Auto merge of rust-lang#71721 - tmandry:rollup-e27pxex, r=tmandry

Rollup of 8 pull requests

Successful merges:

 - rust-lang#71148 (Vec drop and truncate: drop using raw slice *mut [T])
 - rust-lang#71465 (Add a convenience method on `TyCtxt` for checking for thread locals)
 - rust-lang#71567 (Handle build completion message from Cargo)
 - rust-lang#71590 (MIR dump: print pointers consistently with Miri output)
 - rust-lang#71682 (Bump pulldown-cmark)
 - rust-lang#71688 (Allow `Downcast` projections unconditionally in const-checking)
 - rust-lang#71691 (Allow `Unreachable` terminators unconditionally in const-checking)
 - rust-lang#71719 (Update backtrace-sys)

Failed merges:

r? @ghost

Author: bors

Cargo.lock

@@ -135,9 +135,9 @@ dependencies = [
 
 [[package]]
 name = "backtrace-sys"
-version = "0.1.36"
+version = "0.1.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "78848718ee1255a2485d1309ad9cdecfc2e7d0362dd11c6829364c6b35ae1bc7"
+checksum = "18fbebbe1c9d1f383a9cc7e8ccdb471b91c8d024ee9c2ca5b5346121fe8b4399"
 dependencies = [
  "cc",
  "compiler_builtins",
@@ -487,7 +487,7 @@ dependencies = [
  "if_chain",
  "itertools 0.9.0",
  "lazy_static 1.4.0",
- "pulldown-cmark 0.7.0",
+ "pulldown-cmark 0.7.1",
  "quine-mc_cluskey",
  "regex-syntax",
  "semver",
@@ -2657,9 +2657,9 @@ dependencies = [
 
 [[package]]
 name = "pulldown-cmark"
-version = "0.7.0"
+version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2c2d7fd131800e0d63df52aff46201acaab70b431a4a1ec6f0343fe8e64f35a4"
+checksum = "3e142c3b8f49d2200605ee6ba0b1d757310e9e7a72afe78c36ee2ef67300ee00"
 dependencies = [
  "bitflags",
  "memchr",
@@ -4342,7 +4342,7 @@ version = "0.0.0"
 dependencies = [
  "itertools 0.8.0",
  "minifier",
- "pulldown-cmark 0.7.0",
+ "pulldown-cmark 0.7.1",
  "rustc-rayon",
  "serde",
  "serde_json",

src/bootstrap/compile.rs

@@ -1012,4 +1012,7 @@ pub enum CargoMessage<'a> {
     BuildScriptExecuted {
         package_id: Cow<'a, str>,
     },
+    BuildFinished {
+        success: bool,
+    },
 }

src/liballoc/vec.rs

@@ -741,7 +741,7 @@ impl<T> Vec<T> {
                 return;
             }
             let remaining_len = self.len - len;
-            let s = slice::from_raw_parts_mut(self.as_mut_ptr().add(len), remaining_len);
+            let s = ptr::slice_from_raw_parts_mut(self.as_mut_ptr().add(len), remaining_len);
             self.len = len;
             ptr::drop_in_place(s);
         }
@@ -2379,7 +2379,9 @@ unsafe impl<#[may_dangle] T> Drop for Vec<T> {
     fn drop(&mut self) {
         unsafe {
             // use drop for [T]
-            ptr::drop_in_place(&mut self[..]);
+            // use a raw slice to refer to the elements of the vector as weakest necessary type;
+            // could avoid questions of validity in certain cases
+            ptr::drop_in_place(ptr::slice_from_raw_parts_mut(self.as_mut_ptr(), self.len))
         }
         // RawVec handles deallocation
     }
@@ -2596,7 +2598,11 @@ impl<T> IntoIter<T> {
     /// ```
     #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
     pub fn as_mut_slice(&mut self) -> &mut [T] {
-        unsafe { slice::from_raw_parts_mut(self.ptr as *mut T, self.len()) }
+        unsafe { &mut *self.as_raw_mut_slice() }
+    }
+
+    fn as_raw_mut_slice(&mut self) -> *mut [T] {
+        ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
     }
 }
 
