Merge from rustc

30 files changed, 501 insertions, 344 deletions

diff --git a/library/Cargo.lock b/library/Cargo.lock
index b36399d880e..815f5bb1385 100644
--- a/library/Cargo.lock
+++ b/library/Cargo.lock
@@ -339,6 +339,7 @@ dependencies = [
  "std_detect",
  "unwind",
  "wasi",
+ "windows-targets 0.0.0",
 ]
 
 [[package]]
@@ -421,11 +422,15 @@ version = "0.52.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "282be5f36a8ce781fad8c8ae18fa3f9beff57ec1b52cb3de0789201425d9a33d"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.52.5",
 ]
 
 [[package]]
 name = "windows-targets"
+version = "0.0.0"
+
+[[package]]
+name = "windows-targets"
 version = "0.52.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6f0713a46559409d202e70e28227288446bf7841d3211583a4b53e3f6d96e7eb"
diff --git a/library/Cargo.toml b/library/Cargo.toml
index c4513b4c127..d8ece6b0ebd 100644
--- a/library/Cargo.toml
+++ b/library/Cargo.toml
@@ -8,6 +8,7 @@ members = [
 exclude = [
   # stdarch has its own Cargo workspace
   "stdarch",
+  "windows_targets"
 ]
 
 [profile.release.package.compiler_builtins]
diff --git a/library/alloc/src/fmt.rs b/library/alloc/src/fmt.rs
index 4b9b90fc1f1..571fcd177aa 100644
--- a/library/alloc/src/fmt.rs
+++ b/library/alloc/src/fmt.rs
@@ -581,7 +581,7 @@ pub use core::fmt::Alignment;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::Error;
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
-pub use core::fmt::FormatterFn;
+pub use core::fmt::{from_fn, FromFn};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{write, Arguments};
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index 124230812df..e628be1546f 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -2643,14 +2643,54 @@ impl ToString for i8 {
     }
 }
 
-#[doc(hidden)]
+// Generic/generated code can sometimes have multiple, nested references
+// for strings, including `&&&str`s that would never be written
+// by hand. This macro generates twelve layers of nested `&`-impl
+// for primitive strings.
 #[cfg(not(no_global_oom_handling))]
-#[stable(feature = "str_to_string_specialization", since = "1.9.0")]
-impl ToString for str {
-    #[inline]
-    fn to_string(&self) -> String {
-        String::from(self)
-    }
+macro_rules! to_string_str_wrap_in_ref {
+    {x $($x:ident)*} => {
+        &to_string_str_wrap_in_ref! { $($x)* }
+    };
+    {} => { str };
+}
+#[cfg(not(no_global_oom_handling))]
+macro_rules! to_string_expr_wrap_in_deref {
+    {$self:expr ; x $($x:ident)*} => {
+        *(to_string_expr_wrap_in_deref! { $self ; $($x)* })
+    };
+    {$self:expr ;} => { $self };
+}
+#[cfg(not(no_global_oom_handling))]
+macro_rules! to_string_str {
+    {$($($x:ident)*),+} => {
+        $(
+            #[doc(hidden)]
+            #[stable(feature = "str_to_string_specialization", since = "1.9.0")]
+            impl ToString for to_string_str_wrap_in_ref!($($x)*) {
+                #[inline]
+                fn to_string(&self) -> String {
+                    String::from(to_string_expr_wrap_in_deref!(self ; $($x)*))
+                }
+            }
+        )+
+    };
+}
+
+#[cfg(not(no_global_oom_handling))]
+to_string_str! {
+    x x x x x x x x x x x x,
+    x x x x x x x x x x x,
+    x x x x x x x x x x,
+    x x x x x x x x x,
+    x x x x x x x x,
+    x x x x x x x,
+    x x x x x x,
+    x x x x x,
+    x x x x,
+    x x x,
+    x x,
+    x,
 }
 
 #[doc(hidden)]
diff --git a/library/alloc/tests/task.rs b/library/alloc/tests/task.rs
index 034039a1eae..390dec14484 100644
--- a/library/alloc/tests/task.rs
+++ b/library/alloc/tests/task.rs
@@ -4,7 +4,7 @@ use alloc::task::{LocalWake, Wake};
 use core::task::{LocalWaker, Waker};
 
 #[test]
-#[cfg_attr(miri, should_panic)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it fails
+#[cfg_attr(miri, ignore)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it can fail
 fn test_waker_will_wake_clone() {
     struct NoopWaker;
 
@@ -20,7 +20,7 @@ fn test_waker_will_wake_clone() {
 }
 
 #[test]
-#[cfg_attr(miri, should_panic)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it fails
+#[cfg_attr(miri, ignore)] // `will_wake` doesn't guarantee that this test will work, and indeed on Miri it can fail
 fn test_local_waker_will_wake_clone() {
     struct NoopWaker;
 
diff --git a/library/core/src/fmt/builders.rs b/library/core/src/fmt/builders.rs
index 794ca1851b1..467fa17a6f3 100644
--- a/library/core/src/fmt/builders.rs
+++ b/library/core/src/fmt/builders.rs
@@ -1018,7 +1018,8 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     }
 }
 
-/// Implements [`fmt::Debug`] and [`fmt::Display`] using a function.
+/// Creates a type whose [`fmt::Debug`] and [`fmt::Display`] impls are provided with the function
+/// `f`.
 ///
 /// # Examples
 ///
@@ -1030,17 +1031,25 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
 /// assert_eq!(format!("{}", value), "a");
 /// assert_eq!(format!("{:?}", value), "'a'");
 ///
-/// let wrapped = fmt::FormatterFn(|f| write!(f, "{value:?}"));
+/// let wrapped = fmt::from_fn(|f| write!(f, "{value:?}"));
 /// assert_eq!(format!("{}", wrapped), "'a'");
 /// assert_eq!(format!("{:?}", wrapped), "'a'");
 /// ```
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
-pub struct FormatterFn<F>(pub F)
+pub fn from_fn<F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result>(f: F) -> FromFn<F> {
+    FromFn(f)
+}
+
+/// Implements [`fmt::Debug`] and [`fmt::Display`] using a function.
+///
+/// Created with [`from_fn`].
+#[unstable(feature = "debug_closure_helpers", issue = "117729")]
+pub struct FromFn<F>(F)
 where
     F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result;
 
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
-impl<F> fmt::Debug for FormatterFn<F>
+impl<F> fmt::Debug for FromFn<F>
 where
     F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result,
 {
@@ -1050,7 +1059,7 @@ where
 }
 
