// C++11 feature detection
//
// V8_HAS_CXX11_ALIGNAS - alignas specifier supported
+// V8_HAS_CXX11_ALIGNOF - alignof(type) operator supported
// V8_HAS_CXX11_STATIC_ASSERT - static_assert() supported
// V8_HAS_CXX11_DELETE - deleted functions supported
// V8_HAS_CXX11_FINAL - final marker supported
//
// Compiler-specific feature detection
//
-// V8_HAS_ATTRIBUTE___ALIGNED__ - __attribute__((__aligned__(n))) supported
+// V8_HAS___ALIGNOF - __alignof(type) operator supported
+// V8_HAS___ALIGNOF__ - __alignof__(type) operator supported
+// V8_HAS_ATTRIBUTE_ALIGNED - __attribute__((aligned(n))) supported
// V8_HAS_ATTRIBUTE_ALWAYS_INLINE - __attribute__((always_inline)) supported
// V8_HAS_ATTRIBUTE_DEPRECATED - __attribute__((deprecated)) supported
// V8_HAS_ATTRIBUTE_VISIBILITY - __attribute__((visibility)) supported
# define V8_CC_CLANG 1
-# define V8_HAS_ATTRIBUTE___ALIGNED__ (__has_attribute(__aligned__))
+// Clang defines __alignof__ as alias for __alignof
+# define V8_HAS___ALIGNOF 1
+# define V8_HAS___ALIGNOF__ V8_HAS___ALIGNOF
+
+# define V8_HAS_ATTRIBUTE_ALIGNED (__has_attribute(aligned))
# define V8_HAS_ATTRIBUTE_ALWAYS_INLINE (__has_attribute(always_inline))
# define V8_HAS_ATTRIBUTE_DEPRECATED (__has_attribute(deprecated))
# define V8_HAS_ATTRIBUTE_VISIBILITY (__has_attribute(visibility))
# define V8_CC_MINGW 1
# endif
-# define V8_HAS_ATTRIBUTE___ALIGNED__ (V8_GNUC_PREREQ(2, 95, 0))
+# define V8_HAS___ALIGNOF__ (V8_GNUC_PREREQ(4, 3, 0))
+
+# define V8_HAS_ATTRIBUTE_ALIGNED (V8_GNUC_PREREQ(2, 95, 0))
// always_inline is available in gcc 4.0 but not very reliable until 4.4.
// Works around "sorry, unimplemented: inlining failed" build errors with
// older compilers.
// both for forward compatibility.
# if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
# define V8_HAS_CXX11_ALIGNAS (V8_GNUC_PREREQ(4, 8, 0))
+# define V8_HAS_CXX11_ALIGNOF (V8_GNUC_PREREQ(4, 8, 0))
# define V8_HAS_CXX11_STATIC_ASSERT (V8_GNUC_PREREQ(4, 3, 0))
# define V8_HAS_CXX11_DELETE (V8_GNUC_PREREQ(4, 4, 0))
# define V8_HAS_CXX11_OVERRIDE (V8_GNUC_PREREQ(4, 7, 0))
# define V8_CC_MSVC 1
+# define V8_HAS___ALIGNOF 1
+
// Override control was added with Visual Studio 2005, but
// Visual Studio 2010 and earlier spell "final" as "sealed".
# define V8_HAS_CXX11_FINAL (_MSC_VER >= 1700)
// This macro allows to specify memory alignment for structs, classes, etc.
