Auto merge of rust-lang#2665 - RalfJung:rustup, r=RalfJung

Rustup

Author: bors

README.md

@@ -436,8 +436,10 @@ Moreover, Miri recognizes some environment variables:
   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`, only set this if you do not want to use the automatically created sysroot. For
-  directly invoking the Miri driver, this variable (or a `--sysroot` flag) is mandatory.
+  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
+  `--sysroot` flag) is mandatory. When invoking `cargo miri setup`, this indicates where the sysroot
+  will be put.
 * `MIRI_TEST_TARGET` (recognized by the test suite and the `./miri` script) indicates which target
   architecture to test against.  `miri` and `cargo miri` accept the `--target` flag for the same
   purpose.

cargo-miri/src/setup.rs

@@ -17,10 +17,8 @@ pub fn setup(subcommand: &MiriCommand, target: &str, rustc_version: &VersionMeta
     let only_setup = matches!(subcommand, MiriCommand::Setup);
     let ask_user = !only_setup;
     let print_sysroot = only_setup && has_arg_flag("--print-sysroot"); // whether we just print the sysroot path
-    if std::env::var_os("MIRI_SYSROOT").is_some() {
-        if only_setup {
-            println!("WARNING: MIRI_SYSROOT already set, not doing anything.")
-        }
+    if !only_setup && std::env::var_os("MIRI_SYSROOT").is_some() {
+        // Skip setup step if MIRI_SYSROOT is explicitly set, *unless* we are `cargo miri setup`.
         return;
     }
 
@@ -61,8 +59,13 @@ pub fn setup(subcommand: &MiriCommand, target: &str, rustc_version: &VersionMeta
     }
 
     // Determine where to put the sysroot.
-    let user_dirs = directories::ProjectDirs::from("org", "rust-lang", "miri").unwrap();
-    let sysroot_dir = user_dirs.cache_dir();
+    let sysroot_dir = match std::env::var_os("MIRI_SYSROOT") {
+        Some(dir) => PathBuf::from(dir),
+        None => {
+            let user_dirs = directories::ProjectDirs::from("org", "rust-lang", "miri").unwrap();
+            user_dirs.cache_dir().to_owned()
+        }
+    };
     // Sysroot configuration and build details.
     let sysroot_config = if std::env::var_os("MIRI_NO_STD").is_some() {
         SysrootConfig::NoStd
@@ -114,7 +117,7 @@ pub fn setup(subcommand: &MiriCommand, target: &str, rustc_version: &VersionMeta
     // 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);
+    std::env::set_var("MIRI_SYSROOT", &sysroot_dir);
 
     // Do the build.
     if only_setup {
@@ -124,7 +127,7 @@ 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})... ");
     }
-    SysrootBuilder::new(sysroot_dir, target)
+    SysrootBuilder::new(&sysroot_dir, target)
         .build_mode(BuildMode::Check)
         .rustc_version(rustc_version.clone())
         .sysroot_config(sysroot_config)

rust-version

@@ -1 +1 @@
-11fa0850f03ae49fe1053a21bcdcf8a301668ad8
+101e1822c3e54e63996c8aaa014d55716f3937eb

src/stacked_borrows/mod.rs

@@ -1053,7 +1053,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 // pointers we need to retag, so we can stop recursion early.
                 // This optimization is crucial for ZSTs, because they can contain way more fields
                 // than we can ever visit.
-                if !place.layout.is_unsized() && place.layout.size < self.ecx.pointer_size() {
+                if place.layout.is_sized() && place.layout.size < self.ecx.pointer_size() {
                     return Ok(());
                 }