Move internal usages of `alignof`/`__alignof` to use `_LIBCPP_ALIGNOF`.

Summary:
Starting in Clang 8.0 and GCC 8.0, `alignof` and `__alignof` return different values in same cases. Specifically `alignof` and `_Alignof` return the minimum alignment for a type, where as `__alignof` returns the preferred alignment. libc++ currently uses `__alignof` but means to use `alignof`. See  llvm.org/PR39713

This patch introduces the macro `_LIBCPP_ALIGNOF` so we can control which spelling gets used.

This patch does not introduce any ABI guard to provide the old behavior with newer compilers. However, if we decide that is needed, this patch makes it trivial to implement.

I think we should commit this change immediately, and decide what we want to do about the ABI afterwards. 

Reviewers: ldionne, EricWF

Reviewed By: EricWF

Subscribers: christof, libcxx-commits

Differential Revision: https://reviews.llvm.org/D54814

llvm-svn: 347787

6 files changed, 45 insertions, 35 deletions

diff --git a/libcxx/include/__config b/libcxx/include/__config
index e343ad53427..d4b82dd55bb 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1281,6 +1281,16 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #define _LIBCPP_HAS_NO_COROUTINES
 #endif
 
+#ifndef _LIBCPP_CXX03_LANG
+# define _LIBCPP_ALIGNOF(_Tp) alignof(_Tp)
+#elif defined(_LIBCPP_COMPILER_CLANG)
+# define _LIBCPP_ALIGNOF(_Tp) _Alignof(_Tp)
+#else
+// This definition is potentially buggy, but it's only taken with GCC in C++03,
+// which we barely support anyway. See llvm.org/PR39713
+# define _LIBCPP_ALIGNOF(_Tp) __alignof(_Tp)
+#endif
+
 // FIXME: Correct this macro when either (A) a feature test macro for the
 // spaceship operator is provided, or (B) a compiler provides a complete
 // implementation.
diff --git a/libcxx/include/__sso_allocator b/libcxx/include/__sso_allocator
index e16b680ec55..8aca0495d75 100644
--- a/libcxx/include/__sso_allocator
+++ b/libcxx/include/__sso_allocator
@@ -55,14 +55,14 @@ public:
             __allocated_ = true;
             return (pointer)&buf_;
         }
-        return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), __alignof(_Tp)));
+        return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
     }
     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n)
     {
         if (__p == (pointer)&buf_)
             __allocated_ = false;
         else
-            _VSTD::__libcpp_deallocate(__p, __n * sizeof(_Tp), __alignof(_Tp));
+            _VSTD::__libcpp_deallocate(__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
     }
     _LIBCPP_INLINE_VISIBILITY size_type max_size() const throw() {return size_type(~0) / sizeof(_Tp);}
 
diff --git a/libcxx/include/experimental/coroutine b/libcxx/include/experimental/coroutine
index 1eb224a535a..7cb39b81b48 100644
--- a/libcxx/include/experimental/coroutine
+++ b/libcxx/include/experimental/coroutine
@@ -214,7 +214,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     _Promise& promise() const {
         return *static_cast<_Promise*>(
-            __builtin_coro_promise(this->__handle_, __alignof(_Promise), false));
+            __builtin_coro_promise(this->__handle_, _LIBCPP_ALIGNOF(_Promise), false));
     }
 
 public:
@@ -254,7 +254,7 @@ public:
         coroutine_handle __tmp;
         __tmp.__handle_ = __builtin_coro_promise(
             _VSTD::addressof(const_cast<_RawPromise&>(__promise)),
-             __alignof(_Promise), true);
+             _LIBCPP_ALIGNOF(_Promise), true);
         return __tmp;
     }
 };
@@ -272,7 +272,7 @@ public:
   _LIBCPP_INLINE_VISIBILITY
   _Promise& promise() const {
     return *static_cast<_Promise*>(
-      __builtin_coro_promise(this->__handle_, __alignof(_Promise), false));
+      __builtin_coro_promise(this->__handle_, _LIBCPP_ALIGNOF(_Promise), false));
   }
 
