List displays in ascending order

Before:
      (gdb) info display
      Auto-display expressions now in effect:
      Num Enb Expression
      3:   y  1
      2:   y  1
      1:   y  1

After:
      (gdb) info display
      Auto-display expressions now in effect:
      Num Enb Expression
      1:   y  1
      2:   y  1
      3:   y  1

gdb/ChangeLog:
2015-11-24  Pedro Alves  <palves@redhat.com>

	PR 17539
	* printcmd.c (display_command): Append new display at the end of
	the list.

gdb/testsuite/ChangeLog:
2015-11-24  Pedro Alves  <palves@redhat.com>

	PR 17539
	* gdb.base/display.exp: Expect displays to be sorted in ascending
	order.  Use multi_line.
	* gdb.base/solib-display.exp: Likewise.

1 files changed, 12 insertions, 2 deletions

diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index 1744abd432..c676fc7ed7 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -1543,11 +1543,21 @@ display_command (char *arg, int from_tty)
   newobj->exp = expr;
   newobj->block = innermost_block;
   newobj->pspace = current_program_space;
-  newobj->next = display_chain;
   newobj->number = ++display_number;
   newobj->format = fmt;
   newobj->enabled_p = 1;
-  display_chain = newobj;
+  newobj->next = NULL;
+
+  if (display_chain == NULL)
+    display_chain = newobj;
+  else
+    {
+      struct display *last;
+
+      for (last = display_chain; last->next != NULL; last = last->next)
+	;
+      last->next = newobj;
+    }
 
   if (from_tty)
     do_one_display (newobj);