Auto merge of #136809 - workingjubilee:rollup-jk0pew1, r=workingjubilee

Rollup of 12 pull requests

Successful merges:

 - #136053 (coverage: Defer part of counter-creation until codegen)
 - #136201 (Removed dependency on the field-offset crate, alternate approach)
 - #136228 (Simplify Rc::as_ptr docs + typo fix)
 - #136353 (fix(libtest): Enable Instant on Emscripten targets)
 - #136472 ([`compiletest`-related cleanups 2/7] Feed stage number to compiletest directly)
 - #136487 (ci: stop mysql before removing it)
 - #136552 (Use an `Option` for `FindNextFileHandle` in `ReadDir` instead of `INVALID_FILE_HANDLE` sentinel value)
 - #136705 (Some miscellaneous edition-related library tweaks)
 - #136707 (Bump `cc` to v1.2.13 for the compiler workspace)
 - #136790 (Git blame ignore recent formatting commit)
 - #136792 (Don't apply editorconfig to llvm)
 - #136805 (ignore win_delete_self test in Miri)

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

49 files changed, 84 insertions, 87 deletions

diff --git a/library/std/src/alloc.rs b/library/std/src/alloc.rs
index 5d51d6a0c78..3936ed057e6 100644
--- a/library/std/src/alloc.rs
+++ b/library/std/src/alloc.rs
@@ -345,7 +345,7 @@ pub fn take_alloc_error_hook() -> fn(Layout) {
 }
 
 fn default_alloc_error_hook(layout: Layout) {
-    extern "Rust" {
+    unsafe extern "Rust" {
         // This symbol is emitted by rustc next to __rust_alloc_error_handler.
         // Its value depends on the -Zoom={panic,abort} compiler option.
         static __rust_alloc_error_handler_should_panic: u8;
diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs
index 8e50bf11dd0..b47b41d4bc5 100644
--- a/library/std/src/panicking.rs
+++ b/library/std/src/panicking.rs
@@ -54,11 +54,11 @@ pub static EMPTY_PANIC: fn(&'static str) -> ! =
 // One day this may look a little less ad-hoc with the compiler helping out to
 // hook up these functions, but it is not this day!
 #[allow(improper_ctypes)]
-extern "C" {
+unsafe extern "C" {
     fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static);
 }
 
-extern "Rust" {
+unsafe extern "Rust" {
     /// `PanicPayload` lazily performs allocation only when needed (this avoids
     /// allocations when using the "abort" panic runtime).
     fn __rust_start_panic(payload: &mut dyn PanicPayload) -> u32;
diff --git a/library/std/src/sync/mpmc/mod.rs b/library/std/src/sync/mpmc/mod.rs
index 00966ee3ecf..8caa2dcfad9 100644
--- a/library/std/src/sync/mpmc/mod.rs
+++ b/library/std/src/sync/mpmc/mod.rs
@@ -616,9 +616,9 @@ impl<T> Sender<T> {
     #[unstable(feature = "mpmc_channel", issue = "126840")]
     pub fn same_channel(&self, other: &Sender<T>) -> bool {
         match (&self.flavor, &other.flavor) {
-            (SenderFlavor::Array(ref a), SenderFlavor::Array(ref b)) => a == b,
-            (SenderFlavor::List(ref a), SenderFlavor::List(ref b)) => a == b,
-            (SenderFlavor::Zero(ref a), SenderFlavor::Zero(ref b)) => a == b,
+            (SenderFlavor::Array(a), SenderFlavor::Array(b)) => a == b,
+            (SenderFlavor::List(a), SenderFlavor::List(b)) => a == b,
+            (SenderFlavor::Zero(a), SenderFlavor::Zero(b)) => a == b,
             _ => false,
         }
     }
diff --git a/library/std/src/sys/alloc/xous.rs b/library/std/src/sys/alloc/xous.rs
index 321d30e0b11..9d22e16fdf2 100644
--- a/library/std/src/sys/alloc/xous.rs
+++ b/library/std/src/sys/alloc/xous.rs
@@ -8,7 +8,7 @@ use crate::alloc::{GlobalAlloc, Layout, System};
 static mut DLMALLOC: dlmalloc::Dlmalloc = dlmalloc::Dlmalloc::new();
 
 #[cfg(test)]
-extern "Rust" {
+unsafe extern "Rust" {
     #[link_name = "_ZN16__rust_internals3std3sys4xous5alloc8DLMALLOCE"]
     static mut DLMALLOC: dlmalloc::Dlmalloc;
 }
diff --git a/library/std/src/sys/cmath.rs b/library/std/src/sys/cmath.rs
index ee36127cfdf..e3f41f4fdbb 100644
--- a/library/std/src/sys/cmath.rs
+++ b/library/std/src/sys/cmath.rs
@@ -2,7 +2,7 @@
 
 // These symbols are all defined by `libm`,
 // or by `compiler-builtins` on unsupported platforms.
-extern "C" {
+unsafe extern "C" {
     pub fn acos(n: f64) -> f64;
     pub fn asin(n: f64) -> f64;
     pub fn atan(n: f64) -> f64;
diff --git a/library/std/src/sys/pal/hermit/mod.rs b/library/std/src/sys/pal/hermit/mod.rs
index 3d555ad5050..a746b853cbd 100644
--- a/library/std/src/sys/pal/hermit/mod.rs
+++ b/library/std/src/sys/pal/hermit/mod.rs
@@ -78,7 +78,7 @@ pub unsafe extern "C" fn runtime_entry(
     argv: *const *const c_char,
     env: *const *const c_char,
 ) -> ! {
-    extern "C" {
+    unsafe extern "C" {
         fn main(argc: isize, argv: *const *const c_char) -> i32;
     }
 
diff --git a/library/std/src/sys/pal/itron/abi.rs b/library/std/src/sys/pal/itron/abi.rs
index 5eb14bb7e53..49b5251fc0e 100644
--- a/library/std/src/sys/pal/itron/abi.rs
+++ b/library/std/src/sys/pal/itron/abi.rs
@@ -132,7 +132,7 @@ pub struct T_CTSK {
     pub stk: *mut u8,
 }
 
