Re: Problem with pex-win32.c

[Mark Mitchell <mark at codesourcery dot com>]

Here is a sample program which does the right thing (no spurious console
windows, all output visible) when run either from a console or from a
console-free environment, such as a Cygwin xterm.  This is the code
we'll be working into libiberty -- unless someone has a better solution!

-- 
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713

#include <windows.h>
#include <stdio.h>

int main() {
  HANDLE stdin_handle;
  HANDLE stdout_handle;
  HANDLE stderr_handle;
  DWORD dwCreationFlags;
  OSVERSIONINFO version_info;
  STARTUPINFO si;
  PROCESS_INFORMATION pi;

  /* Replace these with handles for pipes, etc.  */
  stdin_handle = GetStdHandle (STD_INPUT_HANDLE);
  stdout_handle = GetStdHandle (STD_OUTPUT_HANDLE);
  stderr_handle = GetStdHandle (STD_ERROR_HANDLE);

  version_info.dwOSVersionInfoSize = sizeof (version_info); 
  GetVersionEx (&version_info);
  if (version_info.dwPlatformId == VER_PLATFORM_WIN32_WINDOWS)
    /* On Windows 95/98/ME the CREATE_NO_WINDOW flag is not
       supported, so we cannot avoid creating a console window.  */
    dwCreationFlags = 0;
  else
    {
      HANDLE conout_handle;

      /* Determine whether or not we have an associated console.  */
      conout_handle = CreateFile("CONOUT$", 
				 GENERIC_WRITE,
				 FILE_SHARE_WRITE,
				 /*lpSecurityAttributes=*/NULL,
				 OPEN_EXISTING,
				 FILE_ATTRIBUTE_NORMAL,
				 /*hTemplateFile=*/NULL);
      if (conout_handle == INVALID_HANDLE_VALUE) 
	/* There is no console associated with this process.  Since
	   the child is a console process, the OS would normally
	   create a new console Window for the child.  Since we'll be
	   redirecting the child's standard streams, we do not need
	   the console window.  */ 
	dwCreationFlags = CREATE_NO_WINDOW;
      else
	{
	  /* There is a console associated with the process, so the OS
	     will not create a new console.  And, if we use
	     CREATE_NO_WINDOW in this situation, the child will have
	     no associated console.  Therefore, if the child's
	     standard streams are connected to the console, the output
	     will be discarded.  */
	  CloseHandle(conout_handle);
	  dwCreationFlags = 0;
	}
    }

  /* Since the child will be a console process, it will, by default,
     connect standard input/output to its console.  However, we want
     the child to use the handles specifically designated above.  In
     addition, if there is no console (such as when we are running in
     a Cygwin X window), then we must redirect the child's
     input/output, as there is no console for the child to use.  */
  memset (&si, 0, sizeof (si));
  si.cb = sizeof (si);
  si.dwFlags = STARTF_USESTDHANDLES;
  si.hStdInput = stdin_handle;
  si.hStdOutput = stdout_handle;
  si.hStdError = stderr_handle;

  fprintf (stderr, "About to invoke child.\n");
  fflush (stderr);
  
  /* Start the child.  */
  CreateProcess ("child.exe",
		 "child.exe",
		 NULL,
		 NULL,
		 /*bInheritHandles=*/TRUE,
		 dwCreationFlags,
		 /*lpEnvironment=*/NULL,
		 /*lpCurrentDirectory=*/NULL,
		 &si,
		 &pi);
  WaitForSingleObject (pi.hProcess, INFINITE);
  CloseHandle (pi.hProcess);
  CloseHandle (pi.hThread);

  fprintf (stderr, "Child done.\n");
  fflush (stderr);
}