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GObject: fix property override type checks

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The property override typecheck was meant to enforce the type on the
overriding property being exactly equal to the type on the interface
property.  Instead, g_type_is_a() was incorrectly used.

We could try to enforce equality, but if a property is read-only then it
should be possible for the implementation to type the property with any
subtype of the type specified on the interface (because returning a more
specific type will still satisfy the interface).  Likewise, if the
property is write-only then it should be possible for the implementation
to type the property with any supertype.

We implement the check this way.

https://bugzilla.gnome.org/show_bug.cgi?id=666616
This commit is contained in:
Ryan Lortie 2011-12-20 18:26:14 -05:00
parent ab0da3c282
commit 5fb7a8e127
1 changed files with 58 additions and 15 deletions
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73
gobject/gobject.c
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@ -1373,22 +1373,65 @@ object_interface_check_properties (gpointer func_data,
continue;
}
/* The implementation paramspec must have a less restrictive
* type than the interface parameter spec for set() and a
* more restrictive type for get(). We just require equality,
* rather than doing something more complicated checking
* the READABLE and WRITABLE flags. We also simplify here
* by only checking the value type, not the G_PARAM_SPEC_TYPE.
/* If the property on the interface is readable then we are
* effectively advertising that reading the property will return a
* value of a specific type. All implementations of the interface
* need to return items of this type -- but may be more
* restrictive. For example, it is legal to have:
*
* GtkWidget *get_item();
*
* that is implemented by a function that always returns a
* GtkEntry. In short: readability implies that the
* implementation value type must be equal or more restrictive.
*
* Similarly, if the property on the interface is writable then
* must be able to accept the property being set to any value of
* that type, including subclasses. In this case, we may also be
* less restrictive. For example, it is legal to have:
*
* set_item (GtkEntry *);
*
* that is implemented by a function that will actually work with
* any GtkWidget. In short: writability implies that the
* implementation value type must be equal or less restrictive.
*
* In the case that the property is both readable and writable
* then the only way that both of the above can be satisfied is
* with a type that is exactly equal.
*/
if (!g_type_is_a (pspecs[n]->value_type, class_pspec->value_type))
g_critical ("Property '%s' on class '%s' has type '%s' "
"which is different from the type '%s', "
"of the property on interface '%s'\n",
pspecs[n]->name,
g_type_name (G_OBJECT_CLASS_TYPE (class)),
g_type_name (G_PARAM_SPEC_VALUE_TYPE (class_pspec)),
g_type_name (G_PARAM_SPEC_VALUE_TYPE (pspecs[n])),
g_type_name (iface_type));
switch (pspecs[n]->flags & (G_PARAM_READABLE | G_PARAM_WRITABLE))
{
case G_PARAM_READABLE | G_PARAM_WRITABLE:
/* class pspec value type must have exact equality with interface */
if (pspecs[n]->value_type != class_pspec->value_type)
g_critical ("Read/writable property '%s' on class '%s' has type '%s' which is not exactly equal to the "
"type '%s' of the property on the interface '%s'\n", pspecs[n]->name,
g_type_name (G_OBJECT_CLASS_TYPE (class)), g_type_name (G_PARAM_SPEC_VALUE_TYPE (class_pspec)),
g_type_name (G_PARAM_SPEC_VALUE_TYPE (pspecs[n])), g_type_name (iface_type));
break;
case G_PARAM_READABLE:
/* class pspec value type equal or more restrictive than interface */
if (!g_type_is_a (class_pspec->value_type, pspecs[n]->value_type))
g_critical ("Read-only property '%s' on class '%s' has type '%s' which is not equal to or more "
"restrictive than the type '%s' of the property on the interface '%s'\n", pspecs[n]->name,
g_type_name (G_OBJECT_CLASS_TYPE (class)), g_type_name (G_PARAM_SPEC_VALUE_TYPE (class_pspec)),
g_type_name (G_PARAM_SPEC_VALUE_TYPE (pspecs[n])), g_type_name (iface_type));
break;
case G_PARAM_WRITABLE:
/* class pspec value type equal or less restrictive than interface */
if (!g_type_is_a (pspecs[n]->value_type, class_pspec->value_type))
g_critical ("Write-only property '%s' on class '%s' has type '%s' which is not equal to or less "
"restrictive than the type '%s' of the property on the interface '%s' \n", pspecs[n]->name,
g_type_name (G_OBJECT_CLASS_TYPE (class)), g_type_name (G_PARAM_SPEC_VALUE_TYPE (class_pspec)),
g_type_name (G_PARAM_SPEC_VALUE_TYPE (pspecs[n])), g_type_name (iface_type));
break;
default:
g_assert_not_reached ();
}
#define SUBSET(a,b,mask) (((a) & ~(b) & (mask)) == 0)