687c0bbee4
std::basic_ios has an operator bool(). In C++11 and later it is explicit, and only allows contextual implicit conversions. However explicit isn't available in C++03 which causes std::istream (et al) to have an implicit conversion to int. This can easily cause ambiguities when calling operator<< and operator>>. This patch uses a "bool-like" type in C++03 to work around this. The "bool-like" type is an arbitrary pointer to member function type. It will not convert to either int or void*, but will convert to bool. git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@290750 91177308-0d34-0410-b5e6-96231b3b80d8
33 lines
1017 B
C++
33 lines
1017 B
C++
//===----------------------------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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// <ios>
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// template <class charT, class traits> class basic_ios
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// operator unspecified-bool-type() const;
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#include <ios>
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#include <type_traits>
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#include <cassert>
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int main()
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{
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std::ios ios(0);
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assert(static_cast<bool>(ios) == !ios.fail());
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ios.setstate(std::ios::failbit);
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assert(static_cast<bool>(ios) == !ios.fail());
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static_assert((!std::is_convertible<std::ios, void*>::value), "");
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static_assert((!std::is_convertible<std::ios, int>::value), "");
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static_assert((!std::is_convertible<std::ios const&, int>::value), "");
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#if TEST_STD_VER >= 11
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static_assert((!std::is_convertible<std::ios, bool>::value), "");
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#endif
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}
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