Auto merge of rust-lang#124633 - matthiaskrgr:rollup-x4kyjp2, r=matth…

…iaskrgr

Rollup of 4 pull requests

Successful merges:

 - rust-lang#124345 (Enable `--check-cfg` by default in UI tests)
 - rust-lang#124412 (io safety: update Unix explanation to use `Arc`)
 - rust-lang#124441 (String.truncate comment microfix (greater or equal))
 - rust-lang#124604 (library/std: Remove unused `gimli-symbolize` feature)

Failed merges:

 - rust-lang#124607 (`rustc_expand` cleanups)
 - rust-lang#124613 (Allow fmt to run on rmake.rs test files)

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

library/alloc/src/string.rs

@@ -1382,7 +1382,7 @@ impl String {
 
     /// Shortens this `String` to the specified length.
     ///
-    /// If `new_len` is greater than the string's current length, this has no
+    /// If `new_len` is greater than or equal to the string's current length, this has no
     /// effect.
     ///
     /// Note that this method has no effect on the allocated capacity

library/std/Cargo.toml

@@ -64,12 +64,10 @@ r-efi-alloc = { version = "1.0.0", features = ['rustc-dep-of-std'] }
 
 [features]
 backtrace = [
-  "gimli-symbolize",
   'addr2line/rustc-dep-of-std',
   'object/rustc-dep-of-std',
   'miniz_oxide/rustc-dep-of-std',
 ]
-gimli-symbolize = []
 
 panic-unwind = ["panic_unwind"]
 profiler = ["profiler_builtins"]

library/std/src/io/mod.rs

@@ -266,7 +266,7 @@
 //! its file descriptors with no operations being performed by any other part of the program.
 //!
 //! Note that exclusive ownership of a file descriptor does *not* imply exclusive ownership of the
-//! underlying kernel object that the file descriptor references (also called "file description" on
+//! underlying kernel object that the file descriptor references (also called "open file description" on
 //! some operating systems). File descriptors basically work like [`Arc`]: when you receive an owned
 //! file descriptor, you cannot know whether there are any other file descriptors that reference the
 //! same kernel object. However, when you create a new kernel object, you know that you are holding

library/std/src/os/unix/io/mod.rs

@@ -12,8 +12,8 @@
 //! | Type               | Analogous to |
 //! | ------------------ | ------------ |
 //! | [`RawFd`]          | `*const _`   |
-//! | [`BorrowedFd<'a>`] | `&'a _`      |
-//! | [`OwnedFd`]        | `Box<_>`     |
+//! | [`BorrowedFd<'a>`] | `&'a Arc<_>` |
+//! | [`OwnedFd`]        | `Arc<_>`     |
 //!
 //! Like raw pointers, `RawFd` values are primitive values. And in new code,
 //! they should be considered unsafe to do I/O on (analogous to dereferencing
@@ -23,22 +23,31 @@
 //! either by adding `unsafe` to APIs that dereference `RawFd` values, or by
 //! using to `BorrowedFd` or `OwnedFd` instead.
 //!
+//! The use of `Arc` for borrowed/owned file descriptors may be surprising. Unix file descriptors
+//! are mere references to internal kernel objects called "open file descriptions", and the same
+//! open file description can be referenced by multiple file descriptors (e.g. if `dup` is used).
+//! State such as the offset within the file is shared among all file descriptors that refer to the
+//! same open file description, and the kernel internally does reference-counting to only close the
+//! underlying resource once all file descriptors referencing it are closed. That's why `Arc` (and
+//! not `Box`) is the closest Rust analogy to an "owned" file descriptor.
+//!
 //! Like references, `BorrowedFd` values are tied to a lifetime, to ensure
 //! that they don't outlive the resource they point to. These are safe to
 //! use. `BorrowedFd` values may be used in APIs which provide safe access to
 //! any system call except for:
 //!
 //!  - `close`, because that would end the dynamic lifetime of the resource
-//!    without ending the lifetime of the file descriptor.
+//!    without ending the lifetime of the file descriptor. (Equivalently:
+//!    an `&Arc<_>` cannot be `drop`ed.)
 //!
 //!  - `dup2`/`dup3`, in the second argument, because this argument is
-//!    closed and assigned a new resource, which may break the assumptions
+//!    closed and assigned a new resource, which may break the assumptions of
 //!    other code using that file descriptor.
 //!
-//! `BorrowedFd` values may be used in APIs which provide safe access to `dup`
-//! system calls, so types implementing `AsFd` or `From<OwnedFd>` should not
-//! assume they always have exclusive access to the underlying file
-//! description.
+//! `BorrowedFd` values may be used in APIs which provide safe access to `dup` system calls, so code
+//! working with `OwnedFd` cannot assume to have exclusive access to the underlying open file
+//! description. (Equivalently: `&Arc` may be used in APIs that provide safe access to `clone`, so
+//! code working with an `Arc` cannot assume that the reference count is 1.)
 //!
 //! `BorrowedFd` values may also be used with `mmap`, since `mmap` uses the
 //! provided file descriptor in a manner similar to `dup` and does not require
@@ -52,8 +61,10 @@
 //! take full responsibility for ensuring that safe Rust code cannot evoke
 //! undefined behavior through it.
 //!
-//! Like boxes, `OwnedFd` values conceptually own the resource they point to,
-//! and free (close) it when they are dropped.
+//! Like `Arc`, `OwnedFd` values conceptually own one reference to the resource they point to,
+//! and decrement the reference count when they are dropped (by calling `close`).
+//! When the reference count reaches 0, the underlying open file description will be freed
+//! by the kernel.
 //!
 //! See the [`io` module docs][io-safety] for a general explanation of I/O safety.
 //!

