Rollup merge of #134040 - clubby789:bootstrap-eprintln, r=jieyouxu

bootstrap: print{ln}! -> eprint{ln}! (take 2)

r? `@jieyouxu`

Reland of #133817 with the `print!`s changed as well.

Author: fmease

src/bootstrap/src/bin/main.rs

@@ -48,9 +48,9 @@ fn main() {
             err => {
                 drop(err);
                 if let Ok(pid) = pid {
-                    println!("WARNING: build directory locked by process {pid}, waiting for lock");
+                    eprintln!("WARNING: build directory locked by process {pid}, waiting for lock");
                 } else {
-                    println!("WARNING: build directory locked, waiting for lock");
+                    eprintln!("WARNING: build directory locked, waiting for lock");
                 }
                 let mut lock = t!(build_lock.write());
                 t!(lock.write(process::id().to_string().as_ref()));
@@ -70,13 +70,13 @@ fn main() {
     // changelog warning, not the `x.py setup` message.
     let suggest_setup = config.config.is_none() && !matches!(config.cmd, Subcommand::Setup { .. });
     if suggest_setup {
-        println!("WARNING: you have not made a `config.toml`");
-        println!(
+        eprintln!("WARNING: you have not made a `config.toml`");
+        eprintln!(
             "HELP: consider running `./x.py setup` or copying `config.example.toml` by running \
             `cp config.example.toml config.toml`"
         );
     } else if let Some(suggestion) = &changelog_suggestion {
-        println!("{suggestion}");
+        eprintln!("{suggestion}");
     }
 
     let pre_commit = config.src.join(".git").join("hooks").join("pre-commit");
@@ -86,13 +86,13 @@ fn main() {
     Build::new(config).build();
 
     if suggest_setup {
-        println!("WARNING: you have not made a `config.toml`");
-        println!(
+        eprintln!("WARNING: you have not made a `config.toml`");
+        eprintln!(
             "HELP: consider running `./x.py setup` or copying `config.example.toml` by running \
             `cp config.example.toml config.toml`"
         );
     } else if let Some(suggestion) = &changelog_suggestion {
-        println!("{suggestion}");
+        eprintln!("{suggestion}");
     }
 
     // Give a warning if the pre-commit script is in pre-commit and not pre-push.
@@ -102,14 +102,14 @@ fn main() {
     if fs::read_to_string(pre_commit).is_ok_and(|contents| {
         contents.contains("https://github.com/rust-lang/rust/issues/77620#issuecomment-705144570")
     }) {
-        println!(
+        eprintln!(
             "WARNING: You have the pre-push script installed to .git/hooks/pre-commit. \
                   Consider moving it to .git/hooks/pre-push instead, which runs less often."
         );
     }
 
     if suggest_setup || changelog_suggestion.is_some() {
-        println!("NOTE: this message was printed twice to make it more likely to be seen");
+        eprintln!("NOTE: this message was printed twice to make it more likely to be seen");
     }
 
     if dump_bootstrap_shims {

src/bootstrap/src/bin/rustc.rs

@@ -306,7 +306,7 @@ fn main() {
         // should run on success, after this block.
     }
     if verbose > 0 {
-        println!("\nDid not run successfully: {status}\n{cmd:?}\n-------------");
+        eprintln!("\nDid not run successfully: {status}\n{cmd:?}\n-------------");
     }
 
     if let Some(mut on_fail) = on_fail {

src/bootstrap/src/core/build_steps/check.rs

@@ -287,7 +287,7 @@ impl Step for CodegenBackend {
     fn run(self, builder: &Builder<'_>) {
         // FIXME: remove once https://github.com/rust-lang/rust/issues/112393 is resolved
         if builder.build.config.vendor && self.backend == "gcc" {
-            println!("Skipping checking of `rustc_codegen_gcc` with vendoring enabled.");
+            eprintln!("Skipping checking of `rustc_codegen_gcc` with vendoring enabled.");
             return;
         }
 

src/bootstrap/src/core/build_steps/compile.rs

@@ -1611,7 +1611,7 @@ impl Step for Sysroot {
         let sysroot = sysroot_dir(compiler.stage);
 
         builder
-            .verbose(|| println!("Removing sysroot {} to avoid caching bugs", sysroot.display()));
+            .verbose(|| eprintln!("Removing sysroot {} to avoid caching bugs", sysroot.display()));
         let _ = fs::remove_dir_all(&sysroot);
         t!(fs::create_dir_all(&sysroot));
 
@@ -1681,7 +1681,7 @@ impl Step for Sysroot {
                     return true;
                 }
                 if !filtered_files.iter().all(|f| f != path.file_name().unwrap()) {
-                    builder.verbose_than(1, || println!("ignoring {}", path.display()));
+                    builder.verbose_than(1, || eprintln!("ignoring {}", path.display()));
                     false
                 } else {
                     true
@@ -2240,7 +2240,7 @@ pub fn stream_cargo(
         cargo.arg(arg);
     }
 
-    builder.verbose(|| println!("running: {cargo:?}"));
+    builder.verbose(|| eprintln!("running: {cargo:?}"));
 
     if builder.config.dry_run() {
         return true;
@@ -2261,12 +2261,12 @@ pub fn stream_cargo(
             Ok(msg) => {
                 if builder.config.json_output {
                     // Forward JSON to stdout.
-                    println!("{line}");
+                    eprintln!("{line}");
                 }
                 cb(msg)
             }
             // If this was informational, just print it out and continue
-            Err(_) => println!("{line}"),
+            Err(_) => eprintln!("{line}"),
         }
     }
 

src/bootstrap/src/core/build_steps/dist.rs

@@ -2080,7 +2080,7 @@ fn maybe_install_llvm(
     {
         let mut cmd = command(llvm_config);
         cmd.arg("--libfiles");
-        builder.verbose(|| println!("running {cmd:?}"));
+        builder.verbose(|| eprintln!("running {cmd:?}"));
         let files = cmd.run_capture_stdout(builder).stdout();
         let build_llvm_out = &builder.llvm_out(builder.config.build);
         let target_llvm_out = &builder.llvm_out(target);

src/bootstrap/src/core/build_steps/format.rs

@@ -107,10 +107,10 @@ fn print_paths(verb: &str, adjective: Option<&str>, paths: &[String]) {
         if let Some(adjective) = adjective { format!("{adjective} ") } else { String::new() };
     if len <= 10 {
         for path in paths {
-            println!("fmt: {verb} {adjective}file {path}");
+            eprintln!("fmt: {verb} {adjective}file {path}");
         }
     } else {
-        println!("fmt: {verb} {len} {adjective}files");
+        eprintln!("fmt: {verb} {len} {adjective}files");
     }
 }
 
@@ -199,7 +199,7 @@ pub fn format(build: &Builder<'_>, check: bool, all: bool, paths: &[PathBuf]) {
                 match get_modified_rs_files(build) {
                     Ok(Some(files)) => {
                         if files.is_empty() {
-                            println!("fmt info: No modified files detected for formatting.");
+                            eprintln!("fmt info: No modified files detected for formatting.");
                             return;
                         }
 

src/bootstrap/src/core/build_steps/setup.rs

@@ -134,7 +134,7 @@ impl Step for Profile {
                     t!(fs::remove_file(path));
                 }
                 _ => {
-                    println!("Exiting.");
+                    eprintln!("Exiting.");
                     crate::exit!(1);
                 }
             }
@@ -184,15 +184,15 @@ pub fn setup(config: &Config, profile: Profile) {
         Profile::Dist => &["dist", "build"],
     };
 
-    println!();
+    eprintln!();
 