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
-impl<F> fmt::Display for FormatterFn<F>
+impl<F> fmt::Display for FromFn<F>
 where
     F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result,
 {
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index 60c0dc76852..45c2b6a6a0f 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -34,7 +34,7 @@ pub enum Alignment {
 }
 
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
-pub use self::builders::FormatterFn;
+pub use self::builders::{from_fn, FromFn};
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub use self::builders::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
 
@@ -1626,6 +1626,11 @@ impl<'a> Formatter<'a> {
         self.buf.write_str(data)
     }
 
+    /// Glue for usage of the [`write!`] macro with implementors of this trait.
+    ///
+    /// This method should generally not be invoked manually, but rather through
+    /// the [`write!`] macro itself.
+    ///
     /// Writes some formatted information into this instance.
     ///
     /// # Examples
diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index 6f1e0cb7471..bd99e90376a 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -2675,12 +2675,12 @@ extern "rust-intrinsic" {
     #[rustc_nounwind]
     pub fn catch_unwind(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
 
-    /// Emits a `!nontemporal` store according to LLVM (see their docs).
-    /// Probably will never become stable.
+    /// Emits a `nontemporal` store, which gives a hint to the CPU that the data should not be held
+    /// in cache. Except for performance, this is fully equivalent to `ptr.write(val)`.
     ///
-    /// Do NOT use this intrinsic; "nontemporal" operations do not exist in our memory model!
-    /// It exists to support current stdarch, but the plan is to change stdarch and remove this intrinsic.
-    /// See <https://github.com/rust-lang/rust/issues/114582> for some more discussion.
+    /// Not all architectures provide such an operation. For instance, x86 does not: while `MOVNT`
+    /// exists, that operation is *not* equivalent to `ptr.write(val)` (`MOVNT` writes can be reordered
+    /// in ways that are not allowed for regular writes).
     #[rustc_nounwind]
     pub fn nontemporal_store<T>(ptr: *mut T, val: T);
 
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 07daa32afa8..e3640627c56 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -170,6 +170,7 @@
 #![feature(internal_impls_macro)]
 #![feature(ip)]
 #![feature(is_ascii_octdigit)]
+#![feature(is_val_statically_known)]
 #![feature(isqrt)]
 #![feature(link_cfg)]
 #![feature(offset_of_enum)]
@@ -192,12 +193,12 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(asm_const))]
 #![cfg_attr(bootstrap, feature(min_exhaustive_patterns))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
-#![feature(asm_const)]
 #![feature(auto_traits)]
 #![feature(cfg_sanitize)]
 #![feature(cfg_target_has_atomic)]
diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index dd88e859b30..17cf2a7b261 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -1496,18 +1496,17 @@ macro_rules! int_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     acc = try_opt!(acc.checked_mul(base));
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        return Some(acc);
+                    }
                 }
                 exp /= 2;
                 base = try_opt!(base.checked_mul(base));
             }
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.checked_mul(base)
         }
 
         /// Strict exponentiation. Computes `self.pow(exp)`, panicking if
@@ -1547,18 +1546,17 @@ macro_rules! int_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     acc = acc.strict_mul(base);
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        return acc;
+                    }
                 }
                 exp /= 2;
                 base = base.strict_mul(base);
             }
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.strict_mul(base)
         }
 
         /// Returns the square root of the number, rounded down.
@@ -2175,6 +2173,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
+        #[rustc_allow_const_fn_unstable(is_val_statically_known)]
         pub const fn wrapping_pow(self, mut exp: u32) -> Self {
             if exp == 0 {
                 return 1;
@@ -2182,19 +2181,36 @@ macro_rules! int_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
-                if (exp & 1) == 1 {
-                    acc = acc.wrapping_mul(base);
+            if intrinsics::is_val_statically_known(exp) {
+                while exp > 1 {
+                    if (exp & 1) == 1 {
+                        acc = acc.wrapping_mul(base);
+                    }
+                    exp /= 2;
+                    base = base.wrapping_mul(base);
                 }
-                exp /= 2;
-                base = base.wrapping_mul(base);
-            }
 
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.wrapping_mul(base)
+                // since exp!=0, finally the exp must be 1.
+                // Deal with the final bit of the exponent separately, since
+                // squaring the base afterwards is not necessary.
+                acc.wrapping_mul(base)
+            } else {
+                // This is faster than the above when the exponent is not known
+                // at compile time. We can't use the same code for the constant
+                // exponent case because LLVM is currently unable to unroll
+                // this loop.
+                loop {
+                    if (exp & 1) == 1 {
+                        acc = acc.wrapping_mul(base);
+                        // since exp!=0, finally the exp must be 1.
+                        if exp == 1 {
+                            return acc;
+                        }
+                    }
+                    exp /= 2;
+                    base = base.wrapping_mul(base);
+                }
+            }
         }
 
         /// Calculates `self` + `rhs`.
@@ -2690,9 +2706,14 @@ macro_rules! int_impl {
             // Scratch space for storing results of overflowing_mul.
             let mut r;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     r = acc.overflowing_mul(base);
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        r.1 |= overflown;
+                        return r;
+                    }
                     acc = r.0;
                     overflown |= r.1;
                 }
@@ -2701,14 +2722,6 @@ macro_rules! int_impl {
                 base = r.0;
                 overflown |= r.1;
             }
-
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            r = acc.overflowing_mul(base);
-            r.1 |= overflown;
-            r
         }
 
         /// Raises self to the power of `exp`, using exponentiation by squaring.
@@ -2728,6 +2741,7 @@ macro_rules! int_impl {
                       without modifying the original"]
         #[inline]
         #[rustc_inherit_overflow_checks]
+        #[rustc_allow_const_fn_unstable(is_val_statically_known)]
         pub const fn pow(self, mut exp: u32) -> Self {
             if exp == 0 {
                 return 1;
@@ -2735,19 +2749,37 @@ macro_rules! int_impl {
             let mut base = self;
             let mut acc = 1;
 
-            while exp > 1 {
-                if (exp & 1) == 1 {
-                    acc = acc * base;
+            if intrinsics::is_val_statically_known(exp) {
+                while exp > 1 {
+                    if (exp & 1) == 1 {
+                        acc = acc * base;
+                    }
+                    exp /= 2;
+                    base = base * base;
                 }
-                exp /= 2;
-                base = base * base;
-            }
 
