Fix an over-release in StdlibUnittest

Fixes rdar://51245681

Author: porglezomp

stdlib/private/StdlibUnittest/GetOSVersion.mm

@@ -18,21 +18,21 @@
 SWIFT_CC(swift) SWIFT_RUNTIME_LIBRARY_VISIBILITY extern "C"
 const char *
 getSystemVersionPlistProperty(const char *PropertyName) {
-  // This function is implemented in Objective-C because Swift does not support
-  // failing initializers.
-  if (!PropertyName)
-    return nullptr;
+  @autoreleasepool {
+    // This function is implemented in Objective-C because Swift does not support
+    // failing initializers.
+    if (!PropertyName)
+      return nullptr;
 
-  NSDictionary *SystemVersion =
-      [NSDictionary dictionaryWithContentsOfFile:
-                        @"/System/Library/CoreServices/SystemVersion.plist"];
-  if (!SystemVersion)
-    return nullptr;
-  NSString *PropertyNameString = [NSString stringWithUTF8String:PropertyName];
-  const char *Result = strdup([SystemVersion[PropertyNameString] UTF8String]);
-  [PropertyNameString release];
-  [SystemVersion release];
-  return Result;
+    NSDictionary *SystemVersion =
+        [NSDictionary dictionaryWithContentsOfFile:
+                            @"/System/Library/CoreServices/SystemVersion.plist"];
+    if (!SystemVersion)
+      return nullptr;
+    NSString *PropertyNameString = [NSString stringWithUTF8String:PropertyName];
+    const char *Result = strdup([SystemVersion[PropertyNameString] UTF8String]);
+    return Result;
+  }
 }
 #endif
 

stdlib/private/StdlibUnittest/StdlibUnittest.swift

@@ -1718,7 +1718,9 @@ func _getSystemVersionPlistPropertyImpl(
 
 func _getSystemVersionPlistProperty(_ propertyName: String) -> String? {
   let cs = _getSystemVersionPlistPropertyImpl(propertyName)
-  return cs.map(String.init(cString:))
+  let str = cs.map(String.init(cString:))
+  free(UnsafeMutableRawPointer(mutating: cs))
+  return str
 }
 #endif
 

test/stdlib/StdlibUnittestOverrelease.swift

@@ -0,0 +1,13 @@
+// RUN: %target-run-simple-swift
+// REQUIRES: executable_test
+
+import Foundation
+import StdlibUnittest
+
+var Suite = TestSuite("Overrelease")
+
+Suite.test("doesntfail").xfail(.never).code { }
+
+autoreleasepool {
+    runAllTests()
+}