-extern "C" {
+unsafe extern "C" {
     #[link_name = "__asp3_acre_tsk"]
     pub fn acre_tsk(pk_ctsk: *const T_CTSK) -> ER_ID;
     #[link_name = "__asp3_get_tid"]
diff --git a/library/std/src/sys/pal/sgx/abi/mem.rs b/library/std/src/sys/pal/sgx/abi/mem.rs
index 18e6d5b3fa2..e6ce15bed3c 100644
--- a/library/std/src/sys/pal/sgx/abi/mem.rs
+++ b/library/std/src/sys/pal/sgx/abi/mem.rs
@@ -12,7 +12,7 @@ pub(crate) unsafe fn rel_ptr_mut<T>(offset: u64) -> *mut T {
     (image_base() + offset) as *mut T
 }
 
-extern "C" {
+unsafe extern "C" {
     static ENCLAVE_SIZE: usize;
     static HEAP_BASE: u64;
     static HEAP_SIZE: usize;
diff --git a/library/std/src/sys/pal/sgx/abi/mod.rs b/library/std/src/sys/pal/sgx/abi/mod.rs
index d8836452e75..f52acc41509 100644
--- a/library/std/src/sys/pal/sgx/abi/mod.rs
+++ b/library/std/src/sys/pal/sgx/abi/mod.rs
@@ -73,7 +73,7 @@ extern "C" fn entry(p1: u64, p2: u64, p3: u64, secondary: bool, p4: u64, p5: u64
 
         EntryReturn(0, 0)
     } else {
-        extern "C" {
+        unsafe extern "C" {
             fn main(argc: isize, argv: *const *const u8) -> isize;
         }
 
diff --git a/library/std/src/sys/pal/sgx/abi/panic.rs b/library/std/src/sys/pal/sgx/abi/panic.rs
index c06b97ee367..67af062b0ff 100644
--- a/library/std/src/sys/pal/sgx/abi/panic.rs
+++ b/library/std/src/sys/pal/sgx/abi/panic.rs
@@ -2,7 +2,7 @@ use super::usercalls::alloc::UserRef;
 use crate::io::{self, Write};
 use crate::{cmp, mem};
 
-extern "C" {
+unsafe extern "C" {
     fn take_debug_panic_buf_ptr() -> *mut u8;
     static DEBUG: u8;
 }
diff --git a/library/std/src/sys/pal/sgx/abi/reloc.rs b/library/std/src/sys/pal/sgx/abi/reloc.rs
index 02dff0ad29f..a4f5e4a0936 100644
--- a/library/std/src/sys/pal/sgx/abi/reloc.rs
+++ b/library/std/src/sys/pal/sgx/abi/reloc.rs
@@ -11,7 +11,7 @@ struct Rela<T> {
 }
 
 pub fn relocate_elf_rela() {
-    extern "C" {
+    unsafe extern "C" {
         static RELA: u64;
         static RELACOUNT: usize;
     }
diff --git a/library/std/src/sys/pal/sgx/abi/thread.rs b/library/std/src/sys/pal/sgx/abi/thread.rs
index 2b23e368cc3..9b37e2baf36 100644
--- a/library/std/src/sys/pal/sgx/abi/thread.rs
+++ b/library/std/src/sys/pal/sgx/abi/thread.rs
@@ -6,7 +6,7 @@ use fortanix_sgx_abi::Tcs;
 /// is a one-to-one correspondence of the ID to the address of the TCS.
 #[unstable(feature = "sgx_platform", issue = "56975")]
 pub fn current() -> Tcs {
-    extern "C" {
+    unsafe extern "C" {
         fn get_tcs_addr() -> *mut u8;
     }
     let addr = unsafe { get_tcs_addr() };
diff --git a/library/std/src/sys/pal/sgx/abi/tls/mod.rs b/library/std/src/sys/pal/sgx/abi/tls/mod.rs
index 34fc2f20d22..7131797003b 100644
--- a/library/std/src/sys/pal/sgx/abi/tls/mod.rs
+++ b/library/std/src/sys/pal/sgx/abi/tls/mod.rs
@@ -22,7 +22,7 @@ macro_rules! dup {
 #[export_name = "_ZN16__rust_internals3std3sys3sgx3abi3tls14TLS_DESTRUCTORE"]
 static TLS_DESTRUCTOR: [AtomicUsize; TLS_KEYS] = dup!((* * * * * * *) (AtomicUsize::new(0)));
 
-extern "C" {
+unsafe extern "C" {
     fn get_tls_ptr() -> *const u8;
     fn set_tls_ptr(tls: *const u8);
 }
diff --git a/library/std/src/sys/pal/sgx/abi/usercalls/raw.rs b/library/std/src/sys/pal/sgx/abi/usercalls/raw.rs
index 943b771498f..28fbbc3c518 100644
--- a/library/std/src/sys/pal/sgx/abi/usercalls/raw.rs
+++ b/library/std/src/sys/pal/sgx/abi/usercalls/raw.rs
@@ -9,7 +9,7 @@ use crate::ptr::NonNull;
 #[repr(C)]
 struct UsercallReturn(u64, u64);
 