-    println!("To get started, try one of the following commands:");
+    eprintln!("To get started, try one of the following commands:");
     for cmd in suggestions {
-        println!("- `x.py {cmd}`");
+        eprintln!("- `x.py {cmd}`");
     }
 
     if profile != Profile::Dist {
-        println!(
+        eprintln!(
             "For more suggestions, see https://rustc-dev-guide.rust-lang.org/building/suggested.html"
         );
     }
@@ -224,7 +224,7 @@ fn setup_config_toml(path: &PathBuf, profile: Profile, config: &Config) {
     t!(fs::write(path, settings));
 
     let include_path = profile.include_path(&config.src);
-    println!("`x.py` will now use the configuration at {}", include_path.display());
+    eprintln!("`x.py` will now use the configuration at {}", include_path.display());
 }
 
 /// Creates a toolchain link for stage1 using `rustup`
@@ -256,7 +256,7 @@ impl Step for Link {
         }
 
         if !rustup_installed(builder) {
-            println!("WARNING: `rustup` is not installed; Skipping `stage1` toolchain linking.");
+            eprintln!("WARNING: `rustup` is not installed; Skipping `stage1` toolchain linking.");
             return;
         }
 
@@ -296,7 +296,7 @@ fn attempt_toolchain_link(builder: &Builder<'_>, stage_path: &str) {
     }
 
     if try_link_toolchain(builder, stage_path) {
-        println!(
+        eprintln!(
             "Added `stage1` rustup toolchain; try `cargo +stage1 build` on a separate rust project to run a newly-built toolchain"
         );
     } else {
@@ -321,14 +321,14 @@ fn toolchain_is_linked(builder: &Builder<'_>) -> bool {
                 return false;
             }
             // The toolchain has already been linked.
-            println!(
+            eprintln!(
                 "`stage1` toolchain already linked; not attempting to link `stage1` toolchain"
             );
         }
         None => {
             // In this case, we don't know if the `stage1` toolchain has been linked;
             // but `rustup` failed, so let's not go any further.
-            println!(
+            eprintln!(
                 "`rustup` failed to list current toolchains; not attempting to link `stage1` toolchain"
             );
         }
@@ -389,12 +389,12 @@ pub fn interactive_path() -> io::Result<Profile> {
         input.parse()
     }
 
-    println!("Welcome to the Rust project! What do you want to do with x.py?");
+    eprintln!("Welcome to the Rust project! What do you want to do with x.py?");
     for ((letter, _), profile) in abbrev_all() {
-        println!("{}) {}: {}", letter, profile, profile.purpose());
+        eprintln!("{}) {}: {}", letter, profile, profile.purpose());
     }
     let template = loop {
-        print!(
+        eprint!(
             "Please choose one ({}): ",
             abbrev_all().map(|((l, _), _)| l).collect::<Vec<_>>().join("/")
         );
@@ -428,7 +428,7 @@ enum PromptResult {
 fn prompt_user(prompt: &str) -> io::Result<Option<PromptResult>> {
     let mut input = String::new();
     loop {
-        print!("{prompt} ");
+        eprint!("{prompt} ");
         io::stdout().flush()?;
         input.clear();
         io::stdin().read_line(&mut input)?;
@@ -490,15 +490,15 @@ fn install_git_hook_maybe(builder: &Builder<'_>, config: &Config) -> io::Result<
         return Ok(());
     }
 
-    println!(
+    eprintln!(
         "\nRust's CI will automatically fail if it doesn't pass `tidy`, the internal tool for ensuring code quality.
 If you'd like, x.py can install a git hook for you that will automatically run `test tidy` before
 pushing your code to ensure your code is up to par. If you decide later that this behavior is
 undesirable, simply delete the `pre-push` file from .git/hooks."
     );
 
     if prompt_user("Would you like to install the git hook?: [y/N]")? != Some(PromptResult::Yes) {
-        println!("Ok, skipping installation!");
+        eprintln!("Ok, skipping installation!");
         return Ok(());
     }
     if !hooks_dir.exists() {
@@ -515,7 +515,7 @@ undesirable, simply delete the `pre-push` file from .git/hooks."
             );
             return Err(e);
         }
-        Ok(_) => println!("Linked `src/etc/pre-push.sh` to `.git/hooks/pre-push`"),
+        Ok(_) => eprintln!("Linked `src/etc/pre-push.sh` to `.git/hooks/pre-push`"),
     };
     Ok(())
 }
@@ -541,7 +541,7 @@ Select which editor you would like to set up [default: None]: ";
 
         let mut input = String::new();
         loop {
-            print!("{}", prompt_str);
+            eprint!("{}", prompt_str);
             io::stdout().flush()?;
             input.clear();
             io::stdin().read_line(&mut input)?;
@@ -656,7 +656,7 @@ impl Step for Editor {
                 if let Some(editor_kind) = editor_kind {
                     while !t!(create_editor_settings_maybe(config, editor_kind.clone())) {}
                 } else {
-                    println!("Ok, skipping editor setup!");
+                    eprintln!("Ok, skipping editor setup!");
                 }
             }
             Err(e) => eprintln!("Could not determine the editor: {e}"),
@@ -689,7 +689,7 @@ fn create_editor_settings_maybe(config: &Config, editor: EditorKind) -> io::Resu
             mismatched_settings = Some(false);
         }
     }
-    println!(
+    eprintln!(
         "\nx.py can automatically install the recommended `{settings_filename}` file for rustc development"
     );
 
@@ -708,7 +708,7 @@ fn create_editor_settings_maybe(config: &Config, editor: EditorKind) -> io::Resu
         Some(PromptResult::Yes) => true,
         Some(PromptResult::Print) => false,
         _ => {
-            println!("Ok, skipping settings!");
+            eprintln!("Ok, skipping settings!");
             return Ok(true);
         }
     };
@@ -735,9 +735,9 @@ fn create_editor_settings_maybe(config: &Config, editor: EditorKind) -> io::Resu
             _ => "Created",
         };
         fs::write(&settings_path, editor.settings_template())?;
-        println!("{verb} `{}`", settings_filename);
+        eprintln!("{verb} `{}`", settings_filename);
     } else {
-        println!("\n{}", editor.settings_template());
+        eprintln!("\n{}", editor.settings_template());
     }
     Ok(should_create)
 }

src/bootstrap/src/core/build_steps/suggest.rs

@@ -66,6 +66,6 @@ pub fn suggest(builder: &Builder<'_>, run: bool) {
             build.build();
         }
     } else {
-        println!("HELP: consider using the `--run` flag to automatically run suggested tests");
+        eprintln!("HELP: consider using the `--run` flag to automatically run suggested tests");
     }
 }

src/bootstrap/src/core/build_steps/test.rs

@@ -471,11 +471,11 @@ impl Miri {
         // We re-use the `cargo` from above.
         cargo.arg("--print-sysroot");
 
-        builder.verbose(|| println!("running: {cargo:?}"));
+        builder.verbose(|| eprintln!("running: {cargo:?}"));
         let stdout = cargo.run_capture_stdout(builder).stdout();
         // Output is "<sysroot>\n".
         let sysroot = stdout.trim_end();
-        builder.verbose(|| println!("`cargo miri setup --print-sysroot` said: {sysroot:?}"));
+        builder.verbose(|| eprintln!("`cargo miri setup --print-sysroot` said: {sysroot:?}"));
         PathBuf::from(sysroot)
     }
 }
@@ -2488,7 +2488,7 @@ fn markdown_test(builder: &Builder<'_>, compiler: Compiler, markdown: &Path) ->
         }
     }
 
