Auto merge of rust-lang#134266 - matthiaskrgr:rollup-cpiuez5, r=<try>

Rollup of 4 pull requests

Successful merges:

 - rust-lang#132038 (Add lint rule for `#[deprecated]` on re-exports)
 - rust-lang#132150 (Fix powerpc64 big-endian FreeBSD ABI)
 - rust-lang#133633 (don't show the full linker args unless `--verbose` is passed)
 - rust-lang#133942 (Clarify how to use `black_box()`)

r? `@ghost`
`@rustbot` modify labels: rollup

try-job: dist-x86_64-linux

Author: bors

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -992,12 +992,12 @@ fn link_natively(
                 let mut output = prog.stderr.clone();
                 output.extend_from_slice(&prog.stdout);
                 let escaped_output = escape_linker_output(&output, flavor);
-                // FIXME: Add UI tests for this error.
                 let err = errors::LinkingFailed {
                     linker_path: &linker_path,
                     exit_status: prog.status,
-                    command: &cmd,
+                    command: cmd,
                     escaped_output,
+                    verbose: sess.opts.verbose,
                 };
                 sess.dcx().emit_err(err);
                 // If MSVC's `link.exe` was expected but the return code

compiler/rustc_codegen_ssa/src/errors.rs

@@ -1,6 +1,7 @@
 //! Errors emitted by codegen_ssa
 
 use std::borrow::Cow;
+use std::ffi::OsString;
 use std::io::Error;
 use std::num::ParseIntError;
 use std::path::{Path, PathBuf};
@@ -345,21 +346,82 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for ThorinErrorWrapper {
 }
 
 pub(crate) struct LinkingFailed<'a> {
-    pub linker_path: &'a PathBuf,
+    pub linker_path: &'a Path,
     pub exit_status: ExitStatus,
-    pub command: &'a Command,
+    pub command: Command,
     pub escaped_output: String,
+    pub verbose: bool,
 }
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
-    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
+    fn into_diag(mut self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::codegen_ssa_linking_failed);
         diag.arg("linker_path", format!("{}", self.linker_path.display()));
         diag.arg("exit_status", format!("{}", self.exit_status));
 
         let contains_undefined_ref = self.escaped_output.contains("undefined reference to");
 
-        diag.note(format!("{:?}", self.command)).note(self.escaped_output);
+        if self.verbose {
+            diag.note(format!("{:?}", self.command));
+        } else {
+            enum ArgGroup {
+                Regular(OsString),
+                Objects(usize),
+                Rlibs(PathBuf, Vec<OsString>),
+            }
+
+            // Omit rust object files and fold rlibs in the error by default to make linker errors a
+            // bit less verbose.
+            let orig_args = self.command.take_args();
+            let mut args: Vec<ArgGroup> = vec![];
+            for arg in orig_args {
+                if arg.as_encoded_bytes().ends_with(b".rcgu.o") {
+                    if let Some(ArgGroup::Objects(n)) = args.last_mut() {
+                        *n += 1;
+                    } else {
+                        args.push(ArgGroup::Objects(1));
+                    }
+                } else if arg.as_encoded_bytes().ends_with(b".rlib") {
+                    let rlib_path = Path::new(&arg);
+                    let dir = rlib_path.parent().unwrap();
+                    let filename = rlib_path.file_name().unwrap().to_owned();
+                    if let Some(ArgGroup::Rlibs(parent, rlibs)) = args.last_mut() {
+                        if parent == dir {
+                            rlibs.push(filename);
+                        } else {
+                            args.push(ArgGroup::Rlibs(dir.to_owned(), vec![filename]));
+                        }
+                    } else {
+                        args.push(ArgGroup::Rlibs(dir.to_owned(), vec![filename]));
+                    }
+                } else {
+                    args.push(ArgGroup::Regular(arg));
+                }
+            }
+            self.command.args(args.into_iter().map(|arg_group| match arg_group {
+                ArgGroup::Regular(arg) => arg,
+                ArgGroup::Objects(n) => OsString::from(format!("<{n} object files omitted>")),
+                ArgGroup::Rlibs(dir, rlibs) => {
+                    let mut arg = dir.into_os_string();
+                    arg.push("/{");
+                    let mut first = true;
+                    for rlib in rlibs {
+                        if !first {
+                            arg.push(",");
+                        }
+                        first = false;
+                        arg.push(rlib);
+                    }
+                    arg.push("}");
+                    arg
+                }
+            }));
+
+            diag.note(format!("{:?}", self.command));
+            diag.note("some arguments are omitted. use `--verbose` to show all linker arguments");
+        }
+
+        diag.note(self.escaped_output);
 
