2011-08-09 Pedro Alves <pedro@codesourcery.com>

gdb/
	* printcmd.c (current_display_number): Update comment.
	(disable_current_display_cleanup): Delete.
	(do_one_display): Use make_cleanup_restore_integer.  Gracefully
	catch errors thrown while evaluating and printing the display.

	gdb/testsuite/
	* gdb.base/display.c (do_loops): New `p_i' local.
	* gdb.base/display.exp: Test displaying a variable that is
	temporarily at a bad address.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+2011-08-09  Pedro Alves  <pedro@codesourcery.com>
+
+	* printcmd.c (current_display_number): Update comment.
+	(disable_current_display_cleanup): Delete.
+	(do_one_display): Use make_cleanup_restore_integer.  Gracefully
+	catch errors thrown while evaluating and printing the display.
+
 2011-08-09  Tom Tromey  <tromey@redhat.com>
 
 	* mi/mi-cmd-break.c (mi_cmd_break_passcount): Fix typo.

gdb/printcmd.c

@@ -129,7 +129,7 @@ show_print_symbol_filename (struct ui_file *file, int from_tty,
 }
 
 /* Number of auto-display expression currently being displayed.
-   So that we can disable it if we get an error or a signal within it.
+   So that we can disable it if we get a signal within it.
    -1 when not doing one.  */
 
 int current_display_number;
@@ -1656,14 +1656,6 @@ undisplay_command (char *args, int from_tty)
   dont_repeat ();
 }
 
-/* Cleanup that just disables the current display.  */
-
-static void
-disable_current_display_cleanup (void *arg)
-{
-  disable_current_display ();
-}
-
 /* Display a single auto-display.  
    Do nothing if the display cannot be printed in the current context,
    or if the display is disabled.  */
@@ -1723,8 +1715,8 @@ do_one_display (struct display *d)
   if (!within_current_scope)
     return;
 
+  old_chain = make_cleanup_restore_integer (&current_display_number);
   current_display_number = d->number;
-  old_chain = make_cleanup (disable_current_display_cleanup, NULL);
 
   annotate_display_begin ();
   printf_filtered ("%d", d->number);
@@ -1732,8 +1724,7 @@ do_one_display (struct display *d)
   printf_filtered (": ");
   if (d->format.size)
     {
-      CORE_ADDR addr;
-      struct value *val;
+      volatile struct gdb_exception ex;
 
       annotate_display_format ();
 
@@ -1755,18 +1746,26 @@ do_one_display (struct display *d)
       else
 	printf_filtered ("  ");
 
-      val = evaluate_expression (d->exp);
-      addr = value_as_address (val);
-      if (d->format.format == 'i')
-	addr = gdbarch_addr_bits_remove (d->exp->gdbarch, addr);
-
       annotate_display_value ();
 
-      do_examine (d->format, d->exp->gdbarch, addr);
+      TRY_CATCH (ex, RETURN_MASK_ERROR)
+        {
+	  struct value *val;
+	  CORE_ADDR addr;
+
+	  val = evaluate_expression (d->exp);
+	  addr = value_as_address (val);
+	  if (d->format.format == 'i')
+	    addr = gdbarch_addr_bits_remove (d->exp->gdbarch, addr);
+	  do_examine (d->format, d->exp->gdbarch, addr);
+	}
+      if (ex.reason < 0)
+	fprintf_filtered (gdb_stdout, _("<error: %s>\n"), ex.message);
     }
   else
     {
       struct value_print_options opts;
+      volatile struct gdb_exception ex;
 
       annotate_display_format ();
 
@@ -1784,16 +1783,23 @@ do_one_display (struct display *d)
 
       get_formatted_print_options (&opts, d->format.format);
       opts.raw = d->format.raw;
-      print_formatted (evaluate_expression (d->exp),
-		       d->format.size, &opts, gdb_stdout);
+
+      TRY_CATCH (ex, RETURN_MASK_ERROR)
+        {
+	  struct value *val;
+
+	  val = evaluate_expression (d->exp);
+	  print_formatted (val, d->format.size, &opts, gdb_stdout);
+	}
+      if (ex.reason < 0)
+	fprintf_filtered (gdb_stdout, _("<error: %s>"), ex.message);
       printf_filtered ("\n");
     }
 
   annotate_display_end ();
 
   gdb_flush (gdb_stdout);
-  discard_cleanups (old_chain);
-  current_display_number = -1;
+  do_cleanups (old_chain);
 }
 
 /* Display all of the values on the auto-display chain which can be

gdb/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2011-08-09  Pedro Alves  <pedro@codesourcery.com>
+
+	* gdb.base/display.c (do_loops): New `p_i' local.
+	* gdb.base/display.exp: Test displaying a variable that is
+	temporarily at a bad address.
+
 2011-08-08  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* gdb.dwarf2/dw2-op-stack-value.S: New file.

gdb/testsuite/gdb.base/display.c

@@ -14,6 +14,8 @@ int do_loops()
     int k=0;
     int j=0;
     float f=3.1415;
+    int *p_i = &i;
+
     for( i = 0; i < LOOP; i++ ) { /* set breakpoint 1 here */
         for( j = 0; j < LOOP; j++ ) {
             for( k = 0; k < LOOP; k++ ) {

gdb/testsuite/gdb.base/display.exp

@@ -119,6 +119,32 @@ gdb_test "undisp" \
     "y"
 
 
+# Test displaying a variable that is temporarily at a bad address.
+# But if we can examine what's at memory address 0, then we'll also be
+# able to display it without error.  Don't run the test in that case.
+set can_read_0 0
+gdb_test_multiple "x 0" "memory at address 0" {
+    -re "0x0:.*Cannot access memory at address 0x0.*$gdb_prompt $" { }
+    -re "0x0:.*Error accessing memory address 0x0.*$gdb_prompt $" { }
+    -re ".*$gdb_prompt $" {
+	set can_read_0 1
+    }
+}
+
+if { !$can_read_0 } {
+    gdb_test "disp *p_i" ".*: \\*p_i = 0"
+    gdb_test "p p_i = 0x0" " = \\(int \\*\\) 0x0"
+    gdb_test "display" ".*: \\*p_i = <error: .*>" "display bad address"
+    gdb_test "p p_i = &i" " = \\(int \\*\\) $hex"
+    gdb_test "display" ".*: \\*p_i = 0" "display good address"
+
+    gdb_test "undisp" \
+	"" \
+	"undisp all again" \
+	".*Delete all auto-display expressions.*y or n. $" \
+	"y"
+}
+
 gdb_test "disab 3" ".*.*" "disab 3"
 gdb_test "cont" ".*Breakpoint 4.*" "watch off"