Make it possible to use ThreadLocalStorage::Slot as a static without

introducing static initializers.

Member variables can stay TLS::Slots and their behavior doesn't change.
Static instances use TLS::StaticSlot instead.

Kind of like http://codereview.chromium.org/8491043 but for TLS.

BUG=none
TEST=none
TBR=agl

Review URL: https://chromiumcodereview.appspot.com/9297010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@119679 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 46 insertions, 28 deletions

diff --git a/base/threading/thread_local_storage.h b/base/threading/thread_local_storage.h
index 214b7e1..30cbd47 100644
--- a/base/threading/thread_local_storage.h
+++ b/base/threading/thread_local_storage.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -25,15 +25,18 @@ class BASE_EXPORT ThreadLocalStorage {
   // stored in thread local storage.
   typedef void (*TLSDestructorFunc)(void* value);
 
-  // A key representing one value stored in TLS.
-  class BASE_EXPORT Slot {
-   public:
-    explicit Slot(TLSDestructorFunc destructor = NULL);
-
-    // This constructor should be used for statics.
-    // It returns an uninitialized Slot.
-    explicit Slot(base::LinkerInitialized x) {}
+  // StaticSlot uses its own struct initializer-list style static
+  // initialization, as base's LINKER_INITIALIZED requires a constructor and on
+  // some compilers (notably gcc 4.4) this still ends up needing runtime
+  // initialization.
+  #define TLS_INITIALIZER {0}
 
+  // A key representing one value stored in TLS.
+  // Initialize like
+  //   ThreadLocalStorage::StaticSlot my_slot = TLS_INITIALIZER;
+  // If you're not using a static variable, use the convenience class
+  // ThreadLocalStorage::Slot (below) instead.
+  struct BASE_EXPORT StaticSlot {
     // Set up the TLS slot.  Called by the constructor.
     // 'destructor' is a pointer to a function to perform per-thread cleanup of
     // this object.  If set to NULL, no cleanup is done for this TLS slot.
@@ -56,7 +59,6 @@ class BASE_EXPORT ThreadLocalStorage {
 
     bool initialized() const { return initialized_; }
 
-   private:
     // The internals of this struct should be considered private.
     bool initialized_;
 #if defined(OS_WIN)
@@ -65,6 +67,22 @@ class BASE_EXPORT ThreadLocalStorage {
     pthread_key_t key_;
 #endif
 
+  };
+
+  // A convenience wrapper around StaticSlot with a constructor. Can be used
+  // as a member variable.
+  class BASE_EXPORT Slot : public StaticSlot {
+   public:
+    // Calls StaticSlot::Initialize().
+    explicit Slot(TLSDestructorFunc destructor = NULL);
+
+   private:
+    using StaticSlot::initialized_;
+#if defined(OS_WIN)
+    using StaticSlot::slot_;
+#elif defined(OS_POSIX)
+    using StaticSlot::key_;
+#endif
     DISALLOW_COPY_AND_ASSIGN(Slot);
   };
 
diff --git a/base/threading/thread_local_storage_posix.cc b/base/threading/thread_local_storage_posix.cc
index 3d0e187..75da5a7 100644
--- a/base/threading/thread_local_storage_posix.cc
+++ b/base/threading/thread_local_storage_posix.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -8,13 +8,13 @@
 
 namespace base {
 
-ThreadLocalStorage::Slot::Slot(TLSDestructorFunc destructor)
-    : initialized_(false),
-      key_(0) {
+ThreadLocalStorage::Slot::Slot(TLSDestructorFunc destructor) {
+  initialized_ = false;
+  key_ = 0;
   Initialize(destructor);
 }
 
-bool ThreadLocalStorage::Slot::Initialize(TLSDestructorFunc destructor) {
+bool ThreadLocalStorage::StaticSlot::Initialize(TLSDestructorFunc destructor) {
   DCHECK(!initialized_);
   int error = pthread_key_create(&key_, destructor);
   if (error) {
@@ -26,7 +26,7 @@ bool ThreadLocalStorage::Slot::Initialize(TLSDestructorFunc destructor) {
   return true;
 }
 
