Consolidate _stdlib_random functions (#2)

* Use the `__has_include` and `GRND_RANDOM` macros

* Use `getentropy` instead of `getrandom`

* Use `std::min` from the <algorithm> header

* Move `#if` out of the `_stdlib_random` function

* Use `getrandom` with "/dev/urandom" fallback

* Use `#pragma comment` to import "Bcrypt.lib"

* <https://docs.microsoft.com/en-us/cpp/preprocessor/comment-c-cpp>
* <https://clang.llvm.org/docs/UsersManual.html#microsoft-extensions>

* Use "/dev/urandom" instead of `SecRandomCopyBytes`

* Use `swift::StaticMutex` for shared "/dev/urandom"

* Add `getrandom_available`; use `O_CLOEXEC` flag

Add platform impl docs

Update copyrights

Fix docs

Add _stdlib_random test

Update _stdlib_random test

Add missing &

Notice about _stdlib_random

Fix docs

Guard on upperBound = 0

Test full range of 8 bit integers

Remove some gyb

Author: benrimmington

benchmark/single-source/RandomShuffle.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

benchmark/single-source/RandomValues.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

benchmark/utils/main.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

stdlib/public/SwiftShims/LibcShims.h

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

stdlib/public/core/Bool.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -88,23 +88,21 @@ public struct Bool {
     self = value
   }
 
-  /// Returns a random Boolean
+  /// Returns a random Boolean value
   ///
   /// - Parameter generator: The random number generator to use when getting a
   ///   random Boolean.
-  /// - Returns: A random Boolean.
+  /// - Returns: A random Boolean value.
   @inlinable
   public static func random<T: RandomNumberGenerator>(
     using generator: inout T
   ) -> Bool {
     return (generator.next() >> 17) & 1 == 0
   }
 
-  /// Returns a random Boolean
+  /// Returns a random Boolean value
   ///
-  /// - Parameter generator: The random number generator to use when getting a
-  ///   random Boolean.
-  /// - Returns: A random Boolean.
+  /// - Returns: A random Boolean value.
   ///
   /// This uses the standard library's default random number generator.
   @inlinable

stdlib/public/core/CMakeLists.txt

@@ -2,7 +2,7 @@
 #
 # This source file is part of the Swift.org open source project
 #
-# Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+# Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 # Licensed under Apache License v2.0 with Runtime Library Exception
 #
 # See https://swift.org/LICENSE.txt for license information
@@ -193,7 +193,6 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
   list(APPEND swift_core_link_flags "-all_load")
   list(APPEND swift_core_framework_depends Foundation)
   list(APPEND swift_core_framework_depends CoreFoundation)
-  list(APPEND swift_core_framework_depends Security)
   list(APPEND swift_core_private_link_libraries icucore)
 else()
   # With the GNU linker the equivalent of -all_load is to tell the linker
@@ -228,10 +227,6 @@ if(CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
       ${EXECINFO_LIBRARY})
 endif()
 
-if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  list(APPEND swift_core_link_flags "$ENV{SystemRoot}/system32/bcrypt.dll")
-endif()
-
 option(SWIFT_CHECK_ESSENTIAL_STDLIB
     "Check core standard library layering by linking its essential subset"
     FALSE)

stdlib/public/core/Collection.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

stdlib/public/core/CollectionAlgorithms.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -304,8 +304,6 @@ extension Sequence {
   /// to `numbers.shuffled()` above is equivalent to calling
   /// `numbers.shuffled(using: &Random.default)`.
   ///
-  /// - Parameter generator: The random number generator to use when shuffling
-  ///   the sequence.
   /// - Returns: A shuffled array of this sequence's elements.
   ///
   /// - Complexity: O(*n*)
@@ -335,6 +333,7 @@ extension MutableCollection {
   public mutating func shuffle<T: RandomNumberGenerator>(
     using generator: inout T
   ) {
+    let count = self.count
     guard count > 1 else { return }
     var amount = count
     var currentIndex = startIndex

