1 //===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_SUPPORT_TYPE_TRAITS_H
18 #define LLVM_SUPPORT_TYPE_TRAITS_H
20 #include "llvm/Support/DataTypes.h"
25 #define LLVM_DEFINED_HAS_FEATURE
26 #define __has_feature(x) 0
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.
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(...);
54 // is_class<> metafunction due to Paul Mensonides (leavings@attbi.com). For
56 // http://groups.google.com/groups?hl=en&selm=000001c1cc83%24e154d5e0%247772e50c%40c161550a&rnum=1
58 enum { value = sizeof(char) == sizeof(dont_use::is_class_helper<T>(0)) };
62 /// isPodLike - This is a type trait that is used to determine whether a given
63 /// type can be copied around with memcpy instead of running ctors etc.
66 #if __has_feature(is_trivially_copyable)
67 // If the compiler supports the is_trivially_copyable trait use it, as it
68 // matches the definition of isPodLike closely.
69 static const bool value = __is_trivially_copyable(T);
71 // If we don't know anything else, we can (at least) assume that all non-class
73 static const bool value = !is_class<T>::value;
77 // std::pair's are pod-like if their elements are.
78 template<typename T, typename U>
79 struct isPodLike<std::pair<T, U> > {
80 static const bool value = isPodLike<T>::value && isPodLike<U>::value;
84 template <class T, T v>
85 struct integral_constant {
87 static const value_type value = v;
88 typedef integral_constant<T,v> type;
89 operator value_type() { return value; }
92 typedef integral_constant<bool, true> true_type;
93 typedef integral_constant<bool, false> false_type;
95 /// \brief Metafunction that determines whether the two given types are
97 template<typename T, typename U> struct is_same : public false_type {};
98 template<typename T> struct is_same<T, T> : public true_type {};
100 /// \brief Metafunction that removes const qualification from a type.
101 template <typename T> struct remove_const { typedef T type; };
102 template <typename T> struct remove_const<const T> { typedef T type; };
104 /// \brief Metafunction that removes volatile qualification from a type.
105 template <typename T> struct remove_volatile { typedef T type; };
106 template <typename T> struct remove_volatile<volatile T> { typedef T type; };
108 /// \brief Metafunction that removes both const and volatile qualification from
110 template <typename T> struct remove_cv {
111 typedef typename remove_const<typename remove_volatile<T>::type>::type type;
114 /// \brief Helper to implement is_integral metafunction.
115 template <typename T> struct is_integral_impl : false_type {};
116 template <> struct is_integral_impl< bool> : true_type {};
117 template <> struct is_integral_impl< char> : true_type {};
118 template <> struct is_integral_impl< signed char> : true_type {};
119 template <> struct is_integral_impl<unsigned char> : true_type {};
120 template <> struct is_integral_impl< wchar_t> : true_type {};
121 template <> struct is_integral_impl< short> : true_type {};
122 template <> struct is_integral_impl<unsigned short> : true_type {};
123 template <> struct is_integral_impl< int> : true_type {};
124 template <> struct is_integral_impl<unsigned int> : true_type {};
125 template <> struct is_integral_impl< long> : true_type {};
126 template <> struct is_integral_impl<unsigned long> : true_type {};
127 template <> struct is_integral_impl< long long> : true_type {};
128 template <> struct is_integral_impl<unsigned long long> : true_type {};
130 /// \brief Metafunction that determines whether the given type is an integral
132 template <typename T>
133 struct is_integral : is_integral_impl<T> {};
135 /// \brief Metafunction to remove reference from a type.
136 template <typename T> struct remove_reference { typedef T type; };
137 template <typename T> struct remove_reference<T&> { typedef T type; };
139 /// \brief Metafunction that determines whether the given type is a pointer
141 template <typename T> struct is_pointer : false_type {};
142 template <typename T> struct is_pointer<T*> : true_type {};
143 template <typename T> struct is_pointer<T* const> : true_type {};
144 template <typename T> struct is_pointer<T* volatile> : true_type {};
145 template <typename T> struct is_pointer<T* const volatile> : true_type {};
147 /// \brief Metafunction that determines whether the given type is either an
148 /// integral type or an enumeration type.
150 /// Note that this accepts potentially more integral types than we whitelist
151 /// above for is_integral because it is based on merely being convertible
152 /// implicitly to an integral type.
153 template <typename T> class is_integral_or_enum {
154 // Provide an overload which can be called with anything implicitly
155 // convertible to an unsigned long long. This should catch integer types and
156 // enumeration types at least. We blacklist classes with conversion operators
158 static double check_int_convertible(unsigned long long);
159 static char check_int_convertible(...);
161 typedef typename remove_reference<T>::type UnderlyingT;
162 static UnderlyingT &nonce_instance;
166 value = (!is_class<UnderlyingT>::value && !is_pointer<UnderlyingT>::value &&
167 !is_same<UnderlyingT, float>::value &&
168 !is_same<UnderlyingT, double>::value &&
169 sizeof(char) != sizeof(check_int_convertible(nonce_instance)))
173 // enable_if_c - Enable/disable a template based on a metafunction
174 template<bool Cond, typename T = void>
179 template<typename T> struct enable_if_c<false, T> { };
181 // enable_if - Enable/disable a template based on a metafunction
182 template<typename Cond, typename T = void>
183 struct enable_if : public enable_if_c<Cond::value, T> { };
186 template<typename Base> char base_of_helper(const volatile Base*);
187 template<typename Base> double base_of_helper(...);
190 /// is_base_of - Metafunction to determine whether one type is a base class of
191 /// (or identical to) another type.
192 template<typename Base, typename Derived>
194 static const bool value
195 = is_class<Base>::value && is_class<Derived>::value &&
196 sizeof(char) == sizeof(dont_use::base_of_helper<Base>((Derived*)0));
199 // remove_pointer - Metafunction to turn Foo* into Foo. Defined in
200 // C++0x [meta.trans.ptr].
201 template <typename T> struct remove_pointer { typedef T type; };
202 template <typename T> struct remove_pointer<T*> { typedef T type; };
203 template <typename T> struct remove_pointer<T*const> { typedef T type; };
204 template <typename T> struct remove_pointer<T*volatile> { typedef T type; };
205 template <typename T> struct remove_pointer<T*const volatile> {
208 template <bool, typename T, typename F>
209 struct conditional { typedef T type; };
211 template <typename T, typename F>
212 struct conditional<false, T, F> { typedef F type; };
216 #ifdef LLVM_DEFINED_HAS_FEATURE