Auto merge of #138521 - cuviper:stable-next, r=<try>

[stable] Release 1.85.1

- [Fix the doctest-merging feature of the 2024 Edition.](#137899)
- [Relax some `target_feature` checks when generating docs.](#137632)
  - DRAFT NOTE: this is not formally `stable-accepted` yet. It also required some fixup to deal with differences in the `Stability` system, but I think it should have the same effect, limited to `rustdoc` execution.
- [Fix errors in `fs::rename` on Windows 1607.](#137528)
- [Downgrade bootstrap `cc` to fix custom targets.](#137460)
- [Skip submodule updates when building Rust from a source tarball.](#137338)

cc `@rust-lang/release`
r? cuviper

try-job: dist-x86_64-linux
try-job: dist-i686-msvc
try-job: i686-msvc
try-job: x86_64-rust-for-linux

Author: bors

.github/workflows/ci.yml

@@ -189,6 +189,20 @@ jobs:
       - name: ensure the stable version number is correct
         run: src/ci/scripts/verify-stable-version-number.sh
 
+      # Temporary fix to unblock CI
+      # Remove the latest Windows SDK for 32-bit Windows MSVC builds.
+      # See issue https://github.com/rust-lang/rust/issues/137733 for more details.
+      - name: Remove Windows SDK 10.0.26100.0
+        shell: powershell
+        if: ${{ matrix.image == 'i686-msvc' || matrix.image == 'dist-i686-msvc' }}
+        run: |
+          $kits = (Get-ItemProperty -path 'HKLM:\SOFTWARE\Microsoft\Windows Kits\Installed Roots').KitsRoot10
+          $sdk_version = "10.0.26100.0"
+
+          foreach ($kind in 'Bin', 'Lib', 'Include') {
+            Remove-Item -Force -Recurse $kits\$kind\$sdk_version -ErrorAction Continue
+          }
+
       - name: run the build
         # Redirect stderr to stdout to avoid reordering the two streams in the GHA logs.
         run: src/ci/scripts/run-build-from-ci.sh 2>&1

RELEASES.md

@@ -1,3 +1,14 @@
+Version 1.85.1 (2025-03-18)
+==========================
+
+<a id="1.85.1"></a>
+
+- [Fix the doctest-merging feature of the 2024 Edition.](https://github.com/rust-lang/rust/pull/137899/)
+- [Relax some `target_feature` checks when generating docs.](https://github.com/rust-lang/rust/pull/137632/)
+- [Fix errors in `fs::rename` on Windows 1607.](https://github.com/rust-lang/rust/pull/137528/)
+- [Downgrade bootstrap `cc` to fix custom targets.](https://github.com/rust-lang/rust/pull/137460/)
+- [Skip submodule updates when building Rust from a source tarball.](https://github.com/rust-lang/rust/pull/137338/)
+
 Version 1.85.0 (2025-02-20)
 ==========================
 

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -10,7 +10,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::parse::feature_err;
 use rustc_span::{Span, Symbol, sym};
-use rustc_target::target_features;
+use rustc_target::target_features::{self, Stability};
 
 use crate::errors;
 
@@ -65,11 +65,16 @@ pub(crate) fn from_target_feature_attr(
             // Only allow target features whose feature gates have been enabled
             // and which are permitted to be toggled.
             if let Err(reason) = stability.toggle_allowed(/*enable*/ true) {
-                tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
-                    span: item.span(),
-                    feature,
-                    reason,
-                });
+                // We skip this error in rustdoc, where we want to allow all target features of
+                // all targets, so we can't check their ABI compatibility and anyway we are not
+                // generating code so "it's fine".
+                if !tcx.sess.opts.actually_rustdoc {
+                    tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
+                        span: item.span(),
+                        feature,
+                        reason,
+                    });
+                }
             } else if let Some(nightly_feature) = stability.requires_nightly()
                 && !rust_features.enabled(nightly_feature)
             {
@@ -149,11 +154,38 @@ pub(crate) fn provide(providers: &mut Providers) {
             assert_eq!(cnum, LOCAL_CRATE);
             let target = &tcx.sess.target;
             if tcx.sess.opts.actually_rustdoc {
-                // rustdoc needs to be able to document functions that use all the features, so
-                // whitelist them all
-                rustc_target::target_features::all_rust_features()
-                    .map(|(a, b)| (a.to_string(), b.compute_toggleability(target)))
-                    .collect()
+                // HACK: rustdoc would like to pretend that we have all the target features, so we
+                // have to merge all the lists into one. To ensure an unstable target never prevents
+                // a stable one from working, we merge the stability info of all instances of the
+                // same target feature name, with the "most stable" taking precedence. And then we
+                // hope that this doesn't cause issues anywhere else in the compiler...
+                let mut result: UnordMap<String, Stability<_>> = Default::default();
+                for (name, stability) in rustc_target::target_features::all_rust_features() {
+                    use std::collections::hash_map::Entry;
+                    match result.entry(name.to_owned()) {
+                        Entry::Vacant(vacant_entry) => {
+                            vacant_entry.insert(stability.compute_toggleability(target));
+                        }
+                        Entry::Occupied(mut occupied_entry) => {
+                            // Merge the two stabilities, "more stable" taking precedence.
+                            match (occupied_entry.get(), &stability) {
+                                (Stability::Stable { .. }, _)
+                                | (
+                                    Stability::Unstable { .. },
+                                    Stability::Unstable { .. } | Stability::Forbidden { .. },
+                                )
+                                | (Stability::Forbidden { .. }, Stability::Forbidden { .. }) => {
+                                    // The stability in the entry is at least as good as the new one, just keep it.
+                                }
+                                _ => {
+                                    // Overwrite stabilite.
+                                    occupied_entry.insert(stability.compute_toggleability(target));
+                                }
+                            }
+                        }
+                    }
+                }
+                result
             } else {
                 tcx.sess
                     .target

