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discussion of this change. Boy are my fingers tired. ;-) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45411 91177308-0d34-0410-b5e6-96231b3b80d8
55 lines
2.1 KiB
C++
55 lines
2.1 KiB
C++
//===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file provides a template class that determines if a type is a class or
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// not. The basic mechanism, based on using the pointer to member function of
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// a zero argument to a function was "boosted" from the boost type_traits
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// library. See http://www.boost.org/ for all the gory details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_TYPE_TRAITS_H
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#define LLVM_SUPPORT_TYPE_TRAITS_H
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// This is actually the conforming implementation which works with abstract
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// classes. However, enough compilers have trouble with it that most will use
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// the one in boost/type_traits/object_traits.hpp. This implementation actually
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// works with VC7.0, but other interactions seem to fail when we use it.
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namespace llvm {
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namespace dont_use
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{
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// These two functions should never be used. They are helpers to
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// the is_class template below. They cannot be located inside
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// is_class because doing so causes at least GCC to think that
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// the value of the "value" enumerator is not constant. Placing
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// them out here (for some strange reason) allows the sizeof
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// operator against them to magically be constant. This is
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// important to make the is_class<T>::value idiom zero cost. it
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// evaluates to a constant 1 or 0 depending on whether the
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// parameter T is a class or not (respectively).
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template<typename T> char is_class_helper(void(T::*)(void));
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template<typename T> double is_class_helper(...);
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}
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template <typename T>
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struct is_class
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{
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// is_class<> metafunction due to Paul Mensonides (leavings@attbi.com). For
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// more details:
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// http://groups.google.com/groups?hl=en&selm=000001c1cc83%24e154d5e0%247772e50c%40c161550a&rnum=1
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public:
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enum { value = sizeof(char) == sizeof(dont_use::is_class_helper<T>(0)) };
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};
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}
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#endif
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