stdlib/String: fix a race in _StringBuffer.grow()

rdar://17855614


Swift SVN r20960

stdlib/unittest/SwiftBlockToCFunctionThunks.cpp

@@ -0,0 +1,40 @@
+//===--- ObjCBlockToFunctionAdapter.cpp -----------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file This file implements C thunks that call ObjC blocks.  These thunks
+/// can be used to implement block-based wrappers for APIs that accept a function
+/// pointer and a context pointer.
+///
+//===----------------------------------------------------------------------===//
+
+extern "C" void *swift_stdlib_getTypeMetadata(void *, void *T) {
+  return T;
+}
+
+extern "C" void *swift_stdlib_executeSwiftClosure(
+    void *Context, const void *ParamMetadata, const void *ResultMetadata);
+
+template <typename Result, typename Param>
+using FunctionPointerType = Result (*)(Param);
+
+static void *executeBlock_VoidPtr_VoidPtr(void *Context) {
+  const void **MetadataPointers = reinterpret_cast<const void **>(Context);
+  return swift_stdlib_executeSwiftClosure(Context, MetadataPointers[0],
+                                          MetadataPointers[1]);
+}
+
+/// Returns a thunk for a 'void *(*)(void *context)' C function.
+extern "C" FunctionPointerType<void *, void *>
+swift_stdlib_getExecuteBlockFunctionPtr_VoidPtr_VoidPtr() {
+  return &executeBlock_VoidPtr_VoidPtr;
+}
+