Visual C++ 2015 error

[Robert Pope]

I upgraded to Windows 10 this weekend, so I decided to upgrade from Visual Studio 2013 to 2015 while I was at it. To my surprise, my chess program doesn't compile anymore. The problem is some generic I/O code I borrowed from the WinBoard forum a long time ago:

Code: Select all

int Bioskey(void) { 
  static int init = 0, pipe; 
  static HANDLE inh; 
  DWORD dw; 
  if (XBoard) { 
    if (!init) { 
      init = 1; 
      inh = GetStdHandle(STD_INPUT_HANDLE); 
      pipe = !GetConsoleMode(inh, &dw); 
      if (!pipe) { 
        SetConsoleMode(inh, dw & ~(ENABLE_MOUSE_INPUT | ENABLE_WINDOW_INPUT)); 
        FlushConsoleInputBuffer(inh); 
      } 
    } 
    if (stdin->_cnt > 0) 
      return stdin->_cnt; 
    if (pipe) { 
      if (!PeekNamedPipe(inh, NULL, 0, NULL, &dw, NULL)) return 1; 
        return dw; 
    } 
    else { 
      GetNumberOfConsoleInputEvents(inh, &dw); 
      return dw <= 1 ? 0 : dw; 
    } 
  } 
  else return _kbhit(); 
} 

It chokes on:
if (stdin->_cnt > 0)
return stdin->_cnt;
with Error C2039: '_cnt': is not a member of '_iobuf'
class "_iobuf" has no member "_cnt"

Any ideas? I've been googling, but can't figure out what the issue is, or how to resolve it.

[jdart]

You are referencing a non-standard variable that you are assuming is part of "stdin". It isn't there anymore in the new Windows version.

This code from Arasan shows how I handle input on Windows:

Code: Select all

 while (!polling_terminated) {
      BOOL bSuccess;
      DWORD dwRead;
      if (_isatty(_fileno(stdin))) {
         // we are reading direct from the console, enable echo & control-char
         // processing
         if (!SetConsoleMode(hStdin, ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT |
                         ENABLE_MOUSE_INPUT | ENABLE_PROCESSED_INPUT)) {
            cerr << "SetConsoleMode failed" << endl;
         }
         bSuccess = ReadConsole(hStdin, buf, 1024, &dwRead, NULL);
      }
      else {
         bSuccess = ReadFile(hStdin, buf, 1024, &dwRead, NULL);
         if (! bSuccess || dwRead == 0) {
            if (doTrace) cout << "# read error from input pipe" << endl;
#ifdef UCI_LOG
            ucilog << "read error from input pipe" << endl << (flush);
#endif
            break;
	 }
      }
      processCmdChars(buf,(int)dwRead);
   }

[Joost Buijs]

This morning I installed VS2015 under Windows 10 and I also have some issues with the IO.

My engine compiles without errors and works fine with Arena, but when I use it with WinBoard/Polyglot the IO just hangs.

Basically I do this:

Code: Select all

void uci::init_io
{
	hStdin = GetStdHandle(STD_INPUT_HANDLE);
	hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
	bPipe = (GetFileType(hStdin) == FILE_TYPE_PIPE);

	if (bPipe) {
		setvbuf(stdin, NULL, _IONBF, 0);
		setvbuf(stdout, NULL, _IONBF, 0);
	}

	fflush(NULL);
}

bool uci::check_io
{
	if (bPipe) { // anonymous pipe
		DWORD dwAvail = 0;
		if (PeekNamedPipe(hStdin, NULL, 0, NULL, &dwAvail, NULL) && dwAvail > 0)
			return true;
		return false;
	}

        // console
        return bool(_kbhit());
}

After this I just read from stdin and write to stdout.

Some time ago I already saw that this code had problems with VS2015 beta and decided to wait for the RTM because I thought it was a flaw of the beta.
The strange thing is that it still works with Arena but that it hangs with WinBoard/Polyglot.

The good thing is that for the first time it looks like the new Microsoft compiler generates somewhat faster code than the Intel compiler does.
I have to check this a little further.

[Joost Buijs]

Although PeekNamedPipe() indicates that there are characters available the subsequent fgets() just blocks and does not return.

I wonder whether it is a bug in the MSVC++ 14.0 library or something else. With MSVC++ 12.0 there are no problems at all.
And there is the strange phenomenon that it does not happen under Arena.

When I have some time I will dive further into it.

[mar]

The problem is some generic I/O code I borrowed from the WinBoard forum a long time ago

If you ran your engine in a separate thread, you could have one simple polling loop in main (or elsewhere),
no need for nonportable windows-specific magic ang ugly polling within search...

[Joost Buijs]

The problem is some generic I/O code I borrowed from the WinBoard forum a long time ago

If you ran your engine in a separate thread, you could have one simple polling loop in main (or elsewhere),
no need for nonportable windows-specific magic ang ugly polling within search...

Handling the IO in a separate thread is a lot cleaner, I agree. In the next version of my engine I will certainly do it this way.

A lot of code I use is at least 15 years old and I never changed it because it always worked.
Now I'm intrigued by the fact that it suddenly breaks in combination with MSVC++ 14.0 and WinBoard/Polyglot.

[Joost Buijs]

Disabling buffering on stdio in combination with fgets() seems to be the culprit.
I don't want to spend more time on it, I will stick to MSVC 12 for the time being.
In the future when I have completely rewritten the IO part I will give it another try.

[Robert Pope]

The problem is some generic I/O code I borrowed from the WinBoard forum a long time ago

If you ran your engine in a separate thread, you could have one simple polling loop in main (or elsewhere),
no need for nonportable windows-specific magic ang ugly polling within search...

True, but then I'd have to get more competent with threads. Trades one can of worms for another.

What's the portable method of threading?

[jdart]

Generally threading code is not portable. Intel has a threading library that may help though (https://www.threadingbuildingblocks.org/).

C++ 11 has portable threading constructs built into the language. So do some other languages (Go for example). For older C++ there is the Boost library.

(I am using none of these: I have #ifdefs and a couple utility classes that help hide platform dependencies).

--Jon

[Robert Pope]

This is driving me crazy. I compiled and ran the following code on MS Visual Studio Professional 2013 (Windows 8.1):

Code: Select all

#include<stdio.h>
int main(int argc, char* argv[])
{
char buf[256];
    setvbuf(stdin, NULL, _IONBF, 0);
    printf("waiting for input\n");
    fgets(buf, 80, stdin);
    printf("received %s\n", buf);
    printf("exiting:\n");
    fgets(buf, 80, stdin);
return 0;
}

The output is as expected:

waiting for input
A
received A

exiting:
B

But if I compile the exact same code in MS Visual Studio Community 2015 (Windows 10), it keeps waiting for input until I press enter twice:

waiting for input
A
B
C
D


received ABCD


exiting:
E
F
G

If I comment out the setvbuf(), it works as expected, but then I am buffering input.