DTrace on Leopard: No probes specified, even when I specify probes

Question

% sudo dtrace -p 2446 'objc$target:NSObject:-init:entry { trace(); }'
dtrace: no probes specified

The manpage suggests that this is the correct format with which to specify a probe on an Objective-C method. I tried -Z, but (unsurprisingly) that just didn't print anything.

[Added] It's not even specific to Objective-C probes. I tried it with a C function from AppKit:

sudo dtrace -p 2446 'pid$target::NSPopAutoreleasePool:entry { trace(); }'
dtrace: no probes specified

So what's wrong? Why does DTrace think I have not specified any probes?

Answer 1

Does the process in question allow dtrace? Apple doesn't always allow dtrace on os x.

Answer 2

I think you mean:

sudo dtrace -p 2446 -n 'objc$target:NSObject:-init:entry { trace(); }'

Answer 3

In addition to what Graham said, your original statement will only find instances of NSObject, not its descendents. You could try

sudo dtrace -p 2446 -n 'objc$target::-init*:entry {}'

to catch all -init variants by all NSObject-derived instances.