stdlib/public/core/FloatingPoint.swift.gyb

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -2395,7 +2395,7 @@ where Self.RawSignificand : FixedWidthInteger,
   ///     // Prints "14.2286325689993"
   ///     // Prints "13.1485686260762"
   ///
-  /// The `random(using:)` static method chooses a random value from a
+  /// The `random(in:using:)` static method chooses a random value from a
   /// continuous uniform distribution in `range`, and then converts that value
   /// to the nearest representable value in this type. Depending on the size and
   /// span of `range`, some concrete values may be represented more frequently
@@ -2414,12 +2414,10 @@ where Self.RawSignificand : FixedWidthInteger,
     in range: ${Range}<Self>,
     using generator: inout T
   ) -> Self {
-%   if 'Closed' not in Range:
     _precondition(
-      range.lowerBound != range.upperBound,
-      "Can't get random value with lowerBound == upperBound"
+      !range.isEmpty,
+      "Can't get random value with an empty range"
     )
-%   end
     let delta = range.upperBound - range.lowerBound
     let rand: Self.RawSignificand
     if Self.RawSignificand.bitWidth == Self.significandBitCount + 1 {

stdlib/public/core/Integers.swift.gyb

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -2513,11 +2513,9 @@ extension ${Range}
   public func randomElement<T: RandomNumberGenerator>(
     using generator: inout T
   ) -> Element? {
-%   if 'Closed' not in Range:
-    guard lowerBound != upperBound else {
+    guard !isEmpty else {
       return nil
     }
-%   end
     let isLowerNegative = Bound.isSigned && lowerBound < 0
     let sameSign = !Bound.isSigned || isLowerNegative == (upperBound < 0)
 %   if 'Closed' not in Range:
@@ -2611,12 +2609,10 @@ where Self.Stride : SignedInteger,
     in range: ${Range}<Self>,
     using generator: inout T
   ) -> Self {
-%   if 'Closed' not in Range:
     _precondition(
-      range.lowerBound != range.upperBound,
-      "Can't get random value with lowerBound == upperBound"
+      !range.isEmpty,
+      "Can't get random value with an empty range"
     )
-%   end
     return range.randomElement(using: &generator)!
   }
   

stdlib/public/core/Random.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -32,7 +32,7 @@ import SwiftShims
 ///         }
 ///
 ///         static func randomWeekday() -> Weekday {
-///             return Weekday.randomWeekday(using: Random.default)
+///             return Weekday.randomWeekday(using: &Random.default)
 ///         }
 ///     }
 ///
@@ -94,6 +94,7 @@ extension RandomNumberGenerator {
   public mutating func next<T: FixedWidthInteger & UnsignedInteger>(
     upperBound: T
   ) -> T {
+    guard upperBound != 0 else { return 0 }
     let tmp = (T.max % upperBound) + 1
     let range = tmp == upperBound ? 0 : tmp
     var random: T = 0
@@ -118,8 +119,19 @@ extension RandomNumberGenerator {
 ///
 /// `Random.default` is safe to use in multiple threads, and uses a
 /// cryptographically secure algorithm whenever possible.
+///
+/// Platform Implementation of `Random`
+/// ===================================
+///
+/// - Apple platforms use `arc4random_buf(3)` for newer versions of their OS,
+///   and for older versions they will read from `/dev/urandom`.
+/// - `Linux`, `Android`, `Cygwin`, `Haiku`, `FreeBSD`, and `PS4` all try to
+///   use `getrandom(2)`, but if it doesn't exist then they read from
+///   `/dev/urandom`.
+/// - `Fuchsia` calls `getentropy(3)`.
+/// - `Windows` calls `BCryptGenRandom`.
 public struct Random : RandomNumberGenerator {
-  /// The shared, default instance of the `Range` random number generator.
+  /// The default instance of the `Random` random number generator.
   public static var `default`: Random {
     get { return Random() }
     set { /* Discard */ }