llvm-project/libcxx/include/__config

// -*- C++ -*-
//===--------------------------- __config ---------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_CONFIG
#define _LIBCPP_CONFIG

#if !defined(_MSC_VER) || defined(__clang__)
#pragma GCC system_header
#endif

#ifdef __GNUC__
#define _GNUC_VER (__GNUC__ * 100 + __GNUC_MINOR__)
#endif

#define _LIBCPP_VERSION 1101

#define _LIBCPP_ABI_VERSION 1

#define _LIBCPP_CONCAT1(_LIBCPP_X,_LIBCPP_Y) _LIBCPP_X##_LIBCPP_Y
#define _LIBCPP_CONCAT(_LIBCPP_X,_LIBCPP_Y) _LIBCPP_CONCAT1(_LIBCPP_X,_LIBCPP_Y)

#define _LIBCPP_NAMESPACE _LIBCPP_CONCAT(__,_LIBCPP_ABI_VERSION)

#ifdef __LITTLE_ENDIAN__
#if __LITTLE_ENDIAN__
#define _LIBCPP_LITTLE_ENDIAN 1
#define _LIBCPP_BIG_ENDIAN    0
#endif  // __LITTLE_ENDIAN__
#endif  // __LITTLE_ENDIAN__

#ifdef __BIG_ENDIAN__
#if __BIG_ENDIAN__
#define _LIBCPP_LITTLE_ENDIAN 0
#define _LIBCPP_BIG_ENDIAN    1
#endif  // __BIG_ENDIAN__
#endif  // __BIG_ENDIAN__

#ifdef __FreeBSD__
# include <sys/endian.h>
#  if _BYTE_ORDER == _LITTLE_ENDIAN
#   define _LIBCPP_LITTLE_ENDIAN 1
#   define _LIBCPP_BIG_ENDIAN    0
# else  // _BYTE_ORDER == _LITTLE_ENDIAN
#   define _LIBCPP_LITTLE_ENDIAN 0
#   define _LIBCPP_BIG_ENDIAN    1
# endif  // _BYTE_ORDER == _LITTLE_ENDIAN
# ifndef __LONG_LONG_SUPPORTED
#  define _LIBCPP_HAS_NO_LONG_LONG
# endif  // __LONG_LONG_SUPPORTED
#endif  // __FreeBSD__

#ifdef __NetBSD__
# include <sys/endian.h>
#  if _BYTE_ORDER == _LITTLE_ENDIAN
#   define _LIBCPP_LITTLE_ENDIAN 1
#   define _LIBCPP_BIG_ENDIAN    0
# else  // _BYTE_ORDER == _LITTLE_ENDIAN
#   define _LIBCPP_LITTLE_ENDIAN 0
#   define _LIBCPP_BIG_ENDIAN    1
# endif  // _BYTE_ORDER == _LITTLE_ENDIAN
# define _LIBCPP_HAS_QUICK_EXIT
#endif  // __NetBSD__

#ifdef _WIN32
#  define _LIBCPP_LITTLE_ENDIAN 1
#  define _LIBCPP_BIG_ENDIAN    0
// Compiler intrinsics (GCC or MSVC)
#  if defined(__clang__) \
   || (defined(_MSC_VER) && _MSC_VER >= 1400) \
   || (defined(__GNUC__) && _GNUC_VER > 403)
#    define _LIBCPP_HAS_IS_BASE_OF
#  endif
#  if defined(_MSC_VER) && !defined(__clang__)
#    define _LIBCPP_MSVC // Using Microsoft Visual C++ compiler
#    define _LIBCPP_TOSTRING2(x) #x
#    define _LIBCPP_TOSTRING(x) _LIBCPP_TOSTRING2(x)
#    define _LIBCPP_WARNING(x) __pragma(message(__FILE__ "(" _LIBCPP_TOSTRING(__LINE__) ") : warning note: " x))
#  endif
#  // If mingw not explicitly detected, assume using MS C runtime only.
#  ifndef __MINGW32__
#    define _LIBCPP_MSVCRT // Using Microsoft's C Runtime library
#  endif
#endif  // _WIN32

#ifdef __linux__
#  if defined(__GNUC__) && _GNUC_VER >= 403
#    define _LIBCPP_HAS_IS_BASE_OF
#  endif
#endif

#ifdef __sun__
# include <sys/isa_defs.h>
# ifdef _LITTLE_ENDIAN
#   define _LIBCPP_LITTLE_ENDIAN 1
#   define _LIBCPP_BIG_ENDIAN    0
# else
#   define _LIBCPP_LITTLE_ENDIAN 0
#   define _LIBCPP_BIG_ENDIAN    1
# endif
#endif // __sun__

#if !defined(_LIBCPP_LITTLE_ENDIAN) || !defined(_LIBCPP_BIG_ENDIAN)
# include <endian.h>
# if __BYTE_ORDER == __LITTLE_ENDIAN
#  define _LIBCPP_LITTLE_ENDIAN 1
#  define _LIBCPP_BIG_ENDIAN    0
# elif __BYTE_ORDER == __BIG_ENDIAN
#  define _LIBCPP_LITTLE_ENDIAN 0
#  define _LIBCPP_BIG_ENDIAN    1
# else  // __BYTE_ORDER == __BIG_ENDIAN
#  error unable to determine endian
# endif
#endif  // !defined(_LIBCPP_LITTLE_ENDIAN) || !defined(_LIBCPP_BIG_ENDIAN)

#ifdef _WIN32

// only really useful for a DLL
#ifdef _LIBCPP_DLL // this should be a compiler builtin define ideally...
# ifdef cxx_EXPORTS
#  define _LIBCPP_HIDDEN
#  define _LIBCPP_FUNC_VIS __declspec(dllexport)
#  define _LIBCPP_TYPE_VIS __declspec(dllexport)
# else
#  define _LIBCPP_HIDDEN
#  define _LIBCPP_FUNC_VIS __declspec(dllimport)
#  define _LIBCPP_TYPE_VIS __declspec(dllimport)
# endif
#else
# define _LIBCPP_HIDDEN
# define _LIBCPP_FUNC_VIS
# define _LIBCPP_TYPE_VIS
#endif

#define _LIBCPP_TYPE_VIS_ONLY
#define _LIBCPP_FUNC_VIS_ONLY

#ifndef _LIBCPP_INLINE_VISIBILITY
# ifdef _LIBCPP_MSVC
#  define _LIBCPP_INLINE_VISIBILITY __forceinline
# else // MinGW GCC and Clang
#  define _LIBCPP_INLINE_VISIBILITY __attribute__ ((__always_inline__))
# endif
#endif

#ifndef _LIBCPP_EXCEPTION_ABI
#define _LIBCPP_EXCEPTION_ABI _LIBCPP_TYPE_VIS
#endif

#ifndef _LIBCPP_ALWAYS_INLINE
# ifdef _LIBCPP_MSVC
#  define _LIBCPP_ALWAYS_INLINE __forceinline
# endif
#endif

#endif // _WIN32

#ifndef __has_attribute
#define __has_attribute(__x) 0
#endif

#ifndef _LIBCPP_HIDDEN
#define _LIBCPP_HIDDEN __attribute__ ((__visibility__("hidden")))
#endif

#ifndef _LIBCPP_FUNC_VIS
#define _LIBCPP_FUNC_VIS __attribute__ ((__visibility__("default")))
#endif

#ifndef _LIBCPP_TYPE_VIS
#  if __has_attribute(__type_visibility__)
#    define _LIBCPP_TYPE_VIS __attribute__ ((__type_visibility__("default")))
#  else
#    define _LIBCPP_TYPE_VIS __attribute__ ((__visibility__("default")))
#  endif
#endif

#ifndef _LIBCPP_TYPE_VIS_ONLY
# define _LIBCPP_TYPE_VIS_ONLY _LIBCPP_TYPE_VIS
#endif

#ifndef _LIBCPP_FUNC_VIS_ONLY
# define _LIBCPP_FUNC_VIS_ONLY _LIBCPP_FUNC_VIS
#endif

#ifndef _LIBCPP_INLINE_VISIBILITY
#define _LIBCPP_INLINE_VISIBILITY __attribute__ ((__visibility__("hidden"), __always_inline__))
#endif

#ifndef _LIBCPP_EXCEPTION_ABI
#define _LIBCPP_EXCEPTION_ABI __attribute__ ((__visibility__("default")))
#endif

#ifndef _LIBCPP_ALWAYS_INLINE
#define _LIBCPP_ALWAYS_INLINE  __attribute__ ((__visibility__("hidden"), __always_inline__))
#endif

#if defined(__clang__)

#if __APPLE__ && !defined(__i386__) && !defined(__x86_64__) && !defined(__arm__)
#define _LIBCPP_ALTERNATE_STRING_LAYOUT
#endif

#if __has_feature(cxx_alignas)
#  define _ALIGNAS_TYPE(x) alignas(x)
#  define _ALIGNAS(x) alignas(x)
#else
#  define _ALIGNAS_TYPE(x) __attribute__((__aligned__(__alignof(x))))
#  define _ALIGNAS(x) __attribute__((__aligned__(x)))
#endif

#if !__has_feature(cxx_alias_templates)
#define _LIBCPP_HAS_NO_TEMPLATE_ALIASES
#endif

#if __cplusplus < 201103L
#ifdef __linux__
#define _LIBCPP_HAS_NO_UNICODE_CHARS
#else
typedef __char16_t char16_t;
typedef __char32_t char32_t;
#endif
#endif

#if !(__has_feature(cxx_exceptions))
#define _LIBCPP_NO_EXCEPTIONS
#endif

#if !(__has_feature(cxx_rtti))
#define _LIBCPP_NO_RTTI
#endif

#if !(__has_feature(cxx_strong_enums))
#define _LIBCPP_HAS_NO_STRONG_ENUMS
#endif

#if !(__has_feature(cxx_decltype))
#define _LIBCPP_HAS_NO_DECLTYPE
#endif

#if __has_feature(cxx_attributes)
#  define _LIBCPP_NORETURN [[noreturn]]
#else
#  define _LIBCPP_NORETURN __attribute__ ((noreturn))
#endif

#if !(__has_feature(cxx_defaulted_functions))
#define _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
#endif  // !(__has_feature(cxx_defaulted_functions))

#if !(__has_feature(cxx_deleted_functions))
#define _LIBCPP_HAS_NO_DELETED_FUNCTIONS
#endif  // !(__has_feature(cxx_deleted_functions))

#if !(__has_feature(cxx_lambdas))
#define _LIBCPP_HAS_NO_LAMBDAS
#endif

#if !(__has_feature(cxx_nullptr))
#define _LIBCPP_HAS_NO_NULLPTR
#endif

#if !(__has_feature(cxx_rvalue_references))
#define _LIBCPP_HAS_NO_RVALUE_REFERENCES
#endif

#if !(__has_feature(cxx_static_assert))
#define _LIBCPP_HAS_NO_STATIC_ASSERT
#endif

#if !(__has_feature(cxx_auto_type))
#define _LIBCPP_HAS_NO_AUTO_TYPE
#endif

#if !(__has_feature(cxx_access_control_sfinae)) || !__has_feature(cxx_trailing_return)
#define _LIBCPP_HAS_NO_ADVANCED_SFINAE
#endif

#if !(__has_feature(cxx_variadic_templates))
#define _LIBCPP_HAS_NO_VARIADICS
#endif

#if !(__has_feature(cxx_trailing_return))
#define _LIBCPP_HAS_NO_TRAILING_RETURN
#endif

#if !(__has_feature(cxx_generalized_initializers))
#define _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
#endif

#if __has_feature(is_base_of)
#  define _LIBCPP_HAS_IS_BASE_OF
#endif

// Objective-C++ features (opt-in)
#if __has_feature(objc_arc)
#define _LIBCPP_HAS_OBJC_ARC
#endif

#if __has_feature(objc_arc_weak)
#define _LIBCPP_HAS_OBJC_ARC_WEAK
#define _LIBCPP_HAS_NO_STRONG_ENUMS
#endif

#if !(__has_feature(cxx_constexpr))
#define _LIBCPP_HAS_NO_CONSTEXPR
#endif

#if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L
#if defined(__FreeBSD__)
#define _LIBCPP_HAS_QUICK_EXIT
#define _LIBCPP_HAS_C11_FEATURES
#elif defined(__linux__)
#include <features.h>
#if __GLIBC_PREREQ(2, 15)
#define _LIBCPP_HAS_QUICK_EXIT
#endif
#if __GLIBC_PREREQ(2, 17)
#define _LIBCPP_HAS_C11_FEATURES
#endif
#endif
#endif

#if (__has_feature(cxx_noexcept))
#  define _NOEXCEPT noexcept
#  define _NOEXCEPT_(x) noexcept(x)
#  define _NOEXCEPT_OR_FALSE(x) noexcept(x)
#else
#  define _NOEXCEPT throw()
#  define _NOEXCEPT_(x)
#  define _NOEXCEPT_OR_FALSE(x) false
#endif

#if __has_feature(underlying_type)
#  define _LIBCXX_UNDERLYING_TYPE(T) __underlying_type(T)
#endif

// Inline namespaces are available in Clang regardless of C++ dialect.
#define _LIBCPP_BEGIN_NAMESPACE_STD namespace std {inline namespace _LIBCPP_NAMESPACE {
#define _LIBCPP_END_NAMESPACE_STD  } }
#define _VSTD std::_LIBCPP_NAMESPACE

namespace std {
  inline namespace _LIBCPP_NAMESPACE {
  }
}

#elif defined(__GNUC__)

#define _ALIGNAS(x) __attribute__((__aligned__(x)))
#define _ALIGNAS_TYPE(x) __attribute__((__aligned__(__alignof(x))))

#define _LIBCPP_NORETURN __attribute__((noreturn))

#if !__EXCEPTIONS
#define _LIBCPP_NO_EXCEPTIONS
#endif

#define _LIBCPP_HAS_NO_TEMPLATE_ALIASES
#define _LIBCPP_HAS_NO_CONSTEXPR

#define _NOEXCEPT throw()
#define _NOEXCEPT_(x)
#define _NOEXCEPT_OR_FALSE(x) false

#ifndef __GXX_EXPERIMENTAL_CXX0X__

#define _LIBCPP_HAS_NO_ADVANCED_SFINAE
#define _LIBCPP_HAS_NO_DECLTYPE
#define _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
#define _LIBCPP_HAS_NO_DELETED_FUNCTIONS
#define _LIBCPP_HAS_NO_NULLPTR
#define _LIBCPP_HAS_NO_STATIC_ASSERT
#define _LIBCPP_HAS_NO_UNICODE_CHARS
#define _LIBCPP_HAS_NO_VARIADICS
#define _LIBCPP_HAS_NO_RVALUE_REFERENCES
#define _LIBCPP_HAS_NO_ALWAYS_INLINE_VARIADICS
#define _LIBCPP_HAS_NO_STRONG_ENUMS

#else  // __GXX_EXPERIMENTAL_CXX0X__

#define _LIBCPP_HAS_NO_TRAILING_RETURN
#define _LIBCPP_HAS_NO_ALWAYS_INLINE_VARIADICS

#if _GNUC_VER < 403
#define _LIBCPP_HAS_NO_RVALUE_REFERENCES
#endif

#if _GNUC_VER < 403
#define _LIBCPP_HAS_NO_STATIC_ASSERT
#endif

#if _GNUC_VER < 404
#define _LIBCPP_HAS_NO_DECLTYPE
#define _LIBCPP_HAS_NO_DELETED_FUNCTIONS
#define _LIBCPP_HAS_NO_UNICODE_CHARS
#define _LIBCPP_HAS_NO_VARIADICS
#define _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
#endif  // _GNUC_VER < 404

#if _GNUC_VER < 406
#define _LIBCPP_HAS_NO_NULLPTR
#endif

#if _GNUC_VER < 407
#define _LIBCPP_HAS_NO_ADVANCED_SFINAE
#define _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
#endif

#endif  // __GXX_EXPERIMENTAL_CXX0X__

#define _LIBCPP_BEGIN_NAMESPACE_STD namespace std { namespace _LIBCPP_NAMESPACE {
#define _LIBCPP_END_NAMESPACE_STD  } }
#define _VSTD std::_LIBCPP_NAMESPACE

namespace std {
namespace _LIBCPP_NAMESPACE {
}
using namespace _LIBCPP_NAMESPACE __attribute__((__strong__));
}

#elif defined(_LIBCPP_MSVC)

#define _LIBCPP_HAS_NO_TEMPLATE_ALIASES
#define _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
#define _LIBCPP_HAS_NO_CONSTEXPR
#define _LIBCPP_HAS_NO_UNICODE_CHARS
#define _LIBCPP_HAS_NO_DELETED_FUNCTIONS
#define _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
#define __alignof__ __alignof
#define _LIBCPP_NORETURN __declspec(noreturn)
#define _ALIGNAS(x) __declspec(align(x))
#define _LIBCPP_HAS_NO_VARIADICS

#define _NOEXCEPT throw ()
#define _NOEXCEPT_(x)
#define _NOEXCEPT_OR_FALSE(x) false

#define _LIBCPP_BEGIN_NAMESPACE_STD namespace std {
#define _LIBCPP_END_NAMESPACE_STD  }
#define _VSTD std

#  define _LIBCPP_WEAK
namespace std {
}

#elif defined(__IBMCPP__)

#define _ALIGNAS(x) __attribute__((__aligned__(x)))
#define _ALIGNAS_TYPE(x) __attribute__((__aligned__(__alignof(x))))
#define _ATTRIBUTE(x) __attribute__((x))
#define _LIBCPP_NORETURN __attribute__((noreturn))

#define _NOEXCEPT throw()
#define _NOEXCEPT_(x)
#define _NOEXCEPT_OR_FALSE(x) false

#define _LIBCPP_HAS_NO_TEMPLATE_ALIASES
#define _LIBCPP_HAS_NO_ADVANCED_SFINAE
#define _LIBCPP_HAS_NO_ALWAYS_INLINE_VARIADICS
#define _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
#define _LIBCPP_HAS_NO_NULLPTR
#define _LIBCPP_HAS_NO_UNICODE_CHARS
#define _LIBCPP_HAS_IS_BASE_OF

#if defined(_AIX)
#define __MULTILOCALE_API
#endif

#define _LIBCPP_BEGIN_NAMESPACE_STD namespace std {inline namespace _LIBCPP_NAMESPACE {
#define _LIBCPP_END_NAMESPACE_STD  } }
#define _VSTD std::_LIBCPP_NAMESPACE

namespace std {
  inline namespace _LIBCPP_NAMESPACE {
  }
}

#endif // __clang__ || __GNUC__ || _MSC_VER || __IBMCPP__

#ifdef _LIBCPP_HAS_NO_UNICODE_CHARS
typedef unsigned short char16_t;
typedef unsigned int   char32_t;
#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS

#ifndef __SIZEOF_INT128__
#define _LIBCPP_HAS_NO_INT128
#endif

#ifdef _LIBCPP_HAS_NO_STATIC_ASSERT

template <bool> struct __static_assert_test;
template <> struct __static_assert_test<true> {};
template <unsigned> struct __static_assert_check {};
#define static_assert(__b, __m) \
    typedef __static_assert_check<sizeof(__static_assert_test<(__b)>)> \
    _LIBCPP_CONCAT(__t, __LINE__)

#endif  // _LIBCPP_HAS_NO_STATIC_ASSERT

#ifdef _LIBCPP_HAS_NO_DECLTYPE
#define decltype(x) __typeof__(x)
#endif

#ifdef _LIBCPP_HAS_NO_CONSTEXPR
#define _LIBCPP_CONSTEXPR
#else
#define _LIBCPP_CONSTEXPR constexpr
#endif

#ifdef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
#define _LIBCPP_DEFAULT {}
#else
#define _LIBCPP_DEFAULT = default;
#endif

#ifdef __GNUC__
#define _NOALIAS __attribute__((__malloc__))
#else
#define _NOALIAS
#endif

#ifndef __has_feature
#define __has_feature(__x) 0
#endif

#if __has_feature(cxx_explicit_conversions) || defined(__IBMCPP__)
#   define _LIBCPP_EXPLICIT explicit
#else
#   define _LIBCPP_EXPLICIT
#endif

