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Objective-C : Implement NSObject attribute.

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This attribute allows pointers to be marked as pointers to
an NSObject-compatible object.  This allows for additional
checking of assignment etc. when refering to pointers to
opaque types.

gcc/c-family/ChangeLog:

	* c-attribs.c (handle_nsobject_attribute): New.
	* c.opt: Add WNSObject-attribute.

gcc/objc/ChangeLog:

	* objc-act.c (objc_compare_types): Handle NSObject type
	attributes.
	(objc_type_valid_for_messaging): Likewise.

gcc/testsuite/ChangeLog:

	* obj-c++.dg/attributes/nsobject-01.mm: New test.
	* objc.dg/attributes/nsobject-01.m: New test.
This commit is contained in:
Iain Sandoe 2020-10-24 15:51:46 +01:00
parent df784801da
commit 0c30bf43eb
5 changed files with 207 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

39
gcc/c-family/c-attribs.c
View file

@ -157,6 +157,7 @@ static tree handle_designated_init_attribute (tree *, tree, tree, int, bool *);
static tree handle_patchable_function_entry_attribute (tree *, tree, tree,
int, bool *);
static tree handle_copy_attribute (tree *, tree, tree, int, bool *);
static tree handle_nsobject_attribute (tree *, tree, tree, int, bool *);
/* Helper to define attribute exclusions. */
#define ATTR_EXCL(name, function, type, variable) \
@ -509,6 +510,9 @@ const struct attribute_spec c_common_attribute_table[] =
handle_noinit_attribute, attr_noinit_exclusions },
{ "access", 1, 3, false, true, true, false,
handle_access_attribute, NULL },
/* Attributes used by Objective-C. */
{ "NSObject", 0, 0, true, false, false, false,
handle_nsobject_attribute, NULL },
{ NULL, 0, 0, false, false, false, false, NULL, NULL }
};
@ -5124,6 +5128,41 @@ handle_patchable_function_entry_attribute (tree *, tree name, tree args,
return NULL_TREE;
}
/* Handle a "NSObject" attributes; arguments as in
struct attribute_spec.handler. */
static tree
handle_nsobject_attribute (tree *node, tree name, tree args,
int /*flags*/, bool *no_add_attrs)
{
*no_add_attrs = true;
/* This attribute only applies to typedefs (or field decls for properties),
we drop it otherwise - but warn about this if enabled. */
if (TREE_CODE (*node) != TYPE_DECL && TREE_CODE (*node) != FIELD_DECL)
{
warning (OPT_WNSObject_attribute, "%qE attribute may be put on a"
" typedef only; attribute is ignored", name);
return NULL_TREE;
}
/* The original implementation only allowed pointers to records, however
recent implementations also allow void *. */
tree type = TREE_TYPE (*node);
if (!type || !POINTER_TYPE_P (type)
|| (TREE_CODE (TREE_TYPE (type)) != RECORD_TYPE
&& !VOID_TYPE_P (TREE_TYPE (type))))
{
error ("%qE attribute is for pointer types only", name);
return NULL_TREE;
}
tree t = tree_cons (name, args, TYPE_ATTRIBUTES (type));
TREE_TYPE (*node) = build_type_attribute_variant (type, t);
return NULL_TREE;
}
/* Attempt to partially validate a single attribute ATTR as if
it were to be applied to an entity OPER. */

4
gcc/c-family/c.opt
View file

@ -256,6 +256,10 @@ U
C ObjC C++ ObjC++ Joined Separate MissingArgError(macro name missing after %qs)
-U<macro> Undefine <macro>.
WNSObject-attribute
C ObjC C++ ObjC++ LTO Var(warn_nsobject_attribute) Warning Init(1)
Warn if the NSObject attribute is applied to a non-typedef.
Wabi
C ObjC C++ ObjC++ LTO Var(warn_abi) Warning
Warn about things that will change when compiling with an ABI-compliant compiler.