@@ -2708,7 +2714,7 @@ unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
         let guard = DropGuard(self);
         // destroy the remaining elements
         unsafe {
-            ptr::drop_in_place(guard.0.as_mut_slice());
+            ptr::drop_in_place(guard.0.as_raw_mut_slice());
         }
         // now `guard` will be dropped and do the rest
     }

src/librustc_codegen_llvm/consts.rs

@@ -212,6 +212,7 @@ impl CodegenCx<'ll, 'tcx> {
         let g = if let Some(def_id) = def_id.as_local() {
             let id = self.tcx.hir().as_local_hir_id(def_id);
             let llty = self.layout_of(ty).llvm_type(self);
+            // FIXME: refactor this to work without accessing the HIR
             let (g, attrs) = match self.tcx.hir().get(id) {
                 Node::Item(&hir::Item { attrs, span, kind: hir::ItemKind::Static(..), .. }) => {
                     let sym_str = sym.as_str();

src/librustc_middle/mir/interpret/error.rs

@@ -438,10 +438,7 @@ impl fmt::Debug for UndefinedBehaviorInfo {
 /// Error information for when the program did something that might (or might not) be correct
 /// to do according to the Rust spec, but due to limitations in the interpreter, the
 /// operation could not be carried out. These limitations can differ between CTFE and the
-/// Miri engine, e.g., CTFE does not support casting pointers to "real" integers.
-///
-/// Currently, we also use this as fall-back error kind for errors that have not been
-/// categorized yet.
+/// Miri engine, e.g., CTFE does not support dereferencing pointers at integral addresses.
 pub enum UnsupportedOpInfo {
     /// Free-form case. Only for errors that are never caught!
     Unsupported(String),
@@ -451,6 +448,9 @@ pub enum UnsupportedOpInfo {
     NoMirFor(DefId),
     /// Encountered a pointer where we needed raw bytes.
     ReadPointerAsBytes,
+    //
+    // The variants below are only reachable from CTFE/const prop, miri will never emit them.
+    //
     /// Encountered raw bytes where we needed a pointer.
     ReadBytesAsPointer,
 }

src/librustc_middle/mir/interpret/mod.rs

@@ -168,15 +168,17 @@ pub enum LitToConstError {
 #[derive(Copy, Clone, Eq, Hash, Ord, PartialEq, PartialOrd)]
 pub struct AllocId(pub u64);
 
+// We want the `Debug` output to be readable as it is used by `derive(Debug)` for
+// all the Miri types.
 impl fmt::Debug for AllocId {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(self, fmt)
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if f.alternate() { write!(f, "a{}", self.0) } else { write!(f, "alloc{}", self.0) }
     }
 }
 
 impl fmt::Display for AllocId {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "alloc{}", self.0)
+        fmt::Debug::fmt(self, f)
     }
 }
 

src/librustc_middle/mir/interpret/pointer.rs

@@ -119,15 +119,33 @@ pub struct Pointer<Tag = (), Id = AllocId> {
 
 static_assert_size!(Pointer, 16);
 
+// We want the `Debug` output to be readable as it is used by `derive(Debug)` for
+// all the Miri types.
+// We have to use `Debug` output for the tag, because `()` does not implement
+// `Display` so we cannot specialize that.
 impl<Tag: fmt::Debug, Id: fmt::Debug> fmt::Debug for Pointer<Tag, Id> {
     default fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}+0x{:x}[{:?}]", self.alloc_id, self.offset.bytes(), self.tag)
+        if f.alternate() {
+            write!(f, "{:#?}+0x{:x}[{:?}]", self.alloc_id, self.offset.bytes(), self.tag)
+        } else {
+            write!(f, "{:?}+0x{:x}[{:?}]", self.alloc_id, self.offset.bytes(), self.tag)
+        }
     }
 }
 // Specialization for no tag
 impl<Id: fmt::Debug> fmt::Debug for Pointer<(), Id> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}+0x{:x}", self.alloc_id, self.offset.bytes())
+        if f.alternate() {
+            write!(f, "{:#?}+0x{:x}", self.alloc_id, self.offset.bytes())
+        } else {
+            write!(f, "{:?}+0x{:x}", self.alloc_id, self.offset.bytes())
+        }
+    }
+}
+
+impl<Tag: fmt::Debug> fmt::Display for Pointer<Tag> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(self, f)
     }
 }
 

src/librustc_middle/mir/interpret/value.rs

@@ -107,6 +107,8 @@ pub enum Scalar<Tag = (), Id = AllocId> {
 #[cfg(target_arch = "x86_64")]
 static_assert_size!(Scalar, 24);
 
+// We want the `Debug` output to be readable as it is used by `derive(Debug)` for
+// all the Miri types.
 impl<Tag: fmt::Debug, Id: fmt::Debug> fmt::Debug for Scalar<Tag, Id> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
@@ -125,11 +127,11 @@ impl<Tag: fmt::Debug, Id: fmt::Debug> fmt::Debug for Scalar<Tag, Id> {
     }
 }
 
