Rollup of 6 pull requests

src/liballoc/sync.rs

@@ -867,12 +867,10 @@ impl<T: ?Sized> Arc<T> {
     unsafe fn drop_slow(&mut self) {
         // Destroy the data at this time, even though we may not free the box
         // allocation itself (there may still be weak pointers lying around).
-        ptr::drop_in_place(&mut self.ptr.as_mut().data);
+        ptr::drop_in_place(Self::get_mut_unchecked(self));
 
-        if self.inner().weak.fetch_sub(1, Release) == 1 {
-            acquire!(self.inner().weak);
-            Global.dealloc(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()))
-        }
+        // Drop the weak ref collectively held by all strong references
+        drop(Weak { ptr: self.ptr });
     }
 
     #[inline]
@@ -1204,7 +1202,7 @@ impl<T: Clone> Arc<T> {
 
         // As with `get_mut()`, the unsafety is ok because our reference was
         // either unique to begin with, or became one upon cloning the contents.
-        unsafe { &mut this.ptr.as_mut().data }
+        unsafe { Self::get_mut_unchecked(this) }
     }
 }
 
@@ -1280,7 +1278,9 @@ impl<T: ?Sized> Arc<T> {
     #[inline]
     #[unstable(feature = "get_mut_unchecked", issue = "63292")]
     pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {
-        &mut this.ptr.as_mut().data
+        // We are careful to *not* create a reference covering the "count" fields, as
+        // this would alias with concurrent access to the reference counts (e.g. by `Weak`).
+        &mut (*this.ptr.as_ptr()).data
     }
 
     /// Determine whether this is the unique reference (including weak refs) to
@@ -1571,6 +1571,13 @@ impl<T> Weak<T> {
     }
 }
 
+/// Helper type to allow accessing the reference counts without
+/// making any assertions about the data field.
+struct WeakInner<'a> {
+    weak: &'a atomic::AtomicUsize,
+    strong: &'a atomic::AtomicUsize,
+}
+
 impl<T: ?Sized> Weak<T> {
     /// Attempts to upgrade the `Weak` pointer to an [`Arc`], delaying
     /// dropping of the inner value if successful.
@@ -1678,8 +1685,18 @@ impl<T: ?Sized> Weak<T> {
     /// Returns `None` when the pointer is dangling and there is no allocated `ArcInner`,
     /// (i.e., when this `Weak` was created by `Weak::new`).
     #[inline]
-    fn inner(&self) -> Option<&ArcInner<T>> {
-        if is_dangling(self.ptr) { None } else { Some(unsafe { self.ptr.as_ref() }) }
+    fn inner(&self) -> Option<WeakInner<'_>> {
+        if is_dangling(self.ptr) {
+            None
+        } else {
+            // We are careful to *not* create a reference covering the "data" field, as
+            // the field may be mutated concurrently (for example, if the last `Arc`
+            // is dropped, the data field will be dropped in-place).
+            Some(unsafe {
+                let ptr = self.ptr.as_ptr();
+                WeakInner { strong: &(*ptr).strong, weak: &(*ptr).weak }
+            })
+        }
     }
 
     /// Returns `true` if the two `Weak`s point to the same allocation (similar to

src/librustc_ast_lowering/expr.rs

@@ -974,20 +974,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_expr_asm(&mut self, sp: Span, asm: &InlineAsm) -> hir::ExprKind<'hir> {
-        let asm_arch = if let Some(asm_arch) = self.sess.asm_arch {
-            asm_arch
-        } else {
+        if self.sess.asm_arch.is_none() {
             struct_span_err!(self.sess, sp, E0472, "asm! is unsupported on this target").emit();
-            return hir::ExprKind::Err;
-        };
-        if asm.options.contains(InlineAsmOptions::ATT_SYNTAX) {
-            match asm_arch {
-                asm::InlineAsmArch::X86 | asm::InlineAsmArch::X86_64 => {}
-                _ => self
-                    .sess
-                    .struct_span_err(sp, "the `att_syntax` option is only supported on x86")
-                    .emit(),
-            }
+        }
+        if asm.options.contains(InlineAsmOptions::ATT_SYNTAX)
+            && !matches!(
+                self.sess.asm_arch,
+                Some(asm::InlineAsmArch::X86 | asm::InlineAsmArch::X86_64)
+            )
+        {
+            self.sess
+                .struct_span_err(sp, "the `att_syntax` option is only supported on x86")
+                .emit();
         }
 
