[PATCH 2/3] serial.c: remove #if 0'd code, and associated unnecessary bits.

[Pedro Alves <palves at redhat dot com>]

This #if 0'd connect command first appears in gdb 4.10 (1993),
seemingly with the ChangeLog entry:

 Fri May 28 17:18:05 1993  Stu Grossman  (grossman@cygnus.com)
 ...
	 * serial.c:  Add start of support for connect command.
 ...

Then later in 4.15, we have:

 Thu Jun  8 15:06:00 1995  Stu Grossman  (grossman@cygnus.com)

	 * serial.c serial.h (serial_open serial_fdopen serial_close):
	 Allow users to open the same device multiple times.  They all get
	 to share the same serial_t.  This is about the only way to have
	 multiple active targets use the same device (for download and
	 debug).

I think this is referring to the download_stratum layer that existed
at the time, which I think made it so that we could have two targets
sharing the same connection, which has been eliminated since.

I audited the current tree for users for serial_open and
serial_fdopen, and couldn't find any case of opening the same device
multiple times, other than the #if 0'd connect command fdopening file
descriptor 0, which is also stdin_serial.  And I find such multi-open
support to be a quite dubious feature.

My next patch fixes a GDB remote/async crash by reference
counting "struct serial", but in a different way to that of the
current reference counting is handled.  So I think it's best to
completely eliminate the current code and start over.

Tested x86_64 Fedora 16 gdbserver.

2012-06-08  Pedro Alves  <palves@redhat.com>

	Remove #if 0'd "connect" command, and unnecessary associated
	refcounting and serial reuse bits.

	* serial.h (struct serial): Remove fields 'next' and 'refcnt'.
	* serial.c (last_serial_opened): Delete.
	(scb_base): Delete.
	(serial_open): Adjust.
	(serial_for_fd): Delete.
	(serial_fdopen_ops, do_serial_close): Adjust.
	(serial_fdopen_ops): Adjust.
	(tty_desc, cleanup_tty, connect_command): Delete #if 0'd code.
---
 gdb/serial.c |  188 ----------------------------------------------------------
 gdb/serial.h |    2 -
 2 files changed, 0 insertions(+), 190 deletions(-)

diff --git a/gdb/serial.c b/gdb/serial.c
index 9b689ba..c1f331d 100644
--- a/gdb/serial.c
+++ b/gdb/serial.c
@@ -33,14 +33,6 @@ static int global_serial_debug_p;
 
 static struct serial_ops *serial_ops_list = NULL;
 
-/* This is the last serial stream opened.  Used by connect command.  */
-
-static struct serial *last_serial_opened = NULL;
-
-/* Pointer to list of scb's.  */
-
-static struct serial *scb_base;
-
 /* Non-NULL gives filename which contains a recording of the remote session,
    suitable for playback by gdbserver.  */
 
@@ -174,13 +166,6 @@ serial_open (const char *name)
   struct serial_ops *ops;
   const char *open_name = name;
 
-  for (scb = scb_base; scb; scb = scb->next)
-    if (scb->name && strcmp (scb->name, name) == 0)
-      {
-	scb->refcnt++;
-	return scb;
-      }
-
   if (strcmp (name, "pc") == 0)
     ops = serial_interface_lookup ("pc");
   else if (strncmp (name, "lpt", 3) == 0)
@@ -220,15 +205,10 @@ serial_open (const char *name)
     }
 
   scb->name = xstrdup (name);
-  scb->next = scb_base;
-  scb->refcnt = 1;
   scb->debug_p = 0;
   scb->async_state = 0;
   scb->async_handler = NULL;
   scb->async_context = NULL;
-  scb_base = scb;
-
-  last_serial_opened = scb;
 
   if (serial_logfile != NULL)
     {
@@ -240,21 +220,6 @@ serial_open (const char *name)
   return scb;
 }
 
-/* Return the open serial device for FD, if found, or NULL if FD
-   is not already opened.  */
-
-struct serial *
-serial_for_fd (int fd)
-{
-  struct serial *scb;
-
-  for (scb = scb_base; scb; scb = scb->next)
-    if (scb->fd == fd)
-      return scb;
-
-  return NULL;
-}
-
 /* Open a new serial stream using a file handle, using serial
    interface ops OPS.  */
 
@@ -263,13 +228,6 @@ serial_fdopen_ops (const int fd, struct serial_ops *ops)
 {
   struct serial *scb;
 
-  scb = serial_for_fd (fd);
-  if (scb)
-    {
-      scb->refcnt++;
-      return scb;
-    }
-
   if (!ops)
     {
       ops = serial_interface_lookup ("terminal");
@@ -289,21 +247,16 @@ serial_fdopen_ops (const int fd, struct serial_ops *ops)
   scb->error_fd = -1;
 
   scb->name = NULL;
-  scb->next = scb_base;
-  scb->refcnt = 1;
   scb->debug_p = 0;
   scb->async_state = 0;
   scb->async_handler = NULL;
   scb->async_context = NULL;
-  scb_base = scb;
 
   if ((ops->fdopen) != NULL)
     (*ops->fdopen) (scb, fd);
   else
     scb->fd = fd;
 
-  last_serial_opened = scb;
-
   return scb;
 }
 
@@ -318,8 +271,6 @@ do_serial_close (struct serial *scb, int really_close)
 {
   struct serial *tmp_scb;
 
