Macro BOOST_CONTRACT

Macro BOOST_CONTRACT_CONSTRUCTOR

BOOST_CONTRACT_CONSTRUCTOR — Program contracts that can be completely disabled at compile-time for constructors.

Synopsis

// In header: <boost/contract_macro.hpp>

BOOST_CONTRACT_CONSTRUCTOR(...)

Description

This is used together with BOOST_CONTRACT_POSTCONDITION, BOOST_CONTRACT_EXCEPT, and BOOST_CONTRACT_OLD to specify postconditions, exception guarantees, and old value copies at body that can be completely disabled at compile-time for constructors (see BOOST_CONTRACT_CONSTRUCTOR_PRECONDITION to specify preconditions for constructors):

class u {
    friend class boost::contract::access;

    BOOST_CONTRACT_INVARIANT({ // Optional (as for static and volatile).
        BOOST_CONTRACT_ASSERT(...);
        ...
    })

public:
    u(...) {
        BOOST_CONTRACT_OLD_PTR(old_type)(old_var);
        BOOST_CONTRACT_CONSTRUCTOR(this)
            // No `PRECONDITION` (use `CONSTRUCTOR_PRECONDITION` if needed).
            BOOST_CONTRACT_OLD([&] { // Optional.
                old_var = BOOST_CONTRACT_OLDOF(old_epxr);
                ...
            })
            BOOST_CONTRACT_POSTCONDITION([&] { // Optional.
                BOOST_CONTRACT_ASSERT(...);
                ...
            })
            BOOST_CONTRACT_EXCEPT([&] { // Optional.
                BOOST_CONTRACT_ASSERT(...);
                ...
            })
        ; // Trailing `;` is required.

        ... // Constructor body.
    }

    ...
};

For optimization, this can be omitted for constructors that do not have postconditions and exception guarantees, within classes that have no invariants.

BOOST_CONTRACT_CONSTRUCTOR(obj) expands to code equivalent to the following (note that no code is generated when BOOST_CONTRACT_NO_CONSTRUCTORS is defined):

#ifndef BOOST_CONTRACT_NO_CONSTRUCTORS
    boost::contract::check internal_var =
            boost::contract::constructor(obj)
#endif

Where:

obj is the object this from the scope of the enclosing constructor declaring the contract. Constructors check all class invariants, including static and volatile invariants (see BOOST_CONTRACT_INVARIANT, BOOST_CONTRACT_STATIC_INVARIANT, and BOOST_CONTRACT_INVARIANT_VOLATILE). (This is a variadic macro parameter so it can contain commas not protected by round parenthesis.)
internal_var is a variable name internally generated by this library (this name is unique but only on different line numbers so this macro cannot be expanded multiple times on the same line).