Auto merge of #66950 - RalfJung:rollup-12d0zx8, r=RalfJung

Rollup of 5 pull requests

Successful merges:

 - #66245 (Conditional compilation for sanitizers)
 - #66654 (Handle const-checks for `&mut` outside of `HasMutInterior`)
 - #66822 (libunwind_panic: adjust miri panic hack)
 - #66827 (handle diverging functions forwarding their return place)
 - #66834 (rustbuild fixes)

Failed merges:

r? @ghost

src/bootstrap/bootstrap.py

@@ -643,7 +643,9 @@ def build_bootstrap(self):
         env["LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib") + \
             (os.pathsep + env["LIBRARY_PATH"]) \
             if "LIBRARY_PATH" in env else ""
-        env["RUSTFLAGS"] = "-Cdebuginfo=2 "
+        # preserve existing RUSTFLAGS
+        env.setdefault("RUSTFLAGS", "")
+        env["RUSTFLAGS"] += " -Cdebuginfo=2"
 
         build_section = "target.{}".format(self.build_triple())
         target_features = []
@@ -652,13 +654,13 @@ def build_bootstrap(self):
         elif self.get_toml("crt-static", build_section) == "false":
             target_features += ["-crt-static"]
         if target_features:
-            env["RUSTFLAGS"] += "-C target-feature=" + (",".join(target_features)) + " "
+            env["RUSTFLAGS"] += " -C target-feature=" + (",".join(target_features))
         target_linker = self.get_toml("linker", build_section)
         if target_linker is not None:
-            env["RUSTFLAGS"] += "-C linker=" + target_linker + " "
-        env["RUSTFLAGS"] += " -Wrust_2018_idioms -Wunused_lifetimes "
+            env["RUSTFLAGS"] += " -C linker=" + target_linker
+        env["RUSTFLAGS"] += " -Wrust_2018_idioms -Wunused_lifetimes"
         if self.get_toml("deny-warnings", "rust") != "false":
-            env["RUSTFLAGS"] += "-Dwarnings "
+            env["RUSTFLAGS"] += " -Dwarnings"
 
         env["PATH"] = os.path.join(self.bin_root(), "bin") + \
             os.pathsep + env["PATH"]

src/bootstrap/install.rs

@@ -260,7 +260,7 @@ install!((self, builder, _config),
     };
     Rustc, "src/librustc", true, only_hosts: true, {
         builder.ensure(dist::Rustc {
-            compiler: self.compiler,
+            compiler: builder.compiler(builder.top_stage, self.target),
         });
         install_rustc(builder, self.compiler.stage, self.target);
     };

src/doc/unstable-book/src/language-features/cfg-sanitize.md

@@ -0,0 +1,36 @@
+# `cfg_sanitize`
+
+The tracking issue for this feature is: [#39699]
+
+[#39699]: https://github.com/rust-lang/rust/issues/39699
+
+------------------------
+
+The `cfg_sanitize` feature makes it possible to execute different code
+depending on whether a particular sanitizer is enabled or not.
+
+## Examples
+
+``` rust
+#![feature(cfg_sanitize)]
+
+#[cfg(sanitize = "thread")]
+fn a() {
+  // ...
+}
+
+#[cfg(not(sanitize = "thread"))]
+fn a() {
+  // ...
+}
+
+fn b() {
+  if cfg!(sanitize = "leak") {
+    // ...
+  } else {
+    // ...
+  }
+}
+
+```
+

src/libcore/intrinsics.rs

@@ -1348,9 +1348,11 @@ extern "rust-intrinsic" {
     pub fn ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;
 
     /// Internal hook used by Miri to implement unwinding.
+    /// Compiles to a NOP during non-Miri codegen.
+    ///
     /// Perma-unstable: do not use
     #[cfg(not(bootstrap))]
-    pub fn miri_start_panic(data: *mut (dyn crate::any::Any + crate::marker::Send)) -> !;
+    pub fn miri_start_panic(data: *mut (dyn crate::any::Any + crate::marker::Send)) -> ();
 }
 
