gvariant tests: workaround libc/compiler "issue"

memcmp() is declared by glibc as follows:

  /* Compare N bytes of S1 and S2.  */
  extern int memcmp (const void *__s1, const void *__s2, size_t __n)
       __THROW __attribute_pure__ __nonnull ((1, 2));

despite the fact that it is valid to call it with a null pointer if the
size is zero.

gcc 4.9.0 contains a new optimisation that sees that we pass a pointer
to this function and concludes that it certainly must not be null,
removing a later check and thereby causing a crash.

We protect the invocation of memcmp() with a condition to prevent gcc
from making this false assumption (arguably under wrong advice from
glibc).

diff --git a/glib/tests/gvariant.c b/glib/tests/gvariant.c
index 122400e..9152a43 100644 (file)
--- a/glib/tests/gvariant.c
+++ b/glib/tests/gvariant.c
@@ -1520,7 +1520,9 @@ test_array (void)
         g_variant_serialiser_serialise (serialised, random_instance_filler,
                                         (gpointer *) instances, n_children);
 
-        g_assert (memcmp (serialised.data, data, serialised.size) == 0);
+        if (serialised.size)
+          g_assert (memcmp (serialised.data, data, serialised.size) == 0);
+
         g_assert (g_variant_serialised_n_children (serialised) == n_children);
 
         for (i = 0; i < n_children; i++)
@@ -1681,7 +1683,9 @@ test_tuple (void)
         g_variant_serialiser_serialise (serialised, random_instance_filler,
                                         (gpointer *) instances, n_children);
 
-        g_assert (memcmp (serialised.data, data, serialised.size) == 0);
+        if (serialised.size)
+          g_assert (memcmp (serialised.data, data, serialised.size) == 0);
+
         g_assert (g_variant_serialised_n_children (serialised) == n_children);
 
         for (i = 0; i < n_children; i++)
@@ -1774,7 +1778,9 @@ test_variant (void)
         g_variant_serialiser_serialise (serialised, random_instance_filler,
                                         (gpointer *) &instance, 1);
 
-        g_assert (memcmp (serialised.data, data, serialised.size) == 0);
+        if (serialised.size)
+          g_assert (memcmp (serialised.data, data, serialised.size) == 0);
+
         g_assert (g_variant_serialised_n_children (serialised) == 1);
 
         child = g_variant_serialised_get_child (serialised, 0);