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc * base
+                // since exp!=0, finally the exp must be 1.
+                // Deal with the final bit of the exponent separately, since
+                // squaring the base afterwards is not necessary and may cause a
+                // needless overflow.
+                acc * base
+            } else {
+                // This is faster than the above when the exponent is not known
+                // at compile time. We can't use the same code for the constant
+                // exponent case because LLVM is currently unable to unroll
+                // this loop.
+                loop {
+                    if (exp & 1) == 1 {
+                        acc = acc * base;
+                        // since exp!=0, finally the exp must be 1.
+                        if exp == 1 {
+                            return acc;
+                        }
+                    }
+                    exp /= 2;
+                    base = base * base;
+                }
+            }
         }
 
         /// Returns the square root of the number, rounded down.
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index a2e17fae768..719a6a55940 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -1622,20 +1622,17 @@ macro_rules! uint_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     acc = try_opt!(acc.checked_mul(base));
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        return Some(acc);
+                    }
                 }
                 exp /= 2;
                 base = try_opt!(base.checked_mul(base));
             }
-
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-
-            acc.checked_mul(base)
         }
 
         /// Strict exponentiation. Computes `self.pow(exp)`, panicking if
@@ -1675,18 +1672,17 @@ macro_rules! uint_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     acc = acc.strict_mul(base);
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        return acc;
+                    }
                 }
                 exp /= 2;
                 base = base.strict_mul(base);
             }
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.strict_mul(base)
         }
 
         /// Saturating integer addition. Computes `self + rhs`, saturating at
@@ -2138,6 +2134,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
+        #[rustc_allow_const_fn_unstable(is_val_statically_known)]
         pub const fn wrapping_pow(self, mut exp: u32) -> Self {
             if exp == 0 {
                 return 1;
@@ -2145,19 +2142,36 @@ macro_rules! uint_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
-                if (exp & 1) == 1 {
-                    acc = acc.wrapping_mul(base);
+            if intrinsics::is_val_statically_known(exp) {
+                while exp > 1 {
+                    if (exp & 1) == 1 {
+                        acc = acc.wrapping_mul(base);
+                    }
+                    exp /= 2;
+                    base = base.wrapping_mul(base);
                 }
-                exp /= 2;
-                base = base.wrapping_mul(base);
-            }
 
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.wrapping_mul(base)
+                // since exp!=0, finally the exp must be 1.
+                // Deal with the final bit of the exponent separately, since
+                // squaring the base afterwards is not necessary.
+                acc.wrapping_mul(base)
+            } else {
+                // This is faster than the above when the exponent is not known
+                // at compile time. We can't use the same code for the constant
+                // exponent case because LLVM is currently unable to unroll
+                // this loop.
+                loop {
+                    if (exp & 1) == 1 {
+                        acc = acc.wrapping_mul(base);
+                        // since exp!=0, finally the exp must be 1.
+                        if exp == 1 {
+                            return acc;
+                        }
+                    }
+                    exp /= 2;
+                    base = base.wrapping_mul(base);
+                }
+            }
         }
 
         /// Calculates `self` + `rhs`.
@@ -2603,9 +2617,14 @@ macro_rules! uint_impl {
             // Scratch space for storing results of overflowing_mul.
             let mut r;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     r = acc.overflowing_mul(base);
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        r.1 |= overflown;
+                        return r;
+                    }
                     acc = r.0;
                     overflown |= r.1;
                 }
@@ -2614,15 +2633,6 @@ macro_rules! uint_impl {
                 base = r.0;
                 overflown |= r.1;
             }
-
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            r = acc.overflowing_mul(base);
-            r.1 |= overflown;
-
-            r
         }
 
         /// Raises self to the power of `exp`, using exponentiation by squaring.
@@ -2640,6 +2650,7 @@ macro_rules! uint_impl {
                       without modifying the original"]
         #[inline]
         #[rustc_inherit_overflow_checks]
+        #[rustc_allow_const_fn_unstable(is_val_statically_known)]
         pub const fn pow(self, mut exp: u32) -> Self {
             if exp == 0 {
                 return 1;
@@ -2647,19 +2658,37 @@ macro_rules! uint_impl {
             let mut base = self;
             let mut acc = 1;
 
-            while exp > 1 {
-                if (exp & 1) == 1 {
-                    acc = acc * base;
+            if intrinsics::is_val_statically_known(exp) {
+                while exp > 1 {
+                    if (exp & 1) == 1 {
+                        acc = acc * base;
+                    }
+                    exp /= 2;
+                    base = base * base;
                 }
-                exp /= 2;
-                base = base * base;
-            }
 
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc * base
+                // since exp!=0, finally the exp must be 1.
+                // Deal with the final bit of the exponent separately, since
+                // squaring the base afterwards is not necessary and may cause a
+                // needless overflow.
+                acc * base
+            } else {
+                // This is faster than the above when the exponent is not known
+                // at compile time. We can't use the same code for the constant
+                // exponent case because LLVM is currently unable to unroll
+                // this loop.
+                loop {
+                    if (exp & 1) == 1 {
+                        acc = acc * base;
+                        // since exp!=0, finally the exp must be 1.
+                        if exp == 1 {
+                            return acc;
+                        }
+                    }
+                    exp /= 2;
+                    base = base * base;
+                }
+            }
         }
 