-    builder.verbose(|| println!("doc tests for: {}", markdown.display()));
+    builder.verbose(|| eprintln!("doc tests for: {}", markdown.display()));
     let mut cmd = builder.rustdoc_cmd(compiler);
     builder.add_rust_test_threads(&mut cmd);
     // allow for unstable options such as new editions

src/bootstrap/src/core/builder/cargo.rs

@@ -523,7 +523,7 @@ impl Builder<'_> {
 
         let sysroot_str = sysroot.as_os_str().to_str().expect("sysroot should be UTF-8");
         if self.is_verbose() && !matches!(self.config.dry_run, DryRun::SelfCheck) {
-            println!("using sysroot {sysroot_str}");
+            eprintln!("using sysroot {sysroot_str}");
         }
 
         let mut rustflags = Rustflags::new(target);

src/bootstrap/src/core/builder/mod.rs

@@ -392,14 +392,14 @@ impl StepDescription {
     fn is_excluded(&self, builder: &Builder<'_>, pathset: &PathSet) -> bool {
         if builder.config.skip.iter().any(|e| pathset.has(e, builder.kind)) {
             if !matches!(builder.config.dry_run, DryRun::SelfCheck) {
-                println!("Skipping {pathset:?} because it is excluded");
+                eprintln!("Skipping {pathset:?} because it is excluded");
             }
             return true;
         }
 
         if !builder.config.skip.is_empty() && !matches!(builder.config.dry_run, DryRun::SelfCheck) {
             builder.verbose(|| {
-                println!(
+                eprintln!(
                     "{:?} not skipped for {:?} -- not in {:?}",
                     pathset, self.name, builder.config.skip
                 )
@@ -1437,11 +1437,11 @@ impl<'a> Builder<'a> {
                 panic!("{}", out);
             }
             if let Some(out) = self.cache.get(&step) {
-                self.verbose_than(1, || println!("{}c {:?}", "  ".repeat(stack.len()), step));
+                self.verbose_than(1, || eprintln!("{}c {:?}", "  ".repeat(stack.len()), step));
 
                 return out;
             }
-            self.verbose_than(1, || println!("{}> {:?}", "  ".repeat(stack.len()), step));
+            self.verbose_than(1, || eprintln!("{}> {:?}", "  ".repeat(stack.len()), step));
             stack.push(Box::new(step.clone()));
         }
 
@@ -1462,7 +1462,7 @@ impl<'a> Builder<'a> {
             let step_string = format!("{step:?}");
             let brace_index = step_string.find('{').unwrap_or(0);
             let type_string = type_name::<S>();
-            println!(
+            eprintln!(
                 "[TIMING] {} {} -- {}.{:03}",
                 &type_string.strip_prefix("bootstrap::").unwrap_or(type_string),
                 &step_string[brace_index..],
@@ -1479,7 +1479,9 @@ impl<'a> Builder<'a> {
             let cur_step = stack.pop().expect("step stack empty");
             assert_eq!(cur_step.downcast_ref(), Some(&step));
         }
-        self.verbose_than(1, || println!("{}< {:?}", "  ".repeat(self.stack.borrow().len()), step));
+        self.verbose_than(1, || {
+            eprintln!("{}< {:?}", "  ".repeat(self.stack.borrow().len()), step)
+        });
         self.cache.put(step, out.clone());
         out
     }

src/bootstrap/src/core/config/config.rs

@@ -1293,7 +1293,7 @@ impl Config {
                     .map(|change_id| change_id.inner.map(crate::find_recent_config_change_ids))
                 {
                     if !changes.is_empty() {
-                        println!(
+                        eprintln!(
                             "WARNING: There have been changes to x.py since you last updated:\n{}",
                             crate::human_readable_changes(&changes)
                         );
@@ -1559,7 +1559,7 @@ impl Config {
         }
 
         if cargo_clippy.is_some() && rustc.is_none() {
-            println!(
+            eprintln!(
                 "WARNING: Using `build.cargo-clippy` without `build.rustc` usually fails due to toolchain conflict."
             );
         }
@@ -1841,7 +1841,7 @@ impl Config {
 
             // FIXME: Remove this option at the end of 2024.
             if parallel_compiler.is_some() {
-                println!(
+                eprintln!(
                     "WARNING: The `rust.parallel-compiler` option is deprecated and does nothing. The parallel compiler (with one thread) is now the default"
                 );
             }
@@ -1873,7 +1873,7 @@ impl Config {
                         if available_backends.contains(&backend) {
                             panic!("Invalid value '{s}' for 'rust.codegen-backends'. Instead, please use '{backend}'.");
                         } else {
-                            println!("HELP: '{s}' for 'rust.codegen-backends' might fail. \
+                            eprintln!("HELP: '{s}' for 'rust.codegen-backends' might fail. \
                                 Codegen backends are mostly defined without the '{CODEGEN_BACKEND_PREFIX}' prefix. \
                                 In this case, it would be referred to as '{backend}'.");
                         }
@@ -1902,7 +1902,7 @@ impl Config {
         // tests may fail due to using a different channel than the one used by the compiler during tests.
         if let Some(commit) = &config.download_rustc_commit {
             if is_user_configured_rust_channel {
-                println!(
+                eprintln!(
                     "WARNING: `rust.download-rustc` is enabled. The `rust.channel` option will be overridden by the CI rustc's channel."
                 );
 
@@ -1992,10 +1992,10 @@ impl Config {
 
             if config.llvm_from_ci {
                 let warn = |option: &str| {
-                    println!(
+                    eprintln!(
                         "WARNING: `{option}` will only be used on `compiler/rustc_llvm` build, not for the LLVM build."
                     );
-                    println!(
+                    eprintln!(
                         "HELP: To use `{option}` for LLVM builds, set `download-ci-llvm` option to false."
                     );
                 };
@@ -2014,12 +2014,12 @@ impl Config {
                 // if they've chosen a different value.
 
                 if libzstd.is_some() {
-                    println!(
+                    eprintln!(
                         "WARNING: when using `download-ci-llvm`, the local `llvm.libzstd` option, \
                         like almost all `llvm.*` options, will be ignored and set by the LLVM CI \
                         artifacts builder config."
                     );
-                    println!(
+                    eprintln!(
                         "HELP: To use `llvm.libzstd` for LLVM/LLD builds, set `download-ci-llvm` option to false."
                     );
                 }
@@ -2088,7 +2088,7 @@ impl Config {
                             if available_backends.contains(&backend) {
                                 panic!("Invalid value '{s}' for 'target.{triple}.codegen-backends'. Instead, please use '{backend}'.");
                             } else {
-                                println!("HELP: '{s}' for 'target.{triple}.codegen-backends' might fail. \
+                                eprintln!("HELP: '{s}' for 'target.{triple}.codegen-backends' might fail. \
                                     Codegen backends are mostly defined without the '{CODEGEN_BACKEND_PREFIX}' prefix. \
                                     In this case, it would be referred to as '{backend}'.");
                             }
@@ -2304,7 +2304,7 @@ impl Config {
         if self.dry_run() {
             return Ok(());
         }
-        self.verbose(|| println!("running: {cmd:?}"));
+        self.verbose(|| eprintln!("running: {cmd:?}"));
         build_helper::util::try_run(cmd, self.is_verbose())
     }
 
@@ -2479,7 +2479,7 @@ impl Config {
                         // This happens when LLVM submodule is updated in CI, we should disable ci-rustc without an error
                         // to not break CI. For non-CI environments, we should return an error.
                         if CiEnv::is_ci() {
-                            println!("WARNING: LLVM submodule has changes, `download-rustc` will be disabled.");
+                            eprintln!("WARNING: LLVM submodule has changes, `download-rustc` will be disabled.");
                             return None;
                         } else {
                             panic!("ERROR: LLVM submodule has changes, `download-rustc` can't be used.");
@@ -2490,8 +2490,8 @@ impl Config {
                         let ci_config_toml = match self.get_builder_toml("ci-rustc") {
                             Ok(ci_config_toml) => ci_config_toml,
                             Err(e) if e.to_string().contains("unknown field") => {
-                                println!("WARNING: CI rustc has some fields that are no longer supported in bootstrap; download-rustc will be disabled.");
-                                println!("HELP: Consider rebasing to a newer commit if available.");
+                                eprintln!("WARNING: CI rustc has some fields that are no longer supported in bootstrap; download-rustc will be disabled.");
+                                eprintln!("HELP: Consider rebasing to a newer commit if available.");
                                 return None;
                             },
                             Err(e) => {
@@ -2516,7 +2516,7 @@ impl Config {
                             .is_some_and(|s| s == "1" || s == "true");
 