-impl<Tag> fmt::Display for Scalar<Tag> {
+impl<Tag: fmt::Debug> fmt::Display for Scalar<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Scalar::Ptr(_) => write!(f, "a pointer"),
-            Scalar::Raw { data, .. } => write!(f, "{}", data),
+            Scalar::Ptr(ptr) => write!(f, "pointer to {}", ptr),
+            Scalar::Raw { .. } => fmt::Debug::fmt(self, f),
         }
     }
 }
@@ -559,16 +561,18 @@ impl<Tag> From<Pointer<Tag>> for ScalarMaybeUndef<Tag> {
     }
 }
 
+// We want the `Debug` output to be readable as it is used by `derive(Debug)` for
+// all the Miri types.
 impl<Tag: fmt::Debug, Id: fmt::Debug> fmt::Debug for ScalarMaybeUndef<Tag, Id> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            ScalarMaybeUndef::Undef => write!(f, "Undef"),
+            ScalarMaybeUndef::Undef => write!(f, "<uninitialized>"),
             ScalarMaybeUndef::Scalar(s) => write!(f, "{:?}", s),
         }
     }
 }
 
-impl<Tag> fmt::Display for ScalarMaybeUndef<Tag> {
+impl<Tag: fmt::Debug> fmt::Display for ScalarMaybeUndef<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             ScalarMaybeUndef::Undef => write!(f, "uninitialized bytes"),

src/librustc_middle/ty/util.rs

@@ -1,6 +1,7 @@
 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
 
 use crate::ich::NodeIdHashingMode;
+use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::mir::interpret::{sign_extend, truncate};
 use crate::ty::layout::IntegerExt;
 use crate::ty::query::TyCtxtAt;
@@ -528,6 +529,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self.static_mutability(def_id).is_some()
     }
 
+    /// Returns `true` if this is a `static` item with the `#[thread_local]` attribute.
+    pub fn is_thread_local_static(&self, def_id: DefId) -> bool {
+        self.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
+    }
+
     /// Returns `true` if the node pointed to by `def_id` is a mutable `static` item.
     pub fn is_mutable_static(&self, def_id: DefId) -> bool {
         self.static_mutability(def_id) == Some(hir::Mutability::Mut)

src/librustc_mir/interpret/machine.rs

@@ -84,6 +84,8 @@ pub trait Machine<'mir, 'tcx>: Sized {
     /// Tag tracked alongside every pointer. This is used to implement "Stacked Borrows"
     /// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
     /// The `default()` is used for pointers to consts, statics, vtables and functions.
+    /// The `Debug` formatting is used for displaying pointers; we cannot use `Display`
+    /// as `()` does not implement that, but it should be "nice" output.
     type PointerTag: ::std::fmt::Debug + Copy + Eq + Hash + 'static;
 
     /// Machines can define extra (non-instance) things that represent values of function pointers.

src/librustc_mir/interpret/memory.rs

@@ -674,7 +674,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
     /// control for this.
     pub fn dump_allocs(&self, mut allocs: Vec<AllocId>) {
         // Cannot be a closure because it is generic in `Tag`, `Extra`.
-        fn write_allocation_track_relocs<'tcx, Tag, Extra>(
+        fn write_allocation_track_relocs<'tcx, Tag: Copy + fmt::Debug, Extra>(
             tcx: TyCtxtAt<'tcx>,
             allocs_to_print: &mut VecDeque<AllocId>,
             alloc: &Allocation<Tag, Extra>,

src/librustc_mir/interpret/operand.rs

@@ -122,11 +122,11 @@ impl<Tag: Copy> std::fmt::Display for ImmTy<'tcx, Tag> {
                         p(cx, s, ty)?;
                         return Ok(());
                     }
-                    write!(f, "{:?}: {}", s.erase_tag(), self.layout.ty)
+                    write!(f, "{}: {}", s.erase_tag(), self.layout.ty)
                 }
                 Immediate::ScalarPair(a, b) => {
                     // FIXME(oli-obk): at least print tuples and slices nicely
-                    write!(f, "({:?}, {:?}): {}", a.erase_tag(), b.erase_tag(), self.layout.ty,)
+                    write!(f, "({}, {}): {}", a.erase_tag(), b.erase_tag(), self.layout.ty,)
                 }
             }
         })