 // Some functions are defined here because they accidentally got made

src/libpanic_unwind/lib.rs

@@ -36,10 +36,7 @@ use core::raw;
 use core::panic::BoxMeUp;
 
 cfg_if::cfg_if! {
-    if #[cfg(miri)] {
-        #[path = "miri.rs"]
-        mod imp;
-    } else if #[cfg(target_os = "emscripten")] {
+    if #[cfg(target_os = "emscripten")] {
         #[path = "emcc.rs"]
         mod imp;
     } else if #[cfg(target_arch = "wasm32")] {
@@ -94,5 +91,14 @@ pub unsafe extern "C" fn __rust_maybe_catch_panic(f: fn(*mut u8),
 #[unwind(allowed)]
 pub unsafe extern "C" fn __rust_start_panic(payload: usize) -> u32 {
     let payload = payload as *mut &mut dyn BoxMeUp;
-    imp::panic(Box::from_raw((*payload).take_box()))
+    let payload = (*payload).take_box();
+
+    // Miri panic support: cfg'd out of normal builds just to be sure.
+    // When going through normal codegen, `miri_start_panic` is a NOP, so the
+    // Miri-enabled sysroot still supports normal unwinding. But when executed in
+    // Miri, this line initiates unwinding.
+    #[cfg(miri)]
+    core::intrinsics::miri_start_panic(payload);
+
+    imp::panic(Box::from_raw(payload))
 }

src/librustc/session/config.rs

@@ -47,6 +47,17 @@ pub enum Sanitizer {
     Thread,
 }
 
+impl fmt::Display for Sanitizer {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            Sanitizer::Address => "address".fmt(f),
+            Sanitizer::Leak => "leak".fmt(f),
+            Sanitizer::Memory => "memory".fmt(f),
+            Sanitizer::Thread => "thread".fmt(f),
+        }
+    }
+}
+
 impl FromStr for Sanitizer {
     type Err = ();
     fn from_str(s: &str) -> Result<Sanitizer, ()> {
@@ -1580,6 +1591,10 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig {
             }
         }
     }
+    if let Some(s) = &sess.opts.debugging_opts.sanitizer {
+        let symbol = Symbol::intern(&s.to_string());
+        ret.insert((sym::sanitize, Some(symbol)));
+    }
     if sess.opts.debug_assertions {
         ret.insert((Symbol::intern("debug_assertions"), None));
     }

src/librustc_codegen_ssa/mir/block.rs

@@ -528,18 +528,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             _ => FnAbi::new(&bx, sig, &extra_args)
         };
 
-        // This should never be reachable at runtime:
-        // We should only emit a call to this intrinsic in #[cfg(miri)] mode,
-        // which means that we will never actually use the generate object files
-        // (we will just be interpreting the MIR)
-        //
-        // Note that we still need to be able to codegen *something* for this intrisnic:
-        // Miri currently uses Xargo to build a special libstd. As a side effect,
-        // we generate normal object files for libstd - while these are never used,
-        // we still need to be able to build them.
+        // For normal codegen, this Miri-specific intrinsic is just a NOP.
         if intrinsic == Some("miri_start_panic") {
-            bx.abort();
-            bx.unreachable();
+            let target = destination.as_ref().unwrap().1;
+            helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
+            helper.funclet_br(self, &mut bx, target);
             return;
         }
 

src/librustc_feature/active.rs

@@ -524,6 +524,9 @@ declare_features! (
     /// Allows the use of `if` and `match` in constants.
     (active, const_if_match, "1.41.0", Some(49146), None),
 
+    /// Allows the use of `#[cfg(sanitize = "option")]`; set when -Zsanitizer is used.
+    (active, cfg_sanitize, "1.41.0", Some(39699), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------

src/librustc_feature/builtin_attrs.rs

@@ -25,6 +25,7 @@ const GATED_CFGS: &[GatedCfg] = &[
     (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
     (sym::target_has_atomic, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
     (sym::target_has_atomic_load_store, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
+    (sym::sanitize, sym::cfg_sanitize, cfg_fn!(cfg_sanitize)),
 ];
 
 /// Find a gated cfg determined by the `pred`icate which is given the cfg's name.

src/librustc_mir/interpret/place.rs

@@ -651,20 +651,28 @@ where
         use rustc::mir::PlaceBase;
 
