Auto merge of #127119 - RalfJung:miri-sync, r=RalfJung

Miri subtree update

r? `@ghost`

Author: bors

.github/workflows/ci.yml

@@ -33,50 +33,7 @@ jobs:
       HOST_TARGET: ${{ matrix.host_target }}
     steps:
       - uses: actions/checkout@v4
-
-      - name: Show Rust version (stable toolchain)
-        run: |
-          rustup show
-          rustc -Vv
-          cargo -V
-
-      # Cache the global cargo directory, but NOT the local `target` directory which
-      # we cannot reuse anyway when the nightly changes (and it grows quite large
-      # over time).
-      - name: Add cache for cargo
-        id: cache
-        uses: actions/cache@v4
-        with:
-          path: |
-            # Taken from <https://doc.rust-lang.org/nightly/cargo/guide/cargo-home.html#caching-the-cargo-home-in-ci>.
-            # Cache package/registry information
-            ~/.cargo/registry/index
-            ~/.cargo/registry/cache
-            ~/.cargo/git/db
-            # Cache installed binaries
-            ~/.cargo/bin
-            ~/.cargo/.crates.toml
-            ~/.cargo/.crates2.json
-          key: cargo-${{ runner.os }}-reset20240425-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: cargo-${{ runner.os }}-reset20240425
-
-      - name: Install tools
-        if: steps.cache.outputs.cache-hit != 'true'
-        run: cargo install -f rustup-toolchain-install-master hyperfine
-
-      - name: Install miri toolchain
-        run: |
-          if [[ ${{ github.event_name }} == 'schedule' ]]; then
-            echo "Building against latest rustc git version"
-            git ls-remote https://github.com/rust-lang/rust/ HEAD | cut -f 1 > rust-version
-          fi
-          ./miri toolchain --host ${{ matrix.host_target }}
-
-      - name: Show Rust version (miri toolchain)
-        run: |
-          rustup show
-          rustc -Vv
-          cargo -V
+      - uses: ./.github/workflows/setup
 
       # The `style` job only runs on Linux; this makes sure the Windows-host-specific
       # code is also covered by clippy.
@@ -92,47 +49,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-
-      # This is exactly duplicated from above. GHA is pretty terrible when it comes
-      # to avoiding code duplication.
-
-      # Cache the global cargo directory, but NOT the local `target` directory which
-      # we cannot reuse anyway when the nightly changes (and it grows quite large
-      # over time).
-      - name: Add cache for cargo
-        id: cache
-        uses: actions/cache@v4
-        with:
-          path: |
-            # Taken from <https://doc.rust-lang.org/nightly/cargo/guide/cargo-home.html#caching-the-cargo-home-in-ci>.
-            # Cache package/registry information
-            ~/.cargo/registry/index
-            ~/.cargo/registry/cache
-            ~/.cargo/git/db
-            # Cache installed binaries
-            ~/.cargo/bin
-            ~/.cargo/.crates.toml
-            ~/.cargo/.crates2.json
-          key: cargo-${{ runner.os }}-reset20240331-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: cargo-${{ runner.os }}-reset20240331
-
-      - name: Install rustup-toolchain-install-master
-        if: steps.cache.outputs.cache-hit != 'true'
-        run: cargo install -f rustup-toolchain-install-master
-
-      - name: Install "master" toolchain
-        run: |
-          if [[ ${{ github.event_name }} == 'schedule' ]]; then
-            echo "Building against latest rustc git version"
-            git ls-remote https://github.com/rust-lang/rust/ HEAD | cut -f 1 > rust-version
-          fi
-          ./miri toolchain
-
-      - name: Show Rust version
-        run: |
-          rustup show
-          rustc -Vv
-          cargo -V
+      - uses: ./.github/workflows/setup
 