                         if disable_ci_rustc_if_incompatible && res.is_err() {
-                            println!("WARNING: download-rustc is disabled with `DISABLE_CI_RUSTC_IF_INCOMPATIBLE` env.");
+                            eprintln!("WARNING: download-rustc is disabled with `DISABLE_CI_RUSTC_IF_INCOMPATIBLE` env.");
                             return None;
                         }
 
@@ -2701,7 +2701,7 @@ impl Config {
             return;
         }
 
-        println!("Updating submodule {relative_path}");
+        eprintln!("Updating submodule {relative_path}");
         self.check_run(
             helpers::git(Some(&self.src))
                 .run_always()
@@ -2824,7 +2824,7 @@ impl Config {
             Some(StringOrBool::Bool(true)) => false,
             Some(StringOrBool::String(s)) if s == "if-unchanged" => {
                 if !self.rust_info.is_managed_git_subrepository() {
-                    println!(
+                    eprintln!(
                         "ERROR: `download-rustc=if-unchanged` is only compatible with Git managed sources."
                     );
                     crate::exit!(1);
@@ -2857,10 +2857,10 @@ impl Config {
                 if if_unchanged {
                     return None;
                 }
-                println!("ERROR: could not find commit hash for downloading rustc");
-                println!("HELP: maybe your repository history is too shallow?");
-                println!("HELP: consider setting `rust.download-rustc=false` in config.toml");
-                println!("HELP: or fetch enough history to include one upstream commit");
+                eprintln!("ERROR: could not find commit hash for downloading rustc");
+                eprintln!("HELP: maybe your repository history is too shallow?");
+                eprintln!("HELP: consider setting `rust.download-rustc=false` in config.toml");
+                eprintln!("HELP: or fetch enough history to include one upstream commit");
                 crate::exit!(1);
             }
         };
@@ -2899,7 +2899,7 @@ impl Config {
         let if_unchanged = || {
             if self.rust_info.is_from_tarball() {
                 // Git is needed for running "if-unchanged" logic.
-                println!(
+                eprintln!(
                     "WARNING: 'if-unchanged' has no effect on tarball sources; ignoring `download-ci-llvm`."
                 );
                 return false;
@@ -2948,10 +2948,10 @@ impl Config {
         // Only commits merged by bors will have CI artifacts.
         let commit = get_closest_merge_commit(Some(&self.src), &self.git_config(), &[]).unwrap();
         if commit.is_empty() {
-            println!("error: could not find commit hash for downloading components from CI");
-            println!("help: maybe your repository history is too shallow?");
-            println!("help: consider disabling `{option_name}`");
-            println!("help: or fetch enough history to include one upstream commit");
+            eprintln!("error: could not find commit hash for downloading components from CI");
+            eprintln!("help: maybe your repository history is too shallow?");
+            eprintln!("help: consider disabling `{option_name}`");
+            eprintln!("help: or fetch enough history to include one upstream commit");
             crate::exit!(1);
         }
 
@@ -2963,14 +2963,14 @@ impl Config {
         if has_changes {
             if if_unchanged {
                 if self.is_verbose() {
-                    println!(
+                    eprintln!(
                         "warning: saw changes to one of {modified_paths:?} since {commit}; \
                             ignoring `{option_name}`"
                     );
                 }
                 return None;
             }
-            println!(
+            eprintln!(
                 "warning: `{option_name}` is enabled, but there are changes to one of {modified_paths:?}"
             );
         }
@@ -3007,7 +3007,7 @@ pub(crate) fn check_incompatible_options_for_ci_llvm(
         ($current:expr, $expected:expr) => {
             if let Some(current) = &$current {
                 if Some(current) != $expected.as_ref() {
-                    println!(
+                    eprintln!(
                         "WARNING: `llvm.{}` has no effect with `llvm.download-ci-llvm`. \
                         Current value: {:?}, Expected value(s): {}{:?}",
                         stringify!($expected).replace("_", "-"),
@@ -3112,7 +3112,7 @@ fn check_incompatible_options_for_ci_rustc(
         ($current:expr, $expected:expr, $config_section:expr) => {
             if let Some(current) = &$current {
                 if Some(current) != $expected.as_ref() {
-                    println!(
+                    eprintln!(
                         "WARNING: `{}` has no effect with `rust.download-rustc`. \
                         Current value: {:?}, Expected value(s): {}{:?}",
                         format!("{}.{}", $config_section, stringify!($expected).replace("_", "-")),

src/bootstrap/src/core/config/flags.rs

@@ -196,12 +196,12 @@ impl Flags {
         if let Ok(HelpVerboseOnly { help: true, verbose: 1.., cmd: subcommand }) =
             HelpVerboseOnly::try_parse_from(normalize_args(args))
         {
-            println!("NOTE: updating submodules before printing available paths");
+            eprintln!("NOTE: updating submodules before printing available paths");
             let config = Config::parse(Self::parse(&[String::from("build")]));
             let build = Build::new(config);
             let paths = Builder::get_help(&build, subcommand);
             if let Some(s) = paths {
-                println!("{s}");
+                eprintln!("{s}");
             } else {
                 panic!("No paths available for subcommand `{}`", subcommand.as_str());
             }

src/bootstrap/src/core/download.rs

@@ -77,7 +77,7 @@ impl Config {
         if self.dry_run() && !cmd.run_always {
             return true;
         }
-        self.verbose(|| println!("running: {cmd:?}"));
+        self.verbose(|| eprintln!("running: {cmd:?}"));
         check_run(cmd, self.is_verbose())
     }
 
@@ -144,7 +144,7 @@ impl Config {
     /// Please see <https://nixos.org/patchelf.html> for more information
     fn fix_bin_or_dylib(&self, fname: &Path) {
         assert_eq!(SHOULD_FIX_BINS_AND_DYLIBS.get(), Some(&true));
-        println!("attempting to patch {}", fname.display());
+        eprintln!("attempting to patch {}", fname.display());
 
         // Only build `.nix-deps` once.
         static NIX_DEPS_DIR: OnceLock<PathBuf> = OnceLock::new();
@@ -206,7 +206,7 @@ impl Config {
     }
 
     fn download_file(&self, url: &str, dest_path: &Path, help_on_error: &str) {
-        self.verbose(|| println!("download {url}"));
+        self.verbose(|| eprintln!("download {url}"));
         // Use a temporary file in case we crash while downloading, to avoid a corrupt download in cache/.
         let tempfile = self.tempdir().join(dest_path.file_name().unwrap());
         // While bootstrap itself only supports http and https downloads, downstream forks might
@@ -226,7 +226,7 @@ impl Config {
     }
 
     fn download_http_with_retries(&self, tempfile: &Path, url: &str, help_on_error: &str) {
-        println!("downloading {url}");
+        eprintln!("downloading {url}");
         // Try curl. If that fails and we are on windows, fallback to PowerShell.
         // options should be kept in sync with
         // src/bootstrap/src/core/download.rs
@@ -341,7 +341,7 @@ impl Config {
             short_path = short_path.strip_prefix(pattern).unwrap_or(short_path);
             let dst_path = dst.join(short_path);
             self.verbose(|| {
-                println!("extracting {} to {}", original_path.display(), dst.display())
+                eprintln!("extracting {} to {}", original_path.display(), dst.display())
             });
             if !t!(member.unpack_in(dst)) {
                 panic!("path traversal attack ??");
@@ -365,7 +365,7 @@ impl Config {
     pub(crate) fn verify(&self, path: &Path, expected: &str) -> bool {
         use sha2::Digest;
 