library/std/src/fs.rs

@@ -2402,7 +2402,7 @@ pub fn symlink_metadata<P: AsRef<Path>>(path: P) -> io::Result<Metadata> {
 /// # Platform-specific behavior
 ///
 /// This function currently corresponds to the `rename` function on Unix
-/// and the `SetFileInformationByHandle` function on Windows.
+/// and the `MoveFileExW` or `SetFileInformationByHandle` function on Windows.
 ///
 /// Because of this, the behavior when both `from` and `to` exist differs. On
 /// Unix, if `from` is a directory, `to` must also be an (empty) directory. If

library/std/src/sys/pal/windows/fs.rs

@@ -1,10 +1,10 @@
 use super::api::{self, WinError};
 use super::{IoResult, to_u16s};
-use crate::alloc::{alloc, handle_alloc_error};
+use crate::alloc::{Layout, alloc, dealloc};
 use crate::borrow::Cow;
 use crate::ffi::{OsStr, OsString, c_void};
 use crate::io::{self, BorrowedCursor, Error, IoSlice, IoSliceMut, SeekFrom};
-use crate::mem::{self, MaybeUninit};
+use crate::mem::{self, MaybeUninit, offset_of};
 use crate::os::windows::io::{AsHandle, BorrowedHandle};
 use crate::os::windows::prelude::*;
 use crate::path::{Path, PathBuf};
@@ -296,6 +296,10 @@ impl OpenOptions {
 impl File {
     pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
         let path = maybe_verbatim(path)?;
+        Self::open_native(&path, opts)
+    }
+
+    fn open_native(path: &[u16], opts: &OpenOptions) -> io::Result<File> {
         let creation = opts.get_creation_mode()?;
         let handle = unsafe {
             c::CreateFileW(
@@ -1234,141 +1238,72 @@ pub fn rename(old: &Path, new: &Path) -> io::Result<()> {
     let old = maybe_verbatim(old)?;
     let new = maybe_verbatim(new)?;
 
