a question using performv

[]d]

this is my problem source

#import <objc/Object.h>
@interface Myclass:Object {
id target;
int iden;
}
- setTarget:(id) nt;
- setIden:(int) ni;
- printnumber:(int)i1 :(int)i2;
@end

@implementation Myclass
- setTarget:(id) nt {
        target = nt;
        return self;
}
- setIden:(int) ni {
        iden = ni;
        return self;
}
- printnumber:(int)i1 :(int)i2 {
        printf("%d - %d %d\n",iden, i1, i2);
        if (target) {
                printf("call target\n");
                [target performv:_cmd :__builtin_apply_args()];
                printf("end target\n");
        }
        printf("%d - %d %d\n",iden, i1, i2);
        return self;
}

@end

int main() {
        id x1;
        id x2;
        x1 = [[[Myclass alloc] init]setIden:1];
        x2 = [[[Myclass alloc] init]setIden:2];
        [x1 setTarget:x2];
        [x1 printnumber:123 :456];
}

gcc -O2 test.m -lobjc -lpthread
will produce

1 - 123 456
call target
2 - 123 456
2 - 123 456
end target
1 - 123 456

and gcc test.m -lobjc -lpthread
will produce

1 - 123 456
call target
2 - 123 456
2 - 123 456
end target
2 - 123 456

outputs

I am wondering if the usage of 

               target performv:_cmd :__builtin_apply_args()];

is correct.

http://developer.apple.com/techpubs/macosx/DeveloperTools/Compiler/Compiler.22.html

make it sound safe to use it the way I did.
I just wish there's a simple way to do this. a portable way.

best regards,
]d