Provide DllMain, and hook to support TLS callbacks.

base/win/dllmain.cc

+// Copyright (c) 2011 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.
+
+// Windows doesn't support pthread_key_create's destr_function, and in fact
+// it's a bit tricky to get code to run when a thread exits.  This is
+// cargo-cult magic from http://www.codeproject.com/threads/tls.asp.
+// We are trying to be compatible with both a LoadLibrary style invocation, as
+// well as static linking. This code only needs to be included if we use
+// LoadLibrary, but it hooks into the "standard" set of TLS callbacks that are
+// provided for static linking.
+
+// Force a reference to _tls_used to make the linker create the TLS directory
+// if it's not already there (that is, even if __declspec(thread) is not used).
+// To make sure we really traverse the whole list, we put down two elements, and
+// then check that we called both functions when we scanned the list.
+// Force a reference to p_thread_callback_dllmain_first_entry and
+// p_thread_callback_dllmain_first_entry to prevent whole program optimization
+// from discarding the variables.
+
+#include <windows.h>
+
+#include "base/logging.h"
+
+// Indicate if another service is scanning the callbacks.
+static bool linker_notifications_are_active = false;
+
+// This will be our mostly no-op callback that we'll list (twice).  We won't
+// deliberately call it, and if it is called, that means we don't need to do any
+// of the scanning anymore.  We expect such a call to arrive via a
+// THREAD_ATTACH message, long before we'd have to perform our THREAD_DETACH
+// callback scans.
+static void NTAPI on_callback(HINSTANCE h, DWORD dwReason, PVOID pv);

[cpu_(ooo_6.6-7.5), 2011/12/06 19:15:50]

use same notation as thread_local_storage_win.cc

[jar (doing other things), 2011/12/06 19:56:26]

Done.

+
+#ifdef _WIN64
+
+#pragma comment(linker, "/INCLUDE:_tls_used")
+#pragma comment(linker, "/INCLUDE:p_thread_callback_dllmain_first_entry")
+#pragma comment(linker, "/INCLUDE:p_thread_callback_dllmain_later_entry")
+
+#else  // _WIN64
+
+#pragma comment(linker, "/INCLUDE:__tls_used")
+#pragma comment(linker, "/INCLUDE:_p_thread_callback_dllmain_first_entry")
+#pragma comment(linker, "/INCLUDE:_p_thread_callback_dllmain_later_entry")
+
+#endif  // _WIN64
+
+// extern "C" suppresses C++ name mangling so we know the symbol names for the
+// linker /INCLUDE:symbol pragmas above.
+extern "C" {
+typedef void (NTAPI *CallbackPointer)(HINSTANCE h, DWORD dwReason, PVOID pv);
+// This tells the linker to run these functions.
+#pragma data_seg(push, old_seg)
+// Use earliest possible name in the .CRT$XL? list of segments.
+#pragma data_seg(".CRT$XLA")
+CallbackPointer p_thread_callback_dllmain_first_entry = on_callback;

[cpu_(ooo_6.6-7.5), 2011/12/06 19:15:50]

this must be const in x64

[jar (doing other things), 2011/12/06 19:56:26]

Done.

+// The latest possible name in the .CRT$XL? (other than *Z, which has a NULL).
+#pragma data_seg(".CRT$XLY")
+CallbackPointer p_thread_callback_dllmain_later_entry = on_callback;

[cpu_(ooo_6.6-7.5), 2011/12/06 19:15:50]

use thread_local_storage_win.cc notation like PIMAGE_TLS_CALLBACK

[jar (doing other things), 2011/12/06 19:56:26]

Done.

+#pragma data_seg(pop, old_seg)
+}  // extern "C"
+
+
+// Make DllMain call the listed callbacks.  This way any third parties that are
+// linked in will also be called.
+BOOL WINAPI DllMain(HINSTANCE h, DWORD reason, PVOID pv) {
+  if (DLL_THREAD_DETACH != reason && DLL_PROCESS_DETACH != reason)
+    return true;  // We won't service THREAD_ATTACH calls.
+
+  if (linker_notifications_are_active)
+    return true;  // Some other service is doing this work.
+
+  // Use our first entry as a starting point, but don't call it.
+  CallbackPointer* it = &p_thread_callback_dllmain_first_entry;
+  while(*++it) {
+    if (*it == p_thread_callback_dllmain_later_entry)
+      continue;  // Don't bother to call our own callbacks.
+    (*it)(h, reason, pv);
+  }
+  // Guarantee that we did a full list, and didn't get "stuck" on some NULL
+  // ahead of time.  The fear is that there migtht be another null in ".CRT$XLA"
+  // the way there is guaranteed to be a NULL in ".CRT$XLZ"
+  // We use a CHECK to ensure that the release bulid, no matter how created, is
+  // compliant with this arrangement.
+  CHECK_GT(*it, p_thread_callback_dllmain_later_entry);
+  return true;
+}
+
+static void NTAPI on_callback(HINSTANCE h, DWORD dwReason, PVOID pv) {
+  // Do nothing.  We were just a place holder in the list used to test that we
+  // call all items.
+  // If we are called, it means that some other system is scanning the callbacks
+  // and we don't need to do so in DllMain().
+  linker_notifications_are_active = true;
+  // Note: If some other routine some how plays this same game... we could both
+  // decide not to do the scanning <sigh>, but this trick should suppress
+  // duplicate calls on Vista, where the runtime takes care of the callbacks,
+  // and allow us to do the callbacks on XP, where we are currently devoid of
+  // callbacks (due to an explicit LoadLibrary call).
+}