unbreak mingw build

[Pedro Alves <palves at redhat dot com>]

One of my previous serial.c patches went too far.  I hadn't noticed
that serial_for_fd is used in mingw-hdep.c, leading to the build
getting broken on mingw.

http://sourceware.org/ml/gdb/2012-06/msg00061.html

This restores the function.  Tested on x86_64 Fedora 16, gdbserver.
asmwarrior confirms mingw gdb works fine with it.

2012-06-13  Pedro Alves  <palves@redhat.com>

	Partial revert of previous change.

	* serial.c (scb_base): New global.
	(serial_for_fd): New.
	(serial_open, serial_fdopen_ops): Link new serial in open serials
	chain.
	(do_serial_close): Unlink serial from the open serials chain.
---
 gdb/serial.c |   35 +++++++++++++++++++++++++++++++++++
 gdb/serial.h |    1 +
 2 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/gdb/serial.c b/gdb/serial.c
index 1140feb..df18b2f 100644
--- a/gdb/serial.c
+++ b/gdb/serial.c
@@ -33,6 +33,10 @@ static int global_serial_debug_p;

 static struct serial_ops *serial_ops_list = 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.  */

@@ -157,6 +161,21 @@ serial_add_interface (struct serial_ops *optable)
   serial_ops_list = optable;
 }

+/* 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 up a device or a network socket, depending upon the syntax of NAME.  */

 struct serial *
@@ -206,10 +225,12 @@ serial_open (const char *name)
     }

   scb->name = xstrdup (name);
+  scb->next = scb_base;
   scb->debug_p = 0;
   scb->async_state = 0;
   scb->async_handler = NULL;
   scb->async_context = NULL;
+  scb_base = scb;

   if (serial_logfile != NULL)
     {
@@ -249,10 +270,12 @@ serial_fdopen_ops (const int fd, struct serial_ops *ops)
   scb->refcnt = 1;

   scb->name = NULL;
+  scb->next = scb_base;
   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);
@@ -296,6 +319,18 @@ do_serial_close (struct serial *scb, int really_close)
   /* For serial_is_open.  */
   scb->bufp = NULL;

+  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;
+      }
+
   serial_unref (scb);
 }

diff --git a/gdb/serial.h b/gdb/serial.h
index 187ed03..b164062 100644
--- a/gdb/serial.h
+++ b/gdb/serial.h
@@ -249,6 +249,7 @@ 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 debug_p;		/* Trace this serial devices operation.  */
     int async_state;		/* Async internal state.  */
     void *async_context;	/* Async event thread's context */