         /// Returns the square root of the number, rounded down.
diff --git a/library/core/src/ops/control_flow.rs b/library/core/src/ops/control_flow.rs
index a2709c66b06..ab73dc19fcc 100644
--- a/library/core/src/ops/control_flow.rs
+++ b/library/core/src/ops/control_flow.rs
@@ -116,7 +116,9 @@ impl<B, C> ops::Try for ControlFlow<B, C> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-impl<B, C> ops::FromResidual for ControlFlow<B, C> {
+// Note: manually specifying the residual type instead of using the default to work around
+// https://github.com/rust-lang/rust/issues/99940
+impl<B, C> ops::FromResidual<ControlFlow<B, convert::Infallible>> for ControlFlow<B, C> {
     #[inline]
     fn from_residual(residual: ControlFlow<B, convert::Infallible>) -> Self {
         match residual {
diff --git a/library/core/src/ops/coroutine.rs b/library/core/src/ops/coroutine.rs
index 13df888d24c..c7d596d74c3 100644
--- a/library/core/src/ops/coroutine.rs
+++ b/library/core/src/ops/coroutine.rs
@@ -69,6 +69,7 @@ pub enum CoroutineState<Y, R> {
 #[lang = "coroutine"]
 #[unstable(feature = "coroutine_trait", issue = "43122")]
 #[fundamental]
+#[must_use = "coroutines are lazy and do nothing unless resumed"]
 pub trait Coroutine<R = ()> {
     /// The type of value this coroutine yields.
     ///
diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index 6c89c810180..9cec79c17ca 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -2495,7 +2495,9 @@ impl<T> ops::Try for Option<T> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-impl<T> ops::FromResidual for Option<T> {
+// Note: manually specifying the residual type instead of using the default to work around
+// https://github.com/rust-lang/rust/issues/99940
+impl<T> ops::FromResidual<Option<convert::Infallible>> for Option<T> {
     #[inline]
     fn from_residual(residual: Option<convert::Infallible>) -> Self {
         match residual {
diff --git a/library/core/src/panic/location.rs b/library/core/src/panic/location.rs
index 8c04994ac0f..930edffd505 100644
--- a/library/core/src/panic/location.rs
+++ b/library/core/src/panic/location.rs
@@ -44,7 +44,7 @@ impl<'a> Location<'a> {
     ///
     /// # Examples
     ///
-    /// ```
+    /// ```standalone
     /// use std::panic::Location;
     ///
     /// /// Returns the [`Location`] at which it is called.
diff --git a/library/core/tests/ops.rs b/library/core/tests/ops.rs
index 2ee0abd399b..501e0f33fe4 100644
--- a/library/core/tests/ops.rs
+++ b/library/core/tests/ops.rs
@@ -1,4 +1,5 @@
 mod control_flow;
+mod from_residual;
 
 use core::ops::{
     Bound, Deref, DerefMut, Range, RangeFrom, RangeFull, RangeInclusive, RangeTo, RangeToInclusive,
diff --git a/library/core/tests/ops/from_residual.rs b/library/core/tests/ops/from_residual.rs
new file mode 100644
index 00000000000..d5c86ccbcd3
--- /dev/null
+++ b/library/core/tests/ops/from_residual.rs
@@ -0,0 +1,26 @@
+//! Regression test that Option and ControlFlow can have downstream FromResidual impls.
+//! cc https://github.com/rust-lang/rust/issues/99940,
+//! This does NOT test that issue in general; Option and ControlFlow's FromResidual
+//! impls in core were changed to not be affected by that issue.
+
+use core::ops::{ControlFlow, FromResidual};
+
+struct Local;
+
+impl<T> FromResidual<Local> for Option<T> {
+    fn from_residual(_: Local) -> Option<T> {
+        unimplemented!()
+    }
+}
+
+impl<B, C> FromResidual<Local> for ControlFlow<B, C> {
+    fn from_residual(_: Local) -> ControlFlow<B, C> {
+        unimplemented!()
+    }
+}
+
+impl<T, E> FromResidual<Local> for Result<T, E> {
+    fn from_residual(_: Local) -> Result<T, E> {
+        unimplemented!()
+    }
+}
diff --git a/library/core/tests/ptr.rs b/library/core/tests/ptr.rs
index bc1940ebf32..78d1b137e63 100644
--- a/library/core/tests/ptr.rs
+++ b/library/core/tests/ptr.rs
@@ -810,9 +810,12 @@ fn ptr_metadata() {
         assert_ne!(address_1, address_2);
         // Different erased type => different vtable pointer
         assert_ne!(address_2, address_3);
-        // Same erased type and same trait => same vtable pointer
-        assert_eq!(address_3, address_4);
-        assert_eq!(address_3, address_5);
+        // Same erased type and same trait => same vtable pointer.
+        // This is *not guaranteed*, so we skip it in Miri.
+        if !cfg!(miri) {
+            assert_eq!(address_3, address_4);
+            assert_eq!(address_3, address_5);
+        }
     }
 }
 
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index 2ce284c85e2..7f23681ee45 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -57,6 +57,9 @@ object = { version = "0.36.0", default-features = false, optional = true, featur
     'archive',
 ] }
 
+[target.'cfg(windows)'.dependencies.windows-targets]
+path = "../windows_targets"
+
 [dev-dependencies]
 rand = { version = "0.8.5", default-features = false, features = ["alloc"] }
 rand_xorshift = "0.3.0"
@@ -116,7 +119,7 @@ std_detect_env_override = ["std_detect/std_detect_env_override"]
 
 # Enable using raw-dylib for Windows imports.
 # This will eventually be the default.
-windows_raw_dylib = []
+windows_raw_dylib = ["windows-targets/windows_raw_dylib"]
 
 [package.metadata.fortanix-sgx]
 # Maximum possible number of threads when testing
diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index 50ae83090c7..80890e61471 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -355,7 +355,13 @@ impl Error for VarError {
 /// }
 /// assert_eq!(env::var(key), Ok("VALUE".to_string()));
 /// ```
-#[rustc_deprecated_safe_2024]
+#[cfg_attr(bootstrap, rustc_deprecated_safe_2024)]
+#[cfg_attr(
+    not(bootstrap),
+    rustc_deprecated_safe_2024(
+        audit_that = "the environment access only happens in single-threaded code"
+    )
+)]
 #[stable(feature = "env", since = "1.0.0")]
 pub unsafe fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(key: K, value: V) {
     let (key, value) = (key.as_ref(), value.as_ref());
@@ -419,7 +425,13 @@ pub unsafe fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(key: K, value: V) {
 /// }
 /// assert!(env::var(key).is_err());
 /// ```
-#[rustc_deprecated_safe_2024]
+#[cfg_attr(bootstrap, rustc_deprecated_safe_2024)]
+#[cfg_attr(
+    not(bootstrap),
+    rustc_deprecated_safe_2024(
+        audit_that = "the environment access only happens in single-threaded code"
+    )
+)]
 #[stable(feature = "env", since = "1.0.0")]
 pub unsafe fn remove_var<K: AsRef<OsStr>>(key: K) {
     let key = key.as_ref();
diff --git a/library/std/src/panic.rs b/library/std/src/panic.rs
index 4c496ade81c..6f0952c41ed 100644
--- a/library/std/src/panic.rs
+++ b/library/std/src/panic.rs
@@ -440,13 +440,12 @@ impl BacktraceStyle {
     }
 
     fn from_u8(s: u8) -> Option<Self> {
-        Some(match s {
-            0 => return None,
-            1 => BacktraceStyle::Short,
-            2 => BacktraceStyle::Full,
-            3 => BacktraceStyle::Off,
-            _ => unreachable!(),
-        })
+        match s {
+            1 => Some(BacktraceStyle::Short),
+            2 => Some(BacktraceStyle::Full),
+            3 => Some(BacktraceStyle::Off),
+            _ => None,
+        }
     }
 }
 