         let mut place_ty = match &place.base {
-            PlaceBase::Local(mir::RETURN_PLACE) => match self.frame().return_place {
-                Some(return_place) => {
-                    // We use our layout to verify our assumption; caller will validate
-                    // their layout on return.
-                    PlaceTy {
-                        place: *return_place,
-                        layout: self.layout_of(
-                            self.subst_from_frame_and_normalize_erasing_regions(
-                                self.frame().body.return_ty()
-                            )
-                        )?,
-                    }
+            PlaceBase::Local(mir::RETURN_PLACE) => {
+                // `return_place` has the *caller* layout, but we want to use our
+                // `layout to verify our assumption. The caller will validate
+                // their layout on return.
+                PlaceTy {
+                    place: match self.frame().return_place {
+                        Some(p) => *p,
+                        // Even if we don't have a return place, we sometimes need to
+                        // create this place, but any attempt to read from / write to it
+                        // (even a ZST read/write) needs to error, so let us make this
+                        // a NULL place.
+                        //
+                        // FIXME: Ideally we'd make sure that the place projections also
+                        // bail out.
+                        None => Place::null(&*self),
+                    },
+                    layout: self.layout_of(
+                        self.subst_from_frame_and_normalize_erasing_regions(
+                            self.frame().body.return_ty()
+                        )
+                    )?,
                 }
-                None => throw_unsup!(InvalidNullPointerUsage),
             },
             PlaceBase::Local(local) => PlaceTy {
                 // This works even for dead/uninitialized locals; we check further when writing
@@ -791,8 +799,8 @@ where
         // to handle padding properly, which is only correct if we never look at this data with the
         // wrong type.
 
-        let ptr = match self.check_mplace_access(dest, None)
-            .expect("places should be checked on creation")
+        // Invalid places are a thing: the return place of a diverging function
+        let ptr = match self.check_mplace_access(dest, None)?
         {
             Some(ptr) => ptr,
             None => return Ok(()), // zero-sized access

src/librustc_mir/lib.rs

@@ -29,6 +29,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(stmt_expr_attributes)]
 #![feature(bool_to_option)]
 #![feature(trait_alias)]
+#![feature(matches_macro)]
 
 #![recursion_limit="256"]
 

src/librustc_mir/transform/check_consts/qualifs.rs

@@ -5,7 +5,7 @@ use rustc::ty::{self, Ty};
 use rustc::hir::def_id::DefId;
 use syntax_pos::DUMMY_SP;
 
-use super::{ConstKind, Item as ConstCx};
+use super::Item as ConstCx;
 
 pub fn in_any_value_of_ty(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> ConstQualifs {
     ConstQualifs {
@@ -33,9 +33,10 @@ pub trait Qualif {
     /// of the type.
     fn in_any_value_of_ty(_cx: &ConstCx<'_, 'tcx>, _ty: Ty<'tcx>) -> bool;
 
-    fn in_static(_cx: &ConstCx<'_, 'tcx>, _def_id: DefId) -> bool {
-        // FIXME(eddyb) should we do anything here for value properties?
-        false
+    fn in_static(cx: &ConstCx<'_, 'tcx>, def_id: DefId) -> bool {
+        // `mir_const_qualif` does return the qualifs in the final value of a `static`, so we could
+        // use value-based qualification here, but we shouldn't do this without a good reason.
+        Self::in_any_value_of_ty(cx, cx.tcx.type_of(def_id))
     }
 
     fn in_projection_structurally(
@@ -217,34 +218,6 @@ impl Qualif for HasMutInterior {
         rvalue: &Rvalue<'tcx>,
     ) -> bool {
         match *rvalue {
-            // Returning `true` for `Rvalue::Ref` indicates the borrow isn't
-            // allowed in constants (and the `Checker` will error), and/or it
-            // won't be promoted, due to `&mut ...` or interior mutability.
-            Rvalue::Ref(_, kind, ref place) => {
-                let ty = place.ty(cx.body, cx.tcx).ty;
-
-                if let BorrowKind::Mut { .. } = kind {
-                    // In theory, any zero-sized value could be borrowed
-                    // mutably without consequences.
-                    match ty.kind {
-                        // Inside a `static mut`, &mut [...] is also allowed.
-                        | ty::Array(..)
-                        | ty::Slice(_)
-                        if cx.const_kind == Some(ConstKind::StaticMut)
-                        => {},
-
-                        // FIXME(eddyb): We only return false for `&mut []` outside a const
-                        // context which seems unnecessary given that this is merely a ZST.
-                        | ty::Array(_, len)
-                        if len.try_eval_usize(cx.tcx, cx.param_env) == Some(0)
-                            && cx.const_kind == None
-                        => {},
-
-                        _ => return true,
-                    }
-                }
-            }
-
             Rvalue::Aggregate(ref kind, _) => {
                 if let AggregateKind::Adt(def, ..) = **kind {
                     if Some(def.did) == cx.tcx.lang_items().unsafe_cell_type() {