Merge branch 'swift-4.0.1-branch'

# Conflicts:
#	Foundation/JSONEncoder.swift
#	Foundation/URLSession/URLSessionTask.swift

Author: phausler

CoreFoundation/Base.subproj/ForSwiftFoundationOnly.h

@@ -33,6 +33,10 @@
 #include <malloc/malloc.h>
 #endif
 
+#if __has_include(<malloc/malloc.h>)
+#include <malloc/malloc.h>
+#endif
+
 _CF_EXPORT_SCOPE_BEGIN
 
 struct __CFSwiftObject {

Foundation/Decimal.swift

@@ -327,6 +327,7 @@ extension Decimal : SignedNumeric {
     }
 
     public mutating func negate() {
+        guard _length != 0 else { return }
         _isNegative = _isNegative == 0 ? 1 : 0
     }
 }
@@ -1282,9 +1283,7 @@ fileprivate func integerSubtract(_ result: inout Decimal, _ left: inout Decimal,
 
 public func NSDecimalSubtract(_ result: UnsafeMutablePointer<Decimal>, _ leftOperand: UnsafePointer<Decimal>, _ rightOperand: UnsafePointer<Decimal>, _ roundingMode: NSDecimalNumber.RoundingMode) -> NSDecimalNumber.CalculationError {
     var r = rightOperand.pointee
-    if r._length != 0 {
-        r.negate()
-    }
+    r.negate()
     return NSDecimalAdd(result, leftOperand, &r, roundingMode)
 }
 // Exact operations. result may be a pointer to same space as leftOperand or rightOperand

TestFoundation/TestDecimal.swift

@@ -289,6 +289,9 @@ class TestDecimal: XCTestCase {
         XCTAssertEqual(.minus, d.sign)
         d.negate()
         XCTAssertEqual(.plus, d.sign)
+        var e = Decimal(0)
+        e.negate()
+        XCTAssertEqual(e, 0)
         XCTAssertTrue(Decimal(3.5).isEqual(to: Decimal(3.5)))
         XCTAssertTrue(Decimal.nan.isEqual(to: Decimal.nan))
         XCTAssertTrue(Decimal(1.28).isLess(than: Decimal(2.24)))