Merge from rustc

library/core/src/num/f128.rs

@@ -145,6 +145,9 @@ impl f128 {
     pub const RADIX: u32 = 2;
 
     /// Number of significant digits in base 2.
+    ///
+    /// Note that the size of the mantissa in the bitwise representation is one
+    /// smaller than this since the leading 1 is not stored explicitly.
     #[unstable(feature = "f128", issue = "116909")]
     pub const MANTISSA_DIGITS: u32 = 113;
 

library/core/src/num/f16.rs

@@ -140,6 +140,9 @@ impl f16 {
     pub const RADIX: u32 = 2;
 
     /// Number of significant digits in base 2.
+    ///
+    /// Note that the size of the mantissa in the bitwise representation is one
+    /// smaller than this since the leading 1 is not stored explicitly.
     #[unstable(feature = "f16", issue = "116909")]
     pub const MANTISSA_DIGITS: u32 = 11;
 

library/core/src/num/f32.rs

@@ -390,6 +390,9 @@ impl f32 {
     pub const RADIX: u32 = 2;
 
     /// Number of significant digits in base 2.
+    ///
+    /// Note that the size of the mantissa in the bitwise representation is one
+    /// smaller than this since the leading 1 is not stored explicitly.
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MANTISSA_DIGITS: u32 = 24;
 

library/core/src/num/f64.rs

@@ -390,6 +390,9 @@ impl f64 {
     pub const RADIX: u32 = 2;
 
     /// Number of significant digits in base 2.
+    ///
+    /// Note that the size of the mantissa in the bitwise representation is one
+    /// smaller than this since the leading 1 is not stored explicitly.
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const MANTISSA_DIGITS: u32 = 53;
     /// Approximate number of significant digits in base 10.

library/std/src/sys/process/unix/unix.rs

@@ -415,6 +415,7 @@ impl Command {
         all(target_os = "linux", target_env = "musl"),
         target_os = "nto",
         target_vendor = "apple",
+        target_os = "cygwin",
     )))]
     fn posix_spawn(
         &mut self,
@@ -433,6 +434,7 @@ impl Command {
         all(target_os = "linux", target_env = "musl"),
         target_os = "nto",
         target_vendor = "apple",
+        target_os = "cygwin",
     ))]
     fn posix_spawn(
         &mut self,
@@ -584,7 +586,7 @@ impl Command {
         /// Some platforms can set a new working directory for a spawned process in the
         /// `posix_spawn` path. This function looks up the function pointer for adding
         /// such an action to a `posix_spawn_file_actions_t` struct.
-        #[cfg(not(all(target_os = "linux", target_env = "musl")))]
+        #[cfg(not(any(all(target_os = "linux", target_env = "musl"), target_os = "cygwin")))]
         fn get_posix_spawn_addchdir() -> Option<PosixSpawnAddChdirFn> {
             use crate::sys::weak::weak;
 
@@ -618,7 +620,9 @@ impl Command {
         /// Weak symbol lookup doesn't work with statically linked libcs, so in cases
         /// where static linking is possible we need to either check for the presence
         /// of the symbol at compile time or know about it upfront.
-        #[cfg(all(target_os = "linux", target_env = "musl"))]
+        ///
+        /// Cygwin doesn't support weak symbol, so just link it.
+        #[cfg(any(all(target_os = "linux", target_env = "musl"), target_os = "cygwin"))]
         fn get_posix_spawn_addchdir() -> Option<PosixSpawnAddChdirFn> {
             // Our minimum required musl supports this function, so we can just use it.
             Some(libc::posix_spawn_file_actions_addchdir_np)

library/std/tests/floats/f128.rs

@@ -112,6 +112,8 @@ fn test_nan() {
     assert!(!nan.is_sign_negative());
     assert!(!nan.is_normal());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f128::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]

library/std/tests/floats/f16.rs

@@ -95,6 +95,8 @@ fn test_nan() {
     assert!(!nan.is_sign_negative());
     assert!(!nan.is_normal());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f16::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]

library/std/tests/floats/f32.rs

@@ -72,6 +72,8 @@ fn test_nan() {
     assert!(nan.is_sign_positive());
     assert!(!nan.is_sign_negative());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f32::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]

library/std/tests/floats/f64.rs

@@ -60,6 +60,8 @@ fn test_nan() {
     assert!(nan.is_sign_positive());
     assert!(!nan.is_sign_negative());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f64::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]