-    let new_len_without_nul_in_bytes = (new.len() - 1).try_into().unwrap();
-
-    // The last field of FILE_RENAME_INFO, the file name, is unsized,
-    // and FILE_RENAME_INFO has two padding bytes.
-    // Therefore we need to make sure to not allocate less than
-    // size_of::<c::FILE_RENAME_INFO>() bytes, which would be the case with
-    // 0 or 1 character paths + a null byte.
-    let struct_size = mem::size_of::<c::FILE_RENAME_INFO>()
-        .max(mem::offset_of!(c::FILE_RENAME_INFO, FileName) + new.len() * mem::size_of::<u16>());
-
-    let struct_size: u32 = struct_size.try_into().unwrap();
-
-    let create_file = |extra_access, extra_flags| {
-        let handle = unsafe {
-            HandleOrInvalid::from_raw_handle(c::CreateFileW(
-                old.as_ptr(),
-                c::SYNCHRONIZE | c::DELETE | extra_access,
-                c::FILE_SHARE_READ | c::FILE_SHARE_WRITE | c::FILE_SHARE_DELETE,
-                ptr::null(),
-                c::OPEN_EXISTING,
-                c::FILE_ATTRIBUTE_NORMAL | c::FILE_FLAG_BACKUP_SEMANTICS | extra_flags,
-                ptr::null_mut(),
-            ))
-        };
-
-        OwnedHandle::try_from(handle).map_err(|_| io::Error::last_os_error())
-    };
-
-    // The following code replicates `MoveFileEx`'s behavior as reverse-engineered from its disassembly.
-    // If `old` refers to a mount point, we move it instead of the target.
-    let handle = match create_file(c::FILE_READ_ATTRIBUTES, c::FILE_FLAG_OPEN_REPARSE_POINT) {
-        Ok(handle) => {
-            let mut file_attribute_tag_info: MaybeUninit<c::FILE_ATTRIBUTE_TAG_INFO> =
-                MaybeUninit::uninit();
-
-            let result = unsafe {
-                cvt(c::GetFileInformationByHandleEx(
-                    handle.as_raw_handle(),
-                    c::FileAttributeTagInfo,
-                    file_attribute_tag_info.as_mut_ptr().cast(),
-                    mem::size_of::<c::FILE_ATTRIBUTE_TAG_INFO>().try_into().unwrap(),
-                ))
+    if unsafe { c::MoveFileExW(old.as_ptr(), new.as_ptr(), c::MOVEFILE_REPLACE_EXISTING) } == 0 {
+        let err = api::get_last_error();
+        // if `MoveFileExW` fails with ERROR_ACCESS_DENIED then try to move
+        // the file while ignoring the readonly attribute.
+        // This is accomplished by calling `SetFileInformationByHandle` with `FileRenameInfoEx`.
+        if err == WinError::ACCESS_DENIED {
+            let mut opts = OpenOptions::new();
+            opts.access_mode(c::DELETE);
+            opts.custom_flags(c::FILE_FLAG_OPEN_REPARSE_POINT | c::FILE_FLAG_BACKUP_SEMANTICS);
+            let Ok(f) = File::open_native(&old, &opts) else { return Err(err).io_result() };
+
+            // Calculate the layout of the `FILE_RENAME_INFO` we pass to `SetFileInformation`
+            // This is a dynamically sized struct so we need to get the position of the last field to calculate the actual size.
+            let Ok(new_len_without_nul_in_bytes): Result<u32, _> = ((new.len() - 1) * 2).try_into()
+            else {
+                return Err(err).io_result();
             };
-
-            if let Err(err) = result {
-                if err.raw_os_error() == Some(c::ERROR_INVALID_PARAMETER as _)
-                    || err.raw_os_error() == Some(c::ERROR_INVALID_FUNCTION as _)
-                {
-                    // `GetFileInformationByHandleEx` documents that not all underlying drivers support all file information classes.
-                    // Since we know we passed the correct arguments, this means the underlying driver didn't understand our request;
-                    // `MoveFileEx` proceeds by reopening the file without inhibiting reparse point behavior.
-                    None
-                } else {
-                    Some(Err(err))
-                }
-            } else {
-                // SAFETY: The struct has been initialized by GetFileInformationByHandleEx
-                let file_attribute_tag_info = unsafe { file_attribute_tag_info.assume_init() };
-                let file_type = FileType::new(
-                    file_attribute_tag_info.FileAttributes,
-                    file_attribute_tag_info.ReparseTag,
-                );
-
-                if file_type.is_symlink() {
-                    // The file is a mount point, junction point or symlink so
-                    // don't reopen the file so that the link gets renamed.
-                    Some(Ok(handle))
-                } else {
-                    // Otherwise reopen the file without inhibiting reparse point behavior.
-                    None
+            let offset: u32 = offset_of!(c::FILE_RENAME_INFO, FileName).try_into().unwrap();
+            let struct_size = offset + new_len_without_nul_in_bytes + 2;
+            let layout =
+                Layout::from_size_align(struct_size as usize, align_of::<c::FILE_RENAME_INFO>())
+                    .unwrap();
+
+            // SAFETY: We allocate enough memory for a full FILE_RENAME_INFO struct and a filename.
+            let file_rename_info;
+            unsafe {
+                file_rename_info = alloc(layout).cast::<c::FILE_RENAME_INFO>();
+                if file_rename_info.is_null() {
+                    return Err(io::ErrorKind::OutOfMemory.into());
                 }
-            }
-        }
-        // The underlying driver may not support `FILE_FLAG_OPEN_REPARSE_POINT`: Retry without it.
-        Err(err) if err.raw_os_error() == Some(c::ERROR_INVALID_PARAMETER as _) => None,
-        Err(err) => Some(Err(err)),
-    }
-    .unwrap_or_else(|| create_file(0, 0))?;
 
-    let layout = core::alloc::Layout::from_size_align(
-        struct_size as _,
-        mem::align_of::<c::FILE_RENAME_INFO>(),
-    )
-    .unwrap();
-
-    let file_rename_info = unsafe { alloc(layout) } as *mut c::FILE_RENAME_INFO;
-
-    if file_rename_info.is_null() {
-        handle_alloc_error(layout);
-    }
-
-    // SAFETY: file_rename_info is a non-null pointer pointing to memory allocated by the global allocator.
-    let mut file_rename_info = unsafe { Box::from_raw(file_rename_info) };
-
-    // SAFETY: We have allocated enough memory for a full FILE_RENAME_INFO struct and a filename.
-    unsafe {
-        (&raw mut (*file_rename_info).Anonymous).write(c::FILE_RENAME_INFO_0 {
-            Flags: c::FILE_RENAME_FLAG_REPLACE_IF_EXISTS | c::FILE_RENAME_FLAG_POSIX_SEMANTICS,
-        });
-
-        (&raw mut (*file_rename_info).RootDirectory).write(ptr::null_mut());
-        (&raw mut (*file_rename_info).FileNameLength).write(new_len_without_nul_in_bytes);
-
-        new.as_ptr()
-            .copy_to_nonoverlapping((&raw mut (*file_rename_info).FileName) as *mut u16, new.len());
-    }
+                (&raw mut (*file_rename_info).Anonymous).write(c::FILE_RENAME_INFO_0 {
+                    Flags: c::FILE_RENAME_FLAG_REPLACE_IF_EXISTS
+                        | c::FILE_RENAME_FLAG_POSIX_SEMANTICS,
+                });
 
