[Bug c++/53683] New: cout doesn't support std::u16string

["rui.maciel at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53683

             Bug #: 53683
           Summary: cout doesn't support std::u16string
    Classification: Unclassified
           Product: gcc
           Version: 4.6.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rui.maciel@gmail.com


Consider the following test program:

<code>
#include <iostream>
#include <string>


int main(void)
{
        std::u16string test;

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

        return 0;
}
</code>

When compiling this code with g++ 4.6.3, with the flags -std=c++0x -Wall
-pedantic, the following error message is displayed:

<message>
main.c++: In function âint main()â:
main.c++:9:15: error: no match for âoperator<<â in âstd::cout << testâ
main.c++:9:15: note: candidates are:
/usr/include/c++/4.6/ostream:110:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT,
_Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ostream_type&
(*)(std::basic_ostream<_CharT, _Traits>::__ostream_type&)) [with _CharT = char,
_Traits = std::char_traits<char>, std::basic_ostream<_CharT,
_Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:110:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to
âstd::basic_ostream<char>::__ostream_type&
(*)(std::basic_ostream<char>::__ostream_type&) {aka std::basic_ostream<char>&
(*)(std::basic_ostream<char>&)}â
/usr/include/c++/4.6/ostream:119:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT,
_Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ios_type&
(*)(std::basic_ostream<_CharT, _Traits>::__ios_type&)) [with _CharT = char,
_Traits = std::char_traits<char>, std::basic_ostream<_CharT,
_Traits>::__ostream_type = std::basic_ostream<char>, std::basic_ostream<_CharT,
_Traits>::__ios_type = std::basic_ios<char>]
/usr/include/c++/4.6/ostream:119:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to
âstd::basic_ostream<char>::__ios_type&
(*)(std::basic_ostream<char>::__ios_type&) {aka std::basic_ios<char>&
(*)(std::basic_ios<char>&)}â
/usr/include/c++/4.6/ostream:129:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT,
_Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char,
_Traits = std::char_traits<char>, std::basic_ostream<_CharT,
_Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:129:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âstd::ios_base&
(*)(std::ios_base&)â
/usr/include/c++/4.6/ostream:167:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long
int) [with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:167:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âlong intâ
/usr/include/c++/4.6/ostream:171:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long
unsigned int) [with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:171:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âlong unsigned intâ
/usr/include/c++/4.6/ostream:175:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool)
[with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:175:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âboolâ
/usr/include/c++/4.6/bits/ostream.tcc:93:5: note: std::basic_ostream<_CharT,
_Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with
_CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.6/bits/ostream.tcc:93:5: note:   no known conversion for
argument 1 from âstd::u16string {aka std::basic_string<char16_t>}â to âshort
intâ
/usr/include/c++/4.6/ostream:182:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short
unsigned int) [with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:182:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âshort unsigned intâ
/usr/include/c++/4.6/bits/ostream.tcc:107:5: note: std::basic_ostream<_CharT,
_Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT =
char, _Traits = std::char_traits<char>]
/usr/include/c++/4.6/bits/ostream.tcc:107:5: note:   no known conversion for
argument 1 from âstd::u16string {aka std::basic_string<char16_t>}â to âintâ
/usr/include/c++/4.6/ostream:193:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT,
_Traits>::operator<<(unsigned int) [with _CharT = char, _Traits =
std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type =
std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:193:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âunsigned intâ
/usr/include/c++/4.6/ostream:202:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long
long int) [with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:202:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âlong long intâ
/usr/include/c++/4.6/ostream:206:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long
long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:206:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âlong long unsigned
intâ
/usr/include/c++/4.6/ostream:211:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT,
_Traits>::operator<<(double) [with _CharT = char, _Traits =
std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type =
std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:211:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âdoubleâ
/usr/include/c++/4.6/ostream:215:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT,
_Traits>::operator<<(float) [with _CharT = char, _Traits =
std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type =
std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:215:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âfloatâ
/usr/include/c++/4.6/ostream:223:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long
double) [with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:223:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âlong doubleâ
/usr/include/c++/4.6/ostream:227:7: note: std::basic_ostream<_CharT,
_Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(const
void*) [with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:227:7: note:   no known conversion for argument 1
from âstd::u16string {aka std::basic_string<char16_t>}â to âconst void*â
/usr/include/c++/4.6/bits/ostream.tcc:121:5: note: std::basic_ostream<_CharT,
_Traits>& std::basic_ostream<_CharT,
_Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__streambuf_type*)
[with _CharT = char, _Traits = std::char_traits<char>,
std::basic_ostream<_CharT, _Traits>::__streambuf_type =
std::basic_streambuf<char>]
/usr/include/c++/4.6/bits/ostream.tcc:121:5: note:   no known conversion for
argument 1 from âstd::u16string {aka std::basic_string<char16_t>}â to
âstd::basic_ostream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}â
/usr/include/c++/4.6/ostream:581:5: note: std::basic_ostream<_CharT, _Traits>&
std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT
= char, _Traits = std::char_traits<char>, _Tp = std::basic_string<char16_t>]
<near match>
/usr/include/c++/4.6/ostream:581:5: note:   no known conversion for argument 1
from âstd::ostream {aka std::basic_ostream<char>}â to
âstd::basic_ostream<char>&&â
/usr/include/c++/4.6/ostream:528:5: note: template<class _Traits>
std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char,
_Traits>&, const unsigned char*)
/usr/include/c++/4.6/ostream:523:5: note: template<class _Traits>
std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char,
_Traits>&, const signed char*)
/usr/include/c++/4.6/ostream:510:5: note: template<class _Traits>
std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char,
_Traits>&, const char*)
/usr/include/c++/4.6/bits/ostream.tcc:323:5: note: template<class _CharT, class
_Traits> std::basic_ostream<_CharT, _Traits>&
std::operator<<(std::basic_ostream<_CharT, _Traits>&, const char*)
/usr/include/c++/4.6/ostream:493:5: note: template<class _CharT, class _Traits>
std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT,
_Traits>&, const _CharT*)
/usr/include/c++/4.6/ostream:473:5: note: template<class _Traits>
std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char,
_Traits>&, unsigned char)
/usr/include/c++/4.6/ostream:468:5: note: template<class _Traits>
std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char,
_Traits>&, signed char)
/usr/include/c++/4.6/ostream:462:5: note: template<class _Traits>
std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char,
_Traits>&, char)
/usr/include/c++/4.6/ostream:456:5: note: template<class _CharT, class _Traits>
std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT,
_Traits>&, char)
/usr/include/c++/4.6/ostream:451:5: note: template<class _CharT, class _Traits>
std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT,
_Traits>&, _CharT)
/usr/include/c++/4.6/bits/basic_string.h:2693:5: note: template<class _CharT,
class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>&
std::operator<<(std::basic_ostream<_CharT, _Traits>&, const
std::basic_string<_CharT, _Traits, _Alloc>&)
</message>

If, in the test program, std::u16string is replaced with std::u32string, the
program is successfully compiled.

It would be nice if std::cout also supported std::u16string objects.