   _LIBCPP_CONSTEXPR explicit operator bool() const _NOEXCEPT { return true; }
diff --git a/libcxx/include/memory b/libcxx/include/memory
index 9fca9fe4181..68fc8cda86f 100644
--- a/libcxx/include/memory
+++ b/libcxx/include/memory
@@ -1797,10 +1797,10 @@ public:
         if (__n > max_size())
             __throw_length_error("allocator<T>::allocate(size_t n)"
                                  " 'n' exceeds maximum supported size");
-        return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), __alignof(_Tp)));
+        return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
         }
     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n) _NOEXCEPT
-        {_VSTD::__libcpp_deallocate((void*)__p, __n * sizeof(_Tp), __alignof(_Tp));}
+        {_VSTD::__libcpp_deallocate((void*)__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));}
     _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT
         {return size_type(~0) / sizeof(_Tp);}
 #if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
@@ -1898,10 +1898,10 @@ public:
         if (__n > max_size())
             __throw_length_error("allocator<const T>::allocate(size_t n)"
                                  " 'n' exceeds maximum supported size");
-        return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), __alignof(_Tp)));
+        return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
     }
     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n) _NOEXCEPT
-        {_VSTD::__libcpp_deallocate((void*) const_cast<_Tp *>(__p), __n * sizeof(_Tp), __alignof(_Tp));}
+        {_VSTD::__libcpp_deallocate((void*) const_cast<_Tp *>(__p), __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));}
     _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT
         {return size_type(~0) / sizeof(_Tp);}
 #if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
@@ -2017,7 +2017,7 @@ get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT
     while (__n > 0)
     {
 #if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
-    if (__is_overaligned_for_new(__alignof(_Tp)))
+    if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
         {
             std::align_val_t __al =
                 std::align_val_t(std::alignment_of<_Tp>::value);
@@ -2028,7 +2028,7 @@ get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT
                 __n * sizeof(_Tp), nothrow));
         }
 #else
-    if (__is_overaligned_for_new(__alignof(_Tp)))
+    if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
         {
             // Since aligned operator new is unavailable, return an empty
             // buffer rather than one with invalid alignment.
@@ -2052,7 +2052,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 void return_temporary_buffer(_Tp* __p) _NOEXCEPT
 {
-  _VSTD::__libcpp_deallocate_unsized((void*)__p, __alignof(_Tp));
+  _VSTD::__libcpp_deallocate_unsized((void*)__p, _LIBCPP_ALIGNOF(_Tp));
 }
 