-    // We don't use `set_file_information_by_handle` here as `FILE_RENAME_INFO` is used for both `FileRenameInfo` and `FileRenameInfoEx`.
-    let result = unsafe {
-        cvt(c::SetFileInformationByHandle(
-            handle.as_raw_handle(),
-            c::FileRenameInfoEx,
-            (&raw const *file_rename_info).cast::<c_void>(),
-            struct_size,
-        ))
-    };
+                (&raw mut (*file_rename_info).RootDirectory).write(ptr::null_mut());
+                // Don't include the NULL in the size
+                (&raw mut (*file_rename_info).FileNameLength).write(new_len_without_nul_in_bytes);
 
-    if let Err(err) = result {
-        if err.raw_os_error() == Some(c::ERROR_INVALID_PARAMETER as _) {
-            // FileRenameInfoEx and FILE_RENAME_FLAG_POSIX_SEMANTICS were added in Windows 10 1607; retry with FileRenameInfo.
-            file_rename_info.Anonymous.ReplaceIfExists = 1;
+                new.as_ptr().copy_to_nonoverlapping(
+                    (&raw mut (*file_rename_info).FileName).cast::<u16>(),
+                    new.len(),
+                );
+            }
 
-            cvt(unsafe {
+            let result = unsafe {
                 c::SetFileInformationByHandle(
-                    handle.as_raw_handle(),
-                    c::FileRenameInfo,
-                    (&raw const *file_rename_info).cast::<c_void>(),
+                    f.as_raw_handle(),
+                    c::FileRenameInfoEx,
+                    file_rename_info.cast::<c_void>(),
                     struct_size,
                 )
-            })?;
+            };
+            unsafe { dealloc(file_rename_info.cast::<u8>(), layout) };
+            if result == 0 {
+                if api::get_last_error() == WinError::DIR_NOT_EMPTY {
+                    return Err(WinError::DIR_NOT_EMPTY).io_result();
+                } else {
+                    return Err(err).io_result();
+                }
+            }
         } else {
-            return Err(err);
+            return Err(err).io_result();
         }
     }
-
     Ok(())
 }
 

src/bootstrap/Cargo.lock

@@ -84,9 +84,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.2.0"
+version = "1.1.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1aeb932158bd710538c73702db6945cb68a8fb08c519e6e12706b94263b36db8"
+checksum = "9540e661f81799159abee814118cc139a2004b3a3aa3ea37724a1b66530b90e0"
 dependencies = [
  "shlex",
 ]

src/bootstrap/Cargo.toml

@@ -36,7 +36,9 @@ test = false
 # Most of the time updating these dependencies requires modifications to the
 # bootstrap codebase(e.g., https://github.com/rust-lang/rust/issues/124565);
 # otherwise, some targets will fail. That's why these dependencies are explicitly pinned.
-cc = "=1.2.0"
+#
+# Do not upgrade this crate unless https://github.com/rust-lang/cc-rs/issues/1317 is fixed.
+cc = "=1.1.22"
 cmake = "=0.1.48"
 
 build_helper = { path = "../build_helper" }

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

@@ -2668,7 +2668,7 @@ impl Config {
     /// used instead to provide a nice error to the user if the submodule is
     /// missing.
     pub(crate) fn update_submodule(&self, relative_path: &str) {
-        if !self.submodules() {
+        if self.rust_info.is_from_tarball() || !self.submodules() {
             return;
         }
 

src/bootstrap/src/lib.rs

@@ -471,6 +471,10 @@ impl Build {
     /// The given `err_hint` will be shown to the user if the submodule is not
     /// checked out and submodule management is disabled.
     pub fn require_submodule(&self, submodule: &str, err_hint: Option<&str>) {
+        if self.rust_info().is_from_tarball() {
+            return;
+        }
+
         // When testing bootstrap itself, it is much faster to ignore
         // submodules. Almost all Steps work fine without their submodules.
         if cfg!(test) && !self.config.submodules() {

src/librustdoc/doctest.rs

@@ -95,7 +95,7 @@ pub(crate) fn generate_args_file(file_path: &Path, options: &RustdocOptions) ->
         .map_err(|error| format!("failed to create args file: {error:?}"))?;
 
     // We now put the common arguments into the file we created.
-    let mut content = vec!["--crate-type=bin".to_string()];
+    let mut content = vec![];
 
     for cfg in &options.cfgs {
         content.push(format!("--cfg={cfg}"));
@@ -488,12 +488,18 @@ pub(crate) struct RunnableDocTest {
     line: usize,
     edition: Edition,
     no_run: bool,
-    is_multiple_tests: bool,
+    merged_test_code: Option<String>,
 }
 
 impl RunnableDocTest {
-    fn path_for_merged_doctest(&self) -> PathBuf {
-        self.test_opts.outdir.path().join(format!("doctest_{}.rs", self.edition))
+    fn path_for_merged_doctest_bundle(&self) -> PathBuf {
+        self.test_opts.outdir.path().join(format!("doctest_bundle_{}.rs", self.edition))
+    }
+    fn path_for_merged_doctest_runner(&self) -> PathBuf {
+        self.test_opts.outdir.path().join(format!("doctest_runner_{}.rs", self.edition))
+    }
+    fn is_multiple_tests(&self) -> bool {
+        self.merged_test_code.is_some()
     }
 }
 