-extern "C" {
+unsafe extern "C" {
     fn usercall(nr: NonZero<u64>, p1: u64, p2: u64, abort: u64, p3: u64, p4: u64)
     -> UsercallReturn;
 }
diff --git a/library/std/src/sys/pal/solid/abi/fs.rs b/library/std/src/sys/pal/solid/abi/fs.rs
index 6864a3e7745..7f2b1f83e85 100644
--- a/library/std/src/sys/pal/solid/abi/fs.rs
+++ b/library/std/src/sys/pal/solid/abi/fs.rs
@@ -31,7 +31,7 @@ pub const DT_WHT: c_uchar = 14;
 
 pub type S_DIR = c_int;
 
-extern "C" {
+unsafe extern "C" {
     pub fn SOLID_FS_Open(fd: *mut c_int, path: *const c_char, mode: c_int) -> c_int;
     pub fn SOLID_FS_Close(fd: c_int) -> c_int;
     pub fn SOLID_FS_Read(fd: c_int, buf: *mut u8, size: usize, result: *mut usize) -> c_int;
diff --git a/library/std/src/sys/pal/solid/abi/mod.rs b/library/std/src/sys/pal/solid/abi/mod.rs
index 4d097057217..819f93f4074 100644
--- a/library/std/src/sys/pal/solid/abi/mod.rs
+++ b/library/std/src/sys/pal/solid/abi/mod.rs
@@ -33,27 +33,27 @@ pub struct SOLID_RTC_TIME {
     pub tm_wday: c_int,
 }
 
-extern "C" {
+unsafe extern "C" {
     pub fn SOLID_RTC_ReadTime(time: *mut SOLID_RTC_TIME) -> c_int;
 }
 
 // `solid_log.h`
-extern "C" {
+unsafe extern "C" {
     pub fn SOLID_LOG_write(s: *const u8, l: usize);
 }
 
 // `solid_mem.h`
-extern "C" {
+unsafe extern "C" {
     pub fn SOLID_TLS_AddDestructor(id: i32, dtor: unsafe extern "C" fn(*mut u8));
 }
 
 // `solid_rng.h`
-extern "C" {
+unsafe extern "C" {
     pub fn SOLID_RNG_SampleRandomBytes(buffer: *mut u8, length: usize) -> c_int;
 }
 
 // `rwlock.h`
-extern "C" {
+unsafe extern "C" {
     pub fn rwl_loc_rdl(id: ID) -> ER;
     pub fn rwl_loc_wrl(id: ID) -> ER;
     pub fn rwl_ploc_rdl(id: ID) -> ER;
diff --git a/library/std/src/sys/pal/solid/abi/sockets.rs b/library/std/src/sys/pal/solid/abi/sockets.rs
index 3c9e3f9ffb9..80802dd42e2 100644
--- a/library/std/src/sys/pal/solid/abi/sockets.rs
+++ b/library/std/src/sys/pal/solid/abi/sockets.rs
@@ -158,7 +158,7 @@ pub struct fd_set {
     pub fds: [c_int; SOLID_NET_FD_SETSIZE],
 }
 
-extern "C" {
+unsafe extern "C" {
     #[link_name = "SOLID_NET_StrError"]
     pub fn strerror(errnum: c_int) -> *const c_char;
 
diff --git a/library/std/src/sys/pal/solid/os.rs b/library/std/src/sys/pal/solid/os.rs
index 57c28aed3b2..e3b2e0aa50f 100644
--- a/library/std/src/sys/pal/solid/os.rs
+++ b/library/std/src/sys/pal/solid/os.rs
@@ -129,7 +129,7 @@ impl Iterator for Env {
 /// Returns a vector of (variable, value) byte-vector pairs for all the
 /// environment variables of the current process.
 pub fn env() -> Env {
-    extern "C" {
+    unsafe extern "C" {
         static mut environ: *const *const c_char;
     }
 
diff --git a/library/std/src/sys/pal/teeos/thread.rs b/library/std/src/sys/pal/teeos/thread.rs
index 15c65240ddd..c779c5f3ed8 100644
--- a/library/std/src/sys/pal/teeos/thread.rs
+++ b/library/std/src/sys/pal/teeos/thread.rs
@@ -16,7 +16,7 @@ pub struct Thread {
 unsafe impl Send for Thread {}
 unsafe impl Sync for Thread {}
 
-extern "C" {
+unsafe extern "C" {
     pub fn TEE_Wait(timeout: u32) -> u32;
 }
 
diff --git a/library/std/src/sys/pal/unix/args.rs b/library/std/src/sys/pal/unix/args.rs
index 8438a61e90f..1c87a79803c 100644
--- a/library/std/src/sys/pal/unix/args.rs
+++ b/library/std/src/sys/pal/unix/args.rs
@@ -147,7 +147,7 @@ mod imp {
     /// This allows `std::env::args` to work even in a `cdylib`, as it does on macOS and Windows.
     #[cfg(all(target_os = "linux", target_env = "gnu"))]
     #[used]
-    #[link_section = ".init_array.00099"]
+    #[unsafe(link_section = ".init_array.00099")]
     static ARGV_INIT_ARRAY: extern "C" fn(
         crate::os::raw::c_int,
         *const *const u8,
@@ -204,7 +204,7 @@ mod imp {
     }
 
     pub fn argc_argv() -> (isize, *const *const c_char) {
-        extern "C" {
+        unsafe extern "C" {
             // These functions are in crt_externs.h.
             fn _NSGetArgc() -> *mut c_int;
             fn _NSGetArgv() -> *mut *mut *mut c_char;
diff --git a/library/std/src/sys/pal/unix/futex.rs b/library/std/src/sys/pal/unix/futex.rs
index 0fc765dc87a..d4551dd6a38 100644
--- a/library/std/src/sys/pal/unix/futex.rs
+++ b/library/std/src/sys/pal/unix/futex.rs
@@ -219,7 +219,7 @@ pub fn futex_wake_all(futex: &AtomicU32) {
 }
 
