Auto merge of rust-lang#104456 - RalfJung:miri, r=RalfJung

update Miri

Not a huge sync, but there was a conflict and [josh](https://github.com/josh-project/josh/) seems to prefer those to be merged back ASAP.

.github/workflows/ci.yml

@@ -67,10 +67,10 @@ jobs:
         shell: bash
         run: |
           if [[ ${{ github.event_name }} == 'schedule' ]]; then
-            ./miri toolchain HEAD --host ${{ matrix.host_target }}
-          else
-            ./miri toolchain "" --host ${{ matrix.host_target }}
+            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
         run: |

CONTRIBUTING.md

@@ -150,7 +150,8 @@ is set the `MIRI_LIB_SRC` environment variable to the `library` folder of a
 `rust-lang/rust` repository checkout. Note that changing files in that directory
 does not automatically trigger a re-build of the standard library; you have to
 clear the Miri build cache manually (on Linux, `rm -rf ~/.cache/miri`;
-and on Windows, `rmdir /S "%LOCALAPPDATA%\rust-lang\miri\cache"`).
+on Windows, `rmdir /S "%LOCALAPPDATA%\rust-lang\miri\cache"`;
+and on macOS, `rm -rf ~/Library/Caches/org.rust-lang.miri`).
 
 ### Benchmarking
 
@@ -208,23 +209,6 @@ We described above the simplest way to get a working build environment for Miri,
 which is to use the version of rustc indicated by `rustc-version`. But
 sometimes, that is not enough.
 
-### Updating `rustc-version`
-
-The `rustc-version` file is regularly updated to keep Miri close to the latest
-version of rustc. Usually, new contributors do not have to worry about this. But
-sometimes a newer rustc is needed for a patch, and sometimes Miri needs fixing
-for changes in rustc. In both cases, `rustc-version` needs updating.
-
-To update the `rustc-version` file and install the latest rustc, you can run:
-```
-./miri toolchain HEAD
-```
-
-Now edit Miri until `./miri test` passes, and submit a PR. Generally, it is
-preferred to separate updating `rustc-version` and doing what it takes to get
-Miri working again, from implementing new features that rely on the updated
-rustc. This avoids blocking all Miri development on landing a big PR.
-
 ### Building Miri with a locally built rustc
 
 [building Miri with a locally built rustc]: #building-miri-with-a-locally-built-rustc
@@ -282,13 +266,13 @@ With this, you should now have a working development setup! See
 ## Advanced topic: Syncing with the rustc repo
 
 We use the [`josh` proxy](https://github.com/josh-project/josh) to transmit
-changes between the rustc and Miri repositories. For now, a fork of josh needs to be built
-from source. This downloads and runs josh:
+changes between the rustc and Miri repositories. For now, the latest git version
+of josh needs to be built from source. This downloads and runs josh:
 
 ```sh
-git clone https://github.com/RalfJung/josh
+git clone https://github.com/josh-project/josh
 cd josh
-cargo run --release -p josh-proxy -- --local=$(pwd)/local --remote=https://github.com --no-background
+cargo run --release -p josh-proxy -- --local=local --remote=https://github.com --no-background
 ```
 
 ### Importing changes from the rustc repo
@@ -298,9 +282,10 @@ We assume we start on an up-to-date master branch in the Miri repo.
 
 ```sh
 # Fetch and merge rustc side of the history. Takes ca 5 min the first time.
+# This will also update the 'rustc-version' file.
 ./miri rustc-pull
-# Update toolchain reference and apply formatting.
-./miri toolchain HEAD && ./miri fmt
+# Update local toolchain and apply formatting.
+./miri toolchain && ./miri fmt
 git commit -am "rustup"
 ```
 

Cargo.toml

@@ -40,7 +40,7 @@ libloading = "0.7"
 
 [dev-dependencies]
 colored = "2"
-ui_test = "0.3.1"
+ui_test = "0.4"
 rustc_version = "0.4"
 # Features chosen to match those required by env_logger, to avoid rebuilds
 regex = { version = "1.5.5", default-features = false, features = ["perf", "std"] }