         // Lower operands to HIR, filter_map skips any operands with invalid
@@ -1001,10 +999,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     Some(match reg {
                         InlineAsmRegOrRegClass::Reg(s) => asm::InlineAsmRegOrRegClass::Reg(
                             asm::InlineAsmReg::parse(
-                                asm_arch,
-                                |feature| {
-                                    self.sess.target_features.contains(&Symbol::intern(feature))
-                                },
+                                sess.asm_arch?,
+                                |feature| sess.target_features.contains(&Symbol::intern(feature)),
                                 s,
                             )
                             .map_err(|e| {
@@ -1015,7 +1011,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         ),
                         InlineAsmRegOrRegClass::RegClass(s) => {
                             asm::InlineAsmRegOrRegClass::RegClass(
-                                asm::InlineAsmRegClass::parse(asm_arch, s)
+                                asm::InlineAsmRegClass::parse(sess.asm_arch?, s)
                                     .map_err(|e| {
                                         let msg = format!(
                                             "invalid register class `{}`: {}",
@@ -1029,33 +1025,38 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         }
                     })
                 };
-                let op = match op {
-                    InlineAsmOperand::In { reg, expr } => hir::InlineAsmOperand::In {
-                        reg: lower_reg(*reg)?,
+
+                // lower_reg is executed last because we need to lower all
+                // sub-expressions even if we throw them away later.
+                let op = match *op {
+                    InlineAsmOperand::In { reg, ref expr } => hir::InlineAsmOperand::In {
                         expr: self.lower_expr_mut(expr),
+                        reg: lower_reg(reg)?,
                     },
-                    InlineAsmOperand::Out { reg, late, expr } => hir::InlineAsmOperand::Out {
-                        reg: lower_reg(*reg)?,
-                        late: *late,
+                    InlineAsmOperand::Out { reg, late, ref expr } => hir::InlineAsmOperand::Out {
+                        late,
                         expr: expr.as_ref().map(|expr| self.lower_expr_mut(expr)),
+                        reg: lower_reg(reg)?,
                     },
-                    InlineAsmOperand::InOut { reg, late, expr } => hir::InlineAsmOperand::InOut {
-                        reg: lower_reg(*reg)?,
-                        late: *late,
-                        expr: self.lower_expr_mut(expr),
-                    },
-                    InlineAsmOperand::SplitInOut { reg, late, in_expr, out_expr } => {
+                    InlineAsmOperand::InOut { reg, late, ref expr } => {
+                        hir::InlineAsmOperand::InOut {
+                            late,
+                            expr: self.lower_expr_mut(expr),
+                            reg: lower_reg(reg)?,
+                        }
+                    }
+                    InlineAsmOperand::SplitInOut { reg, late, ref in_expr, ref out_expr } => {
                         hir::InlineAsmOperand::SplitInOut {
-                            reg: lower_reg(*reg)?,
-                            late: *late,
+                            late,
                             in_expr: self.lower_expr_mut(in_expr),
                             out_expr: out_expr.as_ref().map(|expr| self.lower_expr_mut(expr)),
+                            reg: lower_reg(reg)?,
                         }
                     }
-                    InlineAsmOperand::Const { expr } => {
+                    InlineAsmOperand::Const { ref expr } => {
                         hir::InlineAsmOperand::Const { expr: self.lower_expr_mut(expr) }
                     }
-                    InlineAsmOperand::Sym { expr } => {
+                    InlineAsmOperand::Sym { ref expr } => {
                         hir::InlineAsmOperand::Sym { expr: self.lower_expr_mut(expr) }
                     }
                 };
@@ -1069,6 +1070,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
 
         // Validate template modifiers against the register classes for the operands
+        let asm_arch = sess.asm_arch.unwrap();
         for p in &asm.template {
             if let InlineAsmTemplatePiece::Placeholder {
                 operand_idx,

src/librustc_error_codes/error_codes/E0617.md

@@ -17,3 +17,14 @@ Certain Rust types must be cast before passing them to a variadic function,
 because of arcane ABI rules dictated by the C standard. To fix the error,
 cast the value to the type specified by the error message (which you may need
 to import from `std::os::raw`).
+
+In this case, `c_double` has the same size as `f64` so we can use it directly:
+
+```
+# extern {
+#     fn printf(c: *const i8, ...);
+# }
+unsafe {
+    printf(::std::ptr::null(), 0f64); // ok!
+}
+```

src/librustc_lint/lib.rs

@@ -276,6 +276,7 @@ fn register_builtins(store: &mut LintStore, no_interleave_lints: bool) {
         UNUSED_ALLOCATION,
         UNUSED_DOC_COMMENTS,
         UNUSED_EXTERN_CRATES,
+        UNUSED_CRATE_DEPENDENCIES,
         UNUSED_FEATURES,
         UNUSED_LABELS,
         UNUSED_PARENS,

src/librustc_metadata/creader.rs

@@ -5,6 +5,7 @@ use crate::rmeta::{CrateDep, CrateMetadata, CrateNumMap, CrateRoot, MetadataBlob
 
 use rustc_ast::expand::allocator::{global_allocator_spans, AllocatorKind};
 use rustc_ast::{ast, attr};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::struct_span_err;
@@ -18,6 +19,7 @@ use rustc_middle::middle::cstore::{
 };
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{self, CrateType};
+use rustc_session::lint;
 use rustc_session::output::validate_crate_name;
 use rustc_session::search_paths::PathKind;
 use rustc_session::{CrateDisambiguator, Session};
@@ -49,6 +51,7 @@ pub struct CrateLoader<'a> {
     local_crate_name: Symbol,
     // Mutable output.
     cstore: CStore,
+    used_extern_options: FxHashSet<Symbol>,
 }
 
 pub enum LoadedMacro {
@@ -205,6 +208,7 @@ impl<'a> CrateLoader<'a> {
                 allocator_kind: None,
                 has_global_allocator: false,
             },
+            used_extern_options: Default::default(),
         }
     }
 
