merging in changes to upstream master;

Author: Ellen Arteca

CONTRIBUTING.md

@@ -28,11 +28,6 @@ install that exact version of rustc as a toolchain:
 This will set up a rustup toolchain called `miri` and set it as an override for
 the current directory.
 
-If you want to also have `clippy` installed, you need to run this:
-```
-./rustup-toolchain "" -c clippy
-```
-
 [`rustup-toolchain-install-master`]: https://github.com/kennytm/rustup-toolchain-install-master
 
 ## Building and testing Miri
@@ -131,6 +126,8 @@ development version of Miri using
 
 and then you can use it as if it was installed by `rustup`.  Make sure you use
 the same toolchain when calling `cargo miri` that you used when installing Miri!
+Usually this means you have to write `cargo +miri miri ...` to select the `miri`
+toolchain that was installed by `./rustup-toolchain`.
 
 There's a test for the cargo wrapper in the `test-cargo-miri` directory; run
 `./run-test.py` in there to execute it. Like `./miri test`, this respects the

Cargo.lock

@@ -56,6 +56,7 @@ harness = false
 
 [features]
 default = ["stack-cache"]
-# Will be enabled on CI via `--all-features`.
-expensive-debug-assertions = []
 stack-cache = []
+
+[profile.dev]
+opt-level = 2 # because it's too slow otherwise

Cargo.toml

@@ -65,7 +65,7 @@ in your program, and cannot run all programs:
   not support networking. System API support varies between targets; if you run
   on Windows it is a good idea to use `--target x86_64-unknown-linux-gnu` to get
   better support.
-* Weak memory emulation may [produce weak behaivours](https://github.com/rust-lang/miri/issues/2301)
+* Weak memory emulation may [produce weak behaviours](https://github.com/rust-lang/miri/issues/2301)
   unobservable by compiled programs running on real hardware when `SeqCst` fences are used, and it
   cannot produce all behaviors possibly observable on real hardware.
 

README.md

@@ -0,0 +1,8 @@
+[package]
+name = "slice-get-unchecked"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

bench-cargo-miri/slice-get-unchecked/Cargo.lock

@@ -0,0 +1,12 @@
+//! This is a stripped-down version of the code pattern that causes runtime blowup when printing
+//! backtraces in a failed test under cargo miri test with -Zmiri-disable-isolation.
+//! See https://github.com/rust-lang/miri/issues/2273
+
+fn main() {
+    let x = vec![0u8; 4096];
+    let mut i = 0;
+    while i < x.len() {
+        let _element = unsafe { *x.get_unchecked(i) };
+        i += 1;
+    }
+}

bench-cargo-miri/slice-get-unchecked/Cargo.toml

@@ -5,11 +5,11 @@ set -x
 # Determine configuration
 export RUSTFLAGS="-D warnings"
 export CARGO_INCREMENTAL=0
-export CARGO_EXTRA_FLAGS="--all-features" # in particular, expensive-debug-assertions
+export CARGO_EXTRA_FLAGS="--all-features"
 
 # Prepare
 echo "Build and install miri"
-CARGO_EXTRA_FLAGS="" ./miri install # implicitly locked -- and the *installed* Miri does *not* get the expensive-debug-assertions feature
+./miri install # implicitly locked
 ./miri build --all-targets --locked # the build that all the `./miri test` below will use
 echo