, see https://github.com/rust-lang/rust/issues/49867
+    // for context. (At that time, there was no `-C force-unwind-tables`, so the only solution
+    // was to always emit `uwtable`).
+    base.default_uwtable = true;
     base.crt_static_respected = false;
     base
 }

compiler/rustc_target/src/spec/mod.rs

@@ -1111,6 +1111,10 @@ pub struct TargetOptions {
     /// unwinders.
     pub requires_uwtable: bool,
 
+    /// Whether or not to emit `uwtable` attributes on functions if `-C force-unwind-tables`
+    /// is not specified and `uwtable` is not required on this target.
+    pub default_uwtable: bool,
+
     /// Whether or not SIMD types are passed by reference in the Rust ABI,
     /// typically required if a target can be compiled with a mixed set of
     /// target features. This is `true` by default, and `false` for targets like
@@ -1248,6 +1252,7 @@ impl Default for TargetOptions {
             default_hidden_visibility: false,
             emit_debug_gdb_scripts: true,
             requires_uwtable: false,
+            default_uwtable: false,
             simd_types_indirect: true,
             limit_rdylib_exports: true,
             override_export_symbols: None,
@@ -1711,6 +1716,7 @@ impl Target {
         key!(default_hidden_visibility, bool);
         key!(emit_debug_gdb_scripts, bool);
         key!(requires_uwtable, bool);
+        key!(default_uwtable, bool);
         key!(simd_types_indirect, bool);
         key!(limit_rdylib_exports, bool);
         key!(override_export_symbols, opt_list);
@@ -1947,6 +1953,7 @@ impl ToJson for Target {
         target_option_val!(default_hidden_visibility);
         target_option_val!(emit_debug_gdb_scripts);
         target_option_val!(requires_uwtable);
+        target_option_val!(default_uwtable);
         target_option_val!(simd_types_indirect);
         target_option_val!(limit_rdylib_exports);
         target_option_val!(override_export_symbols);

library/std/src/ffi/c_str.rs

@@ -1036,7 +1036,7 @@ impl fmt::Display for NulError {
 impl From<NulError> for io::Error {
     /// Converts a [`NulError`] into a [`io::Error`].
     fn from(_: NulError) -> io::Error {
-        io::Error::new(io::ErrorKind::InvalidInput, "data provided contains a nul byte")
+        io::Error::new_const(io::ErrorKind::InvalidInput, &"data provided contains a nul byte")
     }
 }
 

library/std/src/fs.rs

@@ -2188,7 +2188,10 @@ impl DirBuilder {
         match path.parent() {
             Some(p) => self.create_dir_all(p)?,
             None => {
-                return Err(io::Error::new(io::ErrorKind::Other, "failed to create whole tree"));
+                return Err(io::Error::new_const(
+                    io::ErrorKind::Other,
+                    &"failed to create whole tree",
+                ));
             }
         }
         match self.inner.mkdir(path) {

library/std/src/io/buffered/bufwriter.rs

@@ -164,9 +164,9 @@ impl<W: Write> BufWriter<W> {
 
             match r {
                 Ok(0) => {
-                    return Err(Error::new(
+                    return Err(Error::new_const(
                         ErrorKind::WriteZero,
-                        "failed to write the buffered data",
+                        &"failed to write the buffered data",
                     ));
                 }
                 Ok(n) => guard.consume(n),

library/std/src/io/cursor.rs

@@ -229,9 +229,9 @@ where
                 self.pos = n;
                 Ok(self.pos)
             }
-            None => Err(Error::new(
+            None => Err(Error::new_const(
                 ErrorKind::InvalidInput,
-                "invalid seek to a negative or overflowing position",
+                &"invalid seek to a negative or overflowing position",
             )),
         }
     }
@@ -328,9 +328,9 @@ fn slice_write_vectored(
 // Resizing write implementation
 fn vec_write(pos_mut: &mut u64, vec: &mut Vec<u8>, buf: &[u8]) -> io::Result<usize> {
     let pos: usize = (*pos_mut).try_into().map_err(|_| {
-        Error::new(
+        Error::new_const(
             ErrorKind::InvalidInput,
-            "cursor position exceeds maximum possible vector length",
+            &"cursor position exceeds maximum possible vector length",
         )
     })?;
     // Make sure the internal buffer is as least as big as where we

library/std/src/io/error.rs

@@ -69,6 +69,8 @@ impl fmt::Debug for Error {
 enum Repr {
     Os(i32),
     Simple(ErrorKind),
+    // &str is a fat pointer, but &&str is a thin pointer.
+    SimpleMessage(ErrorKind, &'static &'static str),
     Custom(Box<Custom>),
 }
 
@@ -259,6 +261,18 @@ impl Error {
         Error { repr: Repr::Custom(Box::new(Custom { kind, error })) }
     }
 
+    /// Creates a new I/O error from a known kind of error as well as a
+    /// constant message.
+    ///
+    /// This function does not allocate.
+    ///
+    /// This function should maybe change to
+    /// `new_const<const MSG: &'static str>(kind: ErrorKind)`
+    /// in the future, when const generics allow that.
+    pub(crate) const fn new_const(kind: ErrorKind, message: &'static &'static str) -> Error {
+        Self { repr: Repr::SimpleMessage(kind, message) }
+    }
+
     /// Returns an error representing the last OS error which occurred.
     ///
     /// This function reads the value of `errno` for the target platform (e.g.
@@ -342,6 +356,7 @@ impl Error {
             Repr::Os(i) => Some(i),
             Repr::Custom(..) => None,
             Repr::Simple(..) => None,
+            Repr::SimpleMessage(..) => None,
         }
     }
 
