LLVM API Documentation
00001 //===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file provides a template class that determines if a type is a class or 00011 // not. The basic mechanism, based on using the pointer to member function of 00012 // a zero argument to a function was "boosted" from the boost type_traits 00013 // library. See http://www.boost.org/ for all the gory details. 00014 // 00015 //===----------------------------------------------------------------------===// 00016 00017 #ifndef LLVM_SUPPORT_TYPE_TRAITS_H 00018 #define LLVM_SUPPORT_TYPE_TRAITS_H 00019 00020 // This is actually the conforming implementation which works with abstract 00021 // classes. However, enough compilers have trouble with it that most will use 00022 // the one in boost/type_traits/object_traits.hpp. This implementation actually 00023 // works with VC7.0, but other interactions seem to fail when we use it. 00024 00025 namespace llvm { 00026 00027 namespace dont_use 00028 { 00029 // These two functions should never be used. They are helpers to 00030 // the is_class template below. They cannot be located inside 00031 // is_class because doing so causes at least GCC to think that 00032 // the value of the "value" enumerator is not constant. Placing 00033 // them out here (for some strange reason) allows the sizeof 00034 // operator against them to magically be constant. This is 00035 // important to make the is_class<T>::value idiom zero cost. it 00036 // evaluates to a constant 1 or 0 depending on whether the 00037 // parameter T is a class or not (respectively). 00038 template<typename T> char is_class_helper(void(T::*)(void)); 00039 template<typename T> double is_class_helper(...); 00040 } 00041 00042 template <typename T> 00043 struct is_class 00044 { 00045 // is_class<> metafunction due to Paul Mensonides (leavings@attbi.com). For 00046 // more details: 00047 // http://groups.google.com/groups?hl=en&selm=000001c1cc83%24e154d5e0%247772e50c%40c161550a&rnum=1 00048 public: 00049 enum { value = sizeof(char) == sizeof(dont_use::is_class_helper<T>(0)) }; 00050 }; 00051 00052 } 00053 00054 #endif