         // Trying to match an error from OS linkers
         // which by now we have no way to translate.

compiler/rustc_passes/src/stability.rs

@@ -411,6 +411,9 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
                 kind = AnnotationKind::DeprecationProhibited;
                 const_stab_inherit = InheritConstStability::Yes;
             }
+            hir::ItemKind::Use(_, _) => {
+                kind = AnnotationKind::DeprecationProhibited;
+            }
             hir::ItemKind::Struct(ref sd, _) => {
                 if let Some(ctor_def_id) = sd.ctor_def_id() {
                     self.annotate(

compiler/rustc_target/src/callconv/powerpc64.rs

@@ -99,7 +99,7 @@ where
     Ty: TyAbiInterface<'a, C> + Copy,
     C: HasDataLayout + HasTargetSpec,
 {
-    let abi = if cx.target_spec().env == "musl" {
+    let abi = if cx.target_spec().env == "musl" || cx.target_spec().os == "freebsd" {
         ELFv2
     } else if cx.target_spec().os == "aix" {
         AIX

compiler/rustc_target/src/spec/targets/powerpc64_unknown_freebsd.rs

@@ -11,7 +11,7 @@ pub(crate) fn target() -> Target {
     Target {
         llvm_target: "powerpc64-unknown-freebsd".into(),
         metadata: crate::spec::TargetMetadata {
-            description: Some("PPC64 FreeBSD (ELFv1 and ELFv2)".into()),
+            description: Some("PPC64 FreeBSD (ELFv2)".into()),
             tier: Some(3),
             host_tools: Some(true),
             std: Some(true),

library/core/src/alloc/mod.rs

@@ -10,11 +10,6 @@ pub use self::global::GlobalAlloc;
 #[stable(feature = "alloc_layout", since = "1.28.0")]
 pub use self::layout::Layout;
 #[stable(feature = "alloc_layout", since = "1.28.0")]
-#[deprecated(
-    since = "1.52.0",
-    note = "Name does not follow std convention, use LayoutError",
-    suggestion = "LayoutError"
-)]
 #[allow(deprecated, deprecated_in_future)]
 pub use self::layout::LayoutErr;
 #[stable(feature = "alloc_layout_error", since = "1.50.0")]