README.md

@@ -432,7 +432,9 @@ Moreover, Miri recognizes some environment variables:
   must point to the `library` subdirectory of a `rust-lang/rust` repository
   checkout. Note that changing files in that directory does not automatically
   trigger a re-build of the standard library; you have to clear the Miri build
-  cache manually (on Linux, `rm -rf ~/.cache/miri`).
+  cache manually (on Linux, `rm -rf ~/.cache/miri`;
+  on Windows, `rmdir /S "%LOCALAPPDATA%\rust-lang\miri\cache"`;
+  and on macOS, `rm -rf ~/Library/Caches/org.rust-lang.miri`).
 * `MIRI_SYSROOT` (recognized by `cargo miri` and the Miri driver) indicates the sysroot to use. When
   using `cargo miri`, this skips the automatic setup -- only set this if you do not want to use the
   automatically created sysroot. For directly invoking the Miri driver, this variable (or a
@@ -568,6 +570,15 @@ extern "Rust" {
     /// program) the contents of a section of program memory, as bytes. Bytes
     /// written using this function will emerge from the interpreter's stderr.
     fn miri_write_to_stderr(bytes: &[u8]);
+
+    /// Miri-provided extern function to allocate memory from the interpreter.
+    /// 
+    /// This is useful when no fundamental way of allocating memory is
+    /// available, e.g. when using `no_std` + `alloc`.
+    fn miri_alloc(size: usize, align: usize) -> *mut u8;
+
+    /// Miri-provided extern function to deallocate memory.
+    fn miri_dealloc(ptr: *mut u8, size: usize, align: usize);
 }
 ```
 

cargo-miri/Cargo.toml

@@ -18,7 +18,7 @@ directories = "4"
 rustc_version = "0.4"
 serde_json = "1.0.40"
 cargo_metadata = "0.15.0"
-rustc-build-sysroot = "0.3.3"
+rustc-build-sysroot = "0.4"
 
 # A noop dependency that changes in the Rust repository, it's a bit of a hack.
 # See the `src/tools/rustc-workspace-hack/README.md` file in `rust-lang/rust`

cargo-miri/src/setup.rs

@@ -5,7 +5,7 @@ use std::ffi::OsStr;
 use std::path::PathBuf;
 use std::process::{self, Command};
 
-use rustc_build_sysroot::{BuildMode, Sysroot, SysrootConfig};
+use rustc_build_sysroot::{BuildMode, SysrootBuilder, SysrootConfig};
 use rustc_version::VersionMeta;
 
 use crate::util::*;
@@ -70,9 +70,11 @@ pub fn setup(subcommand: &MiriCommand, target: &str, rustc_version: &VersionMeta
     let sysroot_config = if std::env::var_os("MIRI_NO_STD").is_some() {
         SysrootConfig::NoStd
     } else {
-        SysrootConfig::WithStd { std_features: &["panic_unwind", "backtrace"] }
+        SysrootConfig::WithStd {
+            std_features: ["panic_unwind", "backtrace"].into_iter().map(Into::into).collect(),
+        }
     };
-    let cargo_cmd = || {
+    let cargo_cmd = {
         let mut command = cargo();
         // Use Miri as rustc to build a libstd compatible with us (and use the right flags).
         // However, when we are running in bootstrap, we cannot just overwrite `RUSTC`,
@@ -106,13 +108,14 @@ pub fn setup(subcommand: &MiriCommand, target: &str, rustc_version: &VersionMeta
             command.stdout(process::Stdio::null());
             command.stderr(process::Stdio::null());
         }
-        // Disable debug assertions in the standard library -- Miri is already slow enough.
-        // But keep the overflow checks, they are cheap. This completely overwrites flags
-        // the user might have set, which is consistent with normal `cargo build` that does
-        // not apply `RUSTFLAGS` to the sysroot either.
-        let rustflags = vec!["-Cdebug-assertions=off".into(), "-Coverflow-checks=on".into()];
-        (command, rustflags)
+
+        command
     };
+    // Disable debug assertions in the standard library -- Miri is already slow enough.
+    // But keep the overflow checks, they are cheap. This completely overwrites flags
+    // the user might have set, which is consistent with normal `cargo build` that does
+    // not apply `RUSTFLAGS` to the sysroot either.
+    let rustflags = &["-Cdebug-assertions=off", "-Coverflow-checks=on"];
     // Make sure all target-level Miri invocations know their sysroot.
     std::env::set_var("MIRI_SYSROOT", &sysroot_dir);
 
@@ -124,8 +127,13 @@ pub fn setup(subcommand: &MiriCommand, target: &str, rustc_version: &VersionMeta
         // We want to be quiet, but still let the user know that something is happening.
         eprint!("Preparing a sysroot for Miri (target: {target})... ");
     }
-    Sysroot::new(&sysroot_dir, target)
-        .build_from_source(&rust_src, BuildMode::Check, sysroot_config, rustc_version, cargo_cmd)
+    SysrootBuilder::new(&sysroot_dir, target)
+        .build_mode(BuildMode::Check)
+        .rustc_version(rustc_version.clone())
+        .sysroot_config(sysroot_config)
+        .rustflags(rustflags)
+        .cargo(cargo_cmd)
+        .build_from_source(&rust_src)
         .unwrap_or_else(|_| {
             if only_setup {
                 show_error!("failed to build sysroot, see error details above")