-        self.verbose(|| println!("verifying {}", path.display()));
+        self.verbose(|| eprintln!("verifying {}", path.display()));
 
         if self.dry_run() {
             return false;
@@ -391,7 +391,7 @@ impl Config {
         let verified = checksum == expected;
 
         if !verified {
-            println!(
+            eprintln!(
                 "invalid checksum: \n\
                 found:    {checksum}\n\
                 expected: {expected}",
@@ -421,7 +421,7 @@ enum DownloadSource {
 /// Functions that are only ever called once, but named for clarify and to avoid thousand-line functions.
 impl Config {
     pub(crate) fn download_clippy(&self) -> PathBuf {
-        self.verbose(|| println!("downloading stage0 clippy artifacts"));
+        self.verbose(|| eprintln!("downloading stage0 clippy artifacts"));
 
         let date = &self.stage0_metadata.compiler.date;
         let version = &self.stage0_metadata.compiler.version;
@@ -518,7 +518,7 @@ impl Config {
     }
 
     pub(crate) fn download_ci_rustc(&self, commit: &str) {
-        self.verbose(|| println!("using downloaded stage2 artifacts from CI (commit {commit})"));
+        self.verbose(|| eprintln!("using downloaded stage2 artifacts from CI (commit {commit})"));
 
         let version = self.artifact_version_part(commit);
         // download-rustc doesn't need its own cargo, it can just use beta's. But it does need the
@@ -539,7 +539,7 @@ impl Config {
 
     #[cfg(not(feature = "bootstrap-self-test"))]
     pub(crate) fn download_beta_toolchain(&self) {
-        self.verbose(|| println!("downloading stage0 beta artifacts"));
+        self.verbose(|| eprintln!("downloading stage0 beta artifacts"));
 
         let date = &self.stage0_metadata.compiler.date;
         let version = &self.stage0_metadata.compiler.version;
@@ -677,7 +677,7 @@ impl Config {
                     return;
                 } else {
                     self.verbose(|| {
-                        println!(
+                        eprintln!(
                             "ignoring cached file {} due to failed verification",
                             tarball.display()
                         )
@@ -776,10 +776,10 @@ download-rustc = false
                     t!(check_incompatible_options_for_ci_llvm(current_config_toml, ci_config_toml));
                 }
                 Err(e) if e.to_string().contains("unknown field") => {
-                    println!(
+                    eprintln!(
                         "WARNING: CI LLVM has some fields that are no longer supported in bootstrap; download-ci-llvm will be disabled."
                     );
-                    println!("HELP: Consider rebasing to a newer commit if available.");
+                    eprintln!("HELP: Consider rebasing to a newer commit if available.");
                 }
                 Err(e) => {
                     eprintln!("ERROR: Failed to parse CI LLVM config.toml: {e}");

src/bootstrap/src/core/sanity.rs

@@ -237,11 +237,11 @@ than building it.
                 stage0_supported_target_list.intersection(&missing_targets_hashset).collect();
 
             if !duplicated_targets.is_empty() {
-                println!(
+                eprintln!(
                     "Following targets supported from the stage0 compiler, please remove them from STAGE0_MISSING_TARGETS list."
                 );
                 for duplicated_target in duplicated_targets {
-                    println!("  {duplicated_target}");
+                    eprintln!("  {duplicated_target}");
                 }
                 std::process::exit(1);
             }

src/bootstrap/src/lib.rs

@@ -406,19 +406,19 @@ impl Build {
             .unwrap()
             .trim();
         if local_release.split('.').take(2).eq(version.split('.').take(2)) {
-            build.verbose(|| println!("auto-detected local-rebuild {local_release}"));
+            build.verbose(|| eprintln!("auto-detected local-rebuild {local_release}"));
             build.local_rebuild = true;
         }
 
-        build.verbose(|| println!("finding compilers"));
+        build.verbose(|| eprintln!("finding compilers"));
         utils::cc_detect::find(&build);
         // When running `setup`, the profile is about to change, so any requirements we have now may
         // be different on the next invocation. Don't check for them until the next time x.py is
         // run. This is ok because `setup` never runs any build commands, so it won't fail if commands are missing.
         //
         // Similarly, for `setup` we don't actually need submodules or cargo metadata.
         if !matches!(build.config.cmd, Subcommand::Setup { .. }) {
-            build.verbose(|| println!("running sanity check"));
+            build.verbose(|| eprintln!("running sanity check"));
             crate::core::sanity::check(&mut build);
 
             // Make sure we update these before gathering metadata so we don't get an error about missing
@@ -436,7 +436,7 @@ impl Build {
             // Now, update all existing submodules.
             build.update_existing_submodules();
 
-            build.verbose(|| println!("learning about cargo"));
+            build.verbose(|| eprintln!("learning about cargo"));
             crate::core::metadata::build(&mut build);
         }
 
@@ -605,7 +605,7 @@ impl Build {
         let stamp = dir.join(".stamp");
         let mut cleared = false;
         if mtime(&stamp) < mtime(input) {
-            self.verbose(|| println!("Dirty - {}", dir.display()));
+            self.verbose(|| eprintln!("Dirty - {}", dir.display()));
             let _ = fs::remove_dir_all(dir);
             cleared = true;
         } else if stamp.exists() {
@@ -890,7 +890,7 @@ impl Build {
         let executed_at = std::panic::Location::caller();
 
         self.verbose(|| {
-            println!("running: {command:?} (created at {created_at}, executed at {executed_at})")
+            eprintln!("running: {command:?} (created at {created_at}, executed at {executed_at})")
         });
 
         let cmd = command.as_command_mut();
@@ -947,7 +947,7 @@ Executed at: {executed_at}"#,
 
         let fail = |message: &str, output: CommandOutput| -> ! {
             if self.is_verbose() {
-                println!("{message}");
+                eprintln!("{message}");
             } else {
                 let (stdout, stderr) = (output.stdout_if_present(), output.stderr_if_present());
                 // If the command captures output, the user would not see any indication that
@@ -957,16 +957,16 @@ Executed at: {executed_at}"#,
                     if let Some(stdout) =
                         output.stdout_if_present().take_if(|s| !s.trim().is_empty())
                     {
-                        println!("STDOUT:\n{stdout}\n");
+                        eprintln!("STDOUT:\n{stdout}\n");
                     }
                     if let Some(stderr) =
                         output.stderr_if_present().take_if(|s| !s.trim().is_empty())
                     {
-                        println!("STDERR:\n{stderr}\n");
+                        eprintln!("STDERR:\n{stderr}\n");
                     }
-                    println!("Command {command:?} has failed. Rerun with -v to see more details.");
+                    eprintln!("Command {command:?} has failed. Rerun with -v to see more details.");
                 } else {
-                    println!("Command has failed. Rerun with -v to see more details.");
+                    eprintln!("Command has failed. Rerun with -v to see more details.");
                 }
             }
             exit!(1);
@@ -1011,7 +1011,7 @@ Executed at: {executed_at}"#,
         match self.config.dry_run {
             DryRun::SelfCheck => (),
             DryRun::Disabled | DryRun::UserSelected => {
-                println!("{msg}");
+                eprintln!("{msg}");
             }
         }
     }
@@ -1666,7 +1666,7 @@ Executed at: {executed_at}"#,
         if self.config.dry_run() {
             return;
         }
-        self.verbose_than(1, || println!("Copy/Link {src:?} to {dst:?}"));
+        self.verbose_than(1, || eprintln!("Copy/Link {src:?} to {dst:?}"));
         if src == dst {
             return;
         }
@@ -1775,7 +1775,7 @@ Executed at: {executed_at}"#,
             return;
         }
         let dst = dstdir.join(src.file_name().unwrap());
-        self.verbose_than(1, || println!("Install {src:?} to {dst:?}"));
+        self.verbose_than(1, || eprintln!("Install {src:?} to {dst:?}"));
         t!(fs::create_dir_all(dstdir));
         if !src.exists() {
             panic!("ERROR: File \"{}\" not found!", src.display());

src/bootstrap/src/utils/cc_detect.rs

@@ -155,15 +155,15 @@ pub fn find_target(build: &Build, target: TargetSelection) {
         build.cxx.borrow_mut().insert(target, compiler);
     }
 
