Stl: <iostream> : When a double-width characters in cout, blank output without permission.

[fsb4000]

Describe the bug
When the full-width character is output in cout, blank is output without permission

Command-line test case

C:\Temp>type main.cpp
//  file encoding: utf-8 or Shift JIS
#include <iostream> 
#include <cstdlib>
using namespace std;

int main()
{ 
    system("chcp 932 > NUL"); // system("chcp 65001 > NUL");
    cout << "あいうえお" << endl;
}

C:\Temp>cl /EHsc /W4 /WX /utf-8 main.cpp
or
C:\Temp>cl /EHsc /W4 /WX main.cpp
Оптимизирующий компилятор Microsoft (R) C/C++ версии 19.27.29109 для x64
(C) Корпорация Майкрософт (Microsoft Corporation).  Все права защищены.

main.cpp
Microsoft (R) Incremental Linker Version 14.27.29109.0
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:main.exe
main.obj

C:\Temp>main.exe
あいうえお

Expected behavior
Should print without additional spaces.
Actually it works. I can't reproduce the bug.
Works for both utf-8 and Shift JIS.

STL version
Microsoft Visual Studio Community 2019 Preview Version 16.7.0 Preview 6.0

Additional context
VSO-441122 / AB#441122 | DevCom-59694

[fsb4000]

wcout and L"str" also works fine:

#include <iostream> 
#include <cstdlib>
#include <cassert>

#include <windows.h>
#include <io.h>
#include <fcntl.h>
using namespace std;

int main()
{ 
    int result =  _setmode(_fileno(stdout), _O_U16TEXT);
    assert(result != -1);
    wcout << L"あいうえお\n";
}

[fsb4000]

If you will test too, check that your cmd font is NSimSun or MSGothic.
The examples don't work with Lucida Console or Consolas fonts.

[cpplearner]

The console adds spacing between hiraganas, to keep hiraganas aligned with letters. I guess that's why the reporter thought that whitespace characters are outputted.

[fsb4000]

I see. Every Unicode symbol fits '2 spaces' in console. and Ansi symbol fits '1 space'.
The issue is better shown even for Cyrylic symbols :)

#include <iostream> 
#include <cstdlib>
using namespace std;

int main()
{ 
    system("chcp 65001 > NUL");
    cout << "ABABABABAB\n"; // English
    cout << "あいうえお\n";
    cout << "АВАВАВАВАВ\n"; // Russian
}

I think this is by design :)

[StephanTLavavej]

Thanks @cpplearner and @fsb4000! I've resolved the DevCom bug with links to your analysis and screenshots.