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[Bug objc/48539] New: Missing warning when messaging a forward-declared class
- From: "nicola at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sun, 10 Apr 2011 11:10:16 +0000
- Subject: [Bug objc/48539] New: Missing warning when messaging a forward-declared class
- Auto-submitted: auto-generated
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48539
Summary: Missing warning when messaging a forward-declared
class
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: objc
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: nicola@gcc.gnu.org
The following testcase compiles with no warnings on GCC 4.7.0 20110326:
#include <objc/objc.h>
@class A;
@interface B
{
id isa;
}
+ (void) doSomething;
@end
void test (void)
{
[A doSomething];
}
While clang produces a hard error:
z.m:14:4: warning: receiver 'A' is a forward class and corresponding @interface
may not exist
[A doSomething];
^
z.m:9:1: note: method 'doSomething' is used for the forward class
+ (void) doSomething;
^
1 warning generated.
In this case, the behaviour of clang seems better. @class is really meant to
resolve recursive declarations; it should always be followed by the
corresponding @interface, particularly if you are going to message the class or
objects of the class.
I would say that GCC should produce at least a warning in this case!
There's also the issue of whether the following testcase should also produce
a warning:
#include <objc/objc.h>
@class A;
@interface B
{
id isa;
}
- (void) doSomething;
@end
void test (A *x)
{
[x doSomething];
}
This is slightly different in that it is an instance message, as opposed to
a class message. Neither GCC nor clang produce any warning or error here, but
it sounds like a warning similar to the one above would be very appropriate.
Thanks