Merge pull request #2676 from compnerd/corruption

Revert "Foundation: fix missing string terminator"

Author: millenomi

Docs/ReleaseNotes_Swift5.md

@@ -156,3 +156,11 @@ A few notes:
 * The exception-throwing API will be deprecated in a future release. It is now marked as `@available(…, deprecated: 100000, …)`, which matches what you would see if `API_TO_BE_DEPRECATED` was used in a Objective-C header.
 
 * Subclassing `NSFileHandle` is strongly discouraged. Many of the new methods are `public` and cannot be overridden.
+
+## `NSString(bytesNoCopy:length:encoding:freeWhenDone:)` deviations from reference implementation
+
+On Windows, `NSString(bytesNoCopy:length:encoding:freeWhenDone:)` deviates from
+the behaviour on Darwin and uses the buffer's `deallocate` routine rather than
+`free`.  This is done to ensure that the correct routine is invoked for
+releasing the resources acquired through `UnsafeMutablePointer.allocate` or
+`UnsafeMutableRawPointer.allocate`.

Sources/Foundation/NSData.swift

@@ -599,12 +599,10 @@ open class NSData : NSObject, NSCopying, NSMutableCopying, NSSecureCoding {
 
         let capacity = estimateBase64Size(length: dataLength)
         let ptr = UnsafeMutableRawPointer.allocate(byteCount: capacity, alignment: 1)
-        defer { ptr.deallocate() }
         let buffer = UnsafeMutableRawBufferPointer(start: ptr, count: capacity)
         let length = NSData.base64EncodeBytes(self, options: options, buffer: buffer)
 
-        let utf8buffer = UnsafeBufferPointer<UInt8>(start: ptr.assumingMemoryBound(to: UInt8.self), count: length)
-        return String(decoding: utf8buffer, as: UTF8.self)
+        return String(bytesNoCopy: ptr, length: length, encoding: .ascii, freeWhenDone: true)!
     }
 
     /// Creates a Base64, UTF-8 encoded Data from the data object using the given options.

Sources/Foundation/NSString.swift

@@ -1359,7 +1359,11 @@ extension NSString {
         // just copy for now since the internal storage will be a copy anyhow
         self.init(bytes: bytes, length: len, encoding: encoding)
         if freeBuffer { // don't take the hint
-            free(bytes)
+#if os(Windows)
+          bytes.deallocate()
+#else
+          free(bytes)
+#endif
         }
     }