Report current thread in -thread-list-ids output

[Vladimir Prus <vladimir at codesourcery dot com>]

This patch makes the MI -thread-list-ids report the current thread.
It is advantageous for a frontend like Eclipse, that does not report
any details about a thread whatsoever except for the id, and whether
a thread is selected. If -thread-list-ids reports current thread, then
Eclipse can use -thread-list-ids as opposed to 'info thread', and be
a little bit faster.

The change in thread.c actually touches MI-only function, so I assume
I'm free to make this change. Eli, does the doc change look good?

- Volodya

commit 52cc9bd1b3137c918c8ecd389d2059684b32a9a0
Author: Vladimir Prus <vladimir@codesourcery.com>
Date:   Fri Jan 30 19:34:11 2009 +0300

    Make -thread-list-ids report the current thread.
    
    	gdb/doc/
    	* gdb.texinfo (GDB/MI Thread Commands): Document the
    	'current-thread-id' field.  Remove the example with zero threads,
    	since current GDB won't ever report that if there's inferior.
    
    	gdb/
    	* thread.c (do_captured_list_thread_ids): Report the current
    	thread id.

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 583d96c..9a4cd68 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -20497,23 +20497,11 @@ Part of @samp{info threads} supplies the same information.
 
 @subsubheading Example
 
-No threads present, besides the main process:
-
-@smallexample
-(gdb)
--thread-list-ids
-^done,thread-ids=@{@},number-of-threads="0"
-(gdb)
-@end smallexample
-
-
-Several threads:
-
 @smallexample
 (gdb)
 -thread-list-ids
 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
-number-of-threads="3"
+current-thread-id="1",number-of-threads="3"
 (gdb)
 @end smallexample
 
diff --git a/gdb/thread.c b/gdb/thread.c
index 8a98b8e..1d6d9c4 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -410,6 +410,7 @@ do_captured_list_thread_ids (struct ui_out *uiout, void *arg)
   struct thread_info *tp;
   int num = 0;
   struct cleanup *cleanup_chain;
+  int current_thread = -1;
 
   prune_threads ();
   target_find_new_threads ();
@@ -420,11 +421,18 @@ do_captured_list_thread_ids (struct ui_out *uiout, void *arg)
     {
       if (tp->state_ == THREAD_EXITED)
 	continue;
+
+      if (ptid_equal (tp->ptid, inferior_ptid))
+	current_thread = tp->num;
+
       num++;
       ui_out_field_int (uiout, "thread-id", tp->num);
     }
 
   do_cleanups (cleanup_chain);
+
+  if (current_thread != -1)
+    ui_out_field_int (uiout, "current-thread-id", current_thread);
   ui_out_field_int (uiout, "number-of-threads", num);
   return GDB_RC_OK;
 }