@@ -465,7 +464,7 @@ static SHOULD_CAPTURE: AtomicU8 = AtomicU8::new(0);
 pub fn set_backtrace_style(style: BacktraceStyle) {
     if cfg!(feature = "backtrace") {
         // If the `backtrace` feature of this crate is enabled, set the backtrace style.
-        SHOULD_CAPTURE.store(style.as_u8(), Ordering::Release);
+        SHOULD_CAPTURE.store(style.as_u8(), Ordering::Relaxed);
     }
 }
 
@@ -498,7 +497,9 @@ pub fn get_backtrace_style() -> Option<BacktraceStyle> {
         // to optimize away callers.
         return None;
     }
-    if let Some(style) = BacktraceStyle::from_u8(SHOULD_CAPTURE.load(Ordering::Acquire)) {
+
+    let current = SHOULD_CAPTURE.load(Ordering::Relaxed);
+    if let Some(style) = BacktraceStyle::from_u8(current) {
         return Some(style);
     }
 
@@ -509,8 +510,11 @@ pub fn get_backtrace_style() -> Option<BacktraceStyle> {
         None if crate::sys::FULL_BACKTRACE_DEFAULT => BacktraceStyle::Full,
         None => BacktraceStyle::Off,
     };
-    set_backtrace_style(format);
-    Some(format)
+
+    match SHOULD_CAPTURE.compare_exchange(0, format.as_u8(), Ordering::Relaxed, Ordering::Relaxed) {
+        Ok(_) => Some(format),
+        Err(new) => BacktraceStyle::from_u8(new),
+    }
 }
 
 #[cfg(test)]
diff --git a/library/std/src/sys/pal/unix/fs.rs b/library/std/src/sys/pal/unix/fs.rs
index bdb83f07857..be13e1ae9b3 100644
--- a/library/std/src/sys/pal/unix/fs.rs
+++ b/library/std/src/sys/pal/unix/fs.rs
@@ -1552,17 +1552,6 @@ impl fmt::Debug for File {
             None
         }
 
-        #[cfg(any(
-            target_os = "linux",
-            target_os = "freebsd",
-            target_os = "hurd",
-            target_os = "netbsd",
-            target_os = "openbsd",
-            target_os = "vxworks",
-            target_os = "solaris",
-            target_os = "illumos",
-            target_vendor = "apple",
-        ))]
         fn get_mode(fd: c_int) -> Option<(bool, bool)> {
             let mode = unsafe { libc::fcntl(fd, libc::F_GETFL) };
             if mode == -1 {
@@ -1576,22 +1565,6 @@ impl fmt::Debug for File {
             }
         }
 
-        #[cfg(not(any(
-            target_os = "linux",
-            target_os = "freebsd",
-            target_os = "hurd",
-            target_os = "netbsd",
-            target_os = "openbsd",
-            target_os = "vxworks",
-            target_os = "solaris",
-            target_os = "illumos",
-            target_vendor = "apple",
-        )))]
-        fn get_mode(_fd: c_int) -> Option<(bool, bool)> {
-            // FIXME(#24570): implement this for other Unix platforms
-            None
-        }
-
         let fd = self.as_raw_fd();
         let mut b = f.debug_struct("File");
         b.field("fd", &fd);
diff --git a/library/std/src/sys/pal/unix/rand.rs b/library/std/src/sys/pal/unix/rand.rs
index 8a78ea8e7cc..cc0852aab43 100644
--- a/library/std/src/sys/pal/unix/rand.rs
+++ b/library/std/src/sys/pal/unix/rand.rs
@@ -2,7 +2,9 @@ pub fn hashmap_random_keys() -> (u64, u64) {
     const KEY_LEN: usize = core::mem::size_of::<u64>();
 
     let mut v = [0u8; KEY_LEN * 2];
-    imp::fill_bytes(&mut v);
+    if let Err(err) = read(&mut v) {
+        panic!("failed to retrieve random hash map seed: {err}");
+    }
 
     let key1 = v[0..KEY_LEN].try_into().unwrap();
     let key2 = v[KEY_LEN..].try_into().unwrap();
@@ -10,27 +12,78 @@ pub fn hashmap_random_keys() -> (u64, u64) {
     (u64::from_ne_bytes(key1), u64::from_ne_bytes(key2))
 }
 
-#[cfg(all(
-    unix,
-    not(target_os = "openbsd"),
-    not(target_os = "netbsd"),
-    not(target_os = "fuchsia"),
-    not(target_os = "redox"),
-    not(target_os = "vxworks"),
-    not(target_os = "emscripten"),
-    not(target_os = "vita"),
-    not(target_vendor = "apple"),
+cfg_if::cfg_if! {
+    if #[cfg(any(
+        target_vendor = "apple",
+        target_os = "openbsd",
+        target_os = "emscripten",
+        target_os = "vita",
+        all(target_os = "netbsd", not(netbsd10)),
+        target_os = "fuchsia",
+        target_os = "vxworks",
+    ))] {
+        // Some systems have a syscall that directly retrieves random data.
+        // If that is guaranteed to be available, use it.
+        use imp::syscall as read;
+    } else {
+        // Otherwise, try the syscall to see if it exists only on some systems
+        // and fall back to reading from the random device otherwise.
+        fn read(bytes: &mut [u8]) -> crate::io::Result<()> {
+            use crate::fs::File;
+            use crate::io::Read;
+            use crate::sync::OnceLock;
+
+            #[cfg(any(
+                target_os = "linux",
+                target_os = "android",
+                target_os = "espidf",
+                target_os = "horizon",
+                target_os = "freebsd",
+                target_os = "dragonfly",
+                target_os = "solaris",
+                target_os = "illumos",
+                netbsd10,
+            ))]
+            if let Some(res) = imp::syscall(bytes) {
+                return res;
+            }
+
+            const PATH: &'static str = if cfg!(target_os = "redox") {
+                "/scheme/rand"
+            } else {
+                "/dev/urandom"
+            };
+
+            static FILE: OnceLock<File> = OnceLock::new();
+
+            FILE.get_or_try_init(|| File::open(PATH))?.read_exact(bytes)
+        }
+    }
+}
+
+// All these systems a `getrandom` syscall.
+//
+// It is not guaranteed to be available, so return None to fallback to the file
+// implementation.
+#[cfg(any(
+    target_os = "linux",
+    target_os = "android",
+    target_os = "espidf",
+    target_os = "horizon",
+    target_os = "freebsd",
+    target_os = "dragonfly",
+    target_os = "solaris",
+    target_os = "illumos",
+    netbsd10,
 ))]
 mod imp {
-    use crate::fs::File;
-    use crate::io::Read;
-    #[cfg(any(target_os = "linux", target_os = "android"))]
-    use crate::sys::weak::syscall;
+    use crate::io::{Error, Result};
+    use crate::sync::atomic::{AtomicBool, Ordering};
+    use crate::sys::os::errno;
 