@@ -512,91 +518,108 @@ fn run_test(
     let rust_out = add_exe_suffix("rust_out".to_owned(), &rustdoc_options.target);
     let output_file = doctest.test_opts.outdir.path().join(rust_out);
 
-    let rustc_binary = rustdoc_options
-        .test_builder
-        .as_deref()
-        .unwrap_or_else(|| rustc_interface::util::rustc_path().expect("found rustc"));
-    let mut compiler = wrapped_rustc_command(&rustdoc_options.test_builder_wrappers, rustc_binary);
+    // Common arguments used for compiling the doctest runner.
+    // On merged doctests, the compiler is invoked twice: once for the test code itself,
+    // and once for the runner wrapper (which needs to use `#![feature]` on stable).
+    let mut compiler_args = vec![];
 
-    compiler.arg(format!("@{}", doctest.global_opts.args_file.display()));
+    compiler_args.push(format!("@{}", doctest.global_opts.args_file.display()));
 
     if let Some(sysroot) = &rustdoc_options.maybe_sysroot {
-        compiler.arg(format!("--sysroot={}", sysroot.display()));
+        compiler_args.push(format!("--sysroot={}", sysroot.display()));
     }
 
-    compiler.arg("--edition").arg(doctest.edition.to_string());
-    if !doctest.is_multiple_tests {
-        // Setting these environment variables is unneeded if this is a merged doctest.
-        compiler.env("UNSTABLE_RUSTDOC_TEST_PATH", &doctest.test_opts.path);
-        compiler.env(
-            "UNSTABLE_RUSTDOC_TEST_LINE",
-            format!("{}", doctest.line as isize - doctest.full_test_line_offset as isize),
-        );
-    }
-    compiler.arg("-o").arg(&output_file);
+    compiler_args.extend_from_slice(&["--edition".to_owned(), doctest.edition.to_string()]);
     if langstr.test_harness {
-        compiler.arg("--test");
+        compiler_args.push("--test".to_owned());
     }
     if rustdoc_options.json_unused_externs.is_enabled() && !langstr.compile_fail {
-        compiler.arg("--error-format=json");
-        compiler.arg("--json").arg("unused-externs");
-        compiler.arg("-W").arg("unused_crate_dependencies");
-        compiler.arg("-Z").arg("unstable-options");
+        compiler_args.push("--error-format=json".to_owned());
+        compiler_args.extend_from_slice(&["--json".to_owned(), "unused-externs".to_owned()]);
+        compiler_args.extend_from_slice(&["-W".to_owned(), "unused_crate_dependencies".to_owned()]);
+        compiler_args.extend_from_slice(&["-Z".to_owned(), "unstable-options".to_owned()]);
     }
 
     if doctest.no_run && !langstr.compile_fail && rustdoc_options.persist_doctests.is_none() {
         // FIXME: why does this code check if it *shouldn't* persist doctests
         //        -- shouldn't it be the negation?
-        compiler.arg("--emit=metadata");
+        compiler_args.push("--emit=metadata".to_owned());
     }
-    compiler.arg("--target").arg(match &rustdoc_options.target {
-        TargetTuple::TargetTuple(s) => s,
-        TargetTuple::TargetJson { path_for_rustdoc, .. } => {
-            path_for_rustdoc.to_str().expect("target path must be valid unicode")
-        }
-    });
+    compiler_args.extend_from_slice(&[
+        "--target".to_owned(),
+        match &rustdoc_options.target {
+            TargetTuple::TargetTuple(s) => s.clone(),
+            TargetTuple::TargetJson { path_for_rustdoc, .. } => {
+                path_for_rustdoc.to_str().expect("target path must be valid unicode").to_owned()
+            }
+        },
+    ]);
     if let ErrorOutputType::HumanReadable(kind, color_config) = rustdoc_options.error_format {
         let short = kind.short();
         let unicode = kind == HumanReadableErrorType::Unicode;
 
         if short {
-            compiler.arg("--error-format").arg("short");
+            compiler_args.extend_from_slice(&["--error-format".to_owned(), "short".to_owned()]);
         }
         if unicode {
-            compiler.arg("--error-format").arg("human-unicode");
+            compiler_args
+                .extend_from_slice(&["--error-format".to_owned(), "human-unicode".to_owned()]);
         }
 
         match color_config {
             ColorConfig::Never => {
-                compiler.arg("--color").arg("never");
+                compiler_args.extend_from_slice(&["--color".to_owned(), "never".to_owned()]);
             }
             ColorConfig::Always => {
-                compiler.arg("--color").arg("always");
+                compiler_args.extend_from_slice(&["--color".to_owned(), "always".to_owned()]);
             }
             ColorConfig::Auto => {
-                compiler.arg("--color").arg(if supports_color { "always" } else { "never" });
+                compiler_args.extend_from_slice(&[
+                    "--color".to_owned(),
+                    if supports_color { "always" } else { "never" }.to_owned(),
+                ]);
             }
         }
     }
 