// Use like:
-// class V8_ALIGNAS(16) MyClass { ... };
-// V8_ALIGNAS(32) int array[42];
+// class V8_ALIGNED(16) MyClass { ... };
+// V8_ALIGNED(32) int array[42];
#if V8_HAS_CXX11_ALIGNAS
-# define V8_ALIGNAS(n) alignas(n)
-#elif V8_HAS_ATTRIBUTE___ALIGNED__
-# define V8_ALIGNAS(n) __attribute__((__aligned__(n)))
+# define V8_ALIGNED(n) alignas(n)
+#elif V8_HAS_ATTRIBUTE_ALIGNED
+# define V8_ALIGNED(n) __attribute__((aligned(n)))
#elif V8_HAS_DECLSPEC_ALIGN
-# define V8_ALIGNAS(n) __declspec(align(n))
+# define V8_ALIGNED(n) __declspec(align(n))
+#else
+# define V8_ALIGNED(n) /* NOT SUPPORTED */
+#endif
+
+
+// This macro is similar to V8_ALIGNED(), but takes a type instead of size
+// in bytes. If the compiler does not supports using the alignment of the
+// |type|, it will align according to the |alignment| instead. For example,
+// Visual Studio C++ cannot combine __declspec(align) and __alignof. The
+// |alignment| must be a literal that is used as a kind of worst-case fallback
+// alignment.
+// Use like:
+// struct V8_ALIGNAS(AnotherClass, 16) NewClass { ... };
+// V8_ALIGNAS(double, 8) int array[100];
+#if V8_HAS_CXX11_ALIGNAS
+# define V8_ALIGNAS(type, alignment) alignas(type)
+#elif V8_HAS___ALIGNOF__ && V8_HAS_ATTRIBUTE_ALIGNED
+# define V8_ALIGNAS(type, alignment) __attribute__((aligned(__alignof__(type))))
+#else
+# define V8_ALIGNAS(type, alignment) V8_ALIGNED(alignment)
+#endif
+
+
+// This macro returns alignment in bytes (an integer power of two) required for
+// any instance of the given type, which is either complete type, an array type,
+// or a reference type.
+// Use like:
+// size_t alignment = V8_ALIGNOF(double);
+#if V8_HAS_CXX11_ALIGNOF
+# define V8_ALIGNOF(type) alignof(type)
+#elif V8_HAS___ALIGNOF
+# define V8_ALIGNOF(type) __alignof(type)
+#elif V8_HAS___ALIGNOF__
+# define V8_ALIGNOF(type) __alignof__(type)
#else
-# define V8_ALIGNAS(n) /* NOT SUPPORTED */
+// Note that alignment of a type within a struct can be less than the
+// alignment of the type stand-alone (because of ancient ABIs), so this
+// should only be used as a last resort.
+namespace v8 { template <typename T> class AlignOfHelper { char c; T t; }; }
+# define V8_ALIGNOF(type) (sizeof(::v8::AlignOfHelper<type>) - sizeof(type))
#endif
#endif // V8CONFIG_H_
#ifndef V8_LAZY_INSTANCE_H_
#define V8_LAZY_INSTANCE_H_
+#include "checks.h"
#include "once.h"
namespace v8 {
namespace internal {
-#define LAZY_STATIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, {} }
+#define LAZY_STATIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, { {} } }
#define LAZY_DYNAMIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, 0 }
// Default to static mode.
// Traits that define how an instance is allocated and accessed.
-// TODO(kalmard): __alignof__ is only defined for GCC > 4.2. Fix alignment issue
-// on MIPS with other compilers.
-#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2))
-#define LAZY_ALIGN(x) __attribute__((aligned(__alignof__(x))))
-#else
-#define LAZY_ALIGN(x)
-#endif
template <typename T>
struct StaticallyAllocatedInstanceTrait {
- typedef char StorageType[sizeof(T)] LAZY_ALIGN(T);
+ // 16-byte alignment fallback to be on the safe side here.
+ struct V8_ALIGNAS(T, 16) StorageType {
+ char x[sizeof(T)];
+ };
+
+ STATIC_ASSERT(V8_ALIGNOF(StorageType) >= V8_ALIGNOF(T));
static T* MutableInstance(StorageType* storage) {
return reinterpret_cast<T*>(storage);
}
};
-#undef LAZY_ALIGN
-
template <typename T>
struct DynamicallyAllocatedInstanceTrait {