     #[cfg(any(target_os = "linux", target_os = "android"))]
     fn getrandom(buf: &mut [u8]) -> libc::ssize_t {
-        use crate::sync::atomic::{AtomicBool, Ordering};
-        use crate::sys::os::errno;
+        use crate::sys::weak::syscall;
 
         // A weak symbol allows interposition, e.g. for perf measurements that want to
         // disable randomness for consistency. Otherwise, we'll try a raw syscall.
@@ -59,6 +112,7 @@ mod imp {
     }
 
     #[cfg(any(
+        target_os = "dragonfly",
         target_os = "espidf",
         target_os = "horizon",
         target_os = "freebsd",
@@ -70,51 +124,11 @@ mod imp {
         unsafe { libc::getrandom(buf.as_mut_ptr().cast(), buf.len(), 0) }
     }
 
-    #[cfg(target_os = "dragonfly")]
-    fn getrandom(buf: &mut [u8]) -> libc::ssize_t {
-        extern "C" {
-            fn getrandom(
-                buf: *mut libc::c_void,
-                buflen: libc::size_t,
-                flags: libc::c_uint,
-            ) -> libc::ssize_t;
-        }
-        unsafe { getrandom(buf.as_mut_ptr().cast(), buf.len(), 0) }
-    }
-
-    #[cfg(not(any(
-        target_os = "linux",
-        target_os = "android",
-        target_os = "espidf",
-        target_os = "horizon",
-        target_os = "freebsd",
-        target_os = "dragonfly",
-        target_os = "solaris",
-        target_os = "illumos",
-        netbsd10
-    )))]
-    fn getrandom_fill_bytes(_buf: &mut [u8]) -> bool {
-        false
-    }
-
-    #[cfg(any(
-        target_os = "linux",
-        target_os = "android",
-        target_os = "espidf",
-        target_os = "horizon",
-        target_os = "freebsd",
-        target_os = "dragonfly",
-        target_os = "solaris",
-        target_os = "illumos",
-        netbsd10
-    ))]
-    fn getrandom_fill_bytes(v: &mut [u8]) -> bool {
-        use crate::sync::atomic::{AtomicBool, Ordering};
-        use crate::sys::os::errno;
-
+    pub fn syscall(v: &mut [u8]) -> Option<Result<()>> {
         static GETRANDOM_UNAVAILABLE: AtomicBool = AtomicBool::new(false);
+
         if GETRANDOM_UNAVAILABLE.load(Ordering::Relaxed) {
-            return false;
+            return None;
         }
 
         let mut read = 0;
@@ -125,8 +139,7 @@ mod imp {
                 if err == libc::EINTR {
                     continue;
                 } else if err == libc::ENOSYS || err == libc::EPERM {
-                    // Fall back to reading /dev/urandom if `getrandom` is not
-                    // supported on the current kernel.
+                    // `getrandom` is not supported on the current system.
                     //
                     // Also fall back in case it is disabled by something like
                     // seccomp or inside of docker.
@@ -142,123 +155,83 @@ mod imp {
                     //     https://github.com/moby/moby/issues/42680
                     //
                     GETRANDOM_UNAVAILABLE.store(true, Ordering::Relaxed);
-                    return false;
+                    return None;
                 } else if err == libc::EAGAIN {
-                    return false;
+                    // getrandom has failed because it would have blocked as the
+                    // non-blocking pool (urandom) has not been initialized in
+                    // the kernel yet due to a lack of entropy. Fallback to
+                    // reading from `/dev/urandom` which will return potentially
+                    // insecure random data to avoid blocking applications which
+                    // could depend on this call without ever knowing they do and
+                    // don't have a work around.
+                    return None;
                 } else {
-                    panic!("unexpected getrandom error: {err}");
+                    return Some(Err(Error::from_raw_os_error(err)));
                 }
             } else {
                 read += result as usize;
             }
         }
-        true
-    }
-
-    pub fn fill_bytes(v: &mut [u8]) {
-        // getrandom_fill_bytes here can fail if getrandom() returns EAGAIN,
-        // meaning it would have blocked because the non-blocking pool (urandom)
-        // has not initialized in the kernel yet due to a lack of entropy. The
-        // fallback we do here is to avoid blocking applications which could
-        // depend on this call without ever knowing they do and don't have a
-        // work around. The PRNG of /dev/urandom will still be used but over a
-        // possibly predictable entropy pool.
-        if getrandom_fill_bytes(v) {
-            return;
-        }
 
-        // getrandom failed because it is permanently or temporarily (because
-        // of missing entropy) unavailable. Open /dev/urandom, read from it,
-        // and close it again.
-        let mut file = File::open("/dev/urandom").expect("failed to open /dev/urandom");
-        file.read_exact(v).expect("failed to read /dev/urandom")
+        Some(Ok(()))
     }
 }
 
-#[cfg(target_vendor = "apple")]
+#[cfg(any(
+    target_os = "macos", // Supported since macOS 10.12+.
+    target_os = "openbsd",
+    target_os = "emscripten",
+    target_os = "vita",
+))]
 mod imp {
-    use libc::{c_int, c_void, size_t};
-
-    use crate::io;
-
-    #[inline(always)]
-    fn random_failure() -> ! {
-        panic!("unexpected random generation error: {}", io::Error::last_os_error());
-    }
-
-    #[cfg(target_os = "macos")]
-    fn getentropy_fill_bytes(v: &mut [u8]) {
-        extern "C" {
-            fn getentropy(bytes: *mut c_void, count: size_t) -> c_int;
-        }
+    use crate::io::{Error, Result};
 
+    pub fn syscall(v: &mut [u8]) -> Result<()> {
         // getentropy(2) permits a maximum buffer size of 256 bytes
         for s in v.chunks_mut(256) {
-            let ret = unsafe { getentropy(s.as_mut_ptr().cast(), s.len()) };
+            let ret = unsafe { libc::getentropy(s.as_mut_ptr().cast(), s.len()) };
             if ret == -1 {
-                random_failure()
+                return Err(Error::last_os_error());
             }
         }
-    }
 
