gvariant: Re-use g_variant_serialised_check() to check alignment

Rather than duplicating the alignment checks when constructing a new
GVariant, re-use the alignment checks from GVariantSerialised. This
ensures that the same checks are done everywhere in the GVariant code.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://gitlab.gnome.org/GNOME/glib/issues/1342

glib/gvariant-core.c

@@ -523,6 +523,7 @@ g_variant_new_from_bytes (const GVariantType *type,
   guint alignment;
   gsize size;
   GBytes *owned_bytes = NULL;
+  GVariantSerialised serialised;
 
   value = g_variant_alloc (type, TRUE, trusted);
 
@@ -535,7 +536,11 @@ g_variant_new_from_bytes (const GVariantType *type,
    * only cause an abort on some architectures — so is unlikely to be caught
    * in testing). Callers can always actively ensure they use the correct
    * alignment to avoid the performance hit. */
-  if ((alignment & (gsize) g_bytes_get_data (bytes, NULL)) != 0)
+  serialised.type_info = value->type_info;
+  serialised.data = (guchar *) g_bytes_get_data (bytes, &serialised.size);
+  serialised.depth = 0;
+
+  if (!g_variant_serialised_check (serialised))
     {
 #ifdef HAVE_POSIX_MEMALIGN
       gpointer aligned_data = NULL;

glib/gvariant-serialiser.c

@@ -127,20 +127,24 @@
  *
  * Checks @serialised for validity according to the invariants described
  * above.
+ *
+ * Returns: %TRUE if @serialised is valid; %FALSE otherwise
  */
-static void
+gboolean
 g_variant_serialised_check (GVariantSerialised serialised)
 {
   gsize fixed_size;
   guint alignment;
 
-  g_assert (serialised.type_info != NULL);
+  if (serialised.type_info == NULL)
+    return FALSE;
   g_variant_type_info_query (serialised.type_info, &alignment, &fixed_size);
 
-  if (fixed_size)
-    g_assert_cmpint (serialised.size, ==, fixed_size);
-  else
-    g_assert (serialised.size == 0 || serialised.data != NULL);
+  if (fixed_size != 0 && serialised.size != fixed_size)
+    return FALSE;
+  else if (fixed_size == 0 &&
+           !(serialised.size == 0 || serialised.data != NULL))
+    return FALSE;
 
   /* Depending on the native alignment requirements of the machine, the
    * compiler will insert either 3 or 7 padding bytes after the char.
@@ -167,10 +171,8 @@ g_variant_serialised_check (GVariantSerialised serialised)
    * Check if this is a small allocation and return without enforcing
    * the alignment assertion if this is the case.
    */
-  if (serialised.size <= alignment)
-    return;
-
-  g_assert_cmpint (alignment & (gsize) serialised.data, ==, 0);
+  return (serialised.size <= alignment ||
+          (alignment & (gsize) serialised.data) == 0);
 }
 
 /* < private >
@@ -1355,7 +1357,7 @@ gvs_variant_is_normal (GVariantSerialised value)
 gsize
 g_variant_serialised_n_children (GVariantSerialised serialised)
 {
-  g_variant_serialised_check (serialised);
+  g_assert (g_variant_serialised_check (serialised));
 
   DISPATCH_CASES (serialised.type_info,
 
@@ -1392,7 +1394,7 @@ g_variant_serialised_get_child (GVariantSerialised serialised,
 {
   GVariantSerialised child;
 
-  g_variant_serialised_check (serialised);
+  g_assert (g_variant_serialised_check (serialised));
 
   if G_LIKELY (index_ < g_variant_serialised_n_children (serialised))
     {
@@ -1400,7 +1402,7 @@ g_variant_serialised_get_child (GVariantSerialised serialised,
 
                       child = gvs_/**/,/**/_get_child (serialised, index_);
                       g_assert (child.size || child.data == NULL);
-                      g_variant_serialised_check (child);
+                      g_assert (g_variant_serialised_check (child));
                       return child;
 
                      )
@@ -1441,7 +1443,7 @@ g_variant_serialiser_serialise (GVariantSerialised        serialised,
                                 const gpointer           *children,
                                 gsize                     n_children)
 {
-  g_variant_serialised_check (serialised);
+  g_assert (g_variant_serialised_check (serialised));
 
   DISPATCH_CASES (serialised.type_info,
 
@@ -1496,7 +1498,7 @@ g_variant_serialised_byteswap (GVariantSerialised serialised)
   gsize fixed_size;
   guint alignment;
 
-  g_variant_serialised_check (serialised);
+  g_assert (g_variant_serialised_check (serialised));
 
   if (!serialised.data)
     return;

glib/gvariant-serialiser.h

@@ -55,6 +55,8 @@ void                            g_variant_serialiser_serialise          (GVarian
                                                                          gsize                     n_children);
 
 /* misc */
+GLIB_AVAILABLE_IN_2_60
+gboolean                        g_variant_serialised_check              (GVariantSerialised        serialised);
 GLIB_AVAILABLE_IN_ALL
 gboolean                        g_variant_serialised_is_normal          (GVariantSerialised        value);
 GLIB_AVAILABLE_IN_ALL