 #[cfg(target_os = "emscripten")]
-extern "C" {
+unsafe extern "C" {
     fn emscripten_futex_wake(addr: *const AtomicU32, count: libc::c_int) -> libc::c_int;
     fn emscripten_futex_wait(
         addr: *const AtomicU32,
@@ -267,7 +267,7 @@ pub mod zircon {
     pub const ZX_ERR_BAD_STATE: zx_status_t = -20;
     pub const ZX_ERR_TIMED_OUT: zx_status_t = -21;
 
-    extern "C" {
+    unsafe extern "C" {
         pub fn zx_clock_get_monotonic() -> zx_time_t;
         pub fn zx_futex_wait(
             value_ptr: *const zx_futex_t,
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index 027df6c5691..c0b56d8d2b2 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -373,24 +373,24 @@ cfg_if::cfg_if! {
             cfg(target_feature = "crt-static"))]
         #[link(name = "dl", cfg(not(target_feature = "crt-static")))]
         #[link(name = "log", cfg(not(target_feature = "crt-static")))]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(target_os = "freebsd")] {
         #[link(name = "execinfo")]
         #[link(name = "pthread")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(target_os = "netbsd")] {
         #[link(name = "pthread")]
         #[link(name = "rt")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(any(target_os = "dragonfly", target_os = "openbsd"))] {
         #[link(name = "pthread")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(target_os = "solaris")] {
         #[link(name = "socket")]
         #[link(name = "posix4")]
         #[link(name = "pthread")]
         #[link(name = "resolv")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(target_os = "illumos")] {
         #[link(name = "socket")]
         #[link(name = "posix4")]
@@ -399,24 +399,24 @@ cfg_if::cfg_if! {
         #[link(name = "nsl")]
         // Use libumem for the (malloc-compatible) allocator
         #[link(name = "umem")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(target_vendor = "apple")] {
         // Link to `libSystem.dylib`.
         //
         // Don't get confused by the presence of `System.framework`,
         // it is a deprecated wrapper over the dynamic library.
         #[link(name = "System")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(target_os = "fuchsia")] {
         #[link(name = "zircon")]
         #[link(name = "fdio")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(all(target_os = "linux", target_env = "uclibc"))] {
         #[link(name = "dl")]
-        extern "C" {}
+        unsafe extern "C" {}
     } else if #[cfg(target_os = "vita")] {
         #[link(name = "pthread", kind = "static", modifiers = "-bundle")]
-        extern "C" {}
+        unsafe extern "C" {}
     }
 }
 
diff --git a/library/std/src/sys/pal/unix/os.rs b/library/std/src/sys/pal/unix/os.rs
index b83772e34c1..04199c56330 100644
--- a/library/std/src/sys/pal/unix/os.rs
+++ b/library/std/src/sys/pal/unix/os.rs
@@ -30,7 +30,7 @@ cfg_if::cfg_if! {
     }
 }
 
-extern "C" {
+unsafe extern "C" {
     #[cfg(not(any(target_os = "dragonfly", target_os = "vxworks", target_os = "rtems")))]
     #[cfg_attr(
         any(
@@ -82,7 +82,7 @@ pub fn errno() -> i32 {
 
 #[cfg(target_os = "rtems")]
 pub fn errno() -> i32 {
-    extern "C" {
+    unsafe extern "C" {
         #[thread_local]
         static _tls_errno: c_int;
     }
@@ -92,7 +92,7 @@ pub fn errno() -> i32 {
 
 #[cfg(target_os = "dragonfly")]
 pub fn errno() -> i32 {
-    extern "C" {
+    unsafe extern "C" {
         #[thread_local]
         static errno: c_int;
     }
@@ -103,7 +103,7 @@ pub fn errno() -> i32 {
 #[cfg(target_os = "dragonfly")]
 #[allow(dead_code)]
 pub fn set_errno(e: i32) {
-    extern "C" {
+    unsafe extern "C" {
         #[thread_local]
         static mut errno: c_int;
     }
@@ -115,7 +115,7 @@ pub fn set_errno(e: i32) {
 
 /// Gets a detailed string description for the given error number.
 pub fn error_string(errno: i32) -> String {
-    extern "C" {
+    unsafe extern "C" {
         #[cfg_attr(
             all(
                 any(target_os = "linux", target_os = "hurd", target_env = "newlib"),
@@ -610,7 +610,7 @@ pub unsafe fn environ() -> *mut *const *const c_char {
 // Use the `environ` static which is part of POSIX.
 #[cfg(not(target_vendor = "apple"))]
 pub unsafe fn environ() -> *mut *const *const c_char {
-    extern "C" {
+    unsafe extern "C" {
         static mut environ: *const *const c_char;
     }
     &raw mut environ
@@ -847,7 +847,7 @@ pub fn getppid() -> u32 {
 
