[Bug objc/48539] New: Missing warning when messaging a forward-declared class

[Bug objc/48539] New: Missing warning when messaging a forward-declared class

[nicola at gcc dot gnu.org]

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

[Bug objc/48539] Missing warning when messaging a forward-declared class

[nicola at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48539

Nicola Pero <nicola at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.04.10 11:11:54
     Ever Confirmed|0                           |1

--- Comment #1 from Nicola Pero <nicola at gcc dot gnu.org> 2011-04-10 11:11:54 UTC ---
Yes, it's confirmed with both 

gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-48)

and

gcc (GCC) 4.7.0 20110326 (experimental)

Thanks

[Bug objc/48539] Missing warning when messaging a forward-declared class

[nicola at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48539

--- Comment #2 from Nicola Pero <nicola at gcc dot gnu.org> 2011-06-02 18:54:34 UTC ---
Author: nicola
Date: Thu Jun  2 18:54:32 2011
New Revision: 174575

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=174575
Log:
In gcc/objc/:
2011-06-02  Nicola Pero  <nicola.pero@meta-innovation.com>

    PR objc/48539
    * objc-act.c (objc_finish_message_expr): Warn if messaging a class
    that was only declared using @class without an @interface.  Warn
    if messaging an instance of a class that was only declared using
    @class without an @interface, unless the receiver was also typed
    with a protocol list.

In gcc/testsuite/:
2011-06-02  Nicola Pero  <nicola.pero@meta-innovation.com>

    PR objc/48539
    * objc.dg/method-5.m: Updated.    
    * objc.dg/method-19.m: Updated.
    * objc.dg/method-lookup-1.m: New.    
    * obj-c++.dg/method-6.mm: Updated.
    * obj-c++.dg/method-7.mm: Updated.
    * obj-c++.dg/method-lookup-1.mm: New.    

Added:
    trunk/gcc/testsuite/obj-c++.dg/method-lookup-1.mm
    trunk/gcc/testsuite/objc.dg/method-lookup-1.m
Modified:
    trunk/gcc/objc/ChangeLog
    trunk/gcc/objc/objc-act.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/obj-c++.dg/method-6.mm
    trunk/gcc/testsuite/obj-c++.dg/method-7.mm
    trunk/gcc/testsuite/objc.dg/method-19.m
    trunk/gcc/testsuite/objc.dg/method-5.m

[Bug objc/48539] Missing warning when messaging a forward-declared class

[nicola at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48539

Nicola Pero <nicola at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
      Known to work|                            |4.7.0
         Resolution|                            |FIXED

--- Comment #3 from Nicola Pero <nicola at gcc dot gnu.org> 2011-06-02 18:58:57 UTC ---
Resolved on trunk.

Thanks