Auto merge of #63395 - Centril:rollup-kt805cj, r=Centril

Rollup of 6 pull requests

Successful merges:

 - #63162 (Miri tests: use xargo to build separate libstd)
 - #63289 (Don't recommend `extern crate` syntax)
 - #63373 (gitignore: add comment explaining policy)
 - #63374 (move of packed fields might or might not occur when they actually are sufficiently aligned)
 - #63381 (reduce visibility)
 - #63387 (Test interaction between `async { ... }` and `?`, `return`, and `break`)

Failed merges:

r? @ghost

6 files changed, 84 insertions, 48 deletions

diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index 23f81c2c876..54b689fb062 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -143,8 +143,11 @@ fn main() {
 
     if let Some(target) = target {
         // The stage0 compiler has a special sysroot distinct from what we
-        // actually downloaded, so we just always pass the `--sysroot` option.
-        cmd.arg("--sysroot").arg(&sysroot);
+        // actually downloaded, so we just always pass the `--sysroot` option,
+        // unless one is already set.
+        if !args.iter().any(|arg| arg == "--sysroot") {
+            cmd.arg("--sysroot").arg(&sysroot);
+        }
 
         cmd.arg("-Zexternal-macro-backtrace");
 
@@ -285,20 +288,6 @@ fn main() {
             }
         }
 
-        // When running miri tests, we need to generate MIR for all libraries
-        if env::var("TEST_MIRI").ok().map_or(false, |val| val == "true") {
-            // The flags here should be kept in sync with `add_miri_default_args`
-            // in miri's `src/lib.rs`.
-            cmd.arg("-Zalways-encode-mir");
-            cmd.arg("--cfg=miri");
-            // These options are preferred by miri, to be able to perform better validation,
-            // but the bootstrap compiler might not understand them.
-            if stage != "0" {
-                cmd.arg("-Zmir-emit-retag");
-                cmd.arg("-Zmir-opt-level=0");
-            }
-        }
-
         if let Ok(map) = env::var("RUSTC_DEBUGINFO_MAP") {
             cmd.arg("--remap-path-prefix").arg(&map);
         }
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 5a75497173e..e54c9360bae 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -543,15 +543,6 @@ impl<'a> Builder<'a> {
             parent: Cell::new(None),
         };
 
-        if kind == Kind::Dist {
-            assert!(
-                !builder.config.test_miri,
-                "Do not distribute with miri enabled.\n\
-                The distributed libraries would include all MIR (increasing binary size).
-                The distributed MIR would include validation statements."
-            );
-        }
-
         builder
     }
 
@@ -981,7 +972,6 @@ impl<'a> Builder<'a> {
                     PathBuf::from("/path/to/nowhere/rustdoc/not/required")
                 },
             )
-            .env("TEST_MIRI", self.config.test_miri.to_string())
             .env("RUSTC_ERROR_METADATA_DST", self.extended_error_dir());
 
