Using gdb info malloc command within xcode (iphone dev)

Question

Hi,

I'm playing with gdb within xcode debugging an iphone app.

Supposedly, I should be able to use the following command:

info malloc <0xaddress>

see http://www.friday.com/bbum/2010/01/10/using-malloc-to-debug-memory-misuse-in-cocoa/ and http://stackoverflow.com/questions/2910861/strange-gdb-error-unable-to-trace/2911197#2911197

I have env vars MallocStackLoggingNoCompact = 1 and NSZombieEnabled = YES set (via the executable in xcode).

However, I am getting this:

2010-10-03 21:29:01.366 memleaktest[10881:307] *** -[one release]: message sent to deallocated instance 0x1646b0
(gdb) info malloc 0x1646b0
Undefined info command: "malloc 0x1646b0".  Try "help info".

What am I missing to run this command? (xcode 3.2.4 and iphone SDK 4.1)