-  last_serial_opened = NULL;
-
   if (serial_logfp)
     {
       fputs_unfiltered ("\nEnd of log\n", serial_logfp);
@@ -330,10 +281,6 @@ do_serial_close (struct serial *scb, int really_close)
       serial_logfp = NULL;
     }
 
-  scb->refcnt--;
-  if (scb->refcnt > 0)
-    return;
-
   /* ensure that the FD has been taken out of async mode.  */
   if (scb->async_handler != NULL)
     serial_async (scb, NULL, NULL);
@@ -344,18 +291,6 @@ do_serial_close (struct serial *scb, int really_close)
   if (scb->name)
     xfree (scb->name);
 
-  if (scb_base == scb)
-    scb_base = scb_base->next;
-  else
-    for (tmp_scb = scb_base; tmp_scb; tmp_scb = tmp_scb->next)
-      {
-	if (tmp_scb->next != scb)
-	  continue;
-
-	tmp_scb->next = tmp_scb->next->next;
-	break;
-      }
-
   xfree (scb);
 }
 
@@ -618,129 +553,6 @@ serial_pipe (struct serial *scbs[2])
   return 0;
 }
 
-#if 0
-/* The connect command is #if 0 because I hadn't thought of an elegant
-   way to wait for I/O on two `struct serial *'s simultaneously.  Two
-   solutions came to mind:
-
-   1) Fork, and have have one fork handle the to user direction,
-   and have the other hand the to target direction.  This
-   obviously won't cut it for MSDOS.
-
-   2) Use something like select.  This assumes that stdin and
-   the target side can both be waited on via the same
-   mechanism.  This may not be true for DOS, if GDB is
-   talking to the target via a TCP socket.
-   -grossman, 8 Jun 93 */
-
-/* Connect the user directly to the remote system.  This command acts just like
-   the 'cu' or 'tip' command.  Use <CR>~. or <CR>~^D to break out.  */
-
-static struct serial *tty_desc;	/* Controlling terminal */
-
-static void
-cleanup_tty (serial_ttystate ttystate)
-{
-  printf_unfiltered ("\r\n[Exiting connect mode]\r\n");
-  serial_set_tty_state (tty_desc, ttystate);
-  xfree (ttystate);
-  serial_close (tty_desc);
-}
-
-static void
-connect_command (char *args, int fromtty)
-{
-  int c;
-  char cur_esc = 0;
-  serial_ttystate ttystate;
-  struct serial *port_desc;		/* TTY port */
-
-  dont_repeat ();
-
-  if (args)
-    fprintf_unfiltered (gdb_stderr,
-			"This command takes no args.  "
-			"They have been ignored.\n");
-
-  printf_unfiltered ("[Entering connect mode.  Use ~. or ~^D to escape]\n");
-
-  tty_desc = serial_fdopen (0);
-  port_desc = last_serial_opened;
-
-  ttystate = serial_get_tty_state (tty_desc);
-
-  serial_raw (tty_desc);
-  serial_raw (port_desc);
-
-  make_cleanup (cleanup_tty, ttystate);
-
-  while (1)
-    {
-      int mask;
-
-      mask = serial_wait_2 (tty_desc, port_desc, -1);
-
-      if (mask & 2)
-	{			/* tty input */
-	  char cx;
-
-	  while (1)
-	    {
-	      c = serial_readchar (tty_desc, 0);
-
-	      if (c == SERIAL_TIMEOUT)
-		break;
-
-	      if (c < 0)
-		perror_with_name (_("connect"));
-
-	      cx = c;
-	      serial_write (port_desc, &cx, 1);
-
-	      switch (cur_esc)
-		{
-		case 0:
-		  if (c == '\r')
-		    cur_esc = c;
-		  break;
-		case '\r':
-		  if (c == '~')
-		    cur_esc = c;
-		  else
-		    cur_esc = 0;
-		  break;
-		case '~':
-		  if (c == '.' || c == '\004')
-		    return;
-		  else
-		    cur_esc = 0;
-		}
-	    }
-	}
-
-      if (mask & 1)
-	{			/* Port input */
-	  char cx;
-
-	  while (1)
-	    {
-	      c = serial_readchar (port_desc, 0);
-
-	      if (c == SERIAL_TIMEOUT)
-		break;
-
-	      if (c < 0)
-		perror_with_name (_("connect"));
-
-	      cx = c;
-
-	      serial_write (tty_desc, &cx, 1);
-	    }
-	}
-    }
-}
-#endif /* 0 */
-
 /* Serial set/show framework.  */
 
 static struct cmd_list_element *serial_set_cmdlist;
diff --git a/gdb/serial.h b/gdb/serial.h
index 02a3b2d..8ba8ae6 100644
--- a/gdb/serial.h
+++ b/gdb/serial.h
@@ -232,8 +232,6 @@ struct serial
 				   still need to wait for this many
 				   more seconds.  */
     char *name;			/* The name of the device or host */
-    struct serial *next;	/* Pointer to the next `struct serial *' */
-    int refcnt;			/* Number of pointers to this block */
     int debug_p;		/* Trace this serial devices operation.  */
     int async_state;		/* Async internal state.  */
     void *async_context;	/* Async event thread's context */