       - name: rustfmt
         run: ./miri fmt --check

.github/workflows/setup/action.yml

@@ -0,0 +1,52 @@
+name: "Miri CI setup"
+description: "Sets up Miri CI"
+runs:
+  using: "composite"
+  steps:
+      - name: Show Rust version (stable toolchain)
+        run: |
+          rustup show
+          rustc -Vv
+          cargo -V
+        shell: bash
+
+      # Cache the global cargo directory, but NOT the local `target` directory which
+      # we cannot reuse anyway when the nightly changes (and it grows quite large
+      # over time).
+      - name: Add cache for cargo
+        id: cache
+        uses: actions/cache@v4
+        with:
+          path: |
+            # Taken from <https://doc.rust-lang.org/nightly/cargo/guide/cargo-home.html#caching-the-cargo-home-in-ci>.
+            # Cache package/registry information
+            ~/.cargo/registry/index
+            ~/.cargo/registry/cache
+            ~/.cargo/git/db
+            # Cache installed binaries
+            ~/.cargo/bin
+            ~/.cargo/.crates.toml
+            ~/.cargo/.crates2.json
+          key: cargo-${{ runner.os }}-${{ hashFiles('**/Cargo.lock', '.github/workflows/**/*.yml') }}
+          restore-keys: cargo-${{ runner.os }}
+
+      - name: Install rustup-toolchain-install-master
+        if: steps.cache.outputs.cache-hit != 'true'
+        run: cargo install -f rustup-toolchain-install-master hyperfine
+        shell: bash
+
+      - name: Install "master" toolchain
+        run: |
+          if [[ ${{ github.event_name }} == 'schedule' ]]; then
+            echo "Building against latest rustc git version"
+            git ls-remote https://github.com/rust-lang/rust/ HEAD | cut -f 1 > rust-version
+          fi
+          ./miri toolchain
+        shell: bash
+
+      - name: Show Rust version (miri toolchain)
+        run: |
+          rustup show
+          rustc -Vv
+          cargo -V
+        shell: bash

README.md

@@ -72,11 +72,13 @@ Further caveats that Miri users should be aware of:
   when `SeqCst` fences are used that are not actually permitted by the Rust memory model, and it
   cannot produce all behaviors possibly observable on real hardware.
 
-Moreover, Miri fundamentally cannot tell you whether your code is *sound*. [Soundness] is the property
-of never causing undefined behavior when invoked from arbitrary safe code, even in combination with
+Moreover, Miri fundamentally cannot ensure that your code is *sound*. [Soundness] is the property of
+never causing undefined behavior when invoked from arbitrary safe code, even in combination with
 other sound code. In contrast, Miri can just tell you if *a particular way of interacting with your
-code* (e.g., a test suite) causes any undefined behavior. It is up to you to ensure sufficient
-coverage.
+code* (e.g., a test suite) causes any undefined behavior *in a particular execution* (of which there
+may be many, e.g. when concurrency or other forms of non-determinism are involved). When Miri finds
+UB, your code is definitely unsound, but when Miri does not find UB, then you may just have to test
+more inputs or more possible non-deterministic choices.
 
 [rust]: https://www.rust-lang.org/
 [mir]: https://github.com/rust-lang/rfcs/blob/master/text/1211-mir.md
@@ -425,8 +427,12 @@ to Miri failing to detect cases of undefined behavior in a program.
   value from a load. This can help diagnose problems that disappear under
   `-Zmiri-disable-weak-memory-emulation`.
 * `-Zmiri-tree-borrows` replaces [Stacked Borrows] with the [Tree Borrows] rules.
-  The soundness rules are already experimental without this flag, but even more
-  so with this flag.
+  Tree Borrows is even more experimental than Stacked Borrows. While Tree Borrows
+  is still sound in the sense of catching all aliasing violations that current versions
+  of the compiler might exploit, it is likely that the eventual final aliasing model
+  of Rust will be stricter than Tree Borrows. In other words, if you use Tree Borrows,
+  even if your code is accepted today, it might be declared UB in the future.
+  This is much less likely with Stacked Borrows.
 * `-Zmiri-force-page-size=<num>` overrides the default page size for an architecture, in multiples of 1k.
   `4` is default for most targets. This value should always be a power of 2 and nonzero.
 * `-Zmiri-unique-is-unique` performs additional aliasing checks for `core::ptr::Unique` to ensure

build.rs

@@ -1,8 +1,10 @@
 fn main() {
     // Don't rebuild miri when nothing changed.
     println!("cargo:rerun-if-changed=build.rs");
-    // Re-export the TARGET environment variable so it can
-    // be accessed by miri.
+    // Re-export the TARGET environment variable so it can be accessed by miri. Needed to know the
+    // "host" triple inside Miri.
     let target = std::env::var("TARGET").unwrap();
     println!("cargo:rustc-env=TARGET={target}");
+    // Allow some cfgs.
+    println!("cargo::rustc-check-cfg=cfg(bootstrap)");
 }

cargo-miri/src/phases.rs

@@ -23,6 +23,12 @@ Subcommands:
     clean                    Clean the Miri cache & target directory
 
 The cargo options are exactly the same as for `cargo run` and `cargo test`, respectively.
+Furthermore, the following extra flags and environment variables are recognized for `run` and `test`:
+
+    --many-seeds[=from..to]  Run the program/tests many times with different seeds in the given range.
+                             The range defaults to `0..64`.
+
+    MIRIFLAGS                Extra flags to pass to the Miri driver. Use this to pass `-Zmiri-...` flags.
 