src/tools/compiletest/src/header.rs

@@ -208,6 +208,8 @@ pub struct TestProps {
     pub llvm_cov_flags: Vec<String>,
     /// Extra flags to pass to LLVM's `filecheck` tool, in tests that use it.
     pub filecheck_flags: Vec<String>,
+    /// Don't automatically insert any `--check-cfg` args
+    pub no_auto_check_cfg: bool,
 }
 
 mod directives {
@@ -249,6 +251,7 @@ mod directives {
     pub const COMPARE_OUTPUT_LINES_BY_SUBSET: &'static str = "compare-output-lines-by-subset";
     pub const LLVM_COV_FLAGS: &'static str = "llvm-cov-flags";
     pub const FILECHECK_FLAGS: &'static str = "filecheck-flags";
+    pub const NO_AUTO_CHECK_CFG: &'static str = "no-auto-check-cfg";
     // This isn't a real directive, just one that is probably mistyped often
     pub const INCORRECT_COMPILER_FLAGS: &'static str = "compiler-flags";
 }
@@ -304,6 +307,7 @@ impl TestProps {
             remap_src_base: false,
             llvm_cov_flags: vec![],
             filecheck_flags: vec![],
+            no_auto_check_cfg: false,
         }
     }
 
@@ -567,6 +571,8 @@ impl TestProps {
                     if let Some(flags) = config.parse_name_value_directive(ln, FILECHECK_FLAGS) {
                         self.filecheck_flags.extend(split_flags(&flags));
                     }
+
+                    config.set_name_directive(ln, NO_AUTO_CHECK_CFG, &mut self.no_auto_check_cfg);
                 },
             );
 
@@ -860,6 +866,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "needs-unwind",
     "needs-wasmtime",
     "needs-xray",
+    "no-auto-check-cfg",
     "no-prefer-dynamic",
     "normalize-stderr-32bit",
     "normalize-stderr-64bit",

src/tools/compiletest/src/runtest.rs

@@ -1028,12 +1028,31 @@ impl<'test> TestCx<'test> {
     }
 
     fn set_revision_flags(&self, cmd: &mut Command) {
+        // Normalize revisions to be lowercase and replace `-`s with `_`s.
+        // Otherwise the `--cfg` flag is not valid.
+        let normalize_revision = |revision: &str| revision.to_lowercase().replace("-", "_");
+
         if let Some(revision) = self.revision {
-            // Normalize revisions to be lowercase and replace `-`s with `_`s.
-            // Otherwise the `--cfg` flag is not valid.
-            let normalized_revision = revision.to_lowercase().replace("-", "_");
+            let normalized_revision = normalize_revision(revision);
             cmd.args(&["--cfg", &normalized_revision]);
         }
+
+        if !self.props.no_auto_check_cfg {
+            let mut check_cfg = String::with_capacity(25);
+
+            // Generate `cfg(FALSE, REV1, ..., REVN)` (for all possible revisions)
+            //
+            // For compatibility reason we consider the `FALSE` cfg to be expected
+            // since it is extensively used in the testsuite.
+            check_cfg.push_str("cfg(FALSE");
+            for revision in &self.props.revisions {
+                check_cfg.push_str(",");
+                check_cfg.push_str(&normalize_revision(&revision));
+            }
+            check_cfg.push_str(")");
+
+            cmd.args(&["--check-cfg", &check_cfg]);
+        }
     }
 
     fn typecheck_source(&self, src: String) -> ProcRes {

tests/rustdoc-ui/argfile/commandline-argfile.rs

@@ -1,13 +1,13 @@
 // Check to see if we can get parameters from an @argsfile file
 //
 //@ check-pass
-//@ compile-flags: --cfg cmdline_set @{{src-base}}/argfile/commandline-argfile.args
+//@ compile-flags: --cfg cmdline_set --check-cfg=cfg(cmdline_set,unbroken)
+//@ compile-flags: @{{src-base}}/argfile/commandline-argfile.args
 