+    let rustc_binary = rustdoc_options
+        .test_builder
+        .as_deref()
+        .unwrap_or_else(|| rustc_interface::util::rustc_path().expect("found rustc"));
+    let mut compiler = wrapped_rustc_command(&rustdoc_options.test_builder_wrappers, rustc_binary);
+
+    compiler.args(&compiler_args);
+
     // If this is a merged doctest, we need to write it into a file instead of using stdin
     // because if the size of the merged doctests is too big, it'll simply break stdin.
-    if doctest.is_multiple_tests {
+    if doctest.is_multiple_tests() {
         // It makes the compilation failure much faster if it is for a combined doctest.
         compiler.arg("--error-format=short");
-        let input_file = doctest.path_for_merged_doctest();
+        let input_file = doctest.path_for_merged_doctest_bundle();
         if std::fs::write(&input_file, &doctest.full_test_code).is_err() {
             // If we cannot write this file for any reason, we leave. All combined tests will be
             // tested as standalone tests.
             return Err(TestFailure::CompileError);
         }
-        compiler.arg(input_file);
         if !rustdoc_options.nocapture {
             // If `nocapture` is disabled, then we don't display rustc's output when compiling
             // the merged doctests.
             compiler.stderr(Stdio::null());
         }
+        // bundled tests are an rlib, loaded by a separate runner executable
+        compiler
+            .arg("--crate-type=lib")
+            .arg("--out-dir")
+            .arg(doctest.test_opts.outdir.path())
+            .arg(input_file);
     } else {
+        compiler.arg("--crate-type=bin").arg("-o").arg(&output_file);
+        // Setting these environment variables is unneeded if this is a merged doctest.
+        compiler.env("UNSTABLE_RUSTDOC_TEST_PATH", &doctest.test_opts.path);
+        compiler.env(
+            "UNSTABLE_RUSTDOC_TEST_LINE",
+            format!("{}", doctest.line as isize - doctest.full_test_line_offset as isize),
+        );
         compiler.arg("-");
         compiler.stdin(Stdio::piped());
         compiler.stderr(Stdio::piped());
@@ -605,8 +628,65 @@ fn run_test(
     debug!("compiler invocation for doctest: {compiler:?}");
 
     let mut child = compiler.spawn().expect("Failed to spawn rustc process");
-    let output = if doctest.is_multiple_tests {
+    let output = if let Some(merged_test_code) = &doctest.merged_test_code {
+        // compile-fail tests never get merged, so this should always pass
         let status = child.wait().expect("Failed to wait");
+
+        // the actual test runner is a separate component, built with nightly-only features;
+        // build it now
+        let runner_input_file = doctest.path_for_merged_doctest_runner();
+
+        let mut runner_compiler =
+            wrapped_rustc_command(&rustdoc_options.test_builder_wrappers, rustc_binary);
+        // the test runner does not contain any user-written code, so this doesn't allow
+        // the user to exploit nightly-only features on stable
+        runner_compiler.env("RUSTC_BOOTSTRAP", "1");
+        runner_compiler.args(compiler_args);
+        runner_compiler.args(&["--crate-type=bin", "-o"]).arg(&output_file);
+        let mut extern_path = std::ffi::OsString::from(format!(
+            "--extern=doctest_bundle_{edition}=",
+            edition = doctest.edition
+        ));
+        for extern_str in &rustdoc_options.extern_strs {
+            if let Some((_cratename, path)) = extern_str.split_once('=') {
+                // Direct dependencies of the tests themselves are
+                // indirect dependencies of the test runner.
+                // They need to be in the library search path.
+                let dir = Path::new(path)
+                    .parent()
+                    .filter(|x| x.components().count() > 0)
+                    .unwrap_or(Path::new("."));
+                runner_compiler.arg("-L").arg(dir);
+            }
+        }
+        let output_bundle_file = doctest
+            .test_opts
+            .outdir
+            .path()
+            .join(format!("libdoctest_bundle_{edition}.rlib", edition = doctest.edition));
+        extern_path.push(&output_bundle_file);
+        runner_compiler.arg(extern_path);
+        runner_compiler.arg(&runner_input_file);
+        if std::fs::write(&runner_input_file, &merged_test_code).is_err() {
+            // If we cannot write this file for any reason, we leave. All combined tests will be
+            // tested as standalone tests.
+            return Err(TestFailure::CompileError);
+        }
+        if !rustdoc_options.nocapture {
+            // If `nocapture` is disabled, then we don't display rustc's output when compiling
+            // the merged doctests.
+            runner_compiler.stderr(Stdio::null());
+        }
+        runner_compiler.arg("--error-format=short");
+        debug!("compiler invocation for doctest runner: {runner_compiler:?}");
+
+        let status = if !status.success() {
+            status
+        } else {
+            let mut child_runner = runner_compiler.spawn().expect("Failed to spawn rustc process");
+            child_runner.wait().expect("Failed to wait")
+        };
+
         process::Output { status, stdout: Vec::new(), stderr: Vec::new() }
     } else {
         let stdin = child.stdin.as_mut().expect("Failed to open stdin");
@@ -683,15 +763,15 @@ fn run_test(
         cmd.arg(&output_file);
     } else {
         cmd = Command::new(&output_file);
-        if doctest.is_multiple_tests {
+        if doctest.is_multiple_tests() {
             cmd.env("RUSTDOC_DOCTEST_BIN_PATH", &output_file);
         }
     }
     if let Some(run_directory) = &rustdoc_options.test_run_directory {
         cmd.current_dir(run_directory);
     }
 