39
gcc/objc/objc-act.c
View file

@ -2476,9 +2476,14 @@ objc_compare_types (tree ltyp, tree rtyp, int argno, tree callee)
if (!POINTER_TYPE_P (ltyp) || !POINTER_TYPE_P (rtyp))
return false;
tree ltyp_attr, rtyp_attr;
do
{
ltyp = TREE_TYPE (ltyp); /* Remove indirections. */
/* Remove indirections, but keep the type attributes from the innermost
pointer type, to check for NSObject. */
ltyp_attr = TYPE_ATTRIBUTES (ltyp);
ltyp = TREE_TYPE (ltyp);
rtyp_attr = TYPE_ATTRIBUTES (rtyp);
rtyp = TREE_TYPE (rtyp);
}
while (POINTER_TYPE_P (ltyp) && POINTER_TYPE_P (rtyp));
@ -2523,17 +2528,23 @@ objc_compare_types (tree ltyp, tree rtyp, int argno, tree callee)
return true;
}
/* We might have void * with NSObject type attr. */
bool l_NSObject_p = ltyp_attr && lookup_attribute ("NSObject", ltyp_attr);
bool r_NSObject_p = rtyp_attr && lookup_attribute ("NSObject", rtyp_attr);
/* Past this point, we are only interested in ObjC class instances,
or 'id' or 'Class'. */
if (TREE_CODE (ltyp) != RECORD_TYPE || TREE_CODE (rtyp) != RECORD_TYPE)
or 'id' or 'Class' (except if the user applied the NSObject type
attribute). */
if ((TREE_CODE (ltyp) != RECORD_TYPE && !l_NSObject_p)
|| (TREE_CODE (rtyp) != RECORD_TYPE && !r_NSObject_p))
return false;
if (!objc_is_object_id (ltyp) && !objc_is_class_id (ltyp)
&& !TYPE_HAS_OBJC_INFO (ltyp))
&& !TYPE_HAS_OBJC_INFO (ltyp) && !l_NSObject_p)
return false;
if (!objc_is_object_id (rtyp) && !objc_is_class_id (rtyp)
&& !TYPE_HAS_OBJC_INFO (rtyp))
&& !TYPE_HAS_OBJC_INFO (rtyp) && !r_NSObject_p)
return false;
/* Past this point, we are committed to returning 'true' to the caller
@ -2567,12 +2578,15 @@ objc_compare_types (tree ltyp, tree rtyp, int argno, tree callee)
rcls = NULL_TREE;
/* If either type is an unqualified 'id', we're done. This is because
an 'id' can be assigned to or from any type with no warnings. */
an 'id' can be assigned to or from any type with no warnings. When
the pointer has NSObject attribute, consider that to be equivalent. */
if (argno != -5)
{
if ((!lproto && objc_is_object_id (ltyp))
|| (!rproto && objc_is_object_id (rtyp)))
return true;
if (l_NSObject_p || r_NSObject_p)
return true;
}
else
{
@ -2580,7 +2594,7 @@ objc_compare_types (tree ltyp, tree rtyp, int argno, tree callee)
general type of object, hence if you try to specialize an
'NSArray *' (ltyp) property with an 'id' (rtyp) one, we need
to warn. */
if (!lproto && objc_is_object_id (ltyp))
if (!lproto && (objc_is_object_id (ltyp) || l_NSObject_p))
return true;
}
@ -8659,11 +8673,19 @@ objc_type_valid_for_messaging (tree type, bool accept_classes)
if (!POINTER_TYPE_P (type))
return false;
/* We will check for an NSObject type attribute on the pointer if other
tests fail. */
tree type_attr = TYPE_ATTRIBUTES (type);
/* Remove the pointer indirection; don't remove more than one
otherwise we'd consider "NSObject **" a valid type for messaging,
which it isn't. */
type = TREE_TYPE (type);
/* We allow void * to have an NSObject type attr. */
if (VOID_TYPE_P (type) && type_attr)
return lookup_attribute ("NSObject", type_attr) != NULL_TREE;
if (TREE_CODE (type) != RECORD_TYPE)
return false;
@ -8676,6 +8698,9 @@ objc_type_valid_for_messaging (tree type, bool accept_classes)
if (TYPE_HAS_OBJC_INFO (type))
return true;
if (type_attr)
return lookup_attribute ("NSObject", type_attr) != NULL_TREE;
return false;
}

