Log all accessed methods in Objective-C with DTrace

I have recently been debugging some Objective-C and Cocoa/Cocoa Touch code.

Not being familiar with all the code and with a TON of methods being accessed in milliseconds, my attempts at stepping through the code just wasn’t working, as clicking ‘Step Into’ as fast as I could keep up and over an hour of stepping through I was still not even close to figuring out what I needed to know.

This lead me to the thought of logging every method that was accessed and then I could step look through it and skip around as needed.
However with 60 some odd files and say maybe 20 methods in each file, that would take a lot of NSLog’s.
I started looking around and was pointed to bbums blog about doing something similar.
However it still would take adding some code, plus I couldn’t get it working right with the iPhone.

This lead me to wonder about DTrace.
After a recent podcast from Scotty at the Mac Developer Network, featuring Colin Wheeler talking about DTrace, I have been very interested in learning more about DTrace.

The difficult thing I have been finding is that since DTrace was originally written for Sun, it is hard to find info related to MacOS and more so Cocoa.

I then found a video from Colin about using DTrace with Cocoa and XCode.

I wasn’t able to get what I wanted working, so I hit Colin up on Twitter and then talked to him a bit in email and he pointed me to the Golden Solution!

The solution is:

So I took that and created a DTrace script.
You can grab it here:

To run it open Terminal and run:
sudo ./logAllMethods.d -p PID

Of course replacing ‘PID’ with the PID of your running program and remembering that for DTrace ‘sudo’ is required.

Also note that this works for iPhone programs running in the iPhone Simulator.
Just look for the PID of your iPhone app within Activity Monitor once it’s running in the simulator.

Be careful as depending on the program it can spit out a TON of data VERY quickly.

Running this against Adium for only a fraction of a second gave me a couple hundred lines of output.

The output looks like this:

tesseract:Desktop dallas$ sudo ./logAllMethods.d -p 4371
dtrace: script ‘./logAllMethods.d’ matched 71222 probes
0 59398 -retain:entry
0 34684 +retain:entry
0 32061 +idleAllMovies::entry
0 32062 -idle:entry
0 34707 -retain:entry
0 32914 -_usingVisualContext:entry
0 32878 -_resyncNaturalSize:entry
0 31935 -loadState:entry
0 31972 -naturalSize:entry

Hopefully this helps someone out there.
Just remember always use the info I post for good.
(or if its for evil make sure it profitable and then send me a cut)

Once again, special thanks to Colin Wheeler.

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