-    let result = if doctest.is_multiple_tests || rustdoc_options.nocapture {
+    let result = if doctest.is_multiple_tests() || rustdoc_options.nocapture {
         cmd.status().map(|status| process::Output {
             status,
             stdout: Vec::new(),
@@ -977,7 +1057,7 @@ fn doctest_run_fn(
         line: scraped_test.line,
         edition: scraped_test.edition(&rustdoc_options),
         no_run: scraped_test.no_run(&rustdoc_options),
-        is_multiple_tests: false,
+        merged_test_code: None,
     };
     let res =
         run_test(runnable_test, &rustdoc_options, doctest.supports_color, report_unused_externs);

src/librustdoc/doctest/runner.rs

@@ -14,6 +14,7 @@ pub(crate) struct DocTestRunner {
     crate_attrs: FxIndexSet<String>,
     ids: String,
     output: String,
+    output_merged_tests: String,
     supports_color: bool,
     nb_tests: usize,
 }
@@ -24,6 +25,7 @@ impl DocTestRunner {
             crate_attrs: FxIndexSet::default(),
             ids: String::new(),
             output: String::new(),
+            output_merged_tests: String::new(),
             supports_color: true,
             nb_tests: 0,
         }
@@ -55,7 +57,8 @@ impl DocTestRunner {
                 scraped_test,
                 ignore,
                 self.nb_tests,
-                &mut self.output
+                &mut self.output,
+                &mut self.output_merged_tests,
             ),
         ));
         self.supports_color &= doctest.supports_color;
@@ -78,25 +81,28 @@ impl DocTestRunner {
 "
         .to_string();
 
+        let mut code_prefix = String::new();
+
         for crate_attr in &self.crate_attrs {
-            code.push_str(crate_attr);
-            code.push('\n');
+            code_prefix.push_str(crate_attr);
+            code_prefix.push('\n');
         }
 
         if opts.attrs.is_empty() {
             // If there aren't any attributes supplied by #![doc(test(attr(...)))], then allow some
             // lints that are commonly triggered in doctests. The crate-level test attributes are
             // commonly used to make tests fail in case they trigger warnings, so having this there in
             // that case may cause some tests to pass when they shouldn't have.
-            code.push_str("#![allow(unused)]\n");
+            code_prefix.push_str("#![allow(unused)]\n");
         }
 
         // Next, any attributes that came from the crate root via #![doc(test(attr(...)))].
         for attr in &opts.attrs {
-            code.push_str(&format!("#![{attr}]\n"));
+            code_prefix.push_str(&format!("#![{attr}]\n"));
         }
 
         code.push_str("extern crate test;\n");
+        writeln!(code, "extern crate doctest_bundle_{edition} as doctest_bundle;").unwrap();
 
         let test_args = test_args.iter().fold(String::new(), |mut x, arg| {
             write!(x, "{arg:?}.to_string(),").unwrap();
@@ -161,20 +167,20 @@ the same process\");
 std::process::Termination::report(test::test_main(test_args, Vec::from(TESTS), None))
 }}",
             nb_tests = self.nb_tests,
-            output = self.output,
+            output = self.output_merged_tests,
             ids = self.ids,
         )
         .expect("failed to generate test code");
         let runnable_test = RunnableDocTest {
-            full_test_code: code,
+            full_test_code: format!("{code_prefix}{code}", code = self.output),
             full_test_line_offset: 0,
             test_opts: test_options,
             global_opts: opts.clone(),
             langstr: LangString::default(),
             line: 0,
             edition,
             no_run: false,
-            is_multiple_tests: true,
+            merged_test_code: Some(code),
         };
         let ret =
             run_test(runnable_test, rustdoc_options, self.supports_color, |_: UnusedExterns| {});
@@ -189,14 +195,15 @@ fn generate_mergeable_doctest(
     ignore: bool,
     id: usize,
     output: &mut String,
+    output_merged_tests: &mut String,
 ) -> String {
     let test_id = format!("__doctest_{id}");
 
     if ignore {
         // We generate nothing else.
-        writeln!(output, "mod {test_id} {{\n").unwrap();
+        writeln!(output, "pub mod {test_id} {{}}\n").unwrap();
     } else {
-        writeln!(output, "mod {test_id} {{\n{}{}", doctest.crates, doctest.maybe_crate_attrs)
+        writeln!(output, "pub mod {test_id} {{\n{}{}", doctest.crates, doctest.maybe_crate_attrs)
             .unwrap();
         if doctest.has_main_fn {
             output.push_str(&doctest.everything_else);
@@ -216,11 +223,17 @@ fn main() {returns_result} {{
             )
             .unwrap();
         }
+        writeln!(
+            output,
+            "\npub fn __main_fn() -> impl std::process::Termination {{ main() }} \n}}\n"
+        )
+        .unwrap();
     }
     let not_running = ignore || scraped_test.langstr.no_run;
     writeln!(
-        output,
+        output_merged_tests,
         "
+mod {test_id} {{
 pub const TEST: test::TestDescAndFn = test::TestDescAndFn::new_doctest(
 {test_name:?}, {ignore}, {file:?}, {line}, {no_run}, {should_panic},
 test::StaticTestFn(
@@ -242,7 +255,7 @@ test::StaticTestFn(
 if let Some(bin_path) = crate::__doctest_mod::doctest_path() {{
     test::assert_test_result(crate::__doctest_mod::doctest_runner(bin_path, {id}))
 }} else {{
-    test::assert_test_result(self::main())
+    test::assert_test_result(doctest_bundle::{test_id}::__main_fn())
 }}
 ",
             )

