* dcrt0.cc (jit_debug): New global.

(initial_env): Set jit_debug when we are automatically starting a gdb process.
* dtable.cc (dtable::get_debugger_info): Don't tty tricks when we are being
debugged by our own captive gdb, as determined by jit_debug == true.
(dtable::init_std_file_from_handle): Detect errors when initializing a tty
early rather than at random points later.
* fhandler.h (fhandler_*::init): Return int to indicate success/failure.
* fhandler.cc (fhandler_base::init): Reflect change in return value.
* pipe.cc (fhandler_pipe::init): Ditto.
(fhandler_pipe::create_selectable): Don't say we're retrying when we aren't.
* fhandler_console.cc (fhandler_console::init): Ditto.  Return success/failure.
* fhandler_serial.cc (fhandler_serial::init): Ditto.
* fhandler_tty.cc (fhandler_tty_slave::init): Ditto.
(fhandler_tty_slave::open): Make debugging output more detailed.
* tty.cc (tty_list::terminate): Don't close I/O handles before all slaves have
checked in.
(tty::slave_alive): Make a non-inlined function.  Check if tty pipe handles can
be created as an additional exists check.
* tty.h (tty::slave_alive): Just define here.

winsup/cygwin/dcrt0.cc

@@ -48,6 +48,8 @@ static char NO_COPY **envp;
 
 static char title_buf[TITLESIZE + 1];
 
+bool NO_COPY jit_debug;
+
 static void
 do_global_dtors ()
 {
@@ -499,6 +501,7 @@ initial_env ()
       if (strstr (buf1, buf))
 	{
 	  error_start_init (p);
+	  jit_debug = true;
 	  try_to_debug ();
 	  console_printf ("*** Sending Break.  gdb may issue spurious SIGTRAP message.\n");
 	  break_here ();