[Boost-users] [Test] BOOST_*_EQUAL_COLLECTIONS ostream problem

Subject: [Boost-users] [Test] BOOST_*_EQUAL_COLLECTIONS ostream problem
From: Thomas Suckow (thomas.suckow_at_[hidden])
Date: 2010-09-02 19:47:10

I am attempting to compare two std::map<string,string> objects in Boost.Test
but am finding that it is trying to stream the std::pair< const string, 
string >
that results from dereferencing the iterator.

/* Simplified Example */
AUTO_TEST_CASE( Map_Same )
{
    std::map< std::string, std::string > x;
    std::map< std::string, std::string > y;
    BOOST_CHECK_EQUAL_COLLECTIONS( x.begin(), x.end(), y.begin(), y.end() );
}

Results in:
/usr/include/boost/test/utils/wrap_stringstream.hpp: In function 
'boost::basic_wrap_stringstream<CharT>& 
boost::operator<<(boost::basic_wrap_stringstream<CharT>&, const T&) 
[with CharT = char, T = std::pair<const std::basic_string<char, 
std::char_traits<char>, std::allocator<char> >, std::basic_string<char, 
std::char_traits<char>, std::allocator<char> > >]':
/usr/include/boost/test/test_tools.hpp:641:   instantiated from 
'boost::test_tools::predicate_result 
boost::test_tools::tt_detail::equal_coll_impl(Left, Left, Right, Right) 
[with Left = std::_Rb_tree_iterator<std::pair<const 
std::basic_string<char, std::char_traits<char>, std::allocator<char> >, 
std::basic_string<char, std::char_traits<char>, std::allocator<char> > > 
 >, Right = std::_Rb_tree_iterator<std::pair<const 
std::basic_string<char, std::char_traits<char>, std::allocator<char> >, 
std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]'

In my application the values a particular entry in the map will not 
reveal the problem, so I chose to suppress printing of the pair:

typedef std::pair< const std::basic_string<char>,std::basic_string<char> 
 > pair_type;
BOOST_TEST_DONT_PRINT_LOG_VALUE( pair_type );

But alas, this did absolutely nothing.  Confused, I tried:

BOOST_CHECK_EQUAL( *x.begin(), *y.begin() );

And it compiled. Remove the suppression and the error returns. So the 
suppression works, just not in conjunction with BOOST_*_EQUAL_COLLECTIONS.

Searching the mailing list revealed a post from 2005.
http://article.gmane.org/gmane.comp.lib.boost.user/13146

He mentions as I also found that equal_coll_impl uses the stream 
operator directly on the dereferenced iterators.  This *appears* to be 
bypassing the code that allows suppression.  Though I may be wrong (I 
can rarely tell with boost).

Can someone check on this and see if I am crazy? In the mean time I 
guess I just have to overload the stream operator.

Regards,
Thomas Suckow