@@ -377,6 +392,7 @@ impl Error {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
+            Repr::SimpleMessage(..) => None,
             Repr::Custom(ref c) => Some(&*c.error),
         }
     }
@@ -448,6 +464,7 @@ impl Error {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
+            Repr::SimpleMessage(..) => None,
             Repr::Custom(ref mut c) => Some(&mut *c.error),
         }
     }
@@ -484,6 +501,7 @@ impl Error {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
+            Repr::SimpleMessage(..) => None,
             Repr::Custom(c) => Some(c.error),
         }
     }
@@ -512,6 +530,7 @@ impl Error {
             Repr::Os(code) => sys::decode_error_kind(code),
             Repr::Custom(ref c) => c.kind,
             Repr::Simple(kind) => kind,
+            Repr::SimpleMessage(kind, _) => kind,
         }
     }
 }
@@ -527,6 +546,9 @@ impl fmt::Debug for Repr {
                 .finish(),
             Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
             Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
+            Repr::SimpleMessage(kind, &message) => {
+                fmt.debug_struct("Error").field("kind", &kind).field("message", &message).finish()
+            }
         }
     }
 }
@@ -541,6 +563,7 @@ impl fmt::Display for Error {
             }
             Repr::Custom(ref c) => c.error.fmt(fmt),
             Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
+            Repr::SimpleMessage(_, &msg) => msg.fmt(fmt),
         }
     }
 }
@@ -551,6 +574,7 @@ impl error::Error for Error {
     fn description(&self) -> &str {
         match self.repr {
             Repr::Os(..) | Repr::Simple(..) => self.kind().as_str(),
+            Repr::SimpleMessage(_, &msg) => msg,
             Repr::Custom(ref c) => c.error.description(),
         }
     }
@@ -560,6 +584,7 @@ impl error::Error for Error {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
+            Repr::SimpleMessage(..) => None,
             Repr::Custom(ref c) => c.error.cause(),
         }
     }
@@ -568,6 +593,7 @@ impl error::Error for Error {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
+            Repr::SimpleMessage(..) => None,
             Repr::Custom(ref c) => c.error.source(),
         }
     }

library/std/src/io/error/tests.rs

@@ -1,9 +1,15 @@
 use super::{Custom, Error, ErrorKind, Repr};
 use crate::error;
 use crate::fmt;
+use crate::mem::size_of;
 use crate::sys::decode_error_kind;
 use crate::sys::os::error_string;
 
+#[test]
+fn test_size() {
+    assert!(size_of::<Error>() <= size_of::<[usize; 2]>());
+}
+
 #[test]
 fn test_debug_error() {
     let code = 6;
@@ -51,3 +57,13 @@ fn test_downcasting() {
     let extracted = err.into_inner().unwrap();
     extracted.downcast::<TestError>().unwrap();
 }
+
+#[test]
+fn test_const() {
+    const E: Error = Error::new_const(ErrorKind::NotFound, &"hello");
+
+    assert_eq!(E.kind(), ErrorKind::NotFound);
+    assert_eq!(E.to_string(), "hello");
+    assert!(format!("{:?}", E).contains("\"hello\""));
+    assert!(format!("{:?}", E).contains("NotFound"));
+}

library/std/src/io/impls.rs

@@ -263,7 +263,7 @@ impl Read for &[u8] {
     #[inline]
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         if buf.len() > self.len() {
-            return Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer"));
+            return Err(Error::new_const(ErrorKind::UnexpectedEof, &"failed to fill whole buffer"));
         }
         let (a, b) = self.split_at(buf.len());
 
@@ -345,7 +345,7 @@ impl Write for &mut [u8] {
         if self.write(data)? == data.len() {
             Ok(())
         } else {
-            Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer"))
+            Err(Error::new_const(ErrorKind::WriteZero, &"failed to write whole buffer"))
         }
     }
 

library/std/src/io/mod.rs

@@ -333,7 +333,7 @@ where
         let ret = f(g.buf);
         if str::from_utf8(&g.buf[g.len..]).is_err() {
             ret.and_then(|_| {
-                Err(Error::new(ErrorKind::InvalidData, "stream did not contain valid UTF-8"))
+                Err(Error::new_const(ErrorKind::InvalidData, &"stream did not contain valid UTF-8"))
             })
         } else {
             g.len = g.buf.len();
@@ -429,7 +429,7 @@ pub(crate) fn default_read_exact<R: Read + ?Sized>(this: &mut R, mut buf: &mut [
         }
     }
     if !buf.is_empty() {
-        Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer"))
+        Err(Error::new_const(ErrorKind::UnexpectedEof, &"failed to fill whole buffer"))
     } else {
         Ok(())
     }
@@ -1437,7 +1437,10 @@ pub trait Write {
         while !buf.is_empty() {
             match self.write(buf) {
                 Ok(0) => {
-                    return Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer"));
+                    return Err(Error::new_const(
+                        ErrorKind::WriteZero,
+                        &"failed to write whole buffer",
+                    ));
                 }
                 Ok(n) => buf = &buf[n..],
                 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
@@ -1502,7 +1505,10 @@ pub trait Write {
         while !bufs.is_empty() {
             match self.write_vectored(bufs) {
                 Ok(0) => {
-                    return Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer"));
+                    return Err(Error::new_const(
+                        ErrorKind::WriteZero,
+                        &"failed to write whole buffer",
+                    ));
                 }
                 Ok(n) => bufs = IoSlice::advance(bufs, n),
                 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
@@ -1576,7 +1582,7 @@ pub trait Write {
                 if output.error.is_err() {
                     output.error
                 } else {
-                    Err(Error::new(ErrorKind::Other, "formatter error"))
+                    Err(Error::new_const(ErrorKind::Other, &"formatter error"))
                 }
             }
         }