gdb/

* exceptions.c (throw_exception): Don't disable the current
	display.
	* printcmd.c (disable_current_display_cleanup): New function.
	(do_one_display): Install a cleanup to disable the current display
	if doing the display throws.

	gdb/testsuite/
	* gdb.trace/unavailable.exp (test_maybe_regvar_display): New
	procedure.
	(gdb_collect_args_test, gdb_collect_locals_test): Use it.

gdb/ChangeLog

@@ -1,3 +1,11 @@
+2011-08-05  Pedro Alves  <pedro@codesourcery.com>
+
+	* exceptions.c (throw_exception): Don't disable the current
+	display.
+	* printcmd.c (disable_current_display_cleanup): New function.
+	(do_one_display): Install a cleanup to disable the current display
+	if doing the display throws.
+
 2011-08-05  Eli Zaretskii  <eliz@gnu.org>
 
 	* python/py-breakpoint.c (gdbpy_initialize_breakpoints): Move the

gdb/exceptions.c

@@ -223,7 +223,6 @@ throw_exception (struct gdb_exception exception)
       bpstat_clear_actions (tp->control.stop_bpstat);
     }
 
-  disable_current_display ();
   do_cleanups (ALL_CLEANUPS);
 
   /* Jump to the containing catch_errors() call, communicating REASON

gdb/printcmd.c

@@ -1656,6 +1656,14 @@ 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.  */
@@ -1663,6 +1671,7 @@ undisplay_command (char *args, int from_tty)
 static void
 do_one_display (struct display *d)
 {
+  struct cleanup *old_chain;
   int within_current_scope;
 
   if (d->enabled_p == 0)
@@ -1715,6 +1724,7 @@ do_one_display (struct display *d)
     return;
 
   current_display_number = d->number;
+  old_chain = make_cleanup (disable_current_display_cleanup, NULL);
 
   annotate_display_begin ();
   printf_filtered ("%d", d->number);
@@ -1782,6 +1792,7 @@ do_one_display (struct display *d)
   annotate_display_end ();
 
   gdb_flush (gdb_stdout);
+  discard_cleanups (old_chain);
   current_display_number = -1;
 }
 

gdb/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2011-08-05  Pedro Alves  <pedro@codesourcery.com>
+
+	* gdb.trace/unavailable.exp (test_maybe_regvar_display): New
+	procedure.
+	(gdb_collect_args_test, gdb_collect_locals_test): Use it.
+
 2011-08-05  Yao Qi  <yao@codesourcery.com>
 
 	* gdb.base/callfuncs.exp: Set language after main.

gdb/testsuite/gdb.trace/unavailable.exp

@@ -103,6 +103,36 @@ proc run_trace_experiment { test_func } {
 	    "tfind test frame"
 }
 
+# Test that "display VAR" works as expected, assuming VAR is wholly
+# unavailable.
+
+proc test_maybe_regvar_display { var } {
+    global gdb_prompt
+
+    # Evaluating VAR's location description may throw an internal
+    # "unavailable" exception, if for example, the value of a register
+    # necessary for computing VAR's location is unavailable.  Such an
+    # exception is caught, and should not cause automatic disablement
+    # of the current display being printed.  (GDB used to disable the
+    # current display whenever any exception was thrown.)
+    set test "display $var"
+    gdb_test_multiple "$test" "$test" {
+	-re "Disabling display ? to avoid infinite recursion.*$gdb_prompt $" {
+	    fail "$test"
+	}
+	-re "display ${var}\r\n1: ${var} = <unavailable>\r\n$gdb_prompt $" {
+	    pass "$test"
+	}
+    }
+    gdb_test "info display" ".*1:\[ \t\]+y\[ \t\]+${var}" "display ${var} is enabled"
+
+    gdb_test "undisp" \
+	"" \
+	"delete $var display" \
+	".*Delete all auto-display expressions.*y or n. $" \
+	"y"
+}
+
 #
 # Test procs
 #
@@ -171,6 +201,8 @@ proc gdb_collect_args_test {} {
     set r "${r}argarray = <unavailable>${cr}"
     gdb_test "info args" "$r" "info args"
 
+    test_maybe_regvar_display "argc"
+
     gdb_test "tfind none" \
 	"#0  end .*" \
 	"cease trace debugging"
@@ -226,6 +258,8 @@ proc gdb_collect_locals_test { func msg } {
     set r "${r}loci = <unavailable>${cr}"
     gdb_test "info locals" "$r" "info locals"
 
+    test_maybe_regvar_display "loci"
+
     gdb_test "tfind none" \
 	"#0  end .*" \
 	"cease trace debugging"