src/version

@@ -1 +1 @@
-1.85.0
+1.85.1

tests/run-make/doctests-merge/rmake.rs

@@ -8,7 +8,6 @@ fn test_and_compare(input_file: &str, stdout_file: &str, edition: &str, dep: &Pa
     let output = cmd
         .input(input_file)
         .arg("--test")
-        .arg("-Zunstable-options")
         .edition(edition)
         .arg("--test-args=--test-threads=1")
         .extern_("foo", dep.display().to_string())

tests/rustdoc-ui/doctest/doctest-output.rs

@@ -2,7 +2,7 @@
 //@[edition2015]edition:2015
 //@[edition2015]aux-build:extern_macros.rs
 //@[edition2015]compile-flags:--test --test-args=--test-threads=1
-//@[edition2024]edition:2015
+//@[edition2024]edition:2024
 //@[edition2024]aux-build:extern_macros.rs
 //@[edition2024]compile-flags:--test --test-args=--test-threads=1
 //@ normalize-stdout: "tests/rustdoc-ui/doctest" -> "$$DIR"

tests/rustdoc-ui/doctest/failed-doctest-test-crate.edition2015.stdout

@@ -0,0 +1,28 @@
+
+running 1 test
+test $DIR/failed-doctest-test-crate.rs - m (line 14) ... FAILED
+
+failures:
+
+---- $DIR/failed-doctest-test-crate.rs - m (line 14) stdout ----
+error[E0432]: unresolved import `test`
+  --> $DIR/failed-doctest-test-crate.rs:15:5
+   |
+LL | use test::*;
+   |     ^^^^ you might be missing crate `test`
+   |
+help: consider importing the `test` crate
+   |
+LL + extern crate test;
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0432`.
+Couldn't compile the test.
+
+failures:
+    $DIR/failed-doctest-test-crate.rs - m (line 14)
+
+test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+

tests/rustdoc-ui/doctest/failed-doctest-test-crate.edition2024.stdout

@@ -0,0 +1,23 @@
+
+running 1 test
+test $DIR/failed-doctest-test-crate.rs - m (line 14) ... FAILED
+
+failures:
+
+---- $DIR/failed-doctest-test-crate.rs - m (line 14) stdout ----
+error[E0432]: unresolved import `test`
+  --> $DIR/failed-doctest-test-crate.rs:15:5
+   |
+LL | use test::*;
+   |     ^^^^ use of undeclared crate or module `test`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0432`.
+Couldn't compile the test.
+
+failures:
+    $DIR/failed-doctest-test-crate.rs - m (line 14)
+
+test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+

tests/rustdoc-ui/doctest/failed-doctest-test-crate.rs

@@ -0,0 +1,17 @@
+// FIXME: if/when the output of the test harness can be tested on its own, this test should be
+// adapted to use that, and that normalize line can go away
+
+//@ revisions: edition2015 edition2024
+//@[edition2015]edition:2015
+//@[edition2024]edition:2024
+//@ compile-flags:--test
+//@ normalize-stdout: "tests/rustdoc-ui/doctest" -> "$$DIR"
+//@ normalize-stdout: "finished in \d+\.\d+s" -> "finished in $$TIME"
+//@ failure-status: 101
+
+/// <https://github.com/rust-lang/rust/pull/137899#discussion_r1976743383>
+///
+/// ```rust
+/// use test::*;
+/// ```
+pub mod m {}

tests/rustdoc-ui/target-feature-stability.rs

@@ -0,0 +1,28 @@
+//! This is a regression test for <https://github.com/rust-lang/rust/issues/137366>, ensuring
+//! that we can use the `neon` target feature on ARM32 targets in rustdoc despite there
+//! being a "forbidden" feature of the same name for aarch64, and rustdoc merging the
+//! target features of all targets.
+//@ check-pass
+//@ revisions: arm aarch64
+//@[arm] compile-flags: --target armv7-unknown-linux-gnueabihf
+//@[arm] needs-llvm-components: arm
+//@[aarch64] compile-flags: --target aarch64-unknown-none-softfloat
+//@[aarch64] needs-llvm-components: aarch64
+
+#![crate_type = "lib"]
+#![feature(no_core, lang_items)]
+#![feature(arm_target_feature)]
+#![no_core]
+
+#[lang = "sized"]
+pub trait Sized {}
+
+// `fp-armv8` is "forbidden" on aarch64 as we tie it to `neon`.
+#[target_feature(enable = "fp-armv8")]
+pub fn fun1() {}
+
+// This would usually be rejected as it changes the ABI.
+// But we disable that check in rustdoc since we are building "for all targets" and the
+// check can't really handle that.
+#[target_feature(enable = "soft-float")]
+pub fn fun2() {}