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#ifndef BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION_HPP_
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#define BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION_HPP_
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// Copyright (C) 2008-2018 Lorenzo Caminiti
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// Distributed under the Boost Software License, Version 1.0 (see accompanying
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// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
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// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
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/** @file
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Program preconditions for constructors.
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*/
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// IMPORTANT: Included by contract_macro.hpp so must #if-guard all its includes.
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#include <boost/contract/core/config.hpp>
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#ifndef BOOST_CONTRACT_NO_PRECONDITIONS
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#include <boost/contract/core/exception.hpp>
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#ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
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#include <boost/contract/detail/checking.hpp>
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#endif
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#endif
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namespace boost { namespace contract {
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/**
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Program preconditions for constructors.
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This class must be the very first base of the class declaring the
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constructor for which preconditions are programmed (that way constructor
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arguments can be checked by preconditions even before they are used to
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initialize other base classes):
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@code
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class u
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#define BASES private boost::contract::constructor_precondition<u>, \
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public b
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: BASES
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{
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friend class boost::contract::access;
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typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types;
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#undef BASES
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public:
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explicit u(unsigned x) :
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boost::contract::constructor_precondition<u>([&] {
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BOOST_CONTRACT_ASSERT(x != 0);
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...
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}),
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b(1.0 / float(x))
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{
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...
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}
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...
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};
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@endcode
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User-defined classes should inherit privately from this class (to not alter the
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public interface of user-defined classes).
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In addition, this class should never be declared as a virtual base (because
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virtual bases are initialized only once across the entire inheritance hierarchy
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preventing preconditions of other base classes from being checked).
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This class cannot be used this way in a @c union because unions cannot have base
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classes in C++.
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Instead, this class is used in a @c union to declare a local object within the
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constructor definition just before @RefFunc{boost::contract::constructor} is
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used (see @RefSect{extras.unions, Unions}).
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@see @RefSect{tutorial.constructors, Constructors}
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@tparam Class The class type of the constructor for which preconditions are
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being programmed.
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*/
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template<class Class>
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class constructor_precondition { // Copyable (has no data).
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public:
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/**
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Construct this object without specifying constructor preconditions.
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This is implicitly called for those constructors of the contracted class
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that do not specify preconditions.
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@note The implementation of this library is optimized so that calling this
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default constructor should amount to negligible compile-time and
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run-time overheads (likely to be optimized away completely by most
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compilers).
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*/
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constructor_precondition() {}
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/**
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Construct this object specifying constructor preconditions.
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@param f Nullary functor called by this library to check constructor
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preconditions @c f().
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Assertions within this functor call are usually programmed
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using @RefMacro{BOOST_CONTRACT_ASSERT}, but any exception thrown
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by a call to this functor indicates a contract failure (and will
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result in this library calling
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@RefFunc{boost::contract::precondition_failure}).
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This functor should capture variables by (constant) value, or
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better by (constant) reference to avoid extra copies.
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*/
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template<typename F>
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explicit constructor_precondition(F const& f) {
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#ifndef BOOST_CONTRACT_NO_PRECONDITIONS
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try {
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#ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
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if(boost::contract::detail::checking::already()) return;
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#ifndef BOOST_CONTRACT_PRECONDITIONS_DISABLE_NO_ASSERTION
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boost::contract::detail::checking k;
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#endif
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#endif
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f();
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} catch(...) { precondition_failure(from_constructor); }
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#endif
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}
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// Default copy operations (so user's derived classes can be copied, etc.).
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};
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} } // namespace
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#endif // #include guard
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