Re: [Boost-users] [Variant] stream output of ICU UnicodeString

Subject: Re: [Boost-users] [Variant] stream output of ICU UnicodeString
From: Mostafa (mostafa_working_away_at_[hidden])
Date: 2011-10-09 15:12:07

On Sun, 09 Oct 2011 06:53:22 -0700, André <andre_at_[hidden]> wrote:

> Hi,
> I'm trying to stream a Boost::Variant with << to std::cout but when I  
> include an UnicodeString member from the ICU Unicode library the  
> compiler doesn't recognices my overloaded operator<< for the  
> UnicodeString.
>
> Here is a test program:

<snip>

>
> I'm using gcc 4.4.5 on Ubuntu 11.04 and boost 1.42.
> Does someone know why the overloaded operator isn't used or how I can  
> get the test program to work?

Keeping in mind that UnicodeString is defined in namespace  
icu_<some-version-number>, what you've pointed out is not limited to  
UnicodeString.  The following simplified example apparently shows ADL  
failing for Boost.Variant when the streaming operator for Foo is defined  
in the global namespace instead of Foo's defining namespace. (gcc 4.0.1,  
boost 1.4.5)

#include <iostream>
#include <boost/variant.hpp>

namespace Bar
{
struct Foo {};
}

std::ostream& operator<<(std::ostream& stream, Bar::Foo const &b) {
return stream << "Foo";
}

int main() {

//Not compiles.
boost::variant<Bar::Foo, char const *, int, double> test;

//Compiles.
//Bar::Foo test;

test = Bar::Foo();

std::cout << test << std::endl;

return 0;
}

Is this a bug in Boost.Variant?

Mostafa