 Examples:
     cargo miri run

miri

@@ -3,5 +3,6 @@ set -e
 # Instead of doing just `cargo run --manifest-path .. $@`, we invoke miri-script binary directly. Invoking `cargo run` goes through
 # rustup (that sets it's own environmental variables), which is undesirable.
 MIRI_SCRIPT_TARGET_DIR="$(dirname "$0")"/miri-script/target
-cargo +stable build $CARGO_EXTRA_FLAGS -q --target-dir "$MIRI_SCRIPT_TARGET_DIR" --manifest-path "$(dirname "$0")"/miri-script/Cargo.toml
+cargo +stable build $CARGO_EXTRA_FLAGS -q --target-dir "$MIRI_SCRIPT_TARGET_DIR" --manifest-path "$(dirname "$0")"/miri-script/Cargo.toml || \
+  ( echo "Failed to build miri-script. Is the 'stable' toolchain installed?"; exit 1 )
 "$MIRI_SCRIPT_TARGET_DIR"/debug/miri-script "$@"

miri-script/src/commands.rs

@@ -252,12 +252,11 @@ impl Command {
         // Fetch given rustc commit.
         cmd!(sh, "git fetch http://localhost:{JOSH_PORT}/rust-lang/rust.git@{commit}{JOSH_FILTER}.git")
             .run()
-            .map_err(|e| {
+            .inspect_err(|_| {
                 // Try to un-do the previous `git commit`, to leave the repo in the state we found it.
                 cmd!(sh, "git reset --hard HEAD^")
                     .run()
                     .expect("FAILED to clean up again after failed `git fetch`, sorry for that");
-                e
             })
             .context("FAILED to fetch new commits, something went wrong (committing the rust-version file has been undone)")?;
 
@@ -545,9 +544,8 @@ impl Command {
         if let Some(seed_range) = many_seeds {
             e.run_many_times(seed_range, |sh, seed| {
                 eprintln!("Trying seed: {seed}");
-                run_miri(sh, Some(format!("-Zmiri-seed={seed}"))).map_err(|err| {
+                run_miri(sh, Some(format!("-Zmiri-seed={seed}"))).inspect_err(|_| {
                     eprintln!("FAILING SEED: {seed}");
-                    err
                 })
             })?;
         } else {

miri-script/src/util.rs

@@ -219,10 +219,9 @@ impl MiriEnv {
                             break;
                         }
                         // Run the command with this seed.
-                        run(&local_shell, cur).map_err(|err| {
+                        run(&local_shell, cur).inspect_err(|_| {
                             // If we failed, tell everyone about this.
                             failed.store(true, Ordering::Relaxed);
-                            err
                         })?;
                         // Check if some other command failed (in which case we'll stop as well).
                         if failed.load(Ordering::Relaxed) {

miri.bat

@@ -5,7 +5,8 @@ set MIRI_SCRIPT_TARGET_DIR=%0\..\miri-script\target
 
 :: If any other steps are added, the "|| exit /b" must be appended to early
 :: return from the script. If not, it will continue execution.
-cargo +stable build %CARGO_EXTRA_FLAGS% -q --target-dir %MIRI_SCRIPT_TARGET_DIR% --manifest-path %0\..\miri-script\Cargo.toml || exit /b
+cargo +stable build %CARGO_EXTRA_FLAGS% -q --target-dir %MIRI_SCRIPT_TARGET_DIR% --manifest-path %0\..\miri-script\Cargo.toml ^
+  || (echo Failed to build miri-script. Is the 'stable' toolchain installed? & exit /b)
 
 :: Forwards all arguments to this file to the executable.
 :: We invoke the binary directly to avoid going through rustup, which would set some extra

rust-version

@@ -1 +1 @@
-f6b4b71ef10307201b52c17b0f9dcf9557cd90ba
+9ed2ab3790ff41bf741dd690befd6a1c1e2b23ca