Fix for the conversion problem:
cppx/stdlib/iostreams_conversion_defect.fix.hpp
#pragma once
//----------------------------------------------------------------------------------------
// PROBLEM DESCRIPTION.
//
// Output of wchar_t const* is only supported via an operator<< template. User-defined
// conversions are not considered for template matching. This results in actual argument
// with user conversion to wchar_t const*, for a wide stream, being presented as the
// pointer value instead of the string.
#include <iostream>
#ifndef CPPX_NO_IOSTREAM_CONVERSION_FIX
namespace std{
template< class Char_traits >
inline auto operator<<(
basic_ostream<wchar_t, Char_traits>& stream,
wchar_t const ch
)
-> basic_ostream<wchar_t, Char_traits>&
{ return operator<< <wchar_t, Char_traits>( stream, ch ); }
template< class Char_traits >
inline auto operator<<(
basic_ostream<wchar_t, Char_traits>& stream,
wchar_t const* const s
)
-> basic_ostream<wchar_t, Char_traits>&
{ return operator<< <wchar_t, Char_traits>( stream, s ); }
} // namespace std
#endif
Setting direct i/o mode in Windows:
This is a standard library extension that's supported by both Visual C++ and MinGW g++.
First, just because it's used in the code, definition of the Ptr type builder (the main drawback of library-provided type builders is that ordinary type inference doesn't kick in, i.e. it's necessary in some cases to still use the raw operator notation):
cppx/core_language/type_builders.hpp
?
template< class T > using Ptr = T*;
?
A helper definition, because it's used in more than one file:
cppx/stdlib/Iostream_mode.hpp
#pragma once
// Mode for a possibly console-attached iostream, such as std::wcout.
namespace cppx {
enum Iostream_mode: int { unknown, utf_8, direct_io };
} // namespace cppx
Mode setters (base functionality):
cppx/stdlib/impl/utf8_mode.for_windows.hpp
#pragma once
// UTF-8 mode for a stream in Windows.
#ifndef _WIN32
# error This is a Windows only implementation.
#endif
#include <cppx/stdlib/Iostream_mode.hpp>
#include <stdio.h> // FILE, stdin, stdout, stderr, etc.
// Non-standard headers, which are de facto standard in Windows:
#include <io.h> // _setmode, _isatty, _fileno etc.
#include <fcntl.h> // _O_WTEXT etc.
namespace cppx {
inline
auto set_utf8_mode( const Ptr< FILE > f )
-> Iostream_mode
{
const int file_number = _fileno( f ); // See docs for error handling.
if( file_number == -1 ) { return Iostream_mode::unknown; }
const int new_mode = (_isatty( file_number )? _O_WTEXT : _O_U8TEXT);
const int previous_mode = _setmode( file_number, new_mode );
return (0?Iostream_mode()
: previous_mode == -1? Iostream_mode::unknown
: new_mode == _O_WTEXT? Iostream_mode::direct_io
: Iostream_mode::utf_8
);
}
} // namespace cppx
cppx/stdlib/impl/utf8_mode.generic.hpp
#pragma once
#include <stdio.h> // FILE, stdin, stdout, stderr, etc.
#include <cppx/core_language/type_builders.hpp> // cppx::Ptr
namespace cppx {
inline
auto set_utf8_mode( const Ptr< FILE > )
-> Iostream_mode
{ return Iostream_mode::unknown; }
} // namespace cppx
cppx/stdlib/utf8_mode.hpp
#pragma once
// UTF-8 mode for a stream. For Unix-land this is a no-op & the locale must be UTF-8.
#include <cppx/core_language/type_builders.hpp> // cppx::Ptr
#include <cppx/stdlib/Iostream_mode.hpp>
namespace cppx {
inline
auto set_utf8_mode( const Ptr< FILE > ) -> Iostream_mode;
} // namespace cppx
#ifdef _WIN32 // This also covers 64-bit Windows.