-    build.verbose(|| println!("CC_{} = {:?}", target.triple, build.cc(target)));
-    build.verbose(|| println!("CFLAGS_{} = {cflags:?}", target.triple));
+    build.verbose(|| eprintln!("CC_{} = {:?}", target.triple, build.cc(target)));
+    build.verbose(|| eprintln!("CFLAGS_{} = {cflags:?}", target.triple));
     if let Ok(cxx) = build.cxx(target) {
         let cxxflags = build.cflags(target, GitRepo::Rustc, CLang::Cxx);
-        build.verbose(|| println!("CXX_{} = {cxx:?}", target.triple));
-        build.verbose(|| println!("CXXFLAGS_{} = {cxxflags:?}", target.triple));
+        build.verbose(|| eprintln!("CXX_{} = {cxx:?}", target.triple));
+        build.verbose(|| eprintln!("CXXFLAGS_{} = {cxxflags:?}", target.triple));
     }
     if let Some(ar) = ar {
-        build.verbose(|| println!("AR_{} = {ar:?}", target.triple));
+        build.verbose(|| eprintln!("AR_{} = {ar:?}", target.triple));
         build.ar.borrow_mut().insert(target, ar);
     }
 

src/bootstrap/src/utils/helpers.rs

@@ -135,7 +135,7 @@ impl Drop for TimeIt {
     fn drop(&mut self) {
         let time = self.1.elapsed();
         if !self.0 {
-            println!("\tfinished in {}.{:03} seconds", time.as_secs(), time.subsec_millis());
+            eprintln!("\tfinished in {}.{:03} seconds", time.as_secs(), time.subsec_millis());
         }
     }
 }
@@ -267,12 +267,12 @@ pub fn check_run(cmd: &mut BootstrapCommand, print_cmd_on_fail: bool) -> bool {
     let status = match cmd.as_command_mut().status() {
         Ok(status) => status,
         Err(e) => {
-            println!("failed to execute command: {cmd:?}\nERROR: {e}");
+            eprintln!("failed to execute command: {cmd:?}\nERROR: {e}");
             return false;
         }
     };
     if !status.success() && print_cmd_on_fail {
-        println!(
+        eprintln!(
             "\n\ncommand did not execute successfully: {cmd:?}\n\
              expected success, got: {status}\n\n"
         );

src/bootstrap/src/utils/metrics.rs

@@ -185,7 +185,7 @@ impl BuildMetrics {
                 if version.format_version == CURRENT_FORMAT_VERSION {
                     t!(serde_json::from_slice::<JsonRoot>(&contents)).invocations
                 } else {
-                    println!(
+                    eprintln!(
                         "WARNING: overriding existing build/metrics.json, as it's not \
                          compatible with build metrics format version {CURRENT_FORMAT_VERSION}."
                     );

src/bootstrap/src/utils/render_tests.rs

@@ -56,7 +56,7 @@ fn run_tests(builder: &Builder<'_>, cmd: &mut BootstrapCommand, stream: bool) ->
     let cmd = cmd.as_command_mut();
     cmd.stdout(Stdio::piped());
 
-    builder.verbose(|| println!("running: {cmd:?}"));
+    builder.verbose(|| eprintln!("running: {cmd:?}"));
 
     let mut process = cmd.spawn().unwrap();
 
@@ -71,7 +71,7 @@ fn run_tests(builder: &Builder<'_>, cmd: &mut BootstrapCommand, stream: bool) ->
 
     let result = process.wait_with_output().unwrap();
     if !result.status.success() && builder.is_verbose() {
-        println!(
+        eprintln!(
             "\n\ncommand did not execute successfully: {cmd:?}\n\
              expected success, got: {}",
             result.status
@@ -135,7 +135,9 @@ impl<'a> Renderer<'a> {
         if self.up_to_date_tests > 0 {
             let n = self.up_to_date_tests;
             let s = if n > 1 { "s" } else { "" };
-            println!("help: ignored {n} up-to-date test{s}; use `--force-rerun` to prevent this\n");
+            eprintln!(
+                "help: ignored {n} up-to-date test{s}; use `--force-rerun` to prevent this\n"
+            );
         }
     }
 
@@ -185,58 +187,58 @@ impl<'a> Renderer<'a> {
     }
 
     fn render_test_outcome_verbose(&self, outcome: Outcome<'_>, test: &TestOutcome) {
-        print!("test {} ... ", test.name);
-        self.builder.colored_stdout(|stdout| outcome.write_long(stdout)).unwrap();
+        eprint!("test {} ... ", test.name);
+        self.builder.colored_stderr(|stdout| outcome.write_long(stdout)).unwrap();
         if let Some(exec_time) = test.exec_time {
-            print!(" ({exec_time:.2?})");
+            eprint!(" ({exec_time:.2?})");
         }
-        println!();
+        eprintln!();
     }
 
     fn render_test_outcome_terse(&mut self, outcome: Outcome<'_>, test: &TestOutcome) {
         if self.terse_tests_in_line != 0 && self.terse_tests_in_line % TERSE_TESTS_PER_LINE == 0 {
             if let Some(total) = self.tests_count {
                 let total = total.to_string();
                 let executed = format!("{:>width$}", self.executed_tests - 1, width = total.len());
-                print!(" {executed}/{total}");
+                eprint!(" {executed}/{total}");
             }
-            println!();
+            eprintln!();
             self.terse_tests_in_line = 0;
         }
 
         self.terse_tests_in_line += 1;
-        self.builder.colored_stdout(|stdout| outcome.write_short(stdout, &test.name)).unwrap();
+        self.builder.colored_stderr(|stdout| outcome.write_short(stdout, &test.name)).unwrap();
         let _ = std::io::stdout().flush();
     }
 
     fn render_suite_outcome(&self, outcome: Outcome<'_>, suite: &SuiteOutcome) {
         // The terse output doesn't end with a newline, so we need to add it ourselves.
         if !self.builder.config.verbose_tests {
-            println!();
+            eprintln!();
         }
 
         if !self.failures.is_empty() {
-            println!("\nfailures:\n");
+            eprintln!("\nfailures:\n");
             for failure in &self.failures {
                 if failure.stdout.is_some() || failure.message.is_some() {
-                    println!("---- {} stdout ----", failure.name);
+                    eprintln!("---- {} stdout ----", failure.name);
                     if let Some(stdout) = &failure.stdout {
-                        println!("{stdout}");
+                        eprintln!("{stdout}");
                     }
                     if let Some(message) = &failure.message {
-                        println!("NOTE: {message}");
+                        eprintln!("NOTE: {message}");
                     }
                 }
             }
 
-            println!("\nfailures:");
+            eprintln!("\nfailures:");
             for failure in &self.failures {
-                println!("    {}", failure.name);
+                eprintln!("    {}", failure.name);
             }
         }
 
         if !self.benches.is_empty() {
-            println!("\nbenchmarks:");
+            eprintln!("\nbenchmarks:");
 
             let mut rows = Vec::new();
             for bench in &self.benches {
@@ -251,13 +253,13 @@ impl<'a> Renderer<'a> {
             let max_1 = rows.iter().map(|r| r.1.len()).max().unwrap_or(0);
             let max_2 = rows.iter().map(|r| r.2.len()).max().unwrap_or(0);
             for row in &rows {
-                println!("    {:<max_0$} {:>max_1$} {:>max_2$}", row.0, row.1, row.2);
+                eprintln!("    {:<max_0$} {:>max_1$} {:>max_2$}", row.0, row.1, row.2);
             }
         }
 
