[glib] subprocess: avoid infinite loop in verify_disposition()

[Christian Hergert <chergert src gnome org>]

commit 83d6c38e0c476894d604ddb55a149284d37d4d39
Author: Christian Hergert <chergert redhat com>
Date:   Tue Jan 3 15:48:46 2017 -0800

    subprocess: avoid infinite loop in verify_disposition()
    
    When performing the verify and building the error string there were two
    possibilities of an infinite loop. The first is the missing twos-complement
    to unset the bit in the filtered flags. The second is the lack of handling
    G_SUBPROCESS_FLAGS_NONE which can return a valid GFlagsValue (and cannot
    unset the bit since the value is zero).
    
    This walks all known values in the GSubprocessFlags type class and check
    if they are set. This has the benefit that we don't call needless functions
    which walk the same table as well as avoiding mutating values to build
    the error string.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=775913

 gio/gsubprocesslauncher.c |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)
---
diff --git a/gio/gsubprocesslauncher.c b/gio/gsubprocesslauncher.c
index a7906d9..d43583a 100644
--- a/gio/gsubprocesslauncher.c
+++ b/gio/gsubprocesslauncher.c
@@ -79,13 +79,16 @@ verify_disposition (const gchar      *stream_name,
       if (n_bits)
         {
           GFlagsClass *class;
-          GFlagsValue *value;
+          guint i;
 
           class = g_type_class_peek (G_TYPE_SUBPROCESS_FLAGS);
-          while ((value = g_flags_get_first_value (class, filtered_flags)))
+
+          for (i = 0; i < class->n_values; i++)
             {
-              g_string_append_printf (err, " %s", value->value_name);
-              filtered_flags &= value->value;
+              const GFlagsValue *value = &class->values[i];
+
+              if (filtered_flags & value->value)
+                g_string_append_printf (err, " %s", value->value_name);
             }
 
           g_type_class_unref (class);