Use C++11 alignment primitives
Removes the compiler-specific base #define ALIGNOF and replace uses with alignof.
Replaces some uses of ALIGNAS with alignas. These are not all replaced,
and a note is added to the definition about the problems with alignas.
This came from https://codereview.chromium.org/2670873002/
Remove base::AlignedMemory and replace with alignas(type) char[size].
std::aligned_storage has some limitations. The style guide is updated to note these and mark it disallowed. It is also updated for alignas and alignof.
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
Review-Url: https://codereview.chromium.org/2932053002
Cr-Commit-Position: refs/heads/master@{#479169}
diff --git a/base/lazy_instance.h b/base/lazy_instance.h
index aaad3f7..99a000ed7 100644
--- a/base/lazy_instance.h
+++ b/base/lazy_instance.h
@@ -41,7 +41,6 @@
#include "base/base_export.h"
#include "base/debug/leak_annotations.h"
#include "base/logging.h"
-#include "base/memory/aligned_memory.h"
#include "base/threading/thread_restrictions.h"
// LazyInstance uses its own struct initializer-list style static
@@ -55,7 +54,7 @@
template <typename Type>
struct LazyInstanceTraitsBase {
static Type* New(void* instance) {
- DCHECK_EQ(reinterpret_cast<uintptr_t>(instance) & (ALIGNOF(Type) - 1), 0u);
+ DCHECK_EQ(reinterpret_cast<uintptr_t>(instance) & (alignof(Type) - 1), 0u);
// Use placement new to initialize our instance in our preallocated space.
// The parenthesis is very important here to force POD type initialization.
return new (instance) Type();
@@ -195,7 +194,7 @@
#endif
return static_cast<Type*>(internal::GetOrCreateLazyPointer(
&private_instance_,
- [this]() { return Traits::New(private_buf_.void_data()); },
+ [this]() { return Traits::New(private_buf_); },
Traits::kRegisterOnExit ? OnExit : nullptr, this));
}
@@ -204,19 +203,31 @@
case 0:
return p == NULL;
case internal::kLazyInstanceStateCreating:
- return static_cast<void*>(p) == private_buf_.void_data();
+ return static_cast<void*>(p) == private_buf_;
default:
return p == instance();
}
}
+ // MSVC gives a warning that the alignment expands the size of the
+ // LazyInstance struct to make the size a multiple of the alignment. This
+ // is expected in this case.
+#if defined(OS_WIN)
+#pragma warning(push)
+#pragma warning(disable: 4324)
+#endif
+
// Effectively private: member data is only public to allow the linker to
// statically initialize it and to maintain a POD class. DO NOT USE FROM
// OUTSIDE THIS CLASS.
-
subtle::AtomicWord private_instance_;
+
// Preallocated space for the Type instance.
- base::AlignedMemory<sizeof(Type), ALIGNOF(Type)> private_buf_;
+ alignas(Type) char private_buf_[sizeof(Type)];
+
+#if defined(OS_WIN)
+#pragma warning(pop)
+#endif
private:
Type* instance() {