 #[cfg(all(target_os = "linux", target_env = "gnu"))]
 pub fn glibc_version() -> Option<(usize, usize)> {
-    extern "C" {
+    unsafe extern "C" {
         fn gnu_get_libc_version() -> *const libc::c_char;
     }
     let version_cstr = unsafe { CStr::from_ptr(gnu_get_libc_version()) };
diff --git a/library/std/src/sys/pal/unix/process/zircon.rs b/library/std/src/sys/pal/unix/process/zircon.rs
index 4035e2370a3..7932bd26d76 100644
--- a/library/std/src/sys/pal/unix/process/zircon.rs
+++ b/library/std/src/sys/pal/unix/process/zircon.rs
@@ -75,7 +75,7 @@ pub struct zx_info_process_t {
     pub reserved1: u32,
 }
 
-extern "C" {
+unsafe extern "C" {
     pub fn zx_job_default() -> zx_handle_t;
 
     pub fn zx_task_kill(handle: zx_handle_t) -> zx_status_t;
@@ -115,7 +115,7 @@ pub struct fdio_spawn_action_t {
     pub reserved1: u64,
 }
 
-extern "C" {
+unsafe extern "C" {
     pub fn fdio_spawn_etc(
         job: zx_handle_t,
         flags: u32,
diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
index 356669980c7..479021af040 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/pal/unix/thread.rs
@@ -23,7 +23,7 @@ mod zircon {
     type zx_status_t = i32;
     pub const ZX_PROP_NAME: u32 = 3;
 
-    extern "C" {
+    unsafe extern "C" {
         pub fn zx_object_set_property(
             handle: zx_handle_t,
             property: u32,
@@ -230,7 +230,7 @@ impl Thread {
     #[cfg(target_os = "vxworks")]
     pub fn set_name(name: &CStr) {
         // FIXME(libc): adding real STATUS, ERROR type eventually.
-        extern "C" {
+        unsafe extern "C" {
             fn taskNameSet(task_id: libc::TASK_ID, task_name: *mut libc::c_char) -> libc::c_int;
         }
 
@@ -506,7 +506,7 @@ pub fn available_parallelism() -> io::Result<NonZero<usize>> {
         } else if #[cfg(target_os = "vxworks")] {
             // Note: there is also `vxCpuConfiguredGet`, closer to _SC_NPROCESSORS_CONF
             // expectations than the actual cores availability.
-            extern "C" {
+            unsafe extern "C" {
                 fn vxCpuEnabledGet() -> libc::cpuset_t;
             }
 
diff --git a/library/std/src/sys/pal/unix/thread_parking.rs b/library/std/src/sys/pal/unix/thread_parking.rs
index 72dd2031479..bef8b4fb363 100644
--- a/library/std/src/sys/pal/unix/thread_parking.rs
+++ b/library/std/src/sys/pal/unix/thread_parking.rs
@@ -8,7 +8,7 @@ use crate::ffi::{c_int, c_void};
 use crate::ptr;
 use crate::time::Duration;
 
-extern "C" {
+unsafe extern "C" {
     fn ___lwp_park60(
         clock_id: clockid_t,
         flags: c_int,
diff --git a/library/std/src/sys/pal/unix/weak.rs b/library/std/src/sys/pal/unix/weak.rs
index 35762f5a53b..5a37598f438 100644
--- a/library/std/src/sys/pal/unix/weak.rs
+++ b/library/std/src/sys/pal/unix/weak.rs
@@ -31,7 +31,7 @@ use crate::{mem, ptr};
 pub(crate) macro weak {
     (fn $name:ident($($t:ty),*) -> $ret:ty) => (
         let ref $name: ExternWeak<unsafe extern "C" fn($($t),*) -> $ret> = {
-            extern "C" {
+            unsafe extern "C" {
                 #[linkage = "extern_weak"]
                 static $name: Option<unsafe extern "C" fn($($t),*) -> $ret>;
             }
diff --git a/library/std/src/sys/pal/wasi/fs.rs b/library/std/src/sys/pal/wasi/fs.rs
index 7779d2b97d7..7705e7f6b88 100644
--- a/library/std/src/sys/pal/wasi/fs.rs
+++ b/library/std/src/sys/pal/wasi/fs.rs
@@ -787,7 +787,7 @@ fn open_parent(p: &Path) -> io::Result<(ManuallyDrop<WasiFd>, PathBuf)> {
             }
         }
 
-        extern "C" {
+        unsafe extern "C" {
             pub fn __wasilibc_find_relpath(
                 path: *const libc::c_char,
                 abs_prefix: *mut *const libc::c_char,
diff --git a/library/std/src/sys/pal/wasi/os.rs b/library/std/src/sys/pal/wasi/os.rs
index f7701360f5a..ba2b65a1f40 100644
--- a/library/std/src/sys/pal/wasi/os.rs
+++ b/library/std/src/sys/pal/wasi/os.rs
@@ -16,7 +16,7 @@ use crate::{fmt, io, str, vec};
 mod libc {
     pub use libc::*;
 
-    extern "C" {
+    unsafe extern "C" {
         pub fn getcwd(buf: *mut c_char, size: size_t) -> *mut c_char;
         pub fn chdir(dir: *const c_char) -> c_int;
         pub fn __wasilibc_get_environ() -> *mut *mut c_char;
@@ -46,7 +46,7 @@ cfg_if::cfg_if! {
 }
 
 pub fn errno() -> i32 {
-    extern "C" {
+    unsafe extern "C" {
         #[thread_local]
         static errno: libc::c_int;
     }
diff --git a/library/std/src/sys/pal/wasi/thread.rs b/library/std/src/sys/pal/wasi/thread.rs
index f5e19f26bfe..0ae02369410 100644
--- a/library/std/src/sys/pal/wasi/thread.rs
+++ b/library/std/src/sys/pal/wasi/thread.rs
@@ -35,7 +35,7 @@ cfg_if::cfg_if! {
 
             pub const _SC_NPROCESSORS_ONLN: ffi::c_int = 84;
 
