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- // 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/check.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);
- DCHECK(ret);
- }
- void PlatformThreadLocalStorage::SetTLSValue(TLSKey key, void* value) {
- BOOL ret = TlsSetValue(key, value);
- DCHECK(ret);
- }
- } // 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 http://www.codeproject.com/threads/tls.asp
- // 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)
- base::internal::PlatformThreadLocalStorage::OnThreadExit();
- }
- // .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"
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