library/core/src/hint.rs

@@ -310,13 +310,17 @@ pub fn spin_loop() {
 /// behavior in the calling code. This property makes `black_box` useful for writing code in which
 /// certain optimizations are not desired, such as benchmarks.
 ///
+/// <div class="warning">
+///
 /// Note however, that `black_box` is only (and can only be) provided on a "best-effort" basis. The
 /// extent to which it can block optimisations may vary depending upon the platform and code-gen
 /// backend used. Programs cannot rely on `black_box` for *correctness*, beyond it behaving as the
 /// identity function. As such, it **must not be relied upon to control critical program behavior.**
 /// This also means that this function does not offer any guarantees for cryptographic or security
 /// purposes.
 ///
+/// </div>
+///
 /// [`std::convert::identity`]: crate::convert::identity
 ///
 /// # When is this useful?
@@ -357,7 +361,7 @@ pub fn spin_loop() {
 /// ```
 /// use std::hint::black_box;
 ///
-/// // Same `contains` function
+/// // Same `contains` function.
 /// fn contains(haystack: &[&str], needle: &str) -> bool {
 ///     haystack.iter().any(|x| x == &needle)
 /// }
@@ -366,8 +370,13 @@ pub fn spin_loop() {
 ///     let haystack = vec!["abc", "def", "ghi", "jkl", "mno"];
 ///     let needle = "ghi";
 ///     for _ in 0..10 {
-///         // Adjust our benchmark loop contents
-///         black_box(contains(black_box(&haystack), black_box(needle)));
+///         // Force the compiler to run `contains`, even though it is a pure function whose
+///         // results are unused.
+///         black_box(contains(
+///             // Prevent the compiler from making assumptions about the input.
+///             black_box(&haystack),
+///             black_box(needle),
+///         ));
 ///     }
 /// }
 /// ```
@@ -382,6 +391,83 @@ pub fn spin_loop() {
 ///
 /// This makes our benchmark much more realistic to how the function would actually be used, where
 /// arguments are usually not known at compile time and the result is used in some way.
+///
+/// # How to use this
+///
+/// In practice, `black_box` serves two purposes:
+///
+/// 1. It prevents the compiler from making optimizations related to the value returned by `black_box`
+/// 2. It forces the value passed to `black_box` to be calculated, even if the return value of `black_box` is unused
+///
+/// ```
+/// use std::hint::black_box;
+///
+/// let zero = 0;
+/// let five = 5;
+///
+/// // The compiler will see this and remove the `* five` call, because it knows that multiplying
+/// // any integer by 0 will result in 0.
+/// let c = zero * five;
+///
+/// // Adding `black_box` here disables the compiler's ability to reason about the first operand in the multiplication.
+/// // It is forced to assume that it can be any possible number, so it cannot remove the `* five`
+/// // operation.
+/// let c = black_box(zero) * five;
+/// ```
+///
+/// While most cases will not be as clear-cut as the above example, it still illustrates how
+/// `black_box` can be used. When benchmarking a function, you usually want to wrap its inputs in
+/// `black_box` so the compiler cannot make optimizations that would be unrealistic in real-life
+/// use.
+///
+/// ```
+/// use std::hint::black_box;
+///
+/// // This is a simple function that increments its input by 1. Note that it is pure, meaning it
+/// // has no side-effects. This function has no effect if its result is unused. (An example of a
+/// // function *with* side-effects is `println!()`.)
+/// fn increment(x: u8) -> u8 {
+///     x + 1
+/// }
+///
+/// // Here, we call `increment` but discard its result. The compiler, seeing this and knowing that
+/// // `increment` is pure, will eliminate this function call entirely. This may not be desired,
+/// // though, especially if we're trying to track how much time `increment` takes to execute.
+/// let _ = increment(black_box(5));
+///
+/// // Here, we force `increment` to be executed. This is because the compiler treats `black_box`
+/// // as if it has side-effects, and thus must compute its input.
+/// let _ = black_box(increment(black_box(5)));
+/// ```
+///
+/// There may be additional situations where you want to wrap the result of a function in
+/// `black_box` to force its execution. This is situational though, and may not have any effect
+/// (such as when the function returns a zero-sized type such as [`()` unit][unit]).
+///
+/// Note that `black_box` has no effect on how its input is treated, only its output. As such,
+/// expressions passed to `black_box` may still be optimized:
+///
+/// ```
+/// use std::hint::black_box;
+///
+/// // The compiler sees this...
+/// let y = black_box(5 * 10);
+///
+/// // ...as this. As such, it will likely simplify `5 * 10` to just `50`.
+/// let _0 = 5 * 10;
+/// let y = black_box(_0);
+/// ```
+///
+/// In the above example, the `5 * 10` expression is considered distinct from the `black_box` call,
+/// and thus is still optimized by the compiler. You can prevent this by moving the multiplication
+/// operation outside of `black_box`:
+///
+/// ```
+/// use std::hint::black_box;
+///
+/// // No assumptions can be made about either operand, so the multiplication is not optimized out.
+/// let y = black_box(5) * black_box(10);
+/// ```
 #[inline]
 #[stable(feature = "bench_black_box", since = "1.66.0")]
 #[rustc_const_unstable(feature = "const_black_box", issue = "none")]

library/std/src/collections/mod.rs

@@ -433,8 +433,7 @@ pub use self::hash_map::HashMap;
 #[doc(inline)]
 pub use self::hash_set::HashSet;
 #[stable(feature = "rust1", since = "1.0.0")]
-// FIXME(#82080) The deprecation here is only theoretical, and does not actually produce a warning.
-#[deprecated(note = "moved to `std::ops::Bound`", since = "1.26.0")]
+// FIXME(#82080) This has moved but #[deprecated] on `use` is unsupported.
 #[doc(hidden)]
 pub use crate::ops::Bound;
 

src/doc/rustc/src/platform-support.md

@@ -343,7 +343,7 @@ target | std | host | notes
 [`powerpc-unknown-openbsd`](platform-support/powerpc-unknown-openbsd.md) | * |  |
 [`powerpc-wrs-vxworks-spe`](platform-support/vxworks.md) | ✓ |  |
 [`powerpc-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
-`powerpc64-unknown-freebsd` | ✓ | ✓ | PPC64 FreeBSD (ELFv1 and ELFv2)
+`powerpc64-unknown-freebsd` | ✓ | ✓ | PPC64 FreeBSD (ELFv2)
 `powerpc64le-unknown-freebsd` | ✓ | ✓ | PPC64LE FreeBSD
 `powerpc-unknown-freebsd` | ? |   | PowerPC FreeBSD
 `powerpc64-unknown-linux-musl` | ? |  | 64-bit PowerPC Linux with musl 1.2.3