src/librustc_mir/transform/check_consts/ops.rs

@@ -53,15 +53,6 @@ pub trait NonConstOp: std::fmt::Debug {
     }
 }
 
-/// A `Downcast` projection.
-#[derive(Debug)]
-pub struct Downcast;
-impl NonConstOp for Downcast {
-    fn feature_gate() -> Option<Symbol> {
-        Some(sym::const_if_match)
-    }
-}
-
 /// A function call where the callee is a pointer.
 #[derive(Debug)]
 pub struct FnCallIndirect;

src/librustc_mir/transform/check_consts/validation.rs

@@ -8,7 +8,6 @@ use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceC
 use rustc_middle::mir::*;
 use rustc_middle::ty::cast::CastTy;
 use rustc_middle::ty::{self, Instance, InstanceDef, TyCtxt};
-use rustc_span::symbol::sym;
 use rustc_span::Span;
 use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
 use rustc_trait_selection::traits::{self, TraitEngine};
@@ -224,7 +223,7 @@ impl Validator<'mir, 'tcx> {
 
         // Ensure that the end result is `Sync` in a non-thread local `static`.
         let should_check_for_sync =
-            const_kind == Some(ConstKind::Static) && !tcx.has_attr(def_id, sym::thread_local);
+            const_kind == Some(ConstKind::Static) && !tcx.is_thread_local_static(def_id);
 
         if should_check_for_sync {
             let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
@@ -267,8 +266,7 @@ impl Validator<'mir, 'tcx> {
     }
 
     fn check_static(&mut self, def_id: DefId, span: Span) {
-        let is_thread_local = self.tcx.has_attr(def_id, sym::thread_local);
-        if is_thread_local {
+        if self.tcx.is_thread_local_static(def_id) {
             self.check_op_spanned(ops::ThreadLocalAccess, span)
         } else {
             self.check_op_spanned(ops::StaticAccess, span)
@@ -474,6 +472,7 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
             }
 
             ProjectionElem::ConstantIndex { .. }
+            | ProjectionElem::Downcast(..)
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Field(..)
             | ProjectionElem::Index(_) => {
@@ -486,10 +485,6 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
                     _ => {}
                 }
             }
-
-            ProjectionElem::Downcast(..) => {
-                self.check_op(ops::Downcast);
-            }
         }
     }
 

src/librustc_mir/transform/promote_consts.rs

@@ -522,7 +522,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                         return Err(Unpromotable);
                     }
 
-                    let is_thread_local = self.tcx.has_attr(def_id, sym::thread_local);
+                    let is_thread_local = self.tcx.is_thread_local_static(def_id);
                     if is_thread_local {
                         return Err(Unpromotable);
                     }

src/librustc_mir/transform/qualify_min_const_fn.rs

@@ -286,11 +286,6 @@ fn check_place(
     while let &[ref proj_base @ .., elem] = cursor {
         cursor = proj_base;
         match elem {
-            ProjectionElem::Downcast(..) if !feature_allowed(tcx, def_id, sym::const_if_match) => {
-                return Err((span, "`match` or `if let` in `const fn` is unstable".into()));
-            }
-            ProjectionElem::Downcast(_symbol, _variant_index) => {}
-
             ProjectionElem::Field(..) => {
                 let base_ty = Place::ty_from(place.local, &proj_base, body, tcx).ty;
                 if let Some(def) = base_ty.ty_adt_def() {
@@ -303,6 +298,7 @@ fn check_place(
                 }
             }
             ProjectionElem::ConstantIndex { .. }
+            | ProjectionElem::Downcast(..)
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Deref
             | ProjectionElem::Index(_) => {}
@@ -344,7 +340,8 @@ fn check_terminator(
         | TerminatorKind::FalseUnwind { .. }
         | TerminatorKind::Goto { .. }
         | TerminatorKind::Return
-        | TerminatorKind::Resume => Ok(()),
+        | TerminatorKind::Resume
+        | TerminatorKind::Unreachable => Ok(()),
 
         TerminatorKind::Drop { location, .. } => check_place(tcx, *location, span, def_id, body),
         TerminatorKind::DropAndReplace { location, value, .. } => {
@@ -360,12 +357,7 @@ fn check_terminator(
             check_operand(tcx, discr, span, def_id, body)
         }
 
-        // FIXME(ecstaticmorse): We probably want to allow `Unreachable` unconditionally.
-        TerminatorKind::Unreachable if feature_allowed(tcx, def_id, sym::const_if_match) => Ok(()),
-
-        TerminatorKind::Abort | TerminatorKind::Unreachable => {
-            Err((span, "const fn with unreachable code is not stable".into()))
-        }
+        TerminatorKind::Abort => Err((span, "abort is not stable in const fn".into())),
         TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => {
             Err((span, "const fn generators are unstable".into()))
         }