Ticket #11705: phxfunction_test_problem.cpp

/***
*
* Test program to illustrate the problem:
*
* "Phoenix function with reference parameter fails to compile under clang 3.5 with C++ 11 support"
*
* Author: David Williams
*
* Boost version: 1.59
* 
* Compiler: Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn)
*
* Program built using C++ 11 support.
*
* Test program based on the phoenix test program function_tests.cpp.
*
***/


#include <iostream>
#include <cmath>
#include <boost/detail/lightweight_test.hpp>
#include <boost/phoenix/core.hpp>
#include <boost/phoenix/operator.hpp>
#include <boost/phoenix/function.hpp>

#define BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
#include <boost/mpl/multiplies.hpp>
#undef BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS


/**
 * Defines a simple phoenix function that allows a flag to be set depending on the integer
 * value used to initiaise the object.
 *
 **/
struct add_int_impl
{
   typedef int result_type;


   add_int_impl(int v)
   {
      _value=v;
   }

        /* 
    * Need this defined for the call BOOST_TEST(add_int(arg1)(flag) == (4)); to compile when 
    * the flags BOOST_RESULT_OF_TR1 or BOOST_RESULT_OF_USE_TR1_WITH_DECLTYPE_FALLBACK are NOT used.
    *
    * Note that both operator functions must be const for them to be valid phoenix functions.
    * This function compiles OK both with and without the int operator()(bool& flag) being defined.
    */
/****
   int operator()(int a) const
   {
        std::cout << "int operator()(int a) called" << std::endl;
      return a + _value;
   }
****/

   /*
    * This can be compiled with no other overloaded operators if we define the param as
    * (const bool& flag) rather than just (bool& flag)
    * But a const reference paramter is not useful here as we want to change the flag
    * depending on the stored integer _value.
    *
    */
   int operator()(bool& flag) const
   {
        std::cout << "int operator()(bool& flag) called" << std::endl;
      if (_value == 4)
         flag=true;
      return _value;
   }

    int _value;
};


// Initialise the function with the value 4.
boost::phoenix::function<add_int_impl> add_int(4);

int main()
{
   using boost::phoenix::arg_names::arg1;

   int i5 = 5;
   bool flag=false;

   /**
    * Test invoking the function object with a bool flag as a reference parameter.
    *
    * This call will only compile under Apple's version of clang 3.5 C++ 11 when one or both of the
    * following conditions are met;
    *
    * 1) The int operator()(int a) const is also defined
    *
    * 2) One of the following flags is defined:
    *
    * BOOST_RESULT_OF_TR1
    * BOOST_RESULT_OF_USE_TR1_WITH_DECLTYPE_FALLBACK
    *
    * The program also compiles if the function signature is changed to use a const 
    * reference parameter, i.e int operator()(const bool& flag) const.
    * However this then means that the parameter value cannot be
    * modified within the body of the function as required.
    *
    * The problem does not occur if the program is compiled using C++ 98 compatibility mode.
    *
    **/

   BOOST_TEST(add_int(arg1)(flag) == (4));

   /**
    * This tests the int operator()(int a) const which under C++ 11 can be defined standalone or
    * with the int operator()(bool& flag) const also defined. The flags BOOST_RESULT_OF_TR1
    * and BOOST_RESULT_OF_USE_TR1_WITH_DECLTYPE_FALLBACK are then NOT required.
    */
   //BOOST_TEST(add_int(arg1)(i5) == (5+4));

   return boost::report_errors();
}