# include "impl/utf8_mode.for_windows.hpp" // Using Windows-specific _setmode.
#else
# include "impl/utf8_mode.generic.hpp" // A do-nothing implementation.
#endif
Configuring the standard streams.
In addition to setting direct console i/o mode or UTF-8 as appropriate in Windows, this fixes the implicit conversion defect; (indirectly) calls setlocale so that wide streams work in Unix-land; sets boolalpha just for good measure, as a more reasonable default; and includes all standard library headers to do with iostreams (I don't show the separate header file that does that, and it is to a degree a personal preference how much to include or whether to do such inclusion at all):
cppx/stdlib/iostreams.hpp
#pragma once
// Standard iostreams but configured to work, plus, as utility, with boolalpha set.
#include <raw_stdlib/iostreams.hpp> // <iostream>, <sstream>, <fstream> etc. for convenience.
#include <cppx/core_language/type_builders.hpp> // cppx::Ptr
#include <cppx/stdlib/utf8_mode.hpp> // stdin etc., stdlib::set_utf8_mode
#include <locale> // std::locale
#include <string> // std::string
#include <cppx/stdlib/impl/iostreams_conversion_defect.fix.hpp> // Support arg conv.
inline auto operator<< ( std::wostream& stream, const std::string& s )
-> std::wostream&
{ return (stream << s.c_str()); }
// The following code's sole purpose is to automatically initialize the streams.
namespace cppx { namespace utf8_iostreams {
using std::locale;
using std::ostream;
using std::cin; using std::cout; using std::cerr; using std::clog;
using std::wostream;
using std::wcin; using std::wcout; using std::wcerr; using std::wclog;
using std::boolalpha;
namespace detail {
using std::wstreambuf;
// Based on "Filtering streambufs" code by James Kanze published at
// <url: http://gabisoft.free.fr/articles/fltrsbf1.html>.
class Correcting_input_buffer
: public wstreambuf
{
private:
wstreambuf* provider_;
wchar_t buffer_;
protected:
auto underflow()
-> int_type override
{
if( gptr() < egptr() ) { return *gptr(); }
const int_type result = provider_->sbumpc();
if( result == L'
' )
{
// Ad hoc workaround for g++ extra newline undesirable behavior:
provider_->pubsync();
}
if( traits_type::not_eof( result ) )
{
buffer_ = result;
setg( &buffer_, &buffer_, &buffer_ + 1 );
}
return result ;
}
public:
Correcting_input_buffer( wstreambuf* a_provider )
: provider_( a_provider )
{}
};
} // namespace detail
class Usage
{
private:
static
void init_once()
{
// In Windows there is no UTF-8 encoding spec for the locale, in Unix-land
// it's the default. From Microsoft's documentation: "If you provide a code
// page like UTF-7 or UTF-8, setlocale will fail, returning NULL". Still
// this call is essential for making the wide streams work correctly in
// Unix-land.
locale::global( locale( "" ) ); // Effects a `setlocale( LC_ALL, "" )`.
for( const Ptr<FILE> c_stream : {stdin, stdout, stderr} )
{
const auto new_mode = set_utf8_mode( c_stream );
if( c_stream == stdin && new_mode == Iostream_mode::direct_io )
{
static detail::Correcting_input_buffer correcting_buffer( wcin.rdbuf() );
wcin.rdbuf( &correcting_buffer );
}
}
for( const Ptr<ostream> stream_ptr : {&cout, &cerr, &clog} )
{
*stream_ptr << boolalpha;
}
for( const Ptr<wostream> stream_ptr : {&wcout, &wcerr, &wclog} )
{
*stream_ptr << boolalpha;
}
}
public:
Usage()
{ static const bool dummy = (init_once(), true); (void) dummy; }
};
namespace detail {
const Usage usage;
} // namespace detail
}} // namespace cppx::utf8_iostreams
The two example programs in the question are fixed simply by including the above header instead of or in addition to <iostream>. When it's in addition to it can be in a separate translation unit (except for the implicit conversion defect fix, if that's desired the header for it must be included somehow). Or e.g. as a forced include in the build command.