-void ThreadLocalStorage::Slot::Free() {
+void ThreadLocalStorage::StaticSlot::Free() {
   DCHECK(initialized_);
   int error = pthread_key_delete(key_);
   if (error)
@@ -34,12 +34,12 @@ void ThreadLocalStorage::Slot::Free() {
   initialized_ = false;
 }
 
-void* ThreadLocalStorage::Slot::Get() const {
+void* ThreadLocalStorage::StaticSlot::Get() const {
   DCHECK(initialized_);
   return pthread_getspecific(key_);
 }
 
-void ThreadLocalStorage::Slot::Set(void* value) {
+void ThreadLocalStorage::StaticSlot::Set(void* value) {
   DCHECK(initialized_);
   int error = pthread_setspecific(key_, value);
   if (error)
diff --git a/base/threading/thread_local_storage_unittest.cc b/base/threading/thread_local_storage_unittest.cc
index 33db1b0..0a6ba6b 100644
--- a/base/threading/thread_local_storage_unittest.cc
+++ b/base/threading/thread_local_storage_unittest.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -26,7 +26,7 @@ const int kFinalTlsValue = 0x7777;
 // How many times must a destructor be called before we really are done.
 const int kNumberDestructorCallRepetitions = 3;
 
-static ThreadLocalStorage::Slot tls_slot(LINKER_INITIALIZED);
+static ThreadLocalStorage::StaticSlot tls_slot = TLS_INITIALIZER;
 
 class ThreadLocalStorageRunner : public DelegateSimpleThread::Delegate {
  public:
diff --git a/base/threading/thread_local_storage_win.cc b/base/threading/thread_local_storage_win.cc
index badadb8..db66248 100644
--- a/base/threading/thread_local_storage_win.cc
+++ b/base/threading/thread_local_storage_win.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -86,13 +86,13 @@ void** ThreadLocalStorage::Initialize() {
   return tls_data;
 }
 
-ThreadLocalStorage::Slot::Slot(TLSDestructorFunc destructor)
-    : initialized_(false),
-      slot_(0) {
+ThreadLocalStorage::Slot::Slot(TLSDestructorFunc destructor) {
+  initialized_ = false;
+  slot_ = 0;
   Initialize(destructor);
 }
 
-bool ThreadLocalStorage::Slot::Initialize(TLSDestructorFunc destructor) {
+bool ThreadLocalStorage::StaticSlot::Initialize(TLSDestructorFunc destructor) {
   if (tls_key_ == TLS_OUT_OF_INDEXES || !TlsGetValue(tls_key_))
     ThreadLocalStorage::Initialize();
 
@@ -110,7 +110,7 @@ bool ThreadLocalStorage::Slot::Initialize(TLSDestructorFunc destructor) {
   return true;
 }
 
-void ThreadLocalStorage::Slot::Free() {
+void ThreadLocalStorage::StaticSlot::Free() {
   // At this time, we don't reclaim old indices for TLS slots.
   // So all we need to do is wipe the destructor.
   DCHECK_GT(slot_, 0);
@@ -120,7 +120,7 @@ void ThreadLocalStorage::Slot::Free() {
   initialized_ = false;
 }
 
-void* ThreadLocalStorage::Slot::Get() const {
+void* ThreadLocalStorage::StaticSlot::Get() const {
   void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
   if (!tls_data)
     tls_data = ThreadLocalStorage::Initialize();
@@ -129,7 +129,7 @@ void* ThreadLocalStorage::Slot::Get() const {
   return tls_data[slot_];
 }
 
-void ThreadLocalStorage::Slot::Set(void* value) {
+void ThreadLocalStorage::StaticSlot::Set(void* value) {
   void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
   if (!tls_data)
     tls_data = ThreadLocalStorage::Initialize();