win: Remove GetModuleFromAddress, deduplicate __ImageBase code.

base/win/wrapped_window_proc.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/win/wrapped_window_proc.h"
 
 #include "base/atomicops.h"
 #include "base/logging.h"
-#include "base/process/memory.h"
 
 namespace {
 
 base::win::WinProcExceptionFilter s_exception_filter = NULL;
 
+HMODULE GetModuleFromWndProc(WNDPROC window_proc) {
+  HMODULE instance = NULL;
+  // Converting a pointer-to-function to a void* is undefined behavior, but
+  // Windows (and POSIX) APIs require it to work.
+  void* address = reinterpret_cast<void*>(window_proc);
+  if (!::GetModuleHandleExA(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
+                            GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+                            static_cast<char*>(address),

[Will Harris, 2016/04/04 01:26:44]

why double cast, why not just reinterpret_cast<> straight from window_proc here?

Is this just to make the static_cast explicit above, for the comment?

[Nico, 2016/04/04 01:38:47]

Yes. I had this inline here, but it looked cramped with the comment in here.

+                            &instance)) {
+    NOTREACHED();
+  }
+  return instance;
+}
+
 }  // namespace.
 
 namespace base {
 namespace win {
 
 WinProcExceptionFilter SetWinProcExceptionFilter(
     WinProcExceptionFilter filter) {
   subtle::AtomicWord rv = subtle::NoBarrier_AtomicExchange(
       reinterpret_cast<subtle::AtomicWord*>(&s_exception_filter),
       reinterpret_cast<subtle::AtomicWord>(filter));
@@ skipping 15 matching lines @@
     HBRUSH background,
     const char16* menu_name,
     HICON large_icon,
     HICON small_icon,
     WNDCLASSEX* class_out) {
   class_out->cbSize = sizeof(WNDCLASSEX);
   class_out->style = style;
   class_out->lpfnWndProc = window_proc;
   class_out->cbClsExtra = class_extra;
   class_out->cbWndExtra = window_extra;
-  class_out->hInstance = base::GetModuleFromAddress(window_proc);
+  // RegisterClassEx uses a handle of the module containing the window procedure
+  // to distinguish identically named classes registered in different modules.
+  class_out->hInstance = GetModuleFromWndProc(window_proc);
   class_out->hIcon = large_icon;
   class_out->hCursor = cursor;
   class_out->hbrBackground = background;
   class_out->lpszMenuName = menu_name;
   class_out->lpszClassName = class_name;
   class_out->hIconSm = small_icon;
 
   // Check if |window_proc| is valid.
   DCHECK(class_out->hInstance != NULL);
 }
 
 }  // namespace win
 }  // namespace base