-            extern "C" {
+            unsafe extern "C" {
                 pub fn pthread_create(
                     native: *mut pthread_t,
                     attr: *const pthread_attr_t,
diff --git a/library/std/src/sys/pal/windows/c.rs b/library/std/src/sys/pal/windows/c.rs
index 9ce3e912caf..8dc61edb603 100644
--- a/library/std/src/sys/pal/windows/c.rs
+++ b/library/std/src/sys/pal/windows/c.rs
@@ -115,7 +115,7 @@ if #[cfg(not(target_vendor = "uwp"))] {
     link(name = "bcryptprimitives", kind = "raw-dylib", import_name_type = "undecorated")
 )]
 #[cfg_attr(not(target_arch = "x86"), link(name = "bcryptprimitives", kind = "raw-dylib"))]
-extern "system" {
+unsafe extern "system" {
     pub fn ProcessPrng(pbdata: *mut u8, cbdata: usize) -> BOOL;
 }
 
@@ -164,7 +164,7 @@ compat_fn_with_fallback! {
     not(target_arch = "x86"),
     link(name = "api-ms-win-core-synch-l1-2-0", kind = "raw-dylib")
 )]
-extern "system" {
+unsafe extern "system" {
     pub fn WaitOnAddress(
         address: *const c_void,
         compareaddress: *const c_void,
diff --git a/library/std/src/sys/pal/windows/compat.rs b/library/std/src/sys/pal/windows/compat.rs
index 42999da1664..2b9838437e9 100644
--- a/library/std/src/sys/pal/windows/compat.rs
+++ b/library/std/src/sys/pal/windows/compat.rs
@@ -39,7 +39,7 @@ use crate::sys::c;
 // See https://docs.microsoft.com/en-us/cpp/c-runtime-library/crt-initialization?view=msvc-170
 #[cfg(target_vendor = "win7")]
 #[used]
-#[link_section = ".CRT$XCT"]
+#[unsafe(link_section = ".CRT$XCT")]
 static INIT_TABLE_ENTRY: unsafe extern "C" fn() = init;
 
 /// Preload some imported functions.
diff --git a/library/std/src/sys/pal/windows/fs.rs b/library/std/src/sys/pal/windows/fs.rs
index bdb55643bb1..b786c79004f 100644
--- a/library/std/src/sys/pal/windows/fs.rs
+++ b/library/std/src/sys/pal/windows/fs.rs
@@ -44,7 +44,7 @@ pub struct FileType {
 }
 
 pub struct ReadDir {
-    handle: FindNextFileHandle,
+    handle: Option<FindNextFileHandle>,
     root: Arc<PathBuf>,
     first: Option<c::WIN32_FIND_DATAW>,
 }
@@ -113,13 +113,13 @@ impl fmt::Debug for ReadDir {
 impl Iterator for ReadDir {
     type Item = io::Result<DirEntry>;
     fn next(&mut self) -> Option<io::Result<DirEntry>> {
-        if self.handle.0 == c::INVALID_HANDLE_VALUE {
+        let Some(handle) = self.handle.as_ref() else {
             // This iterator was initialized with an `INVALID_HANDLE_VALUE` as its handle.
             // Simply return `None` because this is only the case when `FindFirstFileExW` in
             // the construction of this iterator returns `ERROR_FILE_NOT_FOUND` which means
             // no matchhing files can be found.
             return None;
-        }
+        };
         if let Some(first) = self.first.take() {
             if let Some(e) = DirEntry::new(&self.root, &first) {
                 return Some(Ok(e));
@@ -128,7 +128,7 @@ impl Iterator for ReadDir {
         unsafe {
             let mut wfd = mem::zeroed();
             loop {
-                if c::FindNextFileW(self.handle.0, &mut wfd) == 0 {
+                if c::FindNextFileW(handle.0, &mut wfd) == 0 {
                     match api::get_last_error() {
                         WinError::NO_MORE_FILES => return None,
                         WinError { code } => {
@@ -1194,7 +1194,7 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
 
         if find_handle != c::INVALID_HANDLE_VALUE {
             Ok(ReadDir {
-                handle: FindNextFileHandle(find_handle),
+                handle: Some(FindNextFileHandle(find_handle)),
                 root: Arc::new(root),
                 first: Some(wfd),
             })
@@ -1212,11 +1212,7 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
             // See issue #120040: https://github.com/rust-lang/rust/issues/120040.
             let last_error = api::get_last_error();
             if last_error == WinError::FILE_NOT_FOUND {
-                return Ok(ReadDir {
-                    handle: FindNextFileHandle(find_handle),
-                    root: Arc::new(root),
-                    first: None,
-                });
+                return Ok(ReadDir { handle: None, root: Arc::new(root), first: None });
             }
 
             // Just return the error constructed from the raw OS error if the above is not the case.
diff --git a/library/std/src/sys/pal/windows/process/tests.rs b/library/std/src/sys/pal/windows/process/tests.rs
index 9a1eaf42fd9..90f1157d7c4 100644
--- a/library/std/src/sys/pal/windows/process/tests.rs
+++ b/library/std/src/sys/pal/windows/process/tests.rs
@@ -33,7 +33,7 @@ fn test_thread_handle() {
     assert!(p.is_ok());
     let mut p = p.unwrap();
 