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
diff --git a/libcxx/include/type_traits b/libcxx/include/type_traits
index aadb97ba9bf..61c9582cec6 100644
--- a/libcxx/include/type_traits
+++ b/libcxx/include/type_traits
@@ -1649,7 +1649,7 @@ _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool has_unique_object_representations_v
 // alignment_of
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS alignment_of
-    : public integral_constant<size_t, __alignof__(_Tp)> {};
+    : public integral_constant<size_t, _LIBCPP_ALIGNOF(_Tp)> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
@@ -1812,8 +1812,8 @@ struct __static_max<_I0, _I1, _In...>
 template <size_t _Len, class _Type0, class ..._Types>
 struct aligned_union
 {
-    static const size_t alignment_value = __static_max<__alignof__(_Type0),
-                                                       __alignof__(_Types)...>::value;
+    static const size_t alignment_value = __static_max<_LIBCPP_ALIGNOF(_Type0),
+                                                       _LIBCPP_ALIGNOF(_Types)...>::value;
     static const size_t __len = __static_max<_Len, sizeof(_Type0),
                                              sizeof(_Types)...>::value;
     typedef typename aligned_storage<__len, alignment_value>::type type;
diff --git a/libcxx/include/valarray b/libcxx/include/valarray
index 3188b6af49b..07f38c81150 100644
--- a/libcxx/include/valarray
+++ b/libcxx/include/valarray
@@ -2740,7 +2740,7 @@ __val_expr<_ValExpr>::operator valarray<__val_expr::result_type>() const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<result_type*>(
-                    _VSTD::__libcpp_allocate(__n * sizeof(result_type), __alignof(result_type)));
+                    _VSTD::__libcpp_allocate(__n * sizeof(result_type), _LIBCPP_ALIGNOF(result_type)));
         for (size_t __i = 0; __i != __n; ++__r.__end_, ++__i)
             ::new (__r.__end_) result_type(__expr_[__i]);
     }
@@ -2758,7 +2758,7 @@ valarray<_Tp>::valarray(size_t __n)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-            _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+            _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -2793,7 +2793,7 @@ valarray<_Tp>::valarray(const value_type* __p, size_t __n)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-            _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+            _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -2819,7 +2819,7 @@ valarray<_Tp>::valarray(const valarray& __v)
     if (__v.size())
     {
         __begin_ = __end_ = static_cast<value_type*>(
-            _VSTD::__libcpp_allocate(__v.size() * sizeof(value_type), __alignof(value_type)));
+            _VSTD::__libcpp_allocate(__v.size() * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -2857,7 +2857,7 @@ valarray<_Tp>::valarray(initializer_list<value_type> __il)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-_VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+_VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -2887,7 +2887,7 @@ valarray<_Tp>::valarray(const slice_array<value_type>& __sa)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-          _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+          _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -2915,7 +2915,7 @@ valarray<_Tp>::valarray(const gslice_array<value_type>& __ga)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -2945,7 +2945,7 @@ valarray<_Tp>::valarray(const mask_array<value_type>& __ma)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -2975,7 +2975,7 @@ valarray<_Tp>::valarray(const indirect_array<value_type>& __ia)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
@@ -3012,7 +3012,7 @@ valarray<_Tp>::__assign_range(const value_type* __f, const value_type* __l)
     {
         __clear(size());
         __begin_ = static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         __end_ = __begin_ + __n;
         _VSTD::uninitialized_copy(__f, __l, __begin_);
     } else {
@@ -3268,7 +3268,7 @@ valarray<_Tp>::operator+() const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         for (const value_type* __p = __begin_; __n; ++__r.__end_, ++__p, --__n)
             ::new (__r.__end_) value_type(+*__p);
     }
@@ -3286,7 +3286,7 @@ valarray<_Tp>::operator-() const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         for (const value_type* __p = __begin_; __n; ++__r.__end_, ++__p, --__n)
             ::new (__r.__end_) value_type(-*__p);
     }
@@ -3304,7 +3304,7 @@ valarray<_Tp>::operator~() const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         for (const value_type* __p = __begin_; __n; ++__r.__end_, ++__p, --__n)
             ::new (__r.__end_) value_type(~*__p);
     }
@@ -3321,7 +3321,7 @@ valarray<_Tp>::operator!() const
     {
         __r.__begin_ =
             __r.__end_ =
-                static_cast<bool*>(_VSTD::__libcpp_allocate(__n * sizeof(bool), __alignof(bool)));
+                static_cast<bool*>(_VSTD::__libcpp_allocate(__n * sizeof(bool), _LIBCPP_ALIGNOF(bool)));
         for (const value_type* __p = __begin_; __n; ++__r.__end_, ++__p, --__n)
             ::new (__r.__end_) bool(!*__p);
     }
@@ -3642,7 +3642,7 @@ valarray<_Tp>::shift(int __i) const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         const value_type* __sb;
         value_type* __tb;
         value_type* __te;
@@ -3681,7 +3681,7 @@ valarray<_Tp>::cshift(int __i) const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         __i %= static_cast<int>(__n);
         const value_type* __m = __i >= 0 ? __begin_ + __i : __end_ + __i;
         for (const value_type* __s = __m; __s != __end_; ++__r.__end_, ++__s)
@@ -3703,7 +3703,7 @@ valarray<_Tp>::apply(value_type __f(value_type)) const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         for (const value_type* __p = __begin_; __n; ++__r.__end_, ++__p, --__n)
             ::new (__r.__end_) value_type(__f(*__p));
     }
@@ -3721,7 +3721,7 @@ valarray<_Tp>::apply(value_type __f(const value_type&)) const
         __r.__begin_ =
             __r.__end_ =
                 static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
         for (const value_type* __p = __begin_; __n; ++__r.__end_, ++__p, --__n)
             ::new (__r.__end_) value_type(__f(*__p));
     }
@@ -3736,7 +3736,7 @@ void valarray<_Tp>::__clear(size_t __capacity)
   {
     while (__end_ != __begin_)
       (--__end_)->~value_type();
-    _VSTD::__libcpp_deallocate(__begin_, __capacity * sizeof(value_type), __alignof(value_type));
+    _VSTD::__libcpp_deallocate(__begin_, __capacity * sizeof(value_type), _LIBCPP_ALIGNOF(value_type));
     __begin_ = __end_ = nullptr;
   }
 }
@@ -3749,7 +3749,7 @@ valarray<_Tp>::resize(size_t __n, value_type __x)
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
-           _VSTD::__libcpp_allocate(__n * sizeof(value_type), __alignof(value_type)));
+           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {