1//===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file provides a template class that determines if a type is a class or 11// not. The basic mechanism, based on using the pointer to member function of 12// a zero argument to a function was "boosted" from the boost type_traits 13// library. See http://www.boost.org/ for all the gory details. 14// 15//===----------------------------------------------------------------------===// 16 17#ifndef LLVM_SUPPORT_TYPE_TRAITS_H 18#define LLVM_SUPPORT_TYPE_TRAITS_H 19 20#include "llvm/Support/DataTypes.h" 21#include <cstddef> 22#include <utility> 23 24#ifndef __has_feature 25#define LLVM_DEFINED_HAS_FEATURE 26#define __has_feature(x) 0 27#endif 28 29// This is actually the conforming implementation which works with abstract 30// classes. However, enough compilers have trouble with it that most will use 31// the one in boost/type_traits/object_traits.hpp. This implementation actually 32// works with VC7.0, but other interactions seem to fail when we use it. 33 34namespace llvm { 35 36namespace dont_use 37{ 38 // These two functions should never be used. They are helpers to 39 // the is_class template below. They cannot be located inside 40 // is_class because doing so causes at least GCC to think that 41 // the value of the "value" enumerator is not constant. Placing 42 // them out here (for some strange reason) allows the sizeof 43 // operator against them to magically be constant. This is 44 // important to make the is_class<T>::value idiom zero cost. it 45 // evaluates to a constant 1 or 0 depending on whether the 46 // parameter T is a class or not (respectively). 47 template<typename T> char is_class_helper(void(T::*)()); 48 template<typename T> double is_class_helper(...); 49} 50 51template <typename T> 52struct is_class 53{ 54 // is_class<> metafunction due to Paul Mensonides (leavings@attbi.com). For 55 // more details: 56 // http://groups.google.com/groups?hl=en&selm=000001c1cc83%24e154d5e0%247772e50c%40c161550a&rnum=1 57public: 58 static const bool value = 59 sizeof(char) == sizeof(dont_use::is_class_helper<T>(0)); 60}; 61 62 63/// isPodLike - This is a type trait that is used to determine whether a given 64/// type can be copied around with memcpy instead of running ctors etc. 65template <typename T> 66struct isPodLike { 67#if __has_feature(is_trivially_copyable) 68 // If the compiler supports the is_trivially_copyable trait use it, as it 69 // matches the definition of isPodLike closely. 70 static const bool value = __is_trivially_copyable(T); 71#else 72 // If we don't know anything else, we can (at least) assume that all non-class 73 // types are PODs. 74 static const bool value = !is_class<T>::value; 75#endif 76}; 77 78// std::pair's are pod-like if their elements are. 79template<typename T, typename U> 80struct isPodLike<std::pair<T, U> > { 81 static const bool value = isPodLike<T>::value && isPodLike<U>::value; 82}; 83 84 85template <class T, T v> 86struct integral_constant { 87 typedef T value_type; 88 static const value_type value = v; 89 typedef integral_constant<T,v> type; 90 operator value_type() { return value; } 91}; 92 93typedef integral_constant<bool, true> true_type; 94typedef integral_constant<bool, false> false_type; 95 96/// \brief Metafunction that determines whether the two given types are 97/// equivalent. 98template<typename T, typename U> struct is_same : public false_type {}; 99template<typename T> struct is_same<T, T> : public true_type {}; 100 101/// \brief Metafunction that removes const qualification from a type. 102template <typename T> struct remove_const { typedef T type; }; 103template <typename T> struct remove_const<const T> { typedef T type; }; 104 105/// \brief Metafunction that removes volatile qualification from a type. 106template <typename T> struct remove_volatile { typedef T type; }; 107template <typename T> struct remove_volatile<volatile T> { typedef T type; }; 108 109/// \brief Metafunction that removes both const and volatile qualification from 110/// a type. 111template <typename T> struct remove_cv { 112 typedef typename remove_const<typename remove_volatile<T>::type>::type type; 113}; 114 115/// \brief Helper to implement is_integral metafunction. 