-    extern "system" {
+    unsafe extern "system" {
         fn ResumeThread(_: BorrowedHandle<'_>) -> u32;
     }
     unsafe {
diff --git a/library/std/src/sys/pal/xous/os.rs b/library/std/src/sys/pal/xous/os.rs
index b0ab01a6383..307623c0425 100644
--- a/library/std/src/sys/pal/xous/os.rs
+++ b/library/std/src/sys/pal/xous/os.rs
@@ -37,7 +37,7 @@ mod eh_unwinding {
 #[cfg(not(test))]
 mod c_compat {
     use crate::os::xous::ffi::exit;
-    extern "C" {
+    unsafe extern "C" {
         fn main() -> u32;
     }
 
diff --git a/library/std/src/sys/pal/zkvm/abi.rs b/library/std/src/sys/pal/zkvm/abi.rs
index 53332d90e02..d000574f684 100644
--- a/library/std/src/sys/pal/zkvm/abi.rs
+++ b/library/std/src/sys/pal/zkvm/abi.rs
@@ -18,7 +18,7 @@ pub mod fileno {
     pub const JOURNAL: u32 = 3;
 }
 
-extern "C" {
+unsafe extern "C" {
     // Wrappers around syscalls provided by risc0-zkvm-platform:
     pub fn sys_halt();
     pub fn sys_output(output_id: u32, output_value: u32);
diff --git a/library/std/src/sys/personality/gcc.rs b/library/std/src/sys/personality/gcc.rs
index 88a25caeff0..cd2c7899f4b 100644
--- a/library/std/src/sys/personality/gcc.rs
+++ b/library/std/src/sys/personality/gcc.rs
@@ -194,7 +194,7 @@ cfg_if::cfg_if! {
                     }
                 }
                 // defined in libgcc
-                extern "C" {
+                unsafe extern "C" {
                     fn __gnu_unwind_frame(
                         exception_object: *mut uw::_Unwind_Exception,
                         context: *mut uw::_Unwind_Context,
diff --git a/library/std/src/sys/random/arc4random.rs b/library/std/src/sys/random/arc4random.rs
index 32467e9ebaa..e1957bceb90 100644
--- a/library/std/src/sys/random/arc4random.rs
+++ b/library/std/src/sys/random/arc4random.rs
@@ -25,7 +25,7 @@ use libc::arc4random_buf;
     target_os = "vita", // See https://github.com/vitasdk/newlib/blob/b89e5bc183b516945f9ee07eef483ecb916e45ff/newlib/libc/include/stdlib.h#L74
 ))]
 #[cfg_attr(target_os = "haiku", link(name = "bsd"))]
-extern "C" {
+unsafe extern "C" {
     fn arc4random_buf(buf: *mut core::ffi::c_void, nbytes: libc::size_t);
 }
 
diff --git a/library/std/src/sys/random/espidf.rs b/library/std/src/sys/random/espidf.rs
index fd52cb5559c..6f48f7f1f29 100644
--- a/library/std/src/sys/random/espidf.rs
+++ b/library/std/src/sys/random/espidf.rs
@@ -1,6 +1,6 @@
 use crate::ffi::c_void;
 
-extern "C" {
+unsafe extern "C" {
     fn esp_fill_random(buf: *mut c_void, len: usize);
 }
 
diff --git a/library/std/src/sys/random/fuchsia.rs b/library/std/src/sys/random/fuchsia.rs
index 77d72b3c5b7..269e0d9aeeb 100644
--- a/library/std/src/sys/random/fuchsia.rs
+++ b/library/std/src/sys/random/fuchsia.rs
@@ -4,7 +4,7 @@
 //! <https://fuchsia.dev/reference/syscalls/cprng_draw>.
 
 #[link(name = "zircon")]
-extern "C" {
+unsafe extern "C" {
     fn zx_cprng_draw(buffer: *mut u8, len: usize);
 }
 
diff --git a/library/std/src/sys/random/teeos.rs b/library/std/src/sys/random/teeos.rs
index fd6b24e19e9..6ca59cc12c9 100644
--- a/library/std/src/sys/random/teeos.rs
+++ b/library/std/src/sys/random/teeos.rs
@@ -1,4 +1,4 @@
-extern "C" {
+unsafe extern "C" {
     fn TEE_GenerateRandom(randomBuffer: *mut core::ffi::c_void, randomBufferLen: libc::size_t);
 }
 
diff --git a/library/std/src/sys/sync/thread_parking/darwin.rs b/library/std/src/sys/sync/thread_parking/darwin.rs
index 0553c5e19a9..a0d24a91e7c 100644
--- a/library/std/src/sys/sync/thread_parking/darwin.rs
+++ b/library/std/src/sys/sync/thread_parking/darwin.rs
@@ -24,7 +24,7 @@ const DISPATCH_TIME_NOW: dispatch_time_t = 0;
 const DISPATCH_TIME_FOREVER: dispatch_time_t = !0;
 