 #[cfg(not(cmdline_set))]
 compile_error!("cmdline_set not set");
 
 #[cfg(not(unbroken))]
 compile_error!("unbroken not set");
 
-fn main() {
-}
+fn main() {}

tests/ui/argfile/commandline-argfile.rs

@@ -1,13 +1,13 @@
 // Check to see if we can get parameters from an @argsfile file
 //
 //@ build-pass
-//@ compile-flags: --cfg cmdline_set @{{src-base}}/argfile/commandline-argfile.args
+//@ compile-flags: --cfg cmdline_set --check-cfg=cfg(cmdline_set,unbroken)
+//@ compile-flags: @{{src-base}}/argfile/commandline-argfile.args
 
 #[cfg(not(cmdline_set))]
 compile_error!("cmdline_set not set");
 
 #[cfg(not(unbroken))]
 compile_error!("unbroken not set");
 
-fn main() {
-}
+fn main() {}

tests/ui/cfg/cfg-in-crate-1.rs

@@ -1,5 +1,6 @@
 //@ run-pass
-//@ compile-flags: --cfg bar -D warnings
+//@ compile-flags: --cfg bar --check-cfg=cfg(bar) -D warnings
+
 #![cfg(bar)]
 
 fn main() {}

tests/ui/cfg/cfg-macros-foo.rs

@@ -1,5 +1,5 @@
 //@ run-pass
-//@ compile-flags: --cfg foo
+//@ compile-flags: --cfg foo --check-cfg=cfg(foo)
 
 // check that cfg correctly chooses between the macro impls (see also
 // cfg-macros-notfoo.rs)

tests/ui/cfg/cfg-path-error.rs

@@ -1,5 +1,7 @@
 //@ check-fail
 
+#![allow(unexpected_cfgs)] // invalid cfgs
+
 #[cfg(any(foo, foo::bar))]
 //~^ERROR `cfg` predicate key must be an identifier
 fn foo1() {}

tests/ui/cfg/cfg-path-error.stderr

@@ -1,23 +1,23 @@
 error: `cfg` predicate key must be an identifier
-  --> $DIR/cfg-path-error.rs:3:16
+  --> $DIR/cfg-path-error.rs:5:16
    |
 LL | #[cfg(any(foo, foo::bar))]
    |                ^^^^^^^^
 
 error: `cfg` predicate key must be an identifier
-  --> $DIR/cfg-path-error.rs:7:11
+  --> $DIR/cfg-path-error.rs:9:11
    |
 LL | #[cfg(any(foo::bar, foo))]
    |           ^^^^^^^^
 
 error: `cfg` predicate key must be an identifier
-  --> $DIR/cfg-path-error.rs:11:16
+  --> $DIR/cfg-path-error.rs:13:16
    |
 LL | #[cfg(all(foo, foo::bar))]
    |                ^^^^^^^^
 
 error: `cfg` predicate key must be an identifier
-  --> $DIR/cfg-path-error.rs:15:11
+  --> $DIR/cfg-path-error.rs:17:11
    |
 LL | #[cfg(all(foo::bar, foo))]
    |           ^^^^^^^^

tests/ui/cfg/cfg_attr.rs

@@ -1,6 +1,8 @@
 //@ run-pass
 //@ compile-flags:--cfg set1 --cfg set2
-#![allow(dead_code)]
+
+#![allow(dead_code, unexpected_cfgs)]
+
 use std::fmt::Debug;
 
 struct NotDebugable;

tests/ui/cfg/cfgs-on-items.rs

@@ -1,8 +1,7 @@
 //@ run-pass
-//@ compile-flags: --cfg fooA --cfg fooB
+//@ compile-flags: --cfg fooA --cfg fooB --check-cfg=cfg(fooA,fooB,fooC,bar)
 