@@ -445,6 +449,9 @@ impl<'a> CrateLoader<'a> {
         dep_kind: DepKind,
         dep: Option<(&'b CratePaths, &'b CrateDep)>,
     ) -> CrateNum {
+        if dep.is_none() {
+            self.used_extern_options.insert(name);
+        }
         self.maybe_resolve_crate(name, span, dep_kind, dep).unwrap_or_else(|err| err.report())
     }
 
@@ -839,6 +846,26 @@ impl<'a> CrateLoader<'a> {
         });
     }
 
+    fn report_unused_deps(&mut self, krate: &ast::Crate) {
+        // Make a point span rather than covering the whole file
+        let span = krate.span.shrink_to_lo();
+        // Complain about anything left over
+        for (name, _) in self.sess.opts.externs.iter() {
+            if !self.used_extern_options.contains(&Symbol::intern(name)) {
+                self.sess.parse_sess.buffer_lint(
+                    lint::builtin::UNUSED_CRATE_DEPENDENCIES,
+                    span,
+                    ast::CRATE_NODE_ID,
+                    &format!(
+                        "external crate `{}` unused in `{}`: remove the dependency or add `use {} as _;`",
+                        name,
+                        self.local_crate_name,
+                        name),
+                );
+            }
+        }
+    }
+
     pub fn postprocess(&mut self, krate: &ast::Crate) {
         self.inject_profiler_runtime();
         self.inject_allocator_crate(krate);
@@ -847,6 +874,8 @@ impl<'a> CrateLoader<'a> {
         if log_enabled!(log::Level::Info) {
             dump_crates(&self.cstore);
         }
+
+        self.report_unused_deps(krate);
     }
 
     pub fn process_extern_crate(

src/librustc_passes/loops.rs

@@ -9,6 +9,7 @@ use rustc_middle::hir::map::Map;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
+use rustc_span::hygiene::DesugaringKind;
 use rustc_span::Span;
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -203,7 +204,7 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
         label: &Destination,
         cf_type: &str,
     ) -> bool {
-        if self.cx == LabeledBlock {
+        if !span.is_desugaring(DesugaringKind::QuestionMark) && self.cx == LabeledBlock {
             if label.label.is_none() {
                 struct_span_err!(
                     self.sess,

src/librustc_session/lint/builtin.rs

@@ -71,6 +71,12 @@ declare_lint! {
     "extern crates that are never used"
 }
 
+declare_lint! {
+    pub UNUSED_CRATE_DEPENDENCIES,
+    Allow,
+    "crate dependencies that are never used"
+}
+
 declare_lint! {
     pub UNUSED_QUALIFICATIONS,
     Allow,
@@ -523,6 +529,7 @@ declare_lint_pass! {
         UNCONDITIONAL_PANIC,
         UNUSED_IMPORTS,
         UNUSED_EXTERN_CRATES,
+        UNUSED_CRATE_DEPENDENCIES,
         UNUSED_QUALIFICATIONS,
         UNKNOWN_LINTS,
         UNUSED_VARIABLES,

src/test/ui/asm/issue-72570.rs

@@ -0,0 +1,10 @@
+// only-x86_64
+
+#![feature(asm)]
+
+fn main() {
+    unsafe {
+        asm!("", in("invalid") "".len());
+        //~^ ERROR: invalid register `invalid`: unknown register
+    }
+}

src/test/ui/asm/issue-72570.stderr

@@ -0,0 +1,8 @@
+error: invalid register `invalid`: unknown register
+  --> $DIR/issue-72570.rs:7:18
+   |
+LL |         asm!("", in("invalid") "".len());
+   |                  ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+

src/test/ui/label/label_break_value_desugared_break.rs

@@ -0,0 +1,12 @@
+// compile-flags: --edition 2018
+#![feature(label_break_value, try_blocks)]
+
+// run-pass
+fn main() {
+    let _: Result<(), ()> = try {
+        'foo: {
+            Err(())?;
+            break 'foo;
+        }
+    };
+}

src/test/ui/unused-crate-deps/auxiliary/bar.rs

@@ -0,0 +1 @@
+pub const BAR: &str = "bar";

src/test/ui/unused-crate-deps/auxiliary/foo.rs

@@ -0,0 +1,5 @@
+// edition:2018
+// aux-crate:bar=bar.rs
+
+pub const FOO: &str = "foo";
+pub use bar::BAR;