         if let Some(host_linker) = self.linker(compiler.host) {
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 5a5f4ac7252..a5bfafdfdb4 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -128,7 +128,6 @@ pub struct Config {
     pub low_priority: bool,
     pub channel: String,
     pub verbose_tests: bool,
-    pub test_miri: bool,
     pub save_toolstates: Option<PathBuf>,
     pub print_step_timings: bool,
     pub missing_tools: bool,
@@ -315,7 +314,6 @@ struct Rust {
     debug: Option<bool>,
     dist_src: Option<bool>,
     verbose_tests: Option<bool>,
-    test_miri: Option<bool>,
     incremental: Option<bool>,
     save_toolstates: Option<String>,
     codegen_backends: Option<Vec<String>>,
@@ -375,7 +373,6 @@ impl Config {
         config.codegen_tests = true;
         config.ignore_git = false;
         config.rust_dist_src = true;
-        config.test_miri = false;
         config.rust_codegen_backends = vec![INTERNER.intern_str("llvm")];
         config.rust_codegen_backends_dir = "codegen-backends".to_owned();
         config.deny_warnings = true;
@@ -557,7 +554,6 @@ impl Config {
             set(&mut config.channel, rust.channel.clone());
             set(&mut config.rust_dist_src, rust.dist_src);
             set(&mut config.verbose_tests, rust.verbose_tests);
-            set(&mut config.test_miri, rust.test_miri);
             // in the case "false" is set explicitly, do not overwrite the command line args
             if let Some(true) = rust.incremental {
                 config.incremental = true;
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index 298330869b6..346f0cb2039 100755
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -36,7 +36,6 @@ o("docs", "build.docs", "build standard library documentation")
 o("compiler-docs", "build.compiler-docs", "build compiler documentation")
 o("optimize-tests", "rust.optimize-tests", "build tests with optimizations")
 o("parallel-compiler", "rust.parallel-compiler", "build a multi-threaded rustc")
-o("test-miri", "rust.test-miri", "run miri's test suite")
 o("verbose-tests", "rust.verbose-tests", "enable verbose output when running tests")
 o("ccache", "llvm.ccache", "invoke gcc/clang via ccache to reuse object files between builds")
 o("sccache", None, "invoke gcc/clang via sccache to reuse object files between builds")
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index c8ea3157dc9..b72aa78f3de 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -540,9 +540,7 @@ impl Build {
             Mode::Rustc => "-rustc",
             Mode::Codegen => "-codegen",
             Mode::ToolBootstrap => "-bootstrap-tools",
-            Mode::ToolStd => "-tools",
-            Mode::ToolTest => "-tools",
-            Mode::ToolRustc => "-tools",
+            Mode::ToolStd | Mode::ToolTest | Mode::ToolRustc => "-tools",
         };
         self.out.join(&*compiler.host)
                 .join(format!("stage{}{}", compiler.stage, suffix))
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index e5b0a46ba6f..c2c134bfd1d 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -363,11 +363,9 @@ pub struct Miri {
 impl Step for Miri {
     type Output = ();
     const ONLY_HOSTS: bool = true;
-    const DEFAULT: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        let test_miri = run.builder.config.test_miri;
-        run.path("src/tools/miri").default_condition(test_miri)
+        run.path("src/tools/miri")
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -389,26 +387,92 @@ impl Step for Miri {
             extra_features: Vec::new(),
         });
         if let Some(miri) = miri {
-            let mut cargo = tool::prepare_tool_cargo(builder,
-                                                 compiler,
-                                                 Mode::ToolRustc,
-                                                 host,
-                                                 "test",
-                                                 "src/tools/miri",
-                                                 SourceType::Submodule,
-                                                 &[]);
+            // # Run `cargo miri setup`.
+            // As a side-effect, this will install xargo.
+            let mut cargo = tool::prepare_tool_cargo(
+                builder,
+                compiler,
+                Mode::ToolRustc,
+                host,
+                "run",
+                "src/tools/miri",
+                SourceType::Submodule,
+                &[],
+            );
+            cargo
+                .arg("--bin")
+                .arg("cargo-miri")
+                .arg("--")
+                .arg("miri")
+                .arg("setup");
+
+            // Tell `cargo miri` not to worry about the sysroot mismatch (we built with
+            // stage1 but run with stage2).
+            cargo.env("MIRI_SKIP_SYSROOT_CHECK", "1");
+            // Tell `cargo miri setup` where to find the sources.
+            cargo.env("XARGO_RUST_SRC", builder.src.join("src"));
+            // Debug things.
+            cargo.env("RUST_BACKTRACE", "1");
+            // Configure `cargo install` path, and let cargo-miri know that that's where
+            // xargo ends up.
+            cargo.env("CARGO_INSTALL_ROOT", &builder.out); // cargo adds a `bin/`
+            cargo.env("XARGO", builder.out.join("bin").join("xargo"));
+
+            if !try_run(builder, &mut cargo) {
+                return;
+            }
+
+            // # Determine where Miri put its sysroot.
+            // To this end, we run `cargo miri setup --env` and capture the output.
+            // (We do this separately from the above so that when the setup actually
+            // happens we get some output.)
+            // We re-use the `cargo` from above.
+            cargo.arg("--env");
+
+            // FIXME: Is there a way in which we can re-use the usual `run` helpers?
+            let miri_sysroot = if builder.config.dry_run {
+                String::new()
+            } else {
+                builder.verbose(&format!("running: {:?}", cargo));
+                let out = cargo.output()
+                    .expect("We already ran `cargo miri setup` before and that worked");
+                assert!(out.status.success(), "`cargo miri setup` returned with non-0 exit code");
+                // Output is "MIRI_SYSROOT=<str>\n".
+                let stdout = String::from_utf8(out.stdout)
+                    .expect("`cargo miri setup` stdout is not valid UTF-8");
+                let stdout = stdout.trim();
+                builder.verbose(&format!("`cargo miri setup --env` returned: {:?}", stdout));
+                let sysroot = stdout.splitn(2, '=')
+                    .nth(1).expect("`cargo miri setup` stdout did not contain '='");
+                sysroot.to_owned()
+            };
+
+            // # Run `cargo test`.
+            let mut cargo = tool::prepare_tool_cargo(
+                builder,
+                compiler,
+                Mode::ToolRustc,
+                host,
+                "test",
+                "src/tools/miri",
+                SourceType::Submodule,
+                &[],
+            );
 
             // miri tests need to know about the stage sysroot
-            cargo.env("MIRI_SYSROOT", builder.sysroot(compiler));
+            cargo.env("MIRI_SYSROOT", miri_sysroot);
             cargo.env("RUSTC_TEST_SUITE", builder.rustc(compiler));
             cargo.env("RUSTC_LIB_PATH", builder.rustc_libdir(compiler));
             cargo.env("MIRI_PATH", miri);
 
             builder.add_rustc_lib_path(compiler, &mut cargo);
 
-            if try_run(builder, &mut cargo) {
-                builder.save_toolstate("miri", ToolState::TestPass);
+            if !try_run(builder, &mut cargo) {
+                return;
             }
+
+            // # Done!
+            builder.save_toolstate("miri", ToolState::TestPass);
         } else {
             eprintln!("failed to test miri: could not build");
         }