#ifdef _LIBCPP_HAS_NO_STRONG_ENUMS
#define _LIBCPP_DECLARE_STRONG_ENUM(x) struct _LIBCPP_TYPE_VIS x { enum __lx
#define _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(x) \
    __lx __v_; \
    _LIBCPP_ALWAYS_INLINE x(__lx __v) : __v_(__v) {} \
    _LIBCPP_ALWAYS_INLINE explicit x(int __v) : __v_(static_cast<__lx>(__v)) {} \
    _LIBCPP_ALWAYS_INLINE operator int() const {return __v_;} \
    };
#else  // _LIBCPP_HAS_NO_STRONG_ENUMS
#define _LIBCPP_DECLARE_STRONG_ENUM(x) enum class _LIBCPP_TYPE_VIS x
#define _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(x)
#endif  // _LIBCPP_HAS_NO_STRONG_ENUMS

#ifdef _LIBCPP_DEBUG
#   if _LIBCPP_DEBUG == 0
#       define _LIBCPP_DEBUG_LEVEL 1
#   elif _LIBCPP_DEBUG == 1
#       define _LIBCPP_DEBUG_LEVEL 2
#   else
#       error Supported values for _LIBCPP_DEBUG are 0 and 1
#   endif
#   define _LIBCPP_EXTERN_TEMPLATE(...)
#endif

#ifndef _LIBCPP_EXTERN_TEMPLATE
#define _LIBCPP_EXTERN_TEMPLATE(...)
#endif

#ifndef _LIBCPP_EXTERN_TEMPLATE2
#define _LIBCPP_EXTERN_TEMPLATE2(...) extern template __VA_ARGS__;
#endif

#if __APPLE__ && defined(__LP64__) && !defined(__x86_64__)
#define _LIBCPP_NONUNIQUE_RTTI_BIT (1ULL << 63)
#endif

#if defined(__APPLE__) || defined(__FreeBSD__) || defined(_WIN32) || defined(__sun__) || defined(__NetBSD__)
#define _LIBCPP_LOCALE__L_EXTENSIONS 1
#endif

#ifdef __FreeBSD__
#define _DECLARE_C99_LDBL_MATH 1
#endif

#if defined(__APPLE__) || defined(__FreeBSD__)
#define _LIBCPP_HAS_DEFAULTRUNELOCALE
#endif

#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__sun__)
#define _LIBCPP_WCTYPE_IS_MASK
#endif

#ifndef _LIBCPP_TRIVIAL_PAIR_COPY_CTOR
#  define _LIBCPP_TRIVIAL_PAIR_COPY_CTOR 1
#endif

#ifndef _LIBCPP_STD_VER
#  if  __cplusplus <= 201103L
#    define _LIBCPP_STD_VER 11
#  else
#    define _LIBCPP_STD_VER 13  // current year, or date of c++14 ratification
#  endif
#endif  // _LIBCPP_STD_VER

#if _LIBCPP_STD_VER > 11
#define _LIBCPP_DEPRECATED [[deprecated]]
#else
#define _LIBCPP_DEPRECATED
#endif

#if _LIBCPP_STD_VER <= 11
#define _LIBCPP_CONSTEXPR_AFTER_CXX11
#define _LIBCPP_EXPLICIT_AFTER_CXX11
#define _LIBCPP_DEPRECATED_AFTER_CXX11
#else
#define _LIBCPP_CONSTEXPR_AFTER_CXX11 constexpr
#define _LIBCPP_EXPLICIT_AFTER_CXX11 explicit
#define _LIBCPP_DEPRECATED_AFTER_CXX11 [[deprecated]]
#endif

// Try to find out if RTTI is disabled.
// g++ and cl.exe have RTTI on by default and define a macro when it is.
// g++ only defines the macro in 4.3.2 and onwards.
#if !defined(_LIBCPP_NO_RTTI)
#  if defined(__GNUG__) && (__GNUC__ >= 4 && \
   (__GNUC_MINOR__ >= 3 || __GNUC_PATCHLEVEL__ >= 2)) && !defined(__GXX_RTTI)
#    define _LIBCPP_NO_RTTI
#  elif (defined(_MSC_VER) && !defined(__clang__)) && !defined(_CPPRTTI)
#    define _LIBCPP_NO_RTTI
#  endif
#endif

#ifndef _LIBCPP_WEAK
#  define _LIBCPP_WEAK __attribute__((__weak__))
#endif

#endif  // _LIBCPP_CONFIG