-        print!("\ntest result: ");
-        self.builder.colored_stdout(|stdout| outcome.write_long(stdout)).unwrap();
-        println!(
+        eprint!("\ntest result: ");
+        self.builder.colored_stderr(|stdout| outcome.write_long(stdout)).unwrap();
+        eprintln!(
             ". {} passed; {} failed; {} ignored; {} measured; {} filtered out{time}\n",
             suite.passed,
             suite.failed,
@@ -274,7 +276,7 @@ impl<'a> Renderer<'a> {
     fn render_message(&mut self, message: Message) {
         match message {
             Message::Suite(SuiteMessage::Started { test_count }) => {
-                println!("\nrunning {test_count} tests");
+                eprintln!("\nrunning {test_count} tests");
                 self.executed_tests = 0;
                 self.terse_tests_in_line = 0;
                 self.tests_count = Some(test_count);
@@ -314,7 +316,7 @@ impl<'a> Renderer<'a> {
                 self.failures.push(outcome);
             }
             Message::Test(TestMessage::Timeout { name }) => {
-                println!("test {name} has been running for a long time");
+                eprintln!("test {name} has been running for a long time");
             }
             Message::Test(TestMessage::Started) => {} // Not useful
         }

src/bootstrap/src/utils/tarball.rs

@@ -344,7 +344,7 @@ impl<'a> Tarball<'a> {
         // For `x install` tarball files aren't needed, so we can speed up the process by not producing them.
         let compression_profile = if self.builder.kind == Kind::Install {
             self.builder.verbose(|| {
-                println!("Forcing dist.compression-profile = 'no-op' for `x install`.")
+                eprintln!("Forcing dist.compression-profile = 'no-op' for `x install`.")
             });
             // "no-op" indicates that the rust-installer won't produce compressed tarball sources.
             "no-op"

src/tools/compiletest/src/compute_diff.rs

@@ -144,7 +144,7 @@ where
     }
 
     if !wrote_data {
-        println!("note: diff is identical to nightly rustdoc");
+        eprintln!("note: diff is identical to nightly rustdoc");
         assert!(diff_output.metadata().unwrap().len() == 0);
         return false;
     } else if verbose {

src/tools/compiletest/src/debuggers.rs

@@ -20,15 +20,15 @@ pub(crate) fn configure_gdb(config: &Config) -> Option<Arc<Config>> {
     }
 
     if config.remote_test_client.is_some() && !config.target.contains("android") {
-        println!(
+        eprintln!(
             "WARNING: debuginfo tests are not available when \
              testing with remote"
         );
         return None;
     }
 
     if config.target.contains("android") {
-        println!(
+        eprintln!(
             "{} debug-info test uses tcp 5039 port.\
              please reserve it",
             config.target
@@ -50,7 +50,7 @@ pub(crate) fn configure_lldb(config: &Config) -> Option<Arc<Config>> {
     config.lldb_python_dir.as_ref()?;
 
     if let Some(350) = config.lldb_version {
-        println!(
+        eprintln!(
             "WARNING: The used version of LLDB (350) has a \
              known issue that breaks debuginfo tests. See \
              issue #32520 for more information. Skipping all \

src/tools/compiletest/src/lib.rs

@@ -188,8 +188,8 @@ pub fn parse_config(args: Vec<String>) -> Config {
     let (argv0, args_) = args.split_first().unwrap();
     if args.len() == 1 || args[1] == "-h" || args[1] == "--help" {
         let message = format!("Usage: {} [OPTIONS] [TESTNAME...]", argv0);
-        println!("{}", opts.usage(&message));
-        println!();
+        eprintln!("{}", opts.usage(&message));
+        eprintln!();
         panic!()
     }
 
@@ -200,8 +200,8 @@ pub fn parse_config(args: Vec<String>) -> Config {
 
     if matches.opt_present("h") || matches.opt_present("help") {
         let message = format!("Usage: {} [OPTIONS]  [TESTNAME...]", argv0);
-        println!("{}", opts.usage(&message));
-        println!();
+        eprintln!("{}", opts.usage(&message));
+        eprintln!();
         panic!()
     }
 
@@ -508,7 +508,7 @@ pub fn run_tests(config: Arc<Config>) {
             // easy to miss which tests failed, and as such fail to reproduce
             // the failure locally.
 
-            println!(
+            eprintln!(
                 "Some tests failed in compiletest suite={}{} mode={} host={} target={}",
                 config.suite,
                 config

src/tools/compiletest/src/runtest.rs

@@ -131,7 +131,7 @@ pub fn run(config: Arc<Config>, testpaths: &TestPaths, revision: Option<&str>) {
 
     if config.verbose {
         // We're going to be dumping a lot of info. Start on a new line.
-        print!("\n\n");
+        eprintln!("\n");
     }
     debug!("running {:?}", testpaths.file.display());
     let mut props = TestProps::from_file(&testpaths.file, revision, &config);
@@ -353,7 +353,7 @@ impl<'test> TestCx<'test> {
                 {
                     self.error(&format!("{} test did not emit an error", self.config.mode));
                     if self.config.mode == crate::common::Mode::Ui {
-                        println!("note: by default, ui tests are expected not to compile");
+                        eprintln!("note: by default, ui tests are expected not to compile");
                     }
                     proc_res.fatal(None, || ());
                 };
@@ -774,20 +774,20 @@ impl<'test> TestCx<'test> {
                 unexpected.len(),
                 not_found.len()
             ));
-            println!("status: {}\ncommand: {}\n", proc_res.status, proc_res.cmdline);
+            eprintln!("status: {}\ncommand: {}\n", proc_res.status, proc_res.cmdline);
             if !unexpected.is_empty() {
-                println!("{}", "--- unexpected errors (from JSON output) ---".green());
+                eprintln!("{}", "--- unexpected errors (from JSON output) ---".green());
                 for error in &unexpected {
-                    println!("{}", error.render_for_expected());
+                    eprintln!("{}", error.render_for_expected());
                 }
-                println!("{}", "---".green());
+                eprintln!("{}", "---".green());
             }
             if !not_found.is_empty() {
-                println!("{}", "--- not found errors (from test file) ---".red());
+                eprintln!("{}", "--- not found errors (from test file) ---".red());
                 for error in &not_found {
-                    println!("{}", error.render_for_expected());
+                    eprintln!("{}", error.render_for_expected());
                 }
-                println!("{}", "---\n".red());
+                eprintln!("{}", "---\n".red());
             }
             panic!("errors differ from expected");
         }
@@ -1876,18 +1876,18 @@ impl<'test> TestCx<'test> {
 
     fn maybe_dump_to_stdout(&self, out: &str, err: &str) {
         if self.config.verbose {
-            println!("------stdout------------------------------");
-            println!("{}", out);
-            println!("------stderr------------------------------");
-            println!("{}", err);
-            println!("------------------------------------------");
+            eprintln!("------stdout------------------------------");
+            eprintln!("{}", out);
+            eprintln!("------stderr------------------------------");
+            eprintln!("{}", err);
+            eprintln!("------------------------------------------");
         }
     }
 
     fn error(&self, err: &str) {
         match self.revision {
-            Some(rev) => println!("\nerror in revision `{}`: {}", rev, err),
-            None => println!("\nerror: {}", err),
+            Some(rev) => eprintln!("\nerror in revision `{}`: {}", rev, err),
+            None => eprintln!("\nerror: {}", err),
         }
     }
 