-    #[cfg(not(target_os = "macos"))]
-    fn ccrandom_fill_bytes(v: &mut [u8]) {
-        extern "C" {
-            fn CCRandomGenerateBytes(bytes: *mut c_void, count: size_t) -> c_int;
-        }
-
-        let ret = unsafe { CCRandomGenerateBytes(v.as_mut_ptr().cast(), v.len()) };
-        if ret == -1 {
-            random_failure()
-        }
-    }
-
-    pub fn fill_bytes(v: &mut [u8]) {
-        // All supported versions of macOS (10.12+) support getentropy.
-        //
-        // `getentropy` is measurably faster (via Divan) then the other alternatives so its preferred
-        // when usable.
-        #[cfg(target_os = "macos")]
-        getentropy_fill_bytes(v);
-
-        // On Apple platforms, `CCRandomGenerateBytes` and `SecRandomCopyBytes` simply
-        // call into `CCRandomCopyBytes` with `kCCRandomDefault`. `CCRandomCopyBytes`
-        // manages a CSPRNG which is seeded from the kernel's CSPRNG and which runs on
-        // its own thread accessed via GCD. This seems needlessly heavyweight for our purposes
-        // so we only use it on non-Mac OSes where the better entrypoints are blocked.
-        //
-        // `CCRandomGenerateBytes` is used instead of `SecRandomCopyBytes` because the former is accessible
-        // via `libSystem` (libc) while the other needs to link to `Security.framework`.
-        //
-        // Note that while `getentropy` has a available attribute in the macOS headers, the lack
-        // of a header in the iOS (and others) SDK means that its can cause app store rejections.
-        // Just use `CCRandomGenerateBytes` instead.
-        #[cfg(not(target_os = "macos"))]
-        ccrandom_fill_bytes(v);
+        Ok(())
     }
 }
 
-#[cfg(any(target_os = "openbsd", target_os = "emscripten", target_os = "vita"))]
+// On Apple platforms, `CCRandomGenerateBytes` and `SecRandomCopyBytes` simply
+// call into `CCRandomCopyBytes` with `kCCRandomDefault`. `CCRandomCopyBytes`
+// manages a CSPRNG which is seeded from the kernel's CSPRNG and which runs on
+// its own thread accessed via GCD. This seems needlessly heavyweight for our purposes
+// so we only use it when `getentropy` is blocked, which appears to be the case
+// on all platforms except macOS (see #102643).
+//
+// `CCRandomGenerateBytes` is used instead of `SecRandomCopyBytes` because the former is accessible
+// via `libSystem` (libc) while the other needs to link to `Security.framework`.
+#[cfg(all(target_vendor = "apple", not(target_os = "macos")))]
 mod imp {
-    use crate::sys::os::errno;
+    use libc::size_t;
 
-    pub fn fill_bytes(v: &mut [u8]) {
-        // getentropy(2) permits a maximum buffer size of 256 bytes
-        for s in v.chunks_mut(256) {
-            let ret = unsafe { libc::getentropy(s.as_mut_ptr() as *mut libc::c_void, s.len()) };
-            if ret == -1 {
-                panic!("unexpected getentropy error: {}", errno());
-            }
+    use crate::ffi::{c_int, c_void};
+    use crate::io::{Error, Result};
+
+    pub fn syscall(v: &mut [u8]) -> Result<()> {
+        extern "C" {
+            fn CCRandomGenerateBytes(bytes: *mut c_void, count: size_t) -> c_int;
         }
+
+        let ret = unsafe { CCRandomGenerateBytes(v.as_mut_ptr().cast(), v.len()) };
+        if ret != -1 { Ok(()) } else { Err(Error::last_os_error()) }
     }
 }
 
 // FIXME: once the 10.x release becomes the minimum, this can be dropped for simplification.
 #[cfg(all(target_os = "netbsd", not(netbsd10)))]
 mod imp {
+    use crate::io::{Error, Result};
     use crate::ptr;
 
-    pub fn fill_bytes(v: &mut [u8]) {
+    pub fn syscall(v: &mut [u8]) -> Result<()> {
         let mib = [libc::CTL_KERN, libc::KERN_ARND];
         // kern.arandom permits a maximum buffer size of 256 bytes
         for s in v.chunks_mut(256) {
@@ -273,39 +246,30 @@ mod imp {
                     0,
                 )
             };
-            if ret == -1 || s_len != s.len() {
-                panic!(
-                    "kern.arandom sysctl failed! (returned {}, s.len() {}, oldlenp {})",
-                    ret,
-                    s.len(),
-                    s_len
-                );
+            if ret == -1 {
+                return Err(Error::last_os_error());
+            } else if s_len != s.len() {
+                // FIXME(joboet): this can't actually happen, can it?
+                panic!("read less bytes than requested from kern.arandom");
             }
         }
+
+        Ok(())
     }
 }
 
 #[cfg(target_os = "fuchsia")]
 mod imp {
+    use crate::io::Result;
+
     #[link(name = "zircon")]
     extern "C" {
         fn zx_cprng_draw(buffer: *mut u8, len: usize);
     }
 
-    pub fn fill_bytes(v: &mut [u8]) {
-        unsafe { zx_cprng_draw(v.as_mut_ptr(), v.len()) }
-    }
-}
-
-#[cfg(target_os = "redox")]
-mod imp {
-    use crate::fs::File;
-    use crate::io::Read;
-
-    pub fn fill_bytes(v: &mut [u8]) {
-        // Open rand:, read from it, and close it again.
-        let mut file = File::open("rand:").expect("failed to open rand:");
-        file.read_exact(v).expect("failed to read rand:")
+    pub fn syscall(v: &mut [u8]) -> Result<()> {
+        unsafe { zx_cprng_draw(v.as_mut_ptr(), v.len()) };
+        Ok(())
     }
 }
 
@@ -314,25 +278,25 @@ mod imp {
     use core::sync::atomic::AtomicBool;
     use core::sync::atomic::Ordering::Relaxed;
 
-    use crate::io;
+    use crate::io::{Error, Result};
 