src/tools/run-make-support/src/external_deps/rustc.rs

@@ -325,6 +325,12 @@ impl Rustc {
         self
     }
 
+    /// Pass the `--verbose` flag.
+    pub fn verbose(&mut self) -> &mut Self {
+        self.cmd.arg("--verbose");
+        self
+    }
+
     /// `EXTRARSCXXFLAGS`
     pub fn extra_rs_cxx_flags(&mut self) -> &mut Self {
         // Adapted from tools.mk (trimmed):

tests/run-make/link-args-order/rmake.rs

@@ -15,15 +15,17 @@ fn main() {
         .link_args("b c")
         .link_args("d e")
         .link_arg("f")
+        .arg("--print=link-args")
         .run_fail()
-        .assert_stderr_contains(r#""a" "b" "c" "d" "e" "f""#);
+        .assert_stdout_contains(r#""a" "b" "c" "d" "e" "f""#);
     rustc()
         .input("empty.rs")
         .linker_flavor(linker)
         .arg("-Zpre-link-arg=a")
         .arg("-Zpre-link-args=b c")
         .arg("-Zpre-link-args=d e")
         .arg("-Zpre-link-arg=f")
+        .arg("--print=link-args")
         .run_fail()
-        .assert_stderr_contains(r#""a" "b" "c" "d" "e" "f""#);
+        .assert_stdout_contains(r#""a" "b" "c" "d" "e" "f""#);
 }

tests/run-make/link-dedup/rmake.rs

@@ -14,13 +14,13 @@ fn main() {
     rustc().input("depb.rs").run();
     rustc().input("depc.rs").run();
 
-    let output = rustc().input("empty.rs").cfg("bar").run_fail();
-    output.assert_stderr_contains(needle_from_libs(&["testa", "testb", "testa"]));
+    let output = rustc().input("empty.rs").cfg("bar").arg("--print=link-args").run_fail();
+    output.assert_stdout_contains(needle_from_libs(&["testa", "testb", "testa"]));
 
-    let output = rustc().input("empty.rs").run_fail();
-    output.assert_stderr_contains(needle_from_libs(&["testa"]));
-    output.assert_stderr_not_contains(needle_from_libs(&["testb"]));
-    output.assert_stderr_not_contains(needle_from_libs(&["testa", "testa", "testa"]));
+    let output = rustc().input("empty.rs").arg("--print=link-args").run_fail();
+    output.assert_stdout_contains(needle_from_libs(&["testa"]));
+    output.assert_stdout_not_contains(needle_from_libs(&["testb"]));
+    output.assert_stdout_not_contains(needle_from_libs(&["testa", "testa", "testa"]));
     // Adjacent identical native libraries are no longer deduplicated if
     // they come from different crates (https://github.com/rust-lang/rust/pull/103311)
     // so the following will fail:

tests/run-make/linker-warning/fake-linker.rs

@@ -0,0 +1,13 @@
+fn main() {
+    for arg in std::env::args() {
+        match &*arg {
+            "run_make_info" => println!("foo"),
+            "run_make_warn" => eprintln!("warning: bar"),
+            "run_make_error" => {
+                eprintln!("error: baz");
+                std::process::exit(1);
+            }
+            _ => (),
+        }
+    }
+}

tests/run-make/linker-warning/main.rs

@@ -0,0 +1 @@
+fn main() {}

tests/run-make/linker-warning/rmake.rs

@@ -0,0 +1,28 @@
+use run_make_support::{Rustc, rustc};
+
+fn run_rustc() -> Rustc {
+    let mut rustc = rustc();
+    rustc.arg("main.rs").output("main").linker("./fake-linker");
+    rustc
+}
+
+fn main() {
+    // first, compile our linker
+    rustc().arg("fake-linker.rs").output("fake-linker").run();
+
+    // Make sure we don't show the linker args unless `--verbose` is passed
+    run_rustc()
+        .link_arg("run_make_error")
+        .verbose()
+        .run_fail()
+        .assert_stderr_contains_regex("fake-linker.*run_make_error")
+        .assert_stderr_not_contains("object files omitted")
+        .assert_stderr_contains_regex(r"lib[/\\]libstd");
+    run_rustc()
+        .link_arg("run_make_error")
+        .run_fail()
+        .assert_stderr_contains("fake-linker")
+        .assert_stderr_contains("object files omitted")
+        .assert_stderr_contains_regex(r"\{")
+        .assert_stderr_not_contains_regex(r"lib[/\\]libstd");
+}