@@ -1972,7 +1972,7 @@ impl<'test> TestCx<'test> {
         if !self.config.has_html_tidy {
             return;
         }
-        println!("info: generating a diff against nightly rustdoc");
+        eprintln!("info: generating a diff against nightly rustdoc");
 
         let suffix =
             self.safe_revision().map_or("nightly".into(), |path| path.to_owned() + "-nightly");
@@ -2082,7 +2082,7 @@ impl<'test> TestCx<'test> {
                 .output()
                 .unwrap();
             assert!(output.status.success());
-            println!("{}", String::from_utf8_lossy(&output.stdout));
+            eprintln!("{}", String::from_utf8_lossy(&output.stdout));
             eprintln!("{}", String::from_utf8_lossy(&output.stderr));
         } else {
             use colored::Colorize;
@@ -2496,7 +2496,7 @@ impl<'test> TestCx<'test> {
                 )"#
             )
             .replace_all(&output, |caps: &Captures<'_>| {
-                println!("{}", &caps[0]);
+                eprintln!("{}", &caps[0]);
                 caps[0].replace(r"\", "/")
             })
             .replace("\r\n", "\n")
@@ -2601,14 +2601,14 @@ impl<'test> TestCx<'test> {
         if let Err(err) = fs::write(&actual_path, &actual) {
             self.fatal(&format!("failed to write {stream} to `{actual_path:?}`: {err}",));
         }
-        println!("Saved the actual {stream} to {actual_path:?}");
+        eprintln!("Saved the actual {stream} to {actual_path:?}");
 
         let expected_path =
             expected_output_path(self.testpaths, self.revision, &self.config.compare_mode, stream);
 
         if !self.config.bless {
             if expected.is_empty() {
-                println!("normalized {}:\n{}\n", stream, actual);
+                eprintln!("normalized {}:\n{}\n", stream, actual);
             } else {
                 self.show_diff(
                     stream,
@@ -2631,10 +2631,10 @@ impl<'test> TestCx<'test> {
             if let Err(err) = fs::write(&expected_path, &actual) {
                 self.fatal(&format!("failed to write {stream} to `{expected_path:?}`: {err}"));
             }
-            println!("Blessing the {stream} of {test_name} in {expected_path:?}");
+            eprintln!("Blessing the {stream} of {test_name} in {expected_path:?}");
         }
 
-        println!("\nThe actual {0} differed from the expected {0}.", stream);
+        eprintln!("\nThe actual {0} differed from the expected {0}.", stream);
 
         if self.config.bless { 0 } else { 1 }
     }
@@ -2783,7 +2783,7 @@ impl<'test> TestCx<'test> {
         fs::create_dir_all(&incremental_dir).unwrap();
 
         if self.config.verbose {
-            println!("init_incremental_test: incremental_dir={}", incremental_dir.display());
+            eprintln!("init_incremental_test: incremental_dir={}", incremental_dir.display());
         }
     }
 
@@ -2841,7 +2841,7 @@ impl ProcRes {
             }
         }
 
-        println!(
+        eprintln!(
             "status: {}\ncommand: {}\n{}\n{}\n",
             self.status,
             self.cmdline,
@@ -2852,7 +2852,7 @@ impl ProcRes {
 
     pub fn fatal(&self, err: Option<&str>, on_failure: impl FnOnce()) -> ! {
         if let Some(e) = err {
-            println!("\nerror: {}", e);
+            eprintln!("\nerror: {}", e);
         }
         self.print_info();
         on_failure();

src/tools/compiletest/src/runtest/codegen_units.rs

@@ -64,13 +64,13 @@ impl TestCx<'_> {
         if !missing.is_empty() {
             missing.sort();
 
-            println!("\nThese items should have been contained but were not:\n");
+            eprintln!("\nThese items should have been contained but were not:\n");
 
             for item in &missing {
-                println!("{}", item);
+                eprintln!("{}", item);
             }
 
-            println!("\n");
+            eprintln!("\n");
         }
 
         if !unexpected.is_empty() {
@@ -80,24 +80,24 @@ impl TestCx<'_> {
                 sorted
             };
 
-            println!("\nThese items were contained but should not have been:\n");
+            eprintln!("\nThese items were contained but should not have been:\n");
 
             for item in sorted {
-                println!("{}", item);
+                eprintln!("{}", item);
             }
 
-            println!("\n");
+            eprintln!("\n");
         }
 
         if !wrong_cgus.is_empty() {
             wrong_cgus.sort_by_key(|pair| pair.0.name.clone());
-            println!("\nThe following items were assigned to wrong codegen units:\n");
+            eprintln!("\nThe following items were assigned to wrong codegen units:\n");
 
             for &(ref expected_item, ref actual_item) in &wrong_cgus {
-                println!("{}", expected_item.name);
-                println!("  expected: {}", codegen_units_to_str(&expected_item.codegen_units));
-                println!("  actual:   {}", codegen_units_to_str(&actual_item.codegen_units));
-                println!();
+                eprintln!("{}", expected_item.name);
+                eprintln!("  expected: {}", codegen_units_to_str(&expected_item.codegen_units));
+                eprintln!("  actual:   {}", codegen_units_to_str(&actual_item.codegen_units));
+                eprintln!();
             }
         }
 

src/tools/compiletest/src/runtest/debuginfo.rs

@@ -260,7 +260,7 @@ impl TestCx<'_> {
                 cmdline,
             };
             if adb.kill().is_err() {
-                println!("Adb process is already finished.");
+                eprintln!("Adb process is already finished.");
             }
         } else {
             let rust_src_root =
@@ -275,7 +275,7 @@ impl TestCx<'_> {
 
             match self.config.gdb_version {
                 Some(version) => {
-                    println!("NOTE: compiletest thinks it is using GDB version {}", version);
+                    eprintln!("NOTE: compiletest thinks it is using GDB version {}", version);
 
                     if version > extract_gdb_version("7.4").unwrap() {
                         // Add the directory containing the pretty printers to
@@ -297,7 +297,7 @@ impl TestCx<'_> {
                     }
                 }
                 _ => {
-                    println!(
+                    eprintln!(
                         "NOTE: compiletest does not know which version of \
                          GDB it is using"
                     );
@@ -392,10 +392,10 @@ impl TestCx<'_> {
 
         match self.config.lldb_version {
             Some(ref version) => {
-                println!("NOTE: compiletest thinks it is using LLDB version {}", version);
+                eprintln!("NOTE: compiletest thinks it is using LLDB version {}", version);
             }
             _ => {
-                println!(
+                eprintln!(
                     "NOTE: compiletest does not know which version of \
                      LLDB it is using"
                 );

src/tools/compiletest/src/runtest/incremental.rs

@@ -30,7 +30,7 @@ impl TestCx<'_> {
         assert!(incremental_dir.exists(), "init_incremental_test failed to create incremental dir");
 
         if self.config.verbose {
-            print!("revision={:?} props={:#?}", revision, self.props);
+            eprint!("revision={:?} props={:#?}", revision, self.props);
         }
 
         if revision.starts_with("cpass") {

src/tools/compiletest/src/runtest/mir_opt.rs

@@ -89,7 +89,7 @@ impl TestCx<'_> {
                 }
                 let expected_string = fs::read_to_string(&expected_file).unwrap();
                 if dumped_string != expected_string {
-                    print!("{}", write_diff(&expected_string, &dumped_string, 3));
+                    eprint!("{}", write_diff(&expected_string, &dumped_string, 3));
                     panic!(
                         "Actual MIR output differs from expected MIR output {}",
                         expected_file.display()

src/tools/compiletest/src/runtest/rustdoc_json.rs

@@ -29,7 +29,7 @@ impl TestCx<'_> {
 
         if !res.status.success() {
             self.fatal_proc_rec_with_ctx("jsondocck failed!", &res, |_| {
-                println!("Rustdoc Output:");
+                eprintln!("Rustdoc Output:");
                 proc_res.print_info();
             })
         }

src/tools/compiletest/src/runtest/ui.rs

@@ -109,10 +109,10 @@ impl TestCx<'_> {
         }
 
         if errors > 0 {
-            println!("To update references, rerun the tests and pass the `--bless` flag");
+            eprintln!("To update references, rerun the tests and pass the `--bless` flag");
             let relative_path_to_file =
                 self.testpaths.relative_dir.join(self.testpaths.file.file_name().unwrap());
-            println!(
+            eprintln!(
                 "To only update this specific test, also pass `--test-args {}`",
                 relative_path_to_file.display(),
             );

src/tools/compiletest/src/util.rs

@@ -30,7 +30,7 @@ fn path_div() -> &'static str {
 pub fn logv(config: &Config, s: String) {
     debug!("{}", s);
     if config.verbose {
-        println!("{}", s);
+        eprintln!("{}", s);
     }
 }