c ++无法获得"wcout"来打印unicode,并让"cout"工作

Question

不能让"wcout"在多个代码页中打印unicode字符串,同时让"cout"工作

请帮我把这3行一起工作.

std::wcout<<"abc "<<L'\u240d'<<" defg "<<L'?'<<" hijk"<<std::endl;
std::cout<<"hello world from cout! \n";
std::wcout<<"hello world from wcout! \n";

输出:

abc hello world from cout!

我试过了:

#include <io.h> 
#include <fcntl.h>
_setmode(_fileno(stdout), _O_U8TEXT);

问题:"cout"失败了

尝试:

std::locale mylocale("");
std::wcout.imbue(mylocale);

和:

SetConsoleOutputCP(1251);

和

setlocale(LC_ALL, "");

和

SetConsoleCP(CP_UTF8)

没有任何效果

Answer 1

C++说:

[C++11: 27.4.1/3]:对相应的宽字符和窄字符流的混合操作遵循与在FILEs 上混合这些操作相同的语义,如ISO C标准的修订1中所规定的.

和引用文件说:

流的定义已更改为包括文本和二进制流的方向概念.在流与文件关联之后,但在对流执行任何操作之前,该流没有方向.如果将宽字符输入或输出函数应用于没有方向的流,则该流变为面向广的.同样,如果将字节输入或输出操作应用于具有方向的流,则该流将变为面向字节的.此后,只有一个fwide()或多个freopen()函数可以改变流的方向.

字节输入/输出功能不应用于面向广泛的流,宽字符输入/输出功能不应用于面向字节的流.

根据我的解释,这意味着,简而言之,不要混合std::cout和std::wcout.

Answer 2

Microsoft 需要一些非标准的设置_setmode()才能使用wcout或wcin可以工作。这个例子在样板文件上非常繁重，所以没有想象的那么清楚，但它在 clang++、g++ 和 MSVC++ 上运行：

#include <iostream>
#include <locale>
#include <locale.h>
#include <stdlib.h>

#ifndef MS_STDLIB_BUGS // Allow overriding the autodetection.
/* The Microsoft C and C++ runtime libraries that ship with Visual Studio, as
 * of 2017, have a bug that neither stdio, iostreams or wide iostreams can
 * handle Unicode input or output.  Windows needs some non-standard magic to
 * work around that.  This includes programs compiled with MinGW and Clang
 * for the win32 and win64 targets.
 */
#  if ( _MSC_VER || __MINGW32__ || __MSVCRT__ )
    /* This code is being compiled either on MS Visual C++, or MinGW, or
     * clang++ in compatibility mode for either, or is being linked to the
     * msvcrt.dll runtime.
     */
#    define MS_STDLIB_BUGS 1
#  else
#    define MS_STDLIB_BUGS 0
#  endif
#endif

#if MS_STDLIB_BUGS
#  include <io.h>
#  include <fcntl.h>
#endif

#if !HAS_APP17_FILESYSTEM && !HAS_TS_FILESYSTEM && __has_include(<filesystem>)
#  include <filesystem> /* MSVC has this header, but not the standard API. */
#  if __cpp_lib_filesystem >= 201703
#    define HAS_CPP17_FILESYSTEM 1
#  endif
#endif

#if !HAS_CPP17_FILESYSTEM && __has_include(<experimental/filesystem>)
#  include <experimental/filesystem>
/* Microsoft screws this one up, too, by not defining the feature-test
 * macro specified by the standard.
 */
#  if __cpp_lib_experimental_filesystem >= 201406 || MS_STDLIB_BUGS
#    define HAS_TS_FILESYSTEM 1
/* With g++6, this requires -lstdc++fs, AFTER this source file on the
 * command line.
 */
#  endif
#endif

#if HAS_CPP17_FILESYSTEM
  using std::filesystem::absolute;
  using std::filesystem::current_path;
  using std::filesystem::directory_entry;
  using std::filesystem::directory_iterator;
  using std::filesystem::is_directory;
  using std::filesystem::exists;
  using std::filesystem::path;
#elif HAS_TS_FILESYSTEM
  using std::experimental::filesystem::absolute;
  using std::experimental::filesystem::current_path;
  using std::experimental::filesystem::directory_entry;
  using std::experimental::filesystem::directory_iterator;
  using std::experimental::filesystem::is_directory;
  using std::experimental::filesystem::exists;
  using std::experimental::filesystem::path;
#else
#  error "This library has neither <filesystem> nor <experimental/filesystem>."
#endif

void init_locale(void)
// Does magic so that wcout can work.
{
#if MS_STDLIB_BUGS
  // Windows needs a little non-standard magic.
  constexpr char cp_utf16le[] = ".1200"; // UTF-16 little-endian locale.
  setlocale( LC_ALL, cp_utf16le );
  _setmode( _fileno(stdout), _O_WTEXT );
  /* Repeat for _fileno(stdin), if needed. */
#else
  // The correct locale name may vary by OS, e.g., "en_US.utf8".
  constexpr char locale_name[] = "";
  setlocale( LC_ALL, locale_name );
  std::locale::global(std::locale(locale_name));
  std::wcin.imbue(std::locale())
  std::wcout.imbue(std::locale());
#endif
}

using std::endl;

int main( const int argc, const char * const argv[] )
{
  init_locale();

  const path cwd = (argc > 1) ? absolute(path( argv[1], std::locale() ))
                              : absolute(current_path());

  if (exists(cwd)) {
    std::wcout << cwd.wstring() << endl;
  } else {
    std::wcerr << "Path does not exist.\n";
    return EXIT_FAILURE;
  }

  if (is_directory(cwd)) {
    for ( const directory_entry &f : directory_iterator(cwd) )
      std::wcout << f.path().filename().wstring() << endl;
  }

  return EXIT_SUCCESS;
}

这可能比实际需要的复杂得多：std::filesystem截至 2018 年不受支持，但<experimental/filesystem>永远不会被删除。

这是一个简化版本，仅包含wcout开始工作的样板：

#include <iostream>
#include <locale>
#include <locale.h>

#ifndef MS_STDLIB_BUGS
#  if ( _MSC_VER || __MINGW32__ || __MSVCRT__ )
#    define MS_STDLIB_BUGS 1
#  else
#    define MS_STDLIB_BUGS 0
#  endif
#endif

#if MS_STDLIB_BUGS
#  include <io.h>
#  include <fcntl.h>
#endif

void init_locale(void)
{
#if MS_STDLIB_BUGS
  constexpr char cp_utf16le[] = ".1200";
  setlocale( LC_ALL, cp_utf16le );
  _setmode( _fileno(stdout), _O_WTEXT );
#else
  // The correct locale name may vary by OS, e.g., "en_US.utf8".
  constexpr char locale_name[] = "";
  setlocale( LC_ALL, locale_name );
  std::locale::global(std::locale(locale_name));
  std::wcin.imbue(std::locale())
  std::wcout.imbue(std::locale());
#endif
}