 // Contained in libSystem.dylib, which is linked by default.
-extern "C" {
+unsafe extern "C" {
     fn dispatch_time(when: dispatch_time_t, delta: i64) -> dispatch_time_t;
     fn dispatch_semaphore_create(val: isize) -> dispatch_semaphore_t;
     fn dispatch_semaphore_wait(dsema: dispatch_semaphore_t, timeout: dispatch_time_t) -> isize;
diff --git a/library/std/src/sys/thread_local/destructors/linux_like.rs b/library/std/src/sys/thread_local/destructors/linux_like.rs
index f473dc4d79d..817941229ee 100644
--- a/library/std/src/sys/thread_local/destructors/linux_like.rs
+++ b/library/std/src/sys/thread_local/destructors/linux_like.rs
@@ -27,7 +27,7 @@ pub unsafe fn register(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
     #[allow(non_camel_case_types)]
     pub struct c_int(#[allow(dead_code)] pub core::ffi::c_int);
 
-    extern "C" {
+    unsafe extern "C" {
         #[linkage = "extern_weak"]
         static __dso_handle: *mut u8;
         #[linkage = "extern_weak"]
diff --git a/library/std/src/sys/thread_local/guard/apple.rs b/library/std/src/sys/thread_local/guard/apple.rs
index fa25b116622..edcedf21e9e 100644
--- a/library/std/src/sys/thread_local/guard/apple.rs
+++ b/library/std/src/sys/thread_local/guard/apple.rs
@@ -10,7 +10,7 @@ pub fn enable() {
     #[thread_local]
     static REGISTERED: Cell<bool> = Cell::new(false);
 
-    extern "C" {
+    unsafe extern "C" {
         fn _tlv_atexit(dtor: unsafe extern "C" fn(*mut u8), arg: *mut u8);
     }
 
diff --git a/library/std/src/sys/thread_local/guard/windows.rs b/library/std/src/sys/thread_local/guard/windows.rs
index 1752b0e1208..b15a0d7c0bd 100644
--- a/library/std/src/sys/thread_local/guard/windows.rs
+++ b/library/std/src/sys/thread_local/guard/windows.rs
@@ -74,7 +74,7 @@ pub fn enable() {
     unsafe { ptr::from_ref(&CALLBACK).read_volatile() };
 }
 
-#[link_section = ".CRT$XLB"]
+#[unsafe(link_section = ".CRT$XLB")]
 #[cfg_attr(miri, used)] // Miri only considers explicitly `#[used]` statics for `lookup_link_section`
 pub static CALLBACK: unsafe extern "system" fn(*mut c_void, u32, *mut c_void) = tls_callback;
 
diff --git a/library/std/src/sys/thread_local/key/unix.rs b/library/std/src/sys/thread_local/key/unix.rs
index b4b58b34706..93bd0d1f668 100644
--- a/library/std/src/sys/thread_local/key/unix.rs
+++ b/library/std/src/sys/thread_local/key/unix.rs
@@ -8,7 +8,7 @@ mod libc {
     #[allow(non_camel_case_types)]
     pub type pthread_key_t = ffi::c_uint;
 
-    extern "C" {
+    unsafe extern "C" {
         pub fn pthread_key_create(
             key: *mut pthread_key_t,
             destructor: unsafe extern "C" fn(*mut ffi::c_void),
diff --git a/library/std/src/sys/thread_local/key/xous.rs b/library/std/src/sys/thread_local/key/xous.rs
index 2ab4bba7d8e..6c5e6447d19 100644
--- a/library/std/src/sys/thread_local/key/xous.rs
+++ b/library/std/src/sys/thread_local/key/xous.rs
@@ -59,7 +59,7 @@ static TLS_KEY_INDEX: AtomicUsize = AtomicUsize::new(1);
 static DTORS: AtomicPtr<Node> = AtomicPtr::new(ptr::null_mut());
 
 #[cfg(test)]
-extern "Rust" {
+unsafe extern "Rust" {
     #[link_name = "_ZN16__rust_internals3std3sys4xous16thread_local_key13TLS_KEY_INDEXE"]
     static TLS_KEY_INDEX: AtomicUsize;
 
diff --git a/library/std/tests/switch-stdout.rs b/library/std/tests/switch-stdout.rs
index 42011a9b3da..91fe0200f6c 100644
--- a/library/std/tests/switch-stdout.rs
+++ b/library/std/tests/switch-stdout.rs
@@ -14,7 +14,7 @@ use std::os::windows::io::OwnedHandle;
 fn switch_stdout_to(file: OwnedFd) -> OwnedFd {
     use std::os::unix::prelude::*;
 
-    extern "C" {
+    unsafe extern "C" {
         fn dup(old: i32) -> i32;
         fn dup2(old: i32, new: i32) -> i32;
     }
@@ -32,7 +32,7 @@ fn switch_stdout_to(file: OwnedFd) -> OwnedFd {
 fn switch_stdout_to(file: OwnedHandle) -> OwnedHandle {
     use std::os::windows::prelude::*;
 
-    extern "system" {
+    unsafe extern "system" {
         fn GetStdHandle(nStdHandle: u32) -> *mut u8;
         fn SetStdHandle(nStdHandle: u32, handle: *mut u8) -> i32;
     }
diff --git a/library/std/tests/win_delete_self.rs b/library/std/tests/win_delete_self.rs
index 1c3ce4d710c..ce505de69a2 100644
--- a/library/std/tests/win_delete_self.rs
+++ b/library/std/tests/win_delete_self.rs
@@ -2,6 +2,7 @@
 
 /// Attempting to delete a running binary should return an error on Windows.
 #[test]
+#[cfg_attr(miri, ignore)] // `remove_file` does not work in Miri on Windows
 fn win_delete_self() {
     let path = std::env::current_exe().unwrap();
     assert!(std::fs::remove_file(path).is_err());