Cygwin: pty: Implement new pseudo console support.

- In this implementation, pseudo console is created for each native
  console app. Advantages and disadvantages of this implementation
  over the previous implementation are as follows.

  Advantages:
  1) No performance degradation in pty output for cygwin process.
      https://cygwin.com/pipermail/cygwin/2020-February/243858.html
  2) Free from the problem caused by difference of behaviour of control
     sequences between real terminal and pseudo console.
      https://cygwin.com/pipermail/cygwin/2019-December/243281.html
      https://cygwin.com/pipermail/cygwin/2020-February/243855.html
  3) Free from the problem in cgdb and emacs gud.
      https://cygwin.com/pipermail/cygwin/2020-January/243601.html
      https://cygwin.com/pipermail/cygwin/2020-March/244146.html
  4) Redrawing screen on executing native console apps is not necessary.
  5) cygwin-console-helper is not necessary for the pseudo console
     support.
  6) The codes for pseudo console support are much simpler than that
     of the previous one.

  Disadvantages:
  1) The cygwin program which calls console API directly does not work.
  2) The apps which use console API cannot be debugged with gdb. This
     is because pseudo console is not activated since gdb uses
     CreateProcess() rather than exec(). Even with this limitation,
     attaching gdb to native apps, in which pseudo console is already
     activated, works.
  3) Typeahead key inputs are discarded while native console app is
     executed. Simirally, typeahead key inputs while cygwin app is
     executed are not inherited to native console app.
  4) Code page cannot be changed by chcp.com. Acctually, chcp works
     itself and changes code page of its own pseudo console.  However,
     since pseudo console is recreated for another process, it cannot
     inherit the code page.
  5) system_printf() does not work after stderr is closed. (Same with
     cygwin 3.0.7)
  6) Startup time of native console apps is about 3 times slower than
     previous implemenation.
  7) Pseudo console cannot be activated if it is already activated for
     another process on same pty.

1 files changed, 0 insertions, 43 deletions

diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index 52741ce..02a5996 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -1206,18 +1206,6 @@ fhandler_console::close ()
   if (con_ra.rabuf)
     free (con_ra.rabuf);
 
-  /* If already attached to pseudo console, don't call free_console () */
-  cygheap_fdenum cfd (false);
-  while (cfd.next () >= 0)
-    if (cfd->get_major () == DEV_PTYM_MAJOR ||
-	cfd->get_major () == DEV_PTYS_MAJOR)
-      {
-	fhandler_pty_common *t =
-	  (fhandler_pty_common *) (fhandler_base *) cfd;
-	if (get_console_process_id (t->get_helper_process_id (), true))
-	  return 0;
-      }
-
   if (!have_execed)
     free_console ();
   return 0;
@@ -3612,37 +3600,6 @@ fhandler_console::need_invisible ()
 }
 
 DWORD
-fhandler_console::get_console_process_id (DWORD pid, bool match)
-{
-  DWORD tmp;
-  DWORD num, num_req;
-  num = 1;
-  num_req = GetConsoleProcessList (&tmp, num);
-  DWORD *list;
-  while (true)
-    {
-      list = (DWORD *)
-	HeapAlloc (GetProcessHeap (), 0, num_req * sizeof (DWORD));
-      num = num_req;
-      num_req = GetConsoleProcessList (list, num);
-      if (num_req > num)
-	HeapFree (GetProcessHeap (), 0, list);
-      else
-	break;
-    }
-  num = num_req;
-
-  tmp = 0;
-  for (DWORD i=0; i<num; i++)
-    if ((match && list[i] == pid) || (!match && list[i] != pid))
-      /* Last one is the oldest. */
-      /* https://github.com/microsoft/terminal/issues/95 */
-      tmp = list[i];
-  HeapFree (GetProcessHeap (), 0, list);
-  return tmp;
-}
-
-DWORD
 fhandler_console::__acquire_input_mutex (const char *fn, int ln, DWORD ms)
 {
 #ifdef DEBUGGING