blob: 42a7d016fdd119fbb3bea30bfc94fbec1d7701c3 [file] [log] [blame]
// 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/threading/thread_local_storage.h"
#include <windows.h>
#include "base/logging.h"
namespace base {
namespace internal {
bool PlatformThreadLocalStorage::AllocTLS(TLSKey* key) {
TLSKey value = TlsAlloc();
if (value != TLS_OUT_OF_INDEXES) {
*key = value;
return true;
return false;
void PlatformThreadLocalStorage::FreeTLS(TLSKey key) {
BOOL ret = TlsFree(key);
void* PlatformThreadLocalStorage::GetTLSValue(TLSKey key) {
return TlsGetValue(key);
void PlatformThreadLocalStorage::SetTLSValue(TLSKey key, void* value) {
BOOL ret = TlsSetValue(key, value);
} // namespace internal
} // namespace base
// Thread Termination Callbacks.
// Windows doesn't support a per-thread destructor with its
// TLS primitives. So, we build it manually by inserting a
// function to be called on each thread's exit.
// This magic is from
// and it works for VC++ 7.0 and later.
// Force a reference to _tls_used to make the linker create the TLS directory
// if it's not already there. (e.g. if __declspec(thread) is not used).
// Force a reference to p_thread_callback_base to prevent whole program
// optimization from discarding the variable.
#ifdef _WIN64
#pragma comment(linker, "/INCLUDE:_tls_used")
#pragma comment(linker, "/INCLUDE:p_thread_callback_base")
#else // _WIN64
#pragma comment(linker, "/INCLUDE:__tls_used")
#pragma comment(linker, "/INCLUDE:_p_thread_callback_base")
#endif // _WIN64
// Static callback function to call with each thread termination.
void NTAPI OnThreadExit(PVOID module, DWORD reason, PVOID reserved) {
// On XP SP0 & SP1, the DLL_PROCESS_ATTACH is never seen. It is sent on SP2+
// and on W2K and W2K3. So don't assume it is sent.
if (DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason)
// .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are
// called automatically by the OS loader code (not the CRT) when the module is
// loaded and on thread creation. They are NOT called if the module has been
// loaded by a LoadLibrary() call. It must have implicitly been loaded at
// process startup.
// By implicitly loaded, I mean that it is directly referenced by the main EXE
// or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being
// implicitly loaded.
// See VC\crt\src\tlssup.c for reference.
// extern "C" suppresses C++ name mangling so we know the symbol name for the
// linker /INCLUDE:symbol pragma above.
extern "C" {
// The linker must not discard p_thread_callback_base. (We force a reference
// to this variable with a linker /INCLUDE:symbol pragma to ensure that.) If
// this variable is discarded, the OnThreadExit function will never be called.
#ifdef _WIN64
// .CRT section is merged with .rdata on x64 so it must be constant data.
#pragma const_seg(".CRT$XLB")
// When defining a const variable, it must have external linkage to be sure the
// linker doesn't discard it.
extern const PIMAGE_TLS_CALLBACK p_thread_callback_base;
const PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit;
// Reset the default section.
#pragma const_seg()
#else // _WIN64
#pragma data_seg(".CRT$XLB")
PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit;
// Reset the default section.
#pragma data_seg()
#endif // _WIN64
} // extern "C"