 // fooA AND !bar
-
 #[cfg(all(fooA, not(bar)))]
 fn foo1() -> isize { 1 }
 

tests/ui/cfg/diagnostics-not-a-def.rs

@@ -1,4 +1,7 @@
+#![feature(lint_reasons)]
+
 pub mod inner {
+    #[expect(unexpected_cfgs)]
     pub fn i_am_here() {
         #[cfg(feature = "another one that doesn't exist")]
         loop {}

tests/ui/cfg/diagnostics-not-a-def.stderr

@@ -1,5 +1,5 @@
 error[E0425]: cannot find function `i_am_not` in module `inner`
-  --> $DIR/diagnostics-not-a-def.rs:11:12
+  --> $DIR/diagnostics-not-a-def.rs:14:12
    |
 LL |     inner::i_am_not();
    |            ^^^^^^^^ not found in `inner`

tests/ui/cfg/diagnostics-same-crate.rs

@@ -1,3 +1,5 @@
+#![allow(unexpected_cfgs)] // since we want to recognize them as unexpected
+
 pub mod inner {
     #[cfg(FALSE)]
     pub fn uwu() {}

tests/ui/cfg/diagnostics-same-crate.stderr

@@ -1,72 +1,72 @@
 error[E0432]: unresolved import `super::inner::doesnt_exist`
-  --> $DIR/diagnostics-same-crate.rs:28:9
+  --> $DIR/diagnostics-same-crate.rs:30:9
    |
 LL |     use super::inner::doesnt_exist;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^ no `doesnt_exist` in `inner`
    |
 note: found an item that was configured out
-  --> $DIR/diagnostics-same-crate.rs:7:13
+  --> $DIR/diagnostics-same-crate.rs:9:13
    |
 LL |     pub mod doesnt_exist {
    |             ^^^^^^^^^^^^
 
 error[E0432]: unresolved import `super::inner::doesnt_exist`
-  --> $DIR/diagnostics-same-crate.rs:31:23
+  --> $DIR/diagnostics-same-crate.rs:33:23
    |
 LL |     use super::inner::doesnt_exist::hi;
    |                       ^^^^^^^^^^^^ could not find `doesnt_exist` in `inner`
    |
 note: found an item that was configured out
-  --> $DIR/diagnostics-same-crate.rs:7:13
+  --> $DIR/diagnostics-same-crate.rs:9:13
    |
 LL |     pub mod doesnt_exist {
    |             ^^^^^^^^^^^^
 
 error[E0433]: failed to resolve: could not find `doesnt_exist` in `inner`
-  --> $DIR/diagnostics-same-crate.rs:50:12
+  --> $DIR/diagnostics-same-crate.rs:52:12
    |
 LL |     inner::doesnt_exist::hello();
    |            ^^^^^^^^^^^^ could not find `doesnt_exist` in `inner`
    |
 note: found an item that was configured out
-  --> $DIR/diagnostics-same-crate.rs:7:13
+  --> $DIR/diagnostics-same-crate.rs:9:13
    |
 LL |     pub mod doesnt_exist {
    |             ^^^^^^^^^^^^
 
 error[E0425]: cannot find function `uwu` in module `inner`
-  --> $DIR/diagnostics-same-crate.rs:45:12
+  --> $DIR/diagnostics-same-crate.rs:47:12
    |
 LL |     inner::uwu();
    |            ^^^ not found in `inner`
    |
 note: found an item that was configured out
-  --> $DIR/diagnostics-same-crate.rs:3:12
+  --> $DIR/diagnostics-same-crate.rs:5:12
    |
 LL |     pub fn uwu() {}
    |            ^^^
 
 error[E0425]: cannot find function `meow` in module `inner::right`
-  --> $DIR/diagnostics-same-crate.rs:54:19
+  --> $DIR/diagnostics-same-crate.rs:56:19
    |
 LL |     inner::right::meow();
    |                   ^^^^ not found in `inner::right`
    |
 note: found an item that was configured out
-  --> $DIR/diagnostics-same-crate.rs:22:16
+  --> $DIR/diagnostics-same-crate.rs:24:16
    |
 LL |         pub fn meow() {}
    |                ^^^^
    = note: the item is gated behind the `what-a-cool-feature` feature
 
 error[E0425]: cannot find function `uwu` in this scope
-  --> $DIR/diagnostics-same-crate.rs:41:5
+  --> $DIR/diagnostics-same-crate.rs:43:5
    |
 LL |     uwu();
    |     ^^^ not found in this scope
 
 error[E0425]: cannot find function `vanished` in this scope
-  --> $DIR/diagnostics-same-crate.rs:61:5
+  --> $DIR/diagnostics-same-crate.rs:63:5
    |
 LL |     vanished();
    |     ^^^^^^^^ not found in this scope

tests/ui/cfg/expanded-cfg.rs

@@ -1,5 +1,7 @@
 //@ check-pass
 
+#![allow(unexpected_cfgs)] // since we different cfgs
+
 macro_rules! mac {
     {} => {
         #[cfg(attr)]

tests/ui/cfg/future-compat-crate-attributes-using-cfg_attr.rs

@@ -1,5 +1,5 @@
 //@ check-fail
-//@ compile-flags:--cfg foo
+//@ compile-flags:--cfg foo --check-cfg=cfg(foo)
 
 #![cfg_attr(foo, crate_type="bin")]
 //~^ERROR `crate_type` within