66
gcc/testsuite/obj-c++.dg/attributes/nsobject-01.mm Normal file
View file

@ -0,0 +1,66 @@
/* Test handling of the NSObject attribute. */
/* { dg-additional-options "-fsyntax-only " } */
typedef struct AnObj * __attribute__ ((NSObject)) AnObjRef;
typedef struct AnObj * __attribute__ ((__NSObject__)) AnotherObjRef;
/* We allow a void * to be labeled as NSObject. */
typedef void * __attribute__((NSObject)) AnonRef;
typedef struct AnObj * __attribute__((NSObject("foo"))) Bad; // { dg-error {wrong number of arguments specified for 'NSObject' attribute} }
typedef struct AnObj * __attribute__((NSObject(42))) Wrong; // { dg-error {wrong number of arguments specified for 'NSObject' attribute} }
/* Must be a pointer. */
typedef struct AnObj __attribute__((NSObject)) BadRef; // { dg-error {'NSObject' attribute is for pointer types only} }
typedef void * VPtr;
@interface CheckAttrNSObject
{
@public
AnObjRef aor;
/* TODO: synthesize without pre-defined ivars. */
VPtr obj_v;
int bar;
/* TODO: This should warn, even tho the property does not */
__attribute__((NSObject)) struct AnObj *Thing;
}
@property(copy) AnObjRef aor;
typedef struct AnObj * __attribute__((NSObject)) AnObjPtr3;
@property (nonatomic, retain) AnObjPtr3 obj_3;
@property (retain) __attribute__((NSObject)) VPtr obj_v;
//@property (strong, nullable) AnObjPtr3 objp_4;
@property(retain) __attribute__((NSObject)) int bar;
// { dg-error {'NSObject' attribute is for pointer types only} "" { target *-*-* } .-1 }
// { dg-error {'retain' attribute is only valid for Objective-C objects} "" { target *-*-* } .-2 }
@end
void foo ()
{
__attribute__((NSObject)) struct AnObj *AnotherThing; // { dg-warning {'NSObject' attribute may be put on a typedef only; attribute is ignored} }
}
void
setProperty(id self, id value)
{
((CheckAttrNSObject *)self)->aor = value;
}
id
getProperty(id self)
{
return (id)((CheckAttrNSObject *)self)->aor;
}
@implementation CheckAttrNSObject
@synthesize aor;
@dynamic obj_3;
@synthesize obj_v;
@synthesize bar;
@end // { dg-error {invalid conversion} }

66
gcc/testsuite/objc.dg/attributes/nsobject-01.m Normal file
View file

@ -0,0 +1,66 @@
/* Test handling of the NSObject attribute. */
/* { dg-additional-options "-fsyntax-only " } */
typedef struct AnObj * __attribute__ ((NSObject)) AnObjRef;
typedef struct AnObj * __attribute__ ((__NSObject__)) AnotherObjRef;
/* We allow a void * to be labeled as NSObject. */
typedef void * __attribute__((NSObject)) AnonRef;
typedef struct AnObj * __attribute__((NSObject("foo"))) Bad; // { dg-error {wrong number of arguments specified for 'NSObject' attribute} }
typedef struct AnObj * __attribute__((NSObject(42))) Wrong; // { dg-error {wrong number of arguments specified for 'NSObject' attribute} }
/* Must be a pointer. */
typedef struct AnObj __attribute__((NSObject)) BadRef; // { dg-error {'NSObject' attribute is for pointer types only} }
typedef void * VPtr;
@interface CheckAttrNSObject
{
@public
AnObjRef aor;
/* TODO: synthesize without pre-defined ivars. */
VPtr obj_v;
int bar;
/* TODO: This should warn, even tho the property does not */
__attribute__((NSObject)) struct AnObj *Thing;
}
@property(copy) AnObjRef aor;
typedef struct AnObj * __attribute__((NSObject)) AnObjPtr3;
@property (nonatomic, retain) AnObjPtr3 obj_3;
@property (retain) __attribute__((NSObject)) VPtr obj_v;
//@property (strong, nullable) AnObjPtr3 objp_4;
@property(retain) __attribute__((NSObject)) int bar;
// { dg-error {'NSObject' attribute is for pointer types only} "" { target *-*-* } .-1 }
// { dg-error {'retain' attribute is only valid for Objective-C objects} "" { target *-*-* } .-2 }
@end
void foo ()
{
__attribute__((NSObject)) struct AnObj *AnotherThing; // { dg-warning {'NSObject' attribute may be put on a typedef only; attribute is ignored} }
}
void
setProperty(id self, id value)
{
((CheckAttrNSObject *)self)->aor = value;
}
id
getProperty(id self)
{
return (id)((CheckAttrNSObject *)self)->aor;
}
@implementation CheckAttrNSObject
@synthesize aor;
@dynamic obj_3;
@synthesize obj_v;
@synthesize bar; // { dg-warning {returning 'id' from a function with return type 'int'} }
@end // { dg-warning {passing argument} }