116template <typename T> struct is_integral_impl : false_type {}; 117template <> struct is_integral_impl< bool> : true_type {}; 118template <> struct is_integral_impl< char> : true_type {}; 119template <> struct is_integral_impl< signed char> : true_type {}; 120template <> struct is_integral_impl<unsigned char> : true_type {}; 121template <> struct is_integral_impl< wchar_t> : true_type {}; 122template <> struct is_integral_impl< short> : true_type {}; 123template <> struct is_integral_impl<unsigned short> : true_type {}; 124template <> struct is_integral_impl< int> : true_type {}; 125template <> struct is_integral_impl<unsigned int> : true_type {}; 126template <> struct is_integral_impl< long> : true_type {}; 127template <> struct is_integral_impl<unsigned long> : true_type {}; 128template <> struct is_integral_impl< long long> : true_type {}; 129template <> struct is_integral_impl<unsigned long long> : true_type {}; 130 131/// \brief Metafunction that determines whether the given type is an integral 132/// type. 133template <typename T> 134struct is_integral : is_integral_impl<T> {}; 135 136/// \brief Metafunction to remove reference from a type. 137template <typename T> struct remove_reference { typedef T type; }; 138template <typename T> struct remove_reference<T&> { typedef T type; }; 139 140/// \brief Metafunction that determines whether the given type is a pointer 141/// type. 142template <typename T> struct is_pointer : false_type {}; 143template <typename T> struct is_pointer<T*> : true_type {}; 144template <typename T> struct is_pointer<T* const> : true_type {}; 145template <typename T> struct is_pointer<T* volatile> : true_type {}; 146template <typename T> struct is_pointer<T* const volatile> : true_type {}; 147 148/// \brief Metafunction that determines wheather the given type is a reference. 149template <typename T> struct is_reference : false_type {}; 150template <typename T> struct is_reference<T&> : true_type {}; 151 152/// \brief Metafunction that determines whether the given type is either an 153/// integral type or an enumeration type. 154/// 155/// Note that this accepts potentially more integral types than we whitelist 156/// above for is_integral because it is based on merely being convertible 157/// implicitly to an integral type. 158template <typename T> class is_integral_or_enum { 159 // Provide an overload which can be called with anything implicitly 160 // convertible to an unsigned long long. This should catch integer types and 161 // enumeration types at least. We blacklist classes with conversion operators 162 // below. 163 static double check_int_convertible(unsigned long long); 164 static char check_int_convertible(...); 165 166 typedef typename remove_reference<T>::type UnderlyingT; 167 static UnderlyingT &nonce_instance; 168 169public: 170 static const bool 171 value = (!is_class<UnderlyingT>::value && !is_pointer<UnderlyingT>::value && 172 !is_same<UnderlyingT, float>::value && 173 !is_same<UnderlyingT, double>::value && 174 sizeof(char) != sizeof(check_int_convertible(nonce_instance))); 175}; 176 177// enable_if_c - Enable/disable a template based on a metafunction 178template<bool Cond, typename T = void> 179struct enable_if_c { 180 typedef T type; 181}; 182 183template<typename T> struct enable_if_c<false, T> { }; 184 185// enable_if - Enable/disable a template based on a metafunction 186template<typename Cond, typename T = void> 187struct enable_if : public enable_if_c<Cond::value, T> { }; 188 189namespace dont_use { 190 template<typename Base> char base_of_helper(const volatile Base*); 191 template<typename Base> double base_of_helper(...); 192} 193 194/// is_base_of - Metafunction to determine whether one type is a base class of 195/// (or identical to) another type. 196template<typename Base, typename Derived> 197struct is_base_of { 198 static const bool value 199 = is_class<Base>::value && is_class<Derived>::value && 200 sizeof(char) == sizeof(dont_use::base_of_helper<Base>((Derived*)0)); 201}; 202 203// remove_pointer - Metafunction to turn Foo* into Foo. Defined in 204// C++0x [meta.trans.ptr]. 205template <typename T> struct remove_pointer { typedef T type; }; 206template <typename T> struct remove_pointer<T*> { typedef T type; }; 207template <typename T> struct remove_pointer<T*const> { typedef T type; }; 208template <typename T> struct remove_pointer<T*volatile> { typedef T type; }; 209template <typename T> struct remove_pointer<T*const volatile> { 210 typedef T type; }; 211 212// If T is a pointer, just return it. If it is not, return T&. 213template<typename T, typename Enable = void> 214struct add_lvalue_reference_if_not_pointer { typedef T &type; }; 215 216template<typename T> 217struct add_lvalue_reference_if_not_pointer<T, 218 typename enable_if<is_pointer<T> >::type> { 219 typedef T type; 220}; 221 222// If T is a pointer to X, return a pointer to const X. If it is not, return 223// const T. 224template<typename T, typename Enable = void> 225struct add_const_past_pointer { typedef const T type; }; 226 227template<typename T> 228struct add_const_past_pointer<T, typename enable_if<is_pointer<T> >::type> { 229 typedef const typename remove_pointer<T>::type *type; 230}; 231 232template <bool, typename T, typename F> 233struct conditional { typedef T type; }; 234 235template <typename T, typename F> 236struct conditional<false, T, F> { typedef F type; }; 237 238} 239 240#ifdef LLVM_DEFINED_HAS_FEATURE 241#undef __has_feature 242#endif 243 244#endif 245