Sending messages to objects while debugging Objective-C in gdb, without symbols

Question

I'm trying to send messages to Objective-C objects in gdb.

(gdb) p $esi
$2 = (void *) 0x1268160
(gdb) po $esi
<NSArray: 0x1359c0>
(gdb) po [$esi count]
Target does not respond to this message selector.

I can't send any message to it. Am I missing something? Do I really need the symbols, or something else?

Answer 1

If you must override gdb and send a message to an object when it will not let you, you can use performSelector:

(gdb) print (int)[receivedData count]
Target does not respond to this message selector.

(gdb) print (int)[receivedData performSelector:@selector(count) ]
2008-09-15 00:46:35.854 Executable[1008:20b] *** -[NSConcreteMutableData count]:
unrecognized selector sent to instance 0x105f2e0

If you need to pass an argument use withObject:

(gdb) print (int)[receivedData performSelector:@selector(count) withObject:myObject ]

Answer 2

Is it possible that you need to cast $esi?

p (NSUInteger)[(NSArray *)$esi count]