-    pub fn fill_bytes(v: &mut [u8]) {
+    pub fn syscall(v: &mut [u8]) -> Result<()> {
         static RNG_INIT: AtomicBool = AtomicBool::new(false);
         while !RNG_INIT.load(Relaxed) {
             let ret = unsafe { libc::randSecure() };
             if ret < 0 {
-                panic!("couldn't generate random bytes: {}", io::Error::last_os_error());
+                return Err(Error::last_os_error());
             } else if ret > 0 {
                 RNG_INIT.store(true, Relaxed);
                 break;
             }
+
             unsafe { libc::usleep(10) };
         }
+
         let ret = unsafe {
             libc::randABytes(v.as_mut_ptr() as *mut libc::c_uchar, v.len() as libc::c_int)
         };
-        if ret < 0 {
-            panic!("couldn't generate random bytes: {}", io::Error::last_os_error());
-        }
+        if ret >= 0 { Ok(()) } else { Err(Error::last_os_error()) }
     }
 }
diff --git a/library/std/src/sys/pal/windows/alloc.rs b/library/std/src/sys/pal/windows/alloc.rs
index 92b68b26032..2205885687d 100644
--- a/library/std/src/sys/pal/windows/alloc.rs
+++ b/library/std/src/sys/pal/windows/alloc.rs
@@ -4,7 +4,7 @@ use crate::alloc::{GlobalAlloc, Layout, System};
 use crate::ffi::c_void;
 use crate::ptr;
 use crate::sync::atomic::{AtomicPtr, Ordering};
-use crate::sys::c::{self, windows_targets};
+use crate::sys::c;
 use crate::sys::common::alloc::{realloc_fallback, MIN_ALIGN};
 
 #[cfg(test)]
diff --git a/library/std/src/sys/pal/windows/c.rs b/library/std/src/sys/pal/windows/c.rs
index 08b75186aef..2f5d75dc4bc 100644
--- a/library/std/src/sys/pal/windows/c.rs
+++ b/library/std/src/sys/pal/windows/c.rs
@@ -8,8 +8,6 @@
 use core::ffi::{c_uint, c_ulong, c_ushort, c_void, CStr};
 use core::{mem, ptr};
 
-pub(super) mod windows_targets;
-
 mod windows_sys;
 pub use windows_sys::*;
 
diff --git a/library/std/src/sys/pal/windows/c/windows_sys.rs b/library/std/src/sys/pal/windows/c/windows_sys.rs
index 9f22f548195..529c96a0e1e 100644
--- a/library/std/src/sys/pal/windows/c/windows_sys.rs
+++ b/library/std/src/sys/pal/windows/c/windows_sys.rs
@@ -3317,4 +3317,3 @@ pub struct WSADATA {
 #[cfg(target_arch = "arm")]
 pub enum CONTEXT {}
 // ignore-tidy-filelength
-use super::windows_targets;
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index 59720f77465..88b31cd78a6 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -434,25 +434,24 @@ impl Builder {
     ///
     /// [`io::Result`]: crate::io::Result
     #[unstable(feature = "thread_spawn_unchecked", issue = "55132")]
-    pub unsafe fn spawn_unchecked<'a, F, T>(self, f: F) -> io::Result<JoinHandle<T>>
+    pub unsafe fn spawn_unchecked<F, T>(self, f: F) -> io::Result<JoinHandle<T>>
     where
         F: FnOnce() -> T,
-        F: Send + 'a,
-        T: Send + 'a,
+        F: Send,
+        T: Send,
     {
         Ok(JoinHandle(unsafe { self.spawn_unchecked_(f, None) }?))
     }
 
-    unsafe fn spawn_unchecked_<'a, 'scope, F, T>(
+    unsafe fn spawn_unchecked_<'scope, F, T>(
         self,
         f: F,
         scope_data: Option<Arc<scoped::ScopeData>>,
     ) -> io::Result<JoinInner<'scope, T>>
     where
         F: FnOnce() -> T,
-        F: Send + 'a,
-        T: Send + 'a,
-        'scope: 'a,
+        F: Send,
+        T: Send,
     {
         let Builder { name, stack_size } = self;
 
@@ -532,7 +531,7 @@ impl Builder {
             // will call `decrement_num_running_threads` and therefore signal that this thread is
             // done.
             drop(their_packet);
-            // Here, the lifetime `'a` and even `'scope` can end. `main` keeps running for a bit
+            // Here, the lifetime `'scope` can end. `main` keeps running for a bit
             // after that before returning itself.
         };
 
diff --git a/library/test/src/types.rs b/library/test/src/types.rs
index c3be3466cb9..802cab989c6 100644
--- a/library/test/src/types.rs
+++ b/library/test/src/types.rs
@@ -250,3 +250,37 @@ pub struct TestDescAndFn {
     pub desc: TestDesc,
     pub testfn: TestFn,
 }
+
+impl TestDescAndFn {
+    pub const fn new_doctest(
+        test_name: &'static str,
+        ignore: bool,
+        source_file: &'static str,
+        start_line: usize,
+        no_run: bool,
+        should_panic: bool,
+        testfn: TestFn,
+    ) -> Self {
+        Self {
+            desc: TestDesc {
+                name: StaticTestName(test_name),
+                ignore,
+                ignore_message: None,
+                source_file,
+                start_line,
+                start_col: 0,
+                end_line: 0,
+                end_col: 0,
+                compile_fail: false,
+                no_run,
+                should_panic: if should_panic {
+                    options::ShouldPanic::Yes
+                } else {
+                    options::ShouldPanic::No
+                },
+                test_type: TestType::DocTest,
+            },
+            testfn,
+        }
+    }
+}
diff --git a/library/windows_targets/Cargo.toml b/library/windows_targets/Cargo.toml
new file mode 100644
index 00000000000..94d7c821064
--- /dev/null
+++ b/library/windows_targets/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "windows-targets"
+description = "A drop-in replacement for the real windows-targets crate for use in std only."
+version = "0.0.0"
+edition = "2021"
+
+[features]
+# Enable using raw-dylib for Windows imports.
+# This will eventually be the default.
+windows_raw_dylib = []
diff --git a/library/std/src/sys/pal/windows/c/windows_targets.rs b/library/windows_targets/src/lib.rs
index 252bceb7094..1965b6cf4ce 100644
--- a/library/std/src/sys/pal/windows/c/windows_targets.rs
+++ b/library/windows_targets/src/lib.rs
@@ -2,6 +2,10 @@
 //!
 //! This is a simple wrapper around an `extern` block with a `#[link]` attribute.
 //! It's very roughly equivalent to the windows-targets crate.
+#![no_std]
+#![no_core]
+#![feature(decl_macro)]
+#![feature(no_core)]
 
 #[cfg(feature = "windows_raw_dylib")]
 pub macro link {