Windows CogVM stdOut?

Hi DOug,

On Fri, Aug 17, 2012 at 1:57 PM, Douglas McPherson <[hidden email]> wrote:

I'm using FFI to call an external C function which performs a printf. On the Mac such output conveniently displays in Console.app. Anyone know how I can see these printfs on Windows ? I tried starting the image with Cog's CroquetConsole.exe but nothing gets displayed in the console. Ideas?

Thanks,
Doug

phhh... mingw :(.  The VM can write to stdout, but does so not using printf.  here's how it works, all code in platforms/win32/plugins/FilePlugin/sqWin32FilePrims.c.

When the CVM is asked for the stdin/out/err handles it does this for each handle:

    DWORD mode;

...

    files[0].sessionID = thisSession;

    files[0].file = GetStdHandle(STD_INPUT_HANDLE); // & STD_OUTPUT_HANDLE & 1 & STD_ERROR_HANDLE & 2

    files[0].fileSize = 0;

    files[0].writable = false;

    files[0].lastOp = 0; /* unused on win32 */

    files[0].isStdioStream = GetConsoleMode(files[0].file, &mode) != 0;

i.e. isStdioStream == GetConsoleMode(GetStdHandle(STD_INPUT_HANDLE), &mode) != 0;

Then when it wants to write it does

  if (f->isStdioStream)

    WriteConsole(FILE_HANDLE(f), (LPVOID) (byteArrayIndex + startIndex), count, &dwReallyWritten, NULL);

  else

    WriteFile(FILE_HANDLE(f), (LPVOID) (byteArrayIndex + startIndex), count, &dwReallyWritten, NULL);

and to read it does

  if (f->isStdioStream)

    ReadConsole(FILE_HANDLE(f), (LPVOID) (byteArrayIndex+startIndex), count,

                &dwReallyRead, NULL);

  else

    ReadFile(FILE_HANDLE(f), (LPVOID) (byteArrayIndex+startIndex), count,

             &dwReallyRead, NULL);

Now this doesn't really help you with printf, but if you can link your external C code you can redefine printf to invoke the above writing code.  Hence adapted from platforms/win32/vm/sqWin32Intel.c, do something like:

int __cdecl

printf(const char *fmt, ...)

{ va_list al;

  int result;

  va_start(al, fmt);

  wvsprintf(consoleBuffer, fmt, al);

// and then adapt the above to write to the console:

  if (f->isStdioStream)

    WriteConsole(FILE_HANDLE(f), consoleBuffer, strlen(consoleBuffer), &dwReallyWritten, NULL);

  else

    WriteFile(FILE_HANDLE(f), consoleBuffer, strlen(consoleBuffer), &dwReallyWritten, NULL);

  result = vfprintf(stdout, fmt